<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "journalpublishing3.dtd">
<article xml:lang="en" article-type="research-article" xmlns:xlink="http://www.w3.org/1999/xlink">
<?release-delay 0|0?>
<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">IJO</journal-id>
<journal-title-group>
<journal-title>International Journal of Oncology</journal-title></journal-title-group>
<issn pub-type="ppub">1019-6439</issn>
<issn pub-type="epub">1791-2423</issn>
<publisher>
<publisher-name>D.A. Spandidos</publisher-name></publisher></journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3892/ijo.2014.2566</article-id>
<article-id pub-id-type="publisher-id">ijo-45-04-1329</article-id>
<article-categories>
<subj-group>
<subject>Articles</subject></subj-group></article-categories>
<title-group>
<article-title>Redox-directed cancer therapeutics: Taurolidine and Piperlongumine as broadly effective antineoplastic agents (Review)</article-title></title-group>
<contrib-group>
<contrib contrib-type="author">
<name><surname>M&#x000D6;HLER</surname><given-names>HANS</given-names></name><xref rid="af1-ijo-45-04-1329" ref-type="aff">1</xref><xref ref-type="corresp" rid="c1-ijo-45-04-1329"/></contrib>
<contrib contrib-type="author">
<name><surname>PFIRMAN</surname><given-names>ROLF W.</given-names></name><xref rid="af2-ijo-45-04-1329" ref-type="aff">2</xref></contrib>
<contrib contrib-type="author">
<name><surname>FREI</surname><given-names>KARL</given-names></name><xref rid="af3-ijo-45-04-1329" ref-type="aff">3</xref></contrib></contrib-group>
<aff id="af1-ijo-45-04-1329">
<label>1</label>Institute of Pharmacology, University of Zurich and Department of Chemistry and Applied Biosciences, ETH Zurich, 8057 Zurich, Switzerland</aff>
<aff id="af2-ijo-45-04-1329">
<label>2</label>Geistlich Pharma AG, 6110 Wolhusen, University Hospital Zurich, 8091 Zurich, Switzerland</aff>
<aff id="af3-ijo-45-04-1329">
<label>3</label>Department of Neurosurgery, University Hospital Zurich, 8091 Zurich, Switzerland</aff>
<author-notes>
<corresp id="c1-ijo-45-04-1329">Correspondence to: Professor Hanns M&#x000F6;hler, Institute of Pharmacology, University of Zurich and Department of Chemistry and Applied Biosciences, ETH Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland, E-mail: <email>mohler@pharma.uzh.ch</email></corresp></author-notes>
<pub-date pub-type="collection">
<month>10</month>
<year>2014</year></pub-date>
<pub-date pub-type="epub">
<day>28</day>
<month>07</month>
<year>2014</year></pub-date>
<volume>45</volume>
<issue>4</issue>
<fpage>1329</fpage>
<lpage>1336</lpage>
<history>
<date date-type="received">
<day>12</day>
<month>05</month>
<year>2014</year></date>
<date date-type="accepted">
<day>02</day>
<month>07</month>
<year>2014</year></date></history>
<permissions>
<copyright-statement>Copyright &#x000A9; 2014, Spandidos Publications</copyright-statement>
<copyright-year>2014</copyright-year>
<license license-type="open-access" xlink:href="http://creativecommons.org/licenses/by/3.0">
<license-p>This is an open-access article licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. The article may be redistributed, reproduced, and reused for non-commercial purposes, provided the original source is properly cited.</license-p></license></permissions>
<abstract>
<p>Targeting the oxygen stress response pathway is considered a promising strategy to exert antineoplastic activity in a broad spectrum of tumor types. Supporting this view, we summarize the mechanism of action of Taurolidine and Piperlongumine, two antineoplastic agents with strikingly broad tumor selectivity. Taurolidine enhances the oxidative stress (ROS) selectively in tumor cells. Its cytotoxicity for various tumor cells <italic>in vitro</italic> and <italic>in vivo</italic>, which includes tumor stem cells, is based on the induction of programmed cell death, largely via apoptosis but also necroptosis and autophagy. The redox-directed mechanism of action of Taurolidine is apparent from the finding that reducing agents e.g., N-acetylcysteine or glutathione impair its cytotoxicity, while its effectiveness is enhanced by agents which inhibit the cellular anti-oxidant capacity. A similar redox-directed antineoplastic action is shown by Piperlongumine, a recently described experimental drug of plant origin. Taurolidine is particularly advantageous in surgical oncology as this taurine-derivative can be applied perioperatively or systemically with good tolerability as shown in initial clinical applications.</p></abstract>
<kwd-group>
<kwd>antineoplastic agent</kwd>
<kwd>reactive oxygen species</kwd>
<kwd>apoptosis</kwd>
<kwd>autophagy</kwd>
<kwd>necroptosis</kwd></kwd-group></article-meta></front>
<body>
<sec sec-type="other">
<title>1. Introduction</title>
<p>A redox disequilibrium has been recognized in recent years as a specific vulnerability of various tumor cells (<xref rid="b1-ijo-45-04-1329" ref-type="bibr">1</xref>&#x02013;<xref rid="b3-ijo-45-04-1329" ref-type="bibr">3</xref>). By exacerbating the oxidative stress, pro-oxidant drugs achieve antineoplastic activity in a multitude of cancer cells (<xref rid="b1-ijo-45-04-1329" ref-type="bibr">1</xref>,<xref rid="b4-ijo-45-04-1329" ref-type="bibr">4</xref>&#x02013;<xref rid="b6-ijo-45-04-1329" ref-type="bibr">6</xref>). Non-malignant cells, with their high anti-oxidant capacity, are largely resistant to the same degree of deviation from the redox equilibrium resulting in a high selectivity of such drugs for tumor cells (<xref rid="b2-ijo-45-04-1329" ref-type="bibr">2</xref>,<xref rid="b4-ijo-45-04-1329" ref-type="bibr">4</xref>&#x02013;<xref rid="b7-ijo-45-04-1329" ref-type="bibr">7</xref>). In the present review, Taurolidine is described as a redox-directed cancer therapeutic with a broad spectrum of antineoplastic action. In first clinical application in surgical oncology, Taurolidine was well tolerated in patients with glioblastoma and gastrointestinal cancers (<xref rid="b8-ijo-45-04-1329" ref-type="bibr">8</xref>&#x02013;<xref rid="b13-ijo-45-04-1329" ref-type="bibr">13</xref>). In support of the ROS stress pathway being an effective target for broad antineoplastic action, the anticancer activity of Piperlongumine, a plant-derived experimental agent (<xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>,<xref rid="b15-ijo-45-04-1329" ref-type="bibr">15</xref>), is briefly outlined.</p></sec>
<sec sec-type="other">
<title>2. Redox-directed cancer therapeutics</title>
<p>Cancer arises through a multistep, mutagenic process (&#x02018;oncogene dependency&#x02019;) whereby cancer cells acquire a common set of properties that enable tumor cells to proliferate and disseminate metastases (<xref rid="b16-ijo-45-04-1329" ref-type="bibr">16</xref>). As an adaptive response, non-oncogenic pathways such as the oxidative stress response pathways, are also affected (<xref rid="b1-ijo-45-04-1329" ref-type="bibr">1</xref>,<xref rid="b2-ijo-45-04-1329" ref-type="bibr">2</xref>). Reactive oxygen species (ROS), the key mediators of cellular oxidative stress involved in cancer initiation and progression, have recently emerged as promising targets for anticancer drug development. Cancer cells have been reported to harbor elevated levels of ROS and the ability to cope with chronically elevated levels of cellular stress is compromised in a multitude of cancer cells (<xref rid="b1-ijo-45-04-1329" ref-type="bibr">1</xref>&#x02013;<xref rid="b3-ijo-45-04-1329" ref-type="bibr">3</xref>,<xref rid="b17-ijo-45-04-1329" ref-type="bibr">17</xref>). This specific vulnerability of various tumor cells was termed &#x02018;non-oncogene dependency&#x02019; or &#x02018;non-oncogene addiction&#x02019; (<xref rid="b1-ijo-45-04-1329" ref-type="bibr">1</xref>,<xref rid="b4-ijo-45-04-1329" ref-type="bibr">4</xref>,<xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>). Importantly, this dependency may not be shared by many non-transformed cells (<xref rid="b3-ijo-45-04-1329" ref-type="bibr">3</xref>&#x02013;<xref rid="b5-ijo-45-04-1329" ref-type="bibr">5</xref>,<xref rid="b7-ijo-45-04-1329" ref-type="bibr">7</xref>). Their basal ROS levels are low and their anti-oxidant capacity is robust due to the activation of Nrf2, the master regulator of anti-oxidant responses which includes the induction of anti-oxidant enzymes such as catalase or glutathione-S-transferase (<xref rid="b3-ijo-45-04-1329" ref-type="bibr">3</xref>,<xref rid="b5-ijo-45-04-1329" ref-type="bibr">5</xref>,<xref rid="b7-ijo-45-04-1329" ref-type="bibr">7</xref>).</p>
<p>In keeping with this hypothesis, small molecular weight pro-oxidant drugs, which enhance the oxidative stress in tumor cells, are considered as potential antineoplastic agents (<xref rid="b2-ijo-45-04-1329" ref-type="bibr">2</xref>,<xref rid="b3-ijo-45-04-1329" ref-type="bibr">3</xref>,<xref rid="b6-ijo-45-04-1329" ref-type="bibr">6</xref>,<xref rid="b15-ijo-45-04-1329" ref-type="bibr">15</xref>). In contrast, due to the lower basal ROS levels and elevated anti-oxidant capacity, the same pro-oxidant deviation from redox homeostasis would be tolerated by non-malignant cells leading to minimal side-effects (<xref rid="b1-ijo-45-04-1329" ref-type="bibr">1</xref>&#x02013;<xref rid="b3-ijo-45-04-1329" ref-type="bibr">3</xref>,<xref rid="b6-ijo-45-04-1329" ref-type="bibr">6</xref>,<xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>).</p>
<p>In the age of molecularly targeted therapy, drugs with pleiotropic actions such as redox-directed agents, frequently find limited enthusiasm based on the expectation of off-target toxic effects. However, as exemplified in this review, at least some redox-directed agents appear to act selectively on tumor cells. In addition, recent research suggests that it is exactly the pleiotropic mode of action which seems to be uniquely tailored to overcome cancer cell drug resistance originating from a redundancy of oncogenic signaling and rapid mutation (<xref rid="b3-ijo-45-04-1329" ref-type="bibr">3</xref>,<xref rid="b6-ijo-45-04-1329" ref-type="bibr">6</xref>).</p></sec>
<sec sec-type="other">
<title>3. Broad-spectrum antineoplastic activity of Taurolidine</title>
<p>Taurolidine, first synthesized in the 1970s (<xref rid="b18-ijo-45-04-1329" ref-type="bibr">18</xref>) as bis(1,1- dioxoperhydro-1,2,4-thiadizinyl-4)methane, was originally known for its antibacterial and anti-toxin (exo/endotoxin) activity and was tested clinically in the 1980&#x02019;s in the treatment of severe surgical infections, abdominal sepsis and peritonitis (<xref rid="b10-ijo-45-04-1329" ref-type="bibr">10</xref>,<xref rid="b11-ijo-45-04-1329" ref-type="bibr">11</xref>,<xref rid="b13-ijo-45-04-1329" ref-type="bibr">13</xref>). Its antineoplastic activity became apparent in colony forming assays, in which dissociated cells were seeded at very low density and incubated for 2 to 4 weeks. Taurolidine potently prevented cell proliferation (EC<sub>50</sub>, 1 to 7 &#x003BC;g/ml) as shown for glioma cell lines (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>&#x02013;<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>) as well as <italic>ex vivo</italic> human glioblastoma cells (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>). In addition, at higher concentrations, Taurolidine induced acute cytotoxicity (EC<sub>50</sub>, 40 to 80 &#x003BC;g/ml), tested at 24&#x02013;72 h incubation, as shown for a multitude of cultured tumor cell lines such as mesothelioma (<xref rid="b22-ijo-45-04-1329" ref-type="bibr">22</xref>&#x02013;<xref rid="b24-ijo-45-04-1329" ref-type="bibr">24</xref>), prostate (<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>,<xref rid="b25-ijo-45-04-1329" ref-type="bibr">25</xref>), glioblastoma (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>,<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>,<xref rid="b26-ijo-45-04-1329" ref-type="bibr">26</xref>,<xref rid="b27-ijo-45-04-1329" ref-type="bibr">27</xref>), ovarian (<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>,<xref rid="b28-ijo-45-04-1329" ref-type="bibr">28</xref>), leukemia (<xref rid="b28-ijo-45-04-1329" ref-type="bibr">28</xref>), colon (<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>,<xref rid="b29-ijo-45-04-1329" ref-type="bibr">29</xref>&#x02013;<xref rid="b36-ijo-45-04-1329" ref-type="bibr">36</xref>), melanoma (<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>,<xref rid="b37-ijo-45-04-1329" ref-type="bibr">37</xref>,<xref rid="b38-ijo-45-04-1329" ref-type="bibr">38</xref>), osteosarcoma (<xref rid="b40-ijo-45-04-1329" ref-type="bibr">40</xref>,<xref rid="b41-ijo-45-04-1329" ref-type="bibr">41</xref>), pancreatic (<xref rid="b41-ijo-45-04-1329" ref-type="bibr">41</xref>), lung (<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>), esophageal (<xref rid="b42-ijo-45-04-1329" ref-type="bibr">42</xref>) and fibrosarcoma (<xref rid="b41-ijo-45-04-1329" ref-type="bibr">41</xref>,<xref rid="b43-ijo-45-04-1329" ref-type="bibr">43</xref>) as partly summarized by Jacobi <italic>et al</italic> (<xref rid="b44-ijo-45-04-1329" ref-type="bibr">44</xref>). The effectiveness of Taurolidine <italic>in vitro</italic> was largely confirmed <italic>in vivo</italic> using various tumor cell lines as xenografts such as mesothelioma (<xref rid="b23-ijo-45-04-1329" ref-type="bibr">23</xref>), prostate (<xref rid="b25-ijo-45-04-1329" ref-type="bibr">25</xref>), ovarian (<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>,<xref rid="b45-ijo-45-04-1329" ref-type="bibr">45</xref>), colon (<xref rid="b29-ijo-45-04-1329" ref-type="bibr">29</xref>&#x02013;<xref rid="b31-ijo-45-04-1329" ref-type="bibr">31</xref>,<xref rid="b34-ijo-45-04-1329" ref-type="bibr">34</xref>,<xref rid="b35-ijo-45-04-1329" ref-type="bibr">35</xref>) and melanoma (<xref rid="b37-ijo-45-04-1329" ref-type="bibr">37</xref>,<xref rid="b46-ijo-45-04-1329" ref-type="bibr">46</xref>) as well as melanoma cells in a metastatic tumor model (<xref rid="b46-ijo-45-04-1329" ref-type="bibr">46</xref>).</p></sec>
<sec sec-type="other">
<title>4. ROS-dependent cytotoxicity of Taurolidine</title>
<p>As first demonstrated in glioblastoma cells (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>), a ROS-dependent mechanism of Taurolidine-induced cell death became apparent in many tumor cell types. Taurolidine increased the level of ROS as shown in glioblastoma (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>) and mesothelioma cells (<xref rid="b22-ijo-45-04-1329" ref-type="bibr">22</xref>,<xref rid="b24-ijo-45-04-1329" ref-type="bibr">24</xref>). The reducing agent N-acetylcysteine (NAC) was able to block or strongly reduce the cytotoxicity in nearly all tumor cells such as glioblastoma (<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>), mesothelioma cells (<xref rid="b22-ijo-45-04-1329" ref-type="bibr">22</xref>,<xref rid="b24-ijo-45-04-1329" ref-type="bibr">24</xref>), colon carcinoma HT29 cells (<xref rid="b47-ijo-45-04-1329" ref-type="bibr">47</xref>) and Chang liver cells (<xref rid="b47-ijo-45-04-1329" ref-type="bibr">47</xref>) although not in fibrosarcoma HT1080 cells (<xref rid="b47-ijo-45-04-1329" ref-type="bibr">47</xref>). Addition of glutathione similarly prevented cytotoxicity as shown for mesothelioma cells (<xref rid="b22-ijo-45-04-1329" ref-type="bibr">22</xref>). Conversely, a reduction of the glutathione level with DL-buthionin-(S,R)-sulfoximine (BSO) enhanced the ability of Taurolidine to induce cell death as shown for glioblastoma cells (<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>) as well as colon and pancreas carcinoma cells (<xref rid="b47-ijo-45-04-1329" ref-type="bibr">47</xref>). These results underline the central role of ROS in triggering the Taurolidine-induced programmed cell death. Molecularly, Taurolidine may interfere with regulators of redox and ROS homeostasis such as glutathione-S transferase 1.</p></sec>
<sec sec-type="other">
<title>5. Taurolidine and cancer stem cells</title>
<p>In most tumors, the hierarchical model of tumor formation is thought to be operative with cancer stem cells (CSC) contributing to self-renewal and regrowth after debulking of tumor mass by surgery or radiation (<xref rid="b16-ijo-45-04-1329" ref-type="bibr">16</xref>) e.g., in glioblastoma (<xref rid="b48-ijo-45-04-1329" ref-type="bibr">48</xref>). Taurolidine exerted potent cytotoxic activity against murine and human glioma CSCs with ED<sub>50</sub>, 12&#x000B1;2 &#x003BC;g/ml and EC<sub>50</sub>, 13&#x000B1;2 &#x003BC;g/ml, respectively. The CSCs were isolated by the formation of neurospheres from either the murine SMA 560 glioma cell line or from tissue resected from newly diagnosed WHO grade IV glioblastoma patients (KF, unpublished data). These results extend the effectiveness of redox-directed cytotoxicity to CSCs and may strengthen the therapeutic potential of Taurolidine.</p></sec>
<sec sec-type="other">
<title>6. Sparing of normal cells by Taurolidine</title>
<p>Non-tumor cells <italic>in vitro</italic> such as bone marrow cells (<xref rid="b28-ijo-45-04-1329" ref-type="bibr">28</xref>), NIH-3T3 fibroblasts (<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>), non-neoplastic mesothelial cells (<xref rid="b22-ijo-45-04-1329" ref-type="bibr">22</xref>) were not affected by Taurolidine under conditions of tumor cell cytotoxicity. Similarly, <italic>in vivo</italic>, physiological cell proliferation such as leukopoiesis or erythropoiesis (<xref rid="b28-ijo-45-04-1329" ref-type="bibr">28</xref>,<xref rid="b31-ijo-45-04-1329" ref-type="bibr">31</xref>,<xref rid="b44-ijo-45-04-1329" ref-type="bibr">44</xref>) were practically not affected by Taurolidine. The apparent selective induction of cytotoxicity in cancer cells distinguishes Taurolidine from other molecules that partly affect ROS levels, such as paclitaxel, bleomycin, cisplatin or the glutathione synthesis inhibitor BSO (<xref rid="b6-ijo-45-04-1329" ref-type="bibr">6</xref>,<xref rid="b49-ijo-45-04-1329" ref-type="bibr">49</xref>&#x02013;<xref rid="b53-ijo-45-04-1329" ref-type="bibr">53</xref>).</p></sec>
<sec sec-type="other">
<title>7. Good tolerability of Taurolidine in patients</title>
<p>Initially, Taurolidine was tested as an intraperitoneal and intravenous adjunct in the treatment of severe surgical infections (sepsis, peritonitis, pancreatitis), exploiting its activity against antibiotic-resistant bacteria and bacterial toxins. Taurolidine showed good tolerability (<xref rid="b10-ijo-45-04-1329" ref-type="bibr">10</xref>,<xref rid="b11-ijo-45-04-1329" ref-type="bibr">11</xref>,<xref rid="b13-ijo-45-04-1329" ref-type="bibr">13</xref>). In the first clinical experiences with cancer patients in surgical oncology, Taurolidine was likewise well tolerated. In a first case report, a patient with gastric cancer re-recurrence was palliatively treated with 2&#x00025; Taurolidine i.v. for 39 cycles, each cycle consisting of 7 days of treatment per month (300 mg/kg body weight per day). The patient was in good clinical condition as shown by the relevant blood parameters which included an undisturbed leukopoesis and thrombopoesis and no sign of toxicity (<xref rid="b9-ijo-45-04-1329" ref-type="bibr">9</xref>). In a clinical experience with two patients with progressive, non-resectable glioblastoma and conventional therapy, the neurological condition and the quality of life improved in both patients with no sign of tumor progression (&#x02018;partial remission&#x02019;) following two cycles of 21 days each with 2&#x00025; Taurolidine i.v. (20 g/day) (<xref rid="b8-ijo-45-04-1329" ref-type="bibr">8</xref>). In 11 patients with progresssive metastatic melanoma, co-administration of Taurolidine with high rIL-2 enhanced the tolerability of this regime (<xref rid="b54-ijo-45-04-1329" ref-type="bibr">54</xref>). In a multicenter prospective randomized trial, patients with different resectable gastrointestinal (GI) cancers (20 patients each with colon, pancreas or stomach cancer) were treated with a perioperative lavage (2&#x000D7;10 min) consisting of 0.5&#x00025; Taurolidine/heparin versus 0.25&#x00025; povidone- iodine (control). Taurolidine resulted in a reduction of inflammatory cytokines (IL-1, IL-6, IL-10) at 2 and 6 h as measured in peritoneal fluid compared to pre-resection levels (<xref rid="b12-ijo-45-04-1329" ref-type="bibr">12</xref>). There was no change in serum leukocytes and the perioperative complications did not differ. Up to now, the number of GI cancer patients in each group has remained insufficient for a statistical analysis of disease outcome following Taurolidine treatment (<xref rid="b12-ijo-45-04-1329" ref-type="bibr">12</xref>). Nevertheless, in these oncological surgical interventions, Taurolidine did not interfere with post-operative wound healing, which was also demonstrated in a study on the use of Taurolidine in coronary artery bypass grafting in 60 patients (<xref rid="b55-ijo-45-04-1329" ref-type="bibr">55</xref>). These findings confirmed previous findings in rats in which the scar tissue biopsies were examined macroscopically and histopathologically following Taurolidine treatment (<xref rid="b56-ijo-45-04-1329" ref-type="bibr">56</xref>). The perioperative use of Taurolidine solution (2&#x00025;) in surgical oncology (<xref rid="b57-ijo-45-04-1329" ref-type="bibr">57</xref>) promises to be of special benefit as it is administered at the earliest possible therapeutic time window. Perioperatively, circulating tumor cells, which correlate negatively with disease free survival and overall survival (<xref rid="b58-ijo-45-04-1329" ref-type="bibr">58</xref>), would be the prime targets for Taurolidine. By its ability to be cytotoxic to tumor cells and tumor stem cells, perioperative Taurolidine promises to reduce micrometastases and increase survival, as substantiated in a pancreatic cancer model (<xref rid="b59-ijo-45-04-1329" ref-type="bibr">59</xref>). The majority of clinical studies relates to the intraperitoneal administration of Taurolidine, especially in the setting of peritonitis (<xref rid="b11-ijo-45-04-1329" ref-type="bibr">11</xref>,<xref rid="b13-ijo-45-04-1329" ref-type="bibr">13</xref>). In intravenous studies, vein irritation at high doses has been experienced, necessitating direct central administration or peripherally via a PICC line (<xref rid="b57-ijo-45-04-1329" ref-type="bibr">57</xref>).</p></sec>
<sec sec-type="other">
<title>8. Potency of action and plasma levels in patients</title>
<p>Due to its short half-life in man (<xref rid="b60-ijo-45-04-1329" ref-type="bibr">60</xref>) Taurolidine is usually administered by intravenous infusion (2&#x00025; Taurolidine). When administered i.v. intermittently to glioblastoma patients, Taurolidine reached a maximal plasma level of 83&#x000B1;18 &#x003BC;g/ml (<xref rid="b61-ijo-45-04-1329" ref-type="bibr">61</xref>), which is similar to peak values obtained in acutely treated healthy volunteers (<xref rid="b60-ijo-45-04-1329" ref-type="bibr">60</xref>). This plasma concentration is expected to be clinically effective. It is about 20 times higher than the antiproliferative effective concentration of Taurolidine and is in the range of its cytotoxic potency.</p></sec>
<sec sec-type="other">
<title>9. Mechanisms of antineoplastic action</title>
<p>The ROS-dependent induction of programmed cell death by Taurolidine is based on a mixed type of cellular signaling, in particular the induction of caspase-independent apoptosis but also autophagy and programmed necrosis (necroptosis) (<xref rid="f1-ijo-45-04-1329" ref-type="fig">Fig. 1</xref>).</p>
<sec>
<title>Apoptosis</title>
<p>Induction of apoptosis by Taurolidine was first shown in ovarian tumor cells (<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>), also in mesothelioma cells (<xref rid="b1-ijo-45-04-1329" ref-type="bibr">1</xref>,<xref rid="b24-ijo-45-04-1329" ref-type="bibr">24</xref>) but was most extensively studied in glioma cells (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>,<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>,<xref rid="b26-ijo-45-04-1329" ref-type="bibr">26</xref>,<xref rid="b27-ijo-45-04-1329" ref-type="bibr">27</xref>). Within minutes of incubation with Taurolidine, the ROS-induced mitochondrial stress signaling pathway was activated as shown by the depolarization and permeabilisation of the mitochondrial membrane of glioblastoma cells (<xref rid="f2-ijo-45-04-1329" ref-type="fig">Fig. 2</xref>). Concomitantly, as an inducer of apoptosis, the mitochondrial apoptosis-inducing factor (AIF) was transduced from the cytoplasm into the nucleus (<xref rid="f2-ijo-45-04-1329" ref-type="fig">Fig. 2</xref>) (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>). In keeping with the redox-directed mechanism, this process was completely blocked by co-incubation with N-acetyl-cysteine (NAC) (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>). This reducing agent prevented the Taurolidine-induced cell death in practically all tumor cells tested, as described above, supporting the view that induction of apoptosis is the main mechanism of Taurolidine-induced cytotoxicity (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>,<xref rid="b22-ijo-45-04-1329" ref-type="bibr">22</xref>,<xref rid="b24-ijo-45-04-1329" ref-type="bibr">24</xref>,<xref rid="b47-ijo-45-04-1329" ref-type="bibr">47</xref>). Other markers of apoptosis included condensation of chromatin, fragmentation of DNA, externalization of phosphatidylserine and blebbing of the plasma membrane (<xref rid="f3-ijo-45-04-1329" ref-type="fig">Fig. 3</xref>) (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>&#x02013;<xref rid="b21-ijo-45-04-1329" ref-type="bibr">21</xref>,<xref rid="b23-ijo-45-04-1329" ref-type="bibr">23</xref>,<xref rid="b24-ijo-45-04-1329" ref-type="bibr">24</xref>,<xref rid="b27-ijo-45-04-1329" ref-type="bibr">27</xref>).</p>
<p>On the molecular level, the signaling pathways activated by Taurolidine, included the expression of pro-apoptotic transcription factors, the downregulation of the anti-apoptotoc regulator Bcl2, as well as the induction of genes involved in the ER stress response, in protein ubiquitination and in mitochondrial apoptotic pathways (<xref rid="b42-ijo-45-04-1329" ref-type="bibr">42</xref>,<xref rid="b62-ijo-45-04-1329" ref-type="bibr">62</xref>,<xref rid="b63-ijo-45-04-1329" ref-type="bibr">63</xref>). Akt (but not Erk1,2) was inhibited (<xref rid="b22-ijo-45-04-1329" ref-type="bibr">22</xref>). Taurolidine acted synergistically with TRAIL-induced apoptosis (<xref rid="b42-ijo-45-04-1329" ref-type="bibr">42</xref>,<xref rid="b63-ijo-45-04-1329" ref-type="bibr">63</xref>). In keeping with the ROS-dependent mechanism of action, Taurolidine was effective independent of whether p53 was mutated or not (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>,<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>). A significant effect on DNA repair (PARP) was excluded, since PARP inhibition did not interfere with the cytotoxicity of Taurolidine (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>,<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>).</p>
<p>Caspase-dependent pathways of apoptosis played a minor role. In glioblastoma cell lines, but not in <italic>ex vivo</italic> glioma cells, cytochrome <italic>c</italic> translocation was observed only to a very small extent (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>,<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>). Nevertheless, after long-term incubation with Taurolidine (up to 48 h), some cytochrome <italic>c</italic>-dependent caspase activation (caspase 8 and 9) was apparent in prostate, colon and mesothelioma tumor cell lines since cytotoxicity was partly inhibited by a pan-caspase inhibitor (<xref rid="b23-ijo-45-04-1329" ref-type="bibr">23</xref>,<xref rid="b41-ijo-45-04-1329" ref-type="bibr">41</xref>,<xref rid="b45-ijo-45-04-1329" ref-type="bibr">45</xref>). The primary molecular targets of Taurolidine remain to be identified.</p></sec>
<sec>
<title>Autophagy</title>
<p>States of cellular stress, including ROS formation, are known to be strong inducers of autophagy, a caspase-independent process of cell death. In this lysosomal process, cytoplasm and intracellular organelles are sequestered into autophagosomes and delivered to lysosomes for degradation. In glioblastoma cells, incubation with Taurolidine (6&#x02013;24 h) induced autophagy in part of the cells as visualized by the sequestration and lysosomal degradation of intracellular oganelles using transmission electron microscopy (<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>,<xref rid="b41-ijo-45-04-1329" ref-type="bibr">41</xref>). Autophagosomes were also detected by confocal microscopy (<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>). Inhibition by 3-methyl-adenine is likewise in keeping with autophagy (<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>). Autophagy represents an alternative mechanism of cytotoxicity in particular for apoptosis-resistant tumor cells (<xref rid="b64-ijo-45-04-1329" ref-type="bibr">64</xref>).</p></sec>
<sec>
<title>Necrosis</title>
<p>The degree of Taurolidine-induced necrosis was variable. It was negligible in glioma cells but appeared more prevalent in pancreatic and fibrosarcoma cell lines (<xref rid="b47-ijo-45-04-1329" ref-type="bibr">47</xref>). In glioma cell culture (LN229), Taurolidine within 24 h killed 90&#x00025; of the cells as shown by the complete dissolution of the cell morphology (phase contrast microscopy before Annexin-V and PI staining). Of these cells, 53&#x00025; were apoptotic, only 4.6&#x00025; were necrotic (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>,<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>). The latter was largely due to programmed necrosis (necroptosis) since pretreatment with necrostatin-1, a selective inhibitor of the receptor-interacting protein kinase RIP1, had some protective effect (about 40&#x00025;) (<xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>). The large number of unstained glioma cells (42&#x00025;) may point to effects of Taurolidine beyond the induction of apoptosis and necrosis such as autophagy, as described above.</p></sec></sec>
<sec sec-type="other">
<title>10. Supportive anti-angiogenic and anti-inflammatory activities of Taurolidine</title>
<p>Tumors are able to create a permissive microenvironment which includes the ability to induce neo-angiogenesis for maintaining the supply of oxygen and nutrients (<xref rid="b16-ijo-45-04-1329" ref-type="bibr">16</xref>). Besides the induction of the programmed cell death, the antineoplastic activity of Taurolidine includes the inhibition of neo-angiogenesis. Taurolidine inhibited the adhesion of cultured endothelial cells (<xref rid="b65-ijo-45-04-1329" ref-type="bibr">65</xref>), reduced the synthesis of VEGF but not of IL-6 (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>,<xref rid="b31-ijo-45-04-1329" ref-type="bibr">31</xref>) and potently inhibited the VEGF-induced formation of new blood vessels from human endothelial cells <italic>in vitro</italic> (lowest active concentration 1.25 &#x003BC;g/ml) (<xref rid="b65-ijo-45-04-1329" ref-type="bibr">65</xref>). It remains to be seen, wether Taurolidine, besides its cytotoxic effect on tumor cells, may interfere with the neovascularization of tumors <italic>in vivo</italic>.</p>
<p>Taurolidine also showed anti-inflammatory activity as demonstrated early on by the suppression of <italic>E. coli</italic> endotoxin-induced endotoxemia (<xref rid="b66-ijo-45-04-1329" ref-type="bibr">66</xref>) and the endotoxin-induced increase in IL-1&#x003B2; and TNF&#x003B1; synthesis in human peripheral blood monocytes (<xref rid="b67-ijo-45-04-1329" ref-type="bibr">67</xref>) as well as the suppression of the stimulated release of IL-1&#x003B2; from peritoneal macrophages (<xref rid="b34-ijo-45-04-1329" ref-type="bibr">34</xref>). There is a strong link between chronic inflammation and cancer, and NF&#x003BA;B is implicated as a key component in inflammation-induced tumorigenesis (<xref rid="b68-ijo-45-04-1329" ref-type="bibr">68</xref>). In potentially attenuating this process, Taurolidine upregulated the NF&#x003BA;B inhibitor NF&#x003BA;BIA in fibrosarcoma and esophageal cancer cells (<xref rid="b42-ijo-45-04-1329" ref-type="bibr">42</xref>,<xref rid="b63-ijo-45-04-1329" ref-type="bibr">63</xref>). NF&#x003BA;B also regulates the release of the proinflammatory mediators IL-1, IL-6 and TNF&#x003B1;. The anti-inflammatory effect of Taurolidine was proposed to contribute, at least partially, to the attenuation of perioperative tumorigenesis by diminishing the surgery-related inflammation as shown in a rat melanoma model (<xref rid="b46-ijo-45-04-1329" ref-type="bibr">46</xref>,<xref rid="b57-ijo-45-04-1329" ref-type="bibr">57</xref>).</p>
<sec>
<title>11. Piperlongumine, a broad-spectrum antineoplastic agent</title>
<p>The plant alkaloid Piperlongumine (PL), which was previously reported to have antibacterial properties (<xref rid="b69-ijo-45-04-1329" ref-type="bibr">69</xref>), was recently shown to display broad antineoplastic activity by targeting the ROS stress pathway in tumor cells. PL caused a marked increase in ROS selectively in cancer cells as shown in four cancer cell lines (incubation for 1 and 3 h) (<xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>). PL dose-dependently induced cytotoxicity in all 13 different tumor cell lines tested with half maximal effects being reached at 6&#x02013;8 &#x003BC;M (<xref rid="f4-ijo-45-04-1329" ref-type="fig">Fig. 4</xref>) (<xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>). The increase in ROS in tumor cells and the cytotoxicity of PL was reduced by co-incubation with the enzyme catalase or blocked by the addition of NAC (<xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>). PL is thought to interfere with redox and ROS homeostatic regulators such as glutathione-S transferase 1 or carbonyl reductase (<xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>). PL, under comparable conditions, did not cause an increase of ROS or cytotoxicity in normal cells such as endothelial cells, breast epithelial cells, keratinocytes and skin fibroblasts (<xref rid="f4-ijo-45-04-1329" ref-type="fig">Fig. 4</xref>) (<xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>). The PL-induced killing of a broad spectrum of tumor cell lines was based on a mixed type of cellular signaling based largely on the induction of apoptosis (<xref rid="b70-ijo-45-04-1329" ref-type="bibr">70</xref>) but also of autophagy. The latter was triggered via the p38 protein kinase ROS stress response pathway (<xref rid="b71-ijo-45-04-1329" ref-type="bibr">71</xref>). In prostate cells, inhibition of proliferation included the downregulation of the transcription factor NF&#x003BA;B (<xref rid="b72-ijo-45-04-1329" ref-type="bibr">72</xref>). Thus, PL is an interesting broad-spectrum, redox-directed experimental antineoplastic agent.</p></sec>
<sec>
<title>12. Conclusions</title>
<p>Taurolidine is a representative of a novel class of redox-directed, broad-spectrum antineoplastic agents with tumor-selective cytotoxicity. It induces programmed cell death by targeting the oxidative stress response pathway which is compromised in many tumor cells. In initial applications in surgical oncology, Taurolidine i.v. was largely free of significant side-effects and merits further clinical evaluation. Applied perioperatively, Taurolidine promises to reduce circulating tumor cells, a negative predictor for disease-free survival. Taurolidine also inhibits VEGF-induced neo-angiogenesis and may therefore display a dual mode of antineoplastic action. Piperlongumine, an experimental plant-derived agent, is another redox-directed broad-spectrum antineoplastic agent with tumor cell selectivity.</p></sec></sec></body>
<back>
<ref-list>
<title>References</title>
<ref id="b1-ijo-45-04-1329"><label>1</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Luo</surname><given-names>J</given-names></name><name><surname>Solimini</surname><given-names>NL</given-names></name><name><surname>Elledge</surname><given-names>SJ</given-names></name></person-group><article-title>Principles of cancer therapy: oncogene and non-oncogene addiction</article-title><source>Cell</source><volume>136</volume><fpage>823</fpage><lpage>837</lpage><year>2009</year></element-citation></ref>
<ref id="b2-ijo-45-04-1329"><label>2</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Trachootham</surname><given-names>D</given-names></name><name><surname>Alexandre</surname><given-names>J</given-names></name><name><surname>Huang</surname><given-names>P</given-names></name></person-group><article-title>Targeting cancer cells by ROS-mediated mechanisms: a radical therapeutic approach?</article-title><source>Nat Rev Drug Discov</source><volume>8</volume><fpage>579</fpage><lpage>591</lpage><year>2009</year></element-citation></ref>
<ref id="b3-ijo-45-04-1329"><label>3</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Gorrini</surname><given-names>C</given-names></name><name><surname>Harris</surname><given-names>IS</given-names></name><name><surname>Mak</surname><given-names>TW</given-names></name></person-group><article-title>Modulation of oxidative stress as an anticancer strategy</article-title><source>Nat Rev Drug Discov</source><volume>12</volume><fpage>931</fpage><lpage>947</lpage><year>2013</year></element-citation></ref>
<ref id="b4-ijo-45-04-1329"><label>4</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Fruehauf</surname><given-names>JP</given-names></name><name><surname>Meyskens</surname><given-names>FL</given-names><suffix>Jr</suffix></name></person-group><article-title>Reactive oxygen species: a breath of life or death?</article-title><source>Clin Cancer Res</source><volume>13</volume><fpage>789</fpage><lpage>794</lpage><year>2007</year></element-citation></ref>
<ref id="b5-ijo-45-04-1329"><label>5</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Sporn</surname><given-names>MB</given-names></name><name><surname>Liby</surname><given-names>KT</given-names></name></person-group><article-title>NRF2 and cancer: the good, the bad and the importance of context</article-title><source>Nat Rev Cancer</source><volume>12</volume><fpage>564</fpage><lpage>571</lpage><year>2012</year></element-citation></ref>
<ref id="b6-ijo-45-04-1329"><label>6</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Wondrak</surname><given-names>GT</given-names></name></person-group><article-title>Redox-directed cancer therapeutics: molecular merchanisms and opportunities</article-title><source>Antioxid Redox Signal</source><volume>11</volume><fpage>3013</fpage><lpage>3069</lpage><year>2009</year></element-citation></ref>
<ref id="b7-ijo-45-04-1329"><label>7</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Kansanen</surname><given-names>E</given-names></name><name><surname>Kuosmanen</surname><given-names>SM</given-names></name><name><surname>Leinonen</surname><given-names>H</given-names></name><name><surname>Levonen</surname><given-names>AL</given-names></name></person-group><article-title>The Keap1-Nrf2 pathway: mechanism of activation and dysregulation in cancer</article-title><source>Redox Biology</source><volume>1</volume><fpage>45</fpage><lpage>49</lpage><year>2013</year></element-citation></ref>
<ref id="b8-ijo-45-04-1329"><label>8</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Stendel</surname><given-names>R</given-names></name><name><surname>Picht</surname><given-names>T</given-names></name><name><surname>Schilling</surname><given-names>A</given-names></name><name><surname>Heidenreich</surname><given-names>J</given-names></name><name><surname>Loddenkemper</surname><given-names>C</given-names></name><name><surname>J&#x000E4;nisch</surname><given-names>W</given-names></name><name><surname>Brock</surname><given-names>M</given-names></name></person-group><article-title>Treatment of glioblastoma with intravenous Taurolidine. First clinical experience</article-title><source>Anticancer Res</source><volume>24</volume><fpage>1143</fpage><lpage>1147</lpage><year>2004</year></element-citation></ref>
<ref id="b9-ijo-45-04-1329"><label>9</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Braumann</surname><given-names>C</given-names></name><name><surname>Winkler</surname><given-names>G</given-names></name><name><surname>Rogalla</surname><given-names>P</given-names></name><name><surname>Menenakos</surname><given-names>C</given-names></name><name><surname>Jacobi</surname><given-names>CA</given-names></name></person-group><article-title>Prevention of disease progression in a patient with a gastric cancer-recurrence. Outcome after intravenous treatment with the novel antineoplastic agent Taurolidine. Report of a case</article-title><source>World J Surg Oncol</source><volume>4</volume><fpage>34</fpage><year>2006</year></element-citation></ref>
<ref id="b10-ijo-45-04-1329"><label>10</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>McCartney</surname><given-names>AC</given-names></name><name><surname>Browne</surname><given-names>MK</given-names></name></person-group><article-title>Clinical studies on administration of taurolidine in severe sepsis: a preliminary study</article-title><source>Progr Clin Biol Res</source><volume>272</volume><fpage>361</fpage><lpage>371</lpage><year>1988</year></element-citation></ref>
<ref id="b11-ijo-45-04-1329"><label>11</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Staubach</surname><given-names>KH</given-names></name></person-group><article-title>Adjuvant therapy of peritonitis with taurolidine. Modulation of mediator liberation</article-title><source>Langenbecks Arch Chir</source><volume>382</volume><fpage>S26</fpage><lpage>S30</lpage><year>1997</year></element-citation></ref>
<ref id="b12-ijo-45-04-1329"><label>12</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Braumann</surname><given-names>C</given-names></name><name><surname>Gutt</surname><given-names>CN</given-names></name><name><surname>Scheele</surname><given-names>J</given-names></name><name><surname>Menenakos</surname><given-names>C</given-names></name><name><surname>Willems</surname><given-names>W</given-names></name><name><surname>Mueller</surname><given-names>JM</given-names></name><name><surname>Jacobi</surname><given-names>CA</given-names></name></person-group><article-title>Taurolidine reduces the tumor-stimulating cytokine IL 1beta in patients with resectable gastrointestinal cancer: a multicenter prospective randomized trial</article-title><source>World J Surg Oncol</source><volume>7</volume><fpage>32</fpage><lpage>45</lpage><year>2009</year></element-citation></ref>
<ref id="b13-ijo-45-04-1329"><label>13</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Wesch</surname><given-names>G</given-names></name><name><surname>Petermann</surname><given-names>C</given-names></name><name><surname>Linder</surname><given-names>MM</given-names></name></person-group><article-title>Drug therapy of peritonitis: 6-year experience with the chemotherapeutic agent and anti-endotoxin Taurolin</article-title><source>Fortschr Med</source><volume>101</volume><fpage>545</fpage><lpage>550</lpage><year>1983</year></element-citation></ref>
<ref id="b14-ijo-45-04-1329"><label>14</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Raj</surname><given-names>L</given-names></name><name><surname>Ide</surname><given-names>T</given-names></name><name><surname>Gurkar</surname><given-names>AU</given-names></name><name><surname>Foley</surname><given-names>M</given-names></name><name><surname>Schenone</surname><given-names>M</given-names></name><name><surname>Li</surname><given-names>X</given-names></name><name><surname>Tolliday</surname><given-names>NJ</given-names></name><name><surname>Golub</surname><given-names>TR</given-names></name><name><surname>Carr</surname><given-names>SA</given-names></name><name><surname>Shamji</surname><given-names>AF</given-names></name><name><surname>Stern</surname><given-names>AM</given-names></name><name><surname>Mandinova</surname><given-names>A</given-names></name><name><surname>Schreiber</surname><given-names>SL</given-names></name><name><surname>Lee</surname><given-names>SW</given-names></name></person-group><article-title>Selective killing of cancer cells by a small molecule targeting the stress response to ROS</article-title><source>Nature</source><volume>475</volume><fpage>231</fpage><lpage>234</lpage><year>2011</year></element-citation></ref>
<ref id="b15-ijo-45-04-1329"><label>15</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Parkinson</surname><given-names>EI</given-names></name><name><surname>Hergenrother</surname><given-names>PJ</given-names></name></person-group><article-title>Runaway ROS as selective anticancer strategy</article-title><source>Chem Med Chem</source><volume>6</volume><fpage>1957</fpage><lpage>1959</lpage><year>2011</year></element-citation></ref>
<ref id="b16-ijo-45-04-1329"><label>16</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Hanahan</surname><given-names>D</given-names></name><name><surname>Weinberg</surname><given-names>RA</given-names></name></person-group><article-title>Hallmarks of cancer: the next generation</article-title><source>Cell</source><volume>144</volume><fpage>646</fpage><lpage>674</lpage><year>2011</year></element-citation></ref>
<ref id="b17-ijo-45-04-1329"><label>17</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Szatrowski</surname><given-names>TP</given-names></name><name><surname>Nathan</surname><given-names>CF</given-names></name></person-group><article-title>Production of large amounts of hydrogen peroxide by human tumor cells</article-title><source>Cancer Res</source><volume>51</volume><fpage>794</fpage><lpage>798</lpage><year>1991</year></element-citation></ref>
<ref id="b18-ijo-45-04-1329"><label>18</label><element-citation publication-type="book"><person-group person-group-type="author"><name><surname>Pfirrmann</surname><given-names>RW</given-names></name></person-group><source>Taurolin, ein neues Konzept zur antimikrobiellen Chemotherapie chirurgischer Infektionen</source><person-group person-group-type="editor"><name><surname>Br&#x000FC;ckner</surname><given-names>WL</given-names></name><name><surname>Pfirrmann</surname><given-names>RW</given-names></name></person-group><publisher-name>Urban and Schwarzenberg Verlag</publisher-name><year>1985</year><comment>(In German)</comment></element-citation></ref>
<ref id="b19-ijo-45-04-1329"><label>19</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Rodak</surname><given-names>R</given-names></name><name><surname>Kubota</surname><given-names>H</given-names></name><name><surname>Ishihara</surname><given-names>H</given-names></name><name><surname>Eugster</surname><given-names>HP</given-names></name><name><surname>K&#x000F6;n&#x000FC;</surname><given-names>D</given-names></name><name><surname>M&#x000F6;hler</surname><given-names>H</given-names></name><name><surname>Yonekawa</surname><given-names>Y</given-names></name><name><surname>Frei</surname><given-names>K</given-names></name></person-group><article-title>Induction of reactive oxygen intermediates- dependent programmed cell death in human malignant ex vivo glioma cells and inhibition of the vascular endothelial growth factor production by Taurolidine</article-title><source>J Neurosurg</source><volume>102</volume><fpage>1055</fpage><lpage>1068</lpage><year>2005</year></element-citation></ref>
<ref id="b20-ijo-45-04-1329"><label>20</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Stendel</surname><given-names>R</given-names></name><name><surname>Biefer</surname><given-names>HR</given-names></name><name><surname>D&#x000E9;kany</surname><given-names>M</given-names></name><name><surname>Kubota</surname><given-names>H</given-names></name><name><surname>M&#x000FC;nz</surname><given-names>C</given-names></name><name><surname>Wang</surname><given-names>S</given-names></name><name><surname>M&#x000F6;hler</surname><given-names>H</given-names></name><name><surname>Yonekawa</surname><given-names>Y</given-names></name><name><surname>Frei</surname><given-names>K</given-names></name></person-group><article-title>The antibacterial substance Taurolidine exhibits anti-neoplastic action based on a mixed type of programmed cell death</article-title><source>Autophagy</source><volume>5</volume><fpage>194</fpage><lpage>210</lpage><year>2009</year></element-citation></ref>
<ref id="b21-ijo-45-04-1329"><label>21</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Calabresi</surname><given-names>P</given-names></name><name><surname>Goulette</surname><given-names>FA</given-names></name><name><surname>Darnowski</surname><given-names>JW</given-names></name></person-group><article-title>Taurolidine: cytotoxic and mechanistic evaluation of a novel antineoplastic agent</article-title><source>Cancer Res</source><volume>61</volume><fpage>6816</fpage><lpage>6821</lpage><year>2001</year></element-citation></ref>
<ref id="b22-ijo-45-04-1329"><label>22</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Aceto</surname><given-names>N</given-names></name><name><surname>Bertino</surname><given-names>P</given-names></name><name><surname>Barbone</surname><given-names>D</given-names></name><name><surname>Tassi</surname><given-names>G</given-names></name><name><surname>Manzo</surname><given-names>L</given-names></name><name><surname>Porta</surname><given-names>C</given-names></name><name><surname>Mutti</surname><given-names>L</given-names></name><name><surname>Gaudio</surname><given-names>G</given-names></name></person-group><article-title>Taurolidine and oxidative stress: a rationale for local treatment of mesothelioma</article-title><source>Eur Respir J</source><volume>34</volume><fpage>1399</fpage><lpage>1407</lpage><year>2009</year></element-citation></ref>
<ref id="b23-ijo-45-04-1329"><label>23</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Nici</surname><given-names>L</given-names></name><name><surname>Monfils</surname><given-names>B</given-names></name><name><surname>Calabresi</surname><given-names>P</given-names></name></person-group><article-title>The effects of Taurolidine, a novel antineoplastic agent, on human malignant mesothelioma</article-title><source>Clin Cancer Res</source><volume>10</volume><fpage>7655</fpage><lpage>7661</lpage><year>2004</year></element-citation></ref>
<ref id="b24-ijo-45-04-1329"><label>24</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Opitz</surname><given-names>I</given-names></name><name><surname>Sigrist</surname><given-names>B</given-names></name><name><surname>Hillinger</surname><given-names>S</given-names></name><name><surname>Lardinois</surname><given-names>D</given-names></name><name><surname>Stahel</surname><given-names>R</given-names></name><name><surname>Weder</surname><given-names>W</given-names></name><name><surname>Hopkins-Donaldson</surname><given-names>S</given-names></name></person-group><article-title>Taurolidine and povidone-iodine induce different types of cell death in malignant pleural mesothelioma</article-title><source>Lung Cancer</source><volume>56</volume><fpage>327</fpage><lpage>336</lpage><year>2007</year></element-citation></ref>
<ref id="b25-ijo-45-04-1329"><label>25</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Darnowski</surname><given-names>JW</given-names></name><name><surname>Goulette</surname><given-names>FA</given-names></name><name><surname>Cousens</surname><given-names>LP</given-names></name><name><surname>Chatterjee</surname><given-names>D</given-names></name><name><surname>Calabresi</surname><given-names>P</given-names></name></person-group><article-title>Mechanistic and antineoplastic evaluation of Taurolidine in the DU145 model of human prostate cancer</article-title><source>Cancer Chemother Pharmacol</source><volume>54</volume><fpage>249</fpage><lpage>258</lpage><year>2004</year></element-citation></ref>
<ref id="b26-ijo-45-04-1329"><label>26</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Stendel</surname><given-names>R</given-names></name><name><surname>Stoltenburg-Didinger</surname><given-names>G</given-names></name><name><surname>Brock</surname><given-names>M</given-names></name></person-group><article-title>Apoptotic changes in brain tumor cells induced by Taurolidine</article-title><source>J Cancer Res Clin Oncol</source><volume>128</volume><fpage>150</fpage><year>2002</year></element-citation></ref>
<ref id="b27-ijo-45-04-1329"><label>27</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Stendel</surname><given-names>R</given-names></name><name><surname>Stoltenburg-Didinger</surname><given-names>G</given-names></name><name><surname>Al Keikh</surname><given-names>CL</given-names></name><name><surname>Wattroth</surname><given-names>M</given-names></name><name><surname>Brock</surname><given-names>M</given-names></name></person-group><article-title>The effect of Taurolidine on brain tumor cells</article-title><source>Anticancer Res</source><volume>22</volume><fpage>809</fpage><lpage>814</lpage><year>2002</year></element-citation></ref>
<ref id="b28-ijo-45-04-1329"><label>28</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Ribizzi</surname><given-names>I</given-names></name><name><surname>Darnowski</surname><given-names>JW</given-names></name><name><surname>Goulette</surname><given-names>FA</given-names></name><name><surname>Akhtar</surname><given-names>MS</given-names></name><name><surname>Chatterjee</surname><given-names>D</given-names></name><name><surname>Calabresi</surname><given-names>P</given-names></name></person-group><article-title>Taurolidine: preclinical evaluation of a novel, highly selective, agent for bone marrow purging</article-title><source>Bone Marrow Transplant</source><volume>29</volume><fpage>313</fpage><lpage>319</lpage><year>2002</year></element-citation></ref>
<ref id="b29-ijo-45-04-1329"><label>29</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>McCourt</surname><given-names>M</given-names></name><name><surname>Wang</surname><given-names>JH</given-names></name><name><surname>Sookhai</surname><given-names>S</given-names></name><name><surname>Redmond</surname><given-names>HP</given-names></name></person-group><article-title>Taurolidine inhibits tumor cell growth in vitro and in vivo</article-title><source>Ann Surg Oncol</source><volume>7</volume><fpage>685</fpage><lpage>691</lpage><year>2000</year></element-citation></ref>
<ref id="b30-ijo-45-04-1329"><label>30</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Nestler</surname><given-names>G</given-names></name><name><surname>Schulz</surname><given-names>HU</given-names></name><name><surname>Schubert</surname><given-names>D</given-names></name><name><surname>Kr&#x000FC;ger</surname><given-names>S</given-names></name><name><surname>Lippert</surname><given-names>H</given-names></name><name><surname>Pross</surname><given-names>M</given-names></name></person-group><article-title>Impact of Taurolidine on the growth of CC531 coloncarcinoma cells in vitro and in a laparoscopic animal model in rats</article-title><source>Surg Endosc</source><volume>19</volume><fpage>280</fpage><lpage>284</lpage><year>2005</year></element-citation></ref>
<ref id="b31-ijo-45-04-1329"><label>31</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Braumann</surname><given-names>C</given-names></name><name><surname>Schoenbeck</surname><given-names>M</given-names></name><name><surname>Menenakos</surname><given-names>C</given-names></name><name><surname>Kilian</surname><given-names>M</given-names></name><name><surname>Jacobi</surname><given-names>CA</given-names></name></person-group><article-title>Effects of increasing doses of a bolus injection and an intravenous long-term therapy of Taurolidine on subcutaneous (metastic) tumor growth in rats</article-title><source>Clin Exp Metastasis</source><volume>22</volume><fpage>77</fpage><lpage>83</lpage><year>2005</year></element-citation></ref>
<ref id="b32-ijo-45-04-1329"><label>32</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Hoksch</surname><given-names>B</given-names></name><name><surname>Rufer</surname><given-names>B</given-names></name><name><surname>Gazdhar</surname><given-names>A</given-names></name><name><surname>Bilici</surname><given-names>M</given-names></name><name><surname>Beshay</surname><given-names>M</given-names></name><name><surname>Gugger</surname><given-names>M</given-names></name><name><surname>Schmid</surname><given-names>RA</given-names></name></person-group><article-title>Taurolidine in the prevention and therapy of lung metastases</article-title><source>Eur J Cardiothorac Surg</source><volume>36</volume><fpage>1058</fpage><lpage>1063</lpage><year>2009</year></element-citation></ref>
<ref id="b33-ijo-45-04-1329"><label>33</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Chromik</surname><given-names>AM</given-names></name><name><surname>Daigeler</surname><given-names>A</given-names></name><name><surname>Hilgert</surname><given-names>C</given-names></name><name><surname>Bulut</surname><given-names>D</given-names></name><name><surname>Geisler</surname><given-names>A</given-names></name><name><surname>Liu</surname><given-names>V</given-names></name><name><surname>Otte</surname><given-names>JM</given-names></name><name><surname>Uhl</surname><given-names>W</given-names></name><name><surname>Mittelk&#x000F6;tter</surname><given-names>U</given-names></name></person-group><article-title>Synergistic effects in apoptosis induction by Taurolidine and TRAIL in HCT-15 colon carcinoma cells</article-title><source>J Investigat Surg</source><volume>20</volume><fpage>339</fpage><lpage>348</lpage><year>2007</year></element-citation></ref>
<ref id="b34-ijo-45-04-1329"><label>34</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Jacobi</surname><given-names>C</given-names></name><name><surname>Peter</surname><given-names>FJ</given-names></name><name><surname>Wenger</surname><given-names>FA</given-names></name><name><surname>Ordemann</surname><given-names>J</given-names></name><name><surname>M&#x000FC;ller</surname><given-names>JM</given-names></name></person-group><article-title>New therapeutic strategies to avoid intra- and extraperitoneal metastases during laparoscopy: results of a tumor model in the rat</article-title><source>Dig Surg</source><volume>16</volume><fpage>393</fpage><lpage>399</lpage><year>1999</year></element-citation></ref>
<ref id="b35-ijo-45-04-1329"><label>35</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Jacobi</surname><given-names>C</given-names></name><name><surname>Sabat</surname><given-names>R</given-names></name><name><surname>Ordemann</surname><given-names>J</given-names></name><name><surname>Wenger</surname><given-names>F</given-names></name><name><surname>Volk</surname><given-names>H</given-names></name><name><surname>M&#x000FC;ller</surname><given-names>J</given-names></name></person-group><article-title>Peritoneal instillation of taurolidine and heparin for preventing intraperitoneal tumor growth and trocar metastases in laparoscopic operations in the rat model</article-title><source>Langenbecks Arch Chir</source><volume>382</volume><fpage>S31</fpage><lpage>S36</lpage><year>1997</year></element-citation></ref>
<ref id="b36-ijo-45-04-1329"><label>36</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Jacobi</surname><given-names>CA</given-names></name><name><surname>Ordemann</surname><given-names>J</given-names></name><name><surname>B&#x000F6;hm</surname><given-names>B</given-names></name><name><surname>Zieren</surname><given-names>HU</given-names></name><name><surname>Sabat</surname><given-names>R</given-names></name><name><surname>M&#x000FC;ller</surname><given-names>JM</given-names></name></person-group><article-title>Inhibition of peritoneal tumor cell growth and implantation in laparoscopic surgery in a rat model</article-title><source>Am J Surgery</source><volume>174</volume><fpage>359</fpage><lpage>363</lpage><year>1997</year></element-citation></ref>
<ref id="b37-ijo-45-04-1329"><label>37</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Braumann</surname><given-names>C</given-names></name><name><surname>Jacobi</surname><given-names>CA</given-names></name><name><surname>Rogalla</surname><given-names>S</given-names></name><name><surname>Menenakos</surname><given-names>C</given-names></name><name><surname>Fuehrer</surname><given-names>K</given-names></name><name><surname>Trefzer</surname><given-names>U</given-names></name><name><surname>Hofmann</surname><given-names>M</given-names></name></person-group><article-title>The tumor suppressive reagent Taurolidine inhibits growth of malignant melanoma - a mouse model</article-title><source>J Surg Res</source><volume>143</volume><fpage>372</fpage><lpage>378</lpage><year>2007</year></element-citation></ref>
<ref id="b38-ijo-45-04-1329"><label>38</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Sun</surname><given-names>BS</given-names></name><name><surname>Wang</surname><given-names>JH</given-names></name><name><surname>Liu</surname><given-names>LL</given-names></name><name><surname>Gong</surname><given-names>SL</given-names></name><name><surname>Redmond</surname><given-names>HP</given-names></name></person-group><article-title>Taurolidine induces apoptosis of murine melanoma cells in vitro and in vivo by modulation of the Bcl-2 family proteins</article-title><source>J Surg Oncol</source><volume>96</volume><fpage>241</fpage><lpage>248</lpage><year>2007</year></element-citation></ref>
<ref id="b39-ijo-45-04-1329"><label>39</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Walters</surname><given-names>DK</given-names></name><name><surname>Muff</surname><given-names>R</given-names></name><name><surname>Langsam</surname><given-names>B</given-names></name><name><surname>Gruberer</surname><given-names>P</given-names></name><name><surname>Born</surname><given-names>W</given-names></name><name><surname>Fuchs</surname><given-names>B</given-names></name></person-group><article-title>Taurolidine: a novel anti-neoplastic agent induces apoptosis of osterosarcoma cell lines</article-title><source>Invest New Drugs</source><volume>25</volume><fpage>305</fpage><lpage>312</lpage><year>2007</year></element-citation></ref>
<ref id="b40-ijo-45-04-1329"><label>40</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Marley</surname><given-names>K</given-names></name><name><surname>Helfand</surname><given-names>SC</given-names></name><name><surname>Edris</surname><given-names>WA</given-names></name><name><surname>Mata</surname><given-names>JE</given-names></name><name><surname>Gitelman</surname><given-names>AI</given-names></name><name><surname>Medlock</surname><given-names>J</given-names></name><name><surname>S&#x000E9;guin</surname><given-names>B</given-names></name></person-group><article-title>The effects of taurolidine alone and in combination with doxorubicin or carboplatin in canine osteosarcoma in vitro</article-title><source>BMC Veterinary Res</source><volume>9</volume><fpage>15</fpage><lpage>24</lpage><year>2013</year></element-citation></ref>
<ref id="b41-ijo-45-04-1329"><label>41</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Chromik</surname><given-names>AM</given-names></name><name><surname>Daigeler</surname><given-names>A</given-names></name><name><surname>Bulut</surname><given-names>D</given-names></name><name><surname>Flier</surname><given-names>A</given-names></name><name><surname>May</surname><given-names>C</given-names></name><name><surname>Havati</surname><given-names>K</given-names></name><name><surname>Roschinsky</surname><given-names>J</given-names></name><name><surname>S&#x000FC;lberg</surname><given-names>D</given-names></name><name><surname>Ritter</surname><given-names>PR</given-names></name><name><surname>Mittelk&#x000F6;tter</surname><given-names>U</given-names></name><name><surname>Hahn</surname><given-names>SA</given-names></name><name><surname>Uhl</surname><given-names>W</given-names></name></person-group><article-title>Comparative analysis of cell death induction by Taurolidine in different malignant human cancer cell lines</article-title><source>J Exp Clin Cancer Res</source><volume>29</volume><fpage>21</fpage><lpage>37</lpage><year>2010</year></element-citation></ref>
<ref id="b42-ijo-45-04-1329"><label>42</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Daigeler</surname><given-names>A</given-names></name><name><surname>Chromik</surname><given-names>AM</given-names></name><name><surname>Geisler</surname><given-names>A</given-names></name><name><surname>Bulut</surname><given-names>D</given-names></name><name><surname>Hilgert</surname><given-names>C</given-names></name><name><surname>Krieg</surname><given-names>A</given-names></name><name><surname>Klein-Hitpass</surname><given-names>L</given-names></name><name><surname>Lehnhardt</surname><given-names>M</given-names></name><name><surname>Uhl</surname><given-names>W</given-names></name><name><surname>Mittelk&#x000F6;tter</surname><given-names>U</given-names></name></person-group><article-title>Synergistic apoptotic effects of taurolidine and TRAIL on squamous carcinoma cells of the esophagus</article-title><source>Int J Oncol</source><volume>32</volume><fpage>1205</fpage><lpage>1220</lpage><year>2008</year></element-citation></ref>
<ref id="b43-ijo-45-04-1329"><label>43</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Daigeler</surname><given-names>A</given-names></name><name><surname>Chromik</surname><given-names>AM</given-names></name><name><surname>Haendschke</surname><given-names>K</given-names></name><name><surname>Emmelmann</surname><given-names>S</given-names></name><name><surname>Siepmann</surname><given-names>M</given-names></name><name><surname>Hensel</surname><given-names>K</given-names></name><name><surname>Schmitz</surname><given-names>G</given-names></name><name><surname>Klein-Hitpass</surname><given-names>L</given-names></name><name><surname>Steinau</surname><given-names>HU</given-names></name><name><surname>Lehnhardt</surname><given-names>M</given-names></name><name><surname>Hauser</surname><given-names>J</given-names></name></person-group><article-title>Synergistic effects of sonoporation and taurolidin/TRAIL on apoptosis in human fibrosarcoma</article-title><source>Ultrasound Med Biol</source><volume>36</volume><fpage>1893</fpage><lpage>1906</lpage><year>2010</year></element-citation></ref>
<ref id="b44-ijo-45-04-1329"><label>44</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Jacobi</surname><given-names>CA</given-names></name><name><surname>Menenakos</surname><given-names>C</given-names></name><name><surname>Braumann</surname><given-names>C</given-names></name></person-group><article-title>Taurolidine - a new drug with anti-tumor and anti-angiogenic effects</article-title><source>Anticancer Drugs</source><volume>16</volume><fpage>917</fpage><lpage>921</lpage><year>2005</year></element-citation></ref>
<ref id="b45-ijo-45-04-1329"><label>45</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Volz</surname><given-names>J</given-names></name><name><surname>Volz-K&#x000F6;ster</surname><given-names>S</given-names></name><name><surname>Kanis</surname><given-names>S</given-names></name><name><surname>Klee</surname><given-names>D</given-names></name><name><surname>Ahlert</surname><given-names>C</given-names></name><name><surname>Melchert</surname><given-names>F</given-names></name></person-group><article-title>Modulation of tumor-induced lethality after pneumoperitoneum in a mouse model</article-title><source>Cancer</source><volume>89</volume><fpage>262</fpage><lpage>266</lpage><year>2000</year></element-citation></ref>
<ref id="b46-ijo-45-04-1329"><label>46</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Da Costa</surname><given-names>ML</given-names></name><name><surname>Redmond</surname><given-names>HP</given-names></name><name><surname>Bouchier-Hayes</surname><given-names>DJ</given-names></name></person-group><article-title>Taurolidine improves survival by abrogating the accelerated development and proliferation of solid tumors and development of organ metastases from circulating tumor cells released following surgery</article-title><source>J Surg Res</source><volume>101</volume><fpage>111</fpage><lpage>119</lpage><year>2001</year></element-citation></ref>
<ref id="b47-ijo-45-04-1329"><label>47</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Chromik</surname><given-names>AM</given-names></name><name><surname>Daigeler</surname><given-names>A</given-names></name><name><surname>Bulut</surname><given-names>D</given-names></name><name><surname>Flier</surname><given-names>A</given-names></name><name><surname>May</surname><given-names>C</given-names></name><name><surname>Harti</surname><given-names>K</given-names></name><name><surname>Roschinsky</surname><given-names>J</given-names></name><name><surname>S&#x000FC;lberg</surname><given-names>D</given-names></name><name><surname>Ritter</surname><given-names>PR</given-names></name><name><surname>Mittelk&#x000F6;tter</surname><given-names>U</given-names></name><name><surname>Hahn</surname><given-names>SA</given-names></name><name><surname>Uhl</surname><given-names>W</given-names></name></person-group><article-title>Comparative analysis of cell death induction by Taurolidine in different malignant human cancer cell lines</article-title><source>J Exp Clin Res</source><volume>29</volume><fpage>21</fpage><lpage>36</lpage><year>2010</year></element-citation></ref>
<ref id="b48-ijo-45-04-1329"><label>48</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Chen</surname><given-names>L</given-names></name><name><surname>Li</surname><given-names>Y</given-names></name><name><surname>Yu</surname><given-names>TS</given-names></name><name><surname>McKay</surname><given-names>RM</given-names></name><name><surname>Burns</surname><given-names>DK</given-names></name><name><surname>Kernie</surname><given-names>SG</given-names></name><name><surname>Parada</surname><given-names>LF</given-names></name></person-group><article-title>A restricted cell population propagates glioblastoma growth after chemotherapy</article-title><source>Nature</source><volume>488</volume><fpage>522</fpage><lpage>526</lpage><year>2012</year></element-citation></ref>
<ref id="b49-ijo-45-04-1329"><label>49</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Trachootham</surname><given-names>D</given-names></name><name><surname>Zhou</surname><given-names>Y</given-names></name><name><surname>Zhang</surname><given-names>H</given-names></name><name><surname>Demizu</surname><given-names>Y</given-names></name><name><surname>Chen</surname><given-names>Z</given-names></name><name><surname>Pelicano</surname><given-names>H</given-names></name><name><surname>Chiao</surname><given-names>PJ</given-names></name><name><surname>Acxhanta</surname><given-names>G</given-names></name><name><surname>Arlinghaus</surname><given-names>RB</given-names></name><name><surname>Liu</surname><given-names>J</given-names></name><name><surname>Hunag</surname><given-names>P</given-names></name></person-group><article-title>Selective killing of oncogenically trandformed cells through a ROS mediated mechanism by beta-phenylethyl isothiocyanate</article-title><source>Cancer Cell</source><volume>10</volume><fpage>241</fpage><lpage>252</lpage><year>2006</year></element-citation></ref>
<ref id="b50-ijo-45-04-1329"><label>50</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Huang</surname><given-names>P</given-names></name><name><surname>Feng</surname><given-names>L</given-names></name><name><surname>Oldham</surname><given-names>EA</given-names></name><name><surname>Keating</surname><given-names>MJ</given-names></name><name><surname>Plunkett</surname><given-names>W</given-names></name></person-group><article-title>Superoxide dismutase as a target for killing of cancer cells</article-title><source>Nature</source><volume>407</volume><fpage>390</fpage><lpage>395</lpage><year>2000</year></element-citation></ref>
<ref id="b51-ijo-45-04-1329"><label>51</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Shaw</surname><given-names>AT</given-names></name><name><surname>Winslow</surname><given-names>MM</given-names></name><name><surname>Magendantz</surname><given-names>M</given-names></name><name><surname>Ouyang</surname><given-names>C</given-names></name><name><surname>Dowdle</surname><given-names>J</given-names></name><name><surname>Subramanian</surname><given-names>A</given-names></name><name><surname>Lewis</surname><given-names>TA</given-names></name><name><surname>Maglathin</surname><given-names>RL</given-names></name><name><surname>Tolliday</surname><given-names>N</given-names></name><name><surname>Jacks</surname><given-names>T</given-names></name></person-group><article-title>Selective killing of K-ras mutant cancer cells by small molecule inducers of oxidative stress</article-title><source>Proc Natl Acad Sci USA</source><volume>108</volume><fpage>8773</fpage><lpage>8778</lpage><year>2011</year></element-citation></ref>
<ref id="b52-ijo-45-04-1329"><label>52</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Dolam</surname><given-names>S</given-names></name><name><surname>Lessnick</surname><given-names>SL</given-names></name><name><surname>Hahn</surname><given-names>WC</given-names></name><name><surname>Stockwell</surname><given-names>BR</given-names></name></person-group><article-title>Idebtificaton of genotype-selective antitumor agents using syntheticchemical screening in engineered human tumor cells</article-title><source>Cancer Cell</source><volume>3</volume><fpage>285</fpage><lpage>296</lpage><year>2003</year></element-citation></ref>
<ref id="b53-ijo-45-04-1329"><label>53</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Guzman</surname><given-names>ML</given-names></name><name><surname>Rossi</surname><given-names>RM</given-names></name><name><surname>Neelakantan</surname><given-names>S</given-names></name><name><surname>Li</surname><given-names>X</given-names></name><name><surname>Corbett</surname><given-names>CA</given-names></name><name><surname>Hassane</surname><given-names>DC</given-names></name><name><surname>Becker</surname><given-names>MW</given-names></name><name><surname>Bennet</surname><given-names>JM</given-names></name><etal/></person-group><article-title>An orally bioavailable parthenolide analog selectively eradicates acute myelogenous leukemia stem and progenitor cells</article-title><source>Blood</source><volume>110</volume><fpage>4427</fpage><lpage>4435</lpage><year>2007</year></element-citation></ref>
<ref id="b54-ijo-45-04-1329"><label>54</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>O&#x02019;Brien</surname><given-names>G</given-names></name><name><surname>Cahill</surname><given-names>R</given-names></name><name><surname>Bouchier-Hayes</surname><given-names>D</given-names></name><name><surname>Redmond</surname><given-names>P</given-names></name></person-group><article-title>Co-immunotherapy with interleukin-2 and taurolidine for progressive metastatic melanoma</article-title><source>Irish J Med Sci</source><volume>175</volume><fpage>10</fpage><lpage>14</lpage><year>2006</year></element-citation></ref>
<ref id="b55-ijo-45-04-1329"><label>55</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Doddakula</surname><given-names>KK</given-names></name><name><surname>Neary</surname><given-names>PM</given-names></name><name><surname>Wang</surname><given-names>JH</given-names></name><name><surname>Sookhai</surname><given-names>S</given-names></name><name><surname>O&#x02019;Donnel</surname><given-names>A</given-names></name><etal/></person-group><article-title>The antioxidant agent taurolidine potentially reduces ischemia/reperfusion injury through its metabolite taurine</article-title><source>Surgery</source><volume>148</volume><fpage>567</fpage><lpage>572</lpage><year>2010</year></element-citation></ref>
<ref id="b56-ijo-45-04-1329"><label>56</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Braumann</surname><given-names>C</given-names></name><name><surname>Guenther</surname><given-names>N</given-names></name><name><surname>Pohlenz</surname><given-names>J</given-names></name><name><surname>Pfirrmann</surname><given-names>RW</given-names></name><name><surname>Menenakos</surname><given-names>C</given-names></name></person-group><article-title>Wound healing is not impaired in rats undergoing perioperative treatment with the antineoplastic agent taurolidine</article-title><source>Eur Surg Res</source><volume>42</volume><fpage>91</fpage><lpage>96</lpage><year>2009</year></element-citation></ref>
<ref id="b57-ijo-45-04-1329"><label>57</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Neary</surname><given-names>PM</given-names></name><name><surname>Hallihan</surname><given-names>P</given-names></name><name><surname>Wang</surname><given-names>JH</given-names></name><name><surname>Pfirrmann</surname><given-names>R</given-names></name><name><surname>Bouchier-Haves</surname><given-names>HP</given-names></name><name><surname>Redmond</surname><given-names>HP</given-names></name></person-group><article-title>The evolving role of Taurolidine in cancer therapy</article-title><source>Ann Surg Oncol</source><volume>17</volume><fpage>1135</fpage><lpage>1143</lpage><year>2010</year></element-citation></ref>
<ref id="b58-ijo-45-04-1329"><label>58</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Liberko</surname><given-names>M</given-names></name><name><surname>Kolostova</surname><given-names>K</given-names></name><name><surname>Bobek</surname><given-names>V</given-names></name></person-group><article-title>Essentials of circulating tumor cells for clinical research and practice</article-title><source>Cirtic Rev Hematol Oncol</source><volume>88</volume><fpage>338</fpage><lpage>356</lpage><year>2013</year></element-citation></ref>
<ref id="b59-ijo-45-04-1329"><label>59</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Kilian</surname><given-names>M</given-names></name><name><surname>Gregor</surname><given-names>JI</given-names></name><name><surname>Heukamp</surname><given-names>I</given-names></name><name><surname>Braumann</surname><given-names>C</given-names></name><name><surname>Guski</surname><given-names>H</given-names></name><name><surname>Schimke</surname><given-names>I</given-names></name><name><surname>Walz</surname><given-names>MK</given-names></name><name><surname>Jacobi</surname><given-names>CA</given-names></name><name><surname>Wenger</surname><given-names>FA</given-names></name></person-group><article-title>Impact of taurolidine and octreotide on liver metastasis and lipid peroxidation after laparoscopy in chemical induced ductal pancreatic cancer</article-title><source>Invest New Drugs</source><volume>23</volume><fpage>157</fpage><lpage>164</lpage><year>2005</year></element-citation></ref>
<ref id="b60-ijo-45-04-1329"><label>60</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Gong</surname><given-names>L</given-names></name><name><surname>Greenberg</surname><given-names>HE</given-names></name><name><surname>Perhach</surname><given-names>JL</given-names></name><name><surname>Waldman</surname><given-names>SA</given-names></name><name><surname>Kraft</surname><given-names>WK</given-names></name></person-group><article-title>The pharmacokinetics of Taurolidine metabolites in healthy volunteers</article-title><source>J Clin Pharmacol</source><volume>47</volume><fpage>697</fpage><lpage>703</lpage><year>2007</year></element-citation></ref>
<ref id="b61-ijo-45-04-1329"><label>61</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Stendel</surname><given-names>R</given-names></name><name><surname>Scheurer</surname><given-names>L</given-names></name><name><surname>Schlatterer</surname><given-names>K</given-names></name><name><surname>Stalder</surname><given-names>U</given-names></name><name><surname>Pfirrmann</surname><given-names>R</given-names></name><name><surname>Fiss</surname><given-names>I</given-names></name><name><surname>M&#x000F6;hler</surname><given-names>H</given-names></name><name><surname>Bigler</surname><given-names>L</given-names></name></person-group><article-title>Pharmacokinetics of Taurolidine follwing repeated intravenous infusions measured by HPLC-ESI-MS/MS of the derivatives Taurultame and taurinamide in glioblastoma patients</article-title><source>Clin Pharmacokinetics</source><volume>46</volume><fpage>513</fpage><lpage>524</lpage><year>2007</year></element-citation></ref>
<ref id="b62-ijo-45-04-1329"><label>62</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Chromik</surname><given-names>AM</given-names></name><name><surname>Hahn</surname><given-names>SA</given-names></name><name><surname>Daigeler</surname><given-names>A</given-names></name><name><surname>Flier</surname><given-names>A</given-names></name><name><surname>Bulut</surname><given-names>D</given-names></name><name><surname>May</surname><given-names>C</given-names></name><name><surname>Harati</surname><given-names>K</given-names></name><name><surname>Roschinsky</surname><given-names>J</given-names></name><name><surname>S&#x000FC;lberg</surname><given-names>D</given-names></name><name><surname>Weyhe</surname><given-names>D</given-names></name><name><surname>Mittelk&#x000F6;tter</surname><given-names>U</given-names></name><name><surname>Uhl</surname><given-names>W</given-names></name></person-group><article-title>Gene expression analysis of cell death induction by taurolidine in different malignant cell lines</article-title><source>BMC Cancer</source><volume>10</volume><fpage>595</fpage><lpage>608</lpage><year>2010</year></element-citation></ref>
<ref id="b63-ijo-45-04-1329"><label>63</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Daigeler</surname><given-names>A</given-names></name><name><surname>Brenzel</surname><given-names>Ch</given-names></name><name><surname>Bulut</surname><given-names>D</given-names></name><name><surname>Geisler</surname><given-names>A</given-names></name><name><surname>Hilgert</surname><given-names>C</given-names></name><name><surname>Lehnhardt</surname><given-names>M</given-names></name><name><surname>Steinau</surname><given-names>HU</given-names></name><name><surname>Flier</surname><given-names>A</given-names></name><name><surname>Steinstr&#x000E4;sser</surname><given-names>L</given-names></name><name><surname>Klein-Hitpass</surname><given-names>L</given-names></name><name><surname>Mittelk&#x000F6;tter</surname><given-names>U</given-names></name><name><surname>Uhl</surname><given-names>W</given-names></name><name><surname>Chromik</surname><given-names>AM</given-names></name></person-group><article-title>TRAIL and Taurolidine induce apoptosis and decrease proliferation in human fibrosarcoma</article-title><source>J Exp Clin Cancer Res</source><volume>27</volume><fpage>82</fpage><lpage>102</lpage><year>2008</year></element-citation></ref>
<ref id="b64-ijo-45-04-1329"><label>64</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Rubinsztein</surname><given-names>DC</given-names></name><name><surname>Codogno</surname><given-names>P</given-names></name><name><surname>Levine</surname><given-names>B</given-names></name></person-group><article-title>Autophagy modulation as a potential therapeutic target for divers diseases</article-title><source>Nature Rev Drug Disc</source><volume>11</volume><fpage>709</fpage><lpage>730</lpage><year>2012</year></element-citation></ref>
<ref id="b65-ijo-45-04-1329"><label>65</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>M&#x000F6;hler</surname><given-names>T</given-names></name><name><surname>Willhauck-Fleckenstein</surname><given-names>M</given-names></name><name><surname>Schwartz-Albiez</surname><given-names>R</given-names></name><name><surname>Merling</surname><given-names>A</given-names></name><name><surname>M&#x000F6;hler</surname><given-names>H</given-names></name></person-group><article-title>Inhibition of endothelial cell adhesion and in vitro angiogenesis by Taurolidine</article-title><source>Cancer Ther</source><volume>6</volume><fpage>623</fpage><lpage>628</lpage><year>2008</year></element-citation></ref>
<ref id="b66-ijo-45-04-1329"><label>66</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Egan</surname><given-names>BM</given-names></name><name><surname>Bouchier-Hayes</surname><given-names>DJ</given-names></name><name><surname>Condron</surname><given-names>C</given-names></name><name><surname>Kelly</surname><given-names>CJ</given-names></name><name><surname>Abdih</surname><given-names>H</given-names></name></person-group><article-title>Taurolidine attenuates the hemodynamic and respiratory changes associated with endotoxemia</article-title><source>Scock</source><volume>17</volume><fpage>308</fpage><lpage>311</lpage><year>2002</year></element-citation></ref>
<ref id="b67-ijo-45-04-1329"><label>67</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Bedrosian</surname><given-names>I</given-names></name><name><surname>Sofia</surname><given-names>RD</given-names></name><name><surname>Wolff</surname><given-names>SM</given-names></name><name><surname>Dinarello</surname><given-names>CA</given-names></name></person-group><article-title>Taurolidine, an analogue of the amino acid taurine, suppresses interleukin 1 and tumor necrosis factor synthesis in human peripheral blood mononuclear cells</article-title><source>Cytokine</source><volume>3</volume><fpage>568</fpage><lpage>575</lpage><year>1991</year></element-citation></ref>
<ref id="b68-ijo-45-04-1329"><label>68</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Grivennikov</surname><given-names>SI</given-names></name><name><surname>Greten</surname><given-names>FR</given-names></name><name><surname>Karin</surname><given-names>M</given-names></name></person-group><article-title>Immunity, inflammation and cancer</article-title><source>Cell</source><volume>140</volume><fpage>883</fpage><lpage>899</lpage><year>2010</year></element-citation></ref>
<ref id="b69-ijo-45-04-1329"><label>69</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Reddy</surname><given-names>PS</given-names></name><name><surname>Jamil</surname><given-names>K</given-names></name><name><surname>Madhusudhan</surname><given-names>P</given-names></name><name><surname>Anjani</surname><given-names>G</given-names></name></person-group><article-title>Antibacterial activity of isolates of from <italic>Piper longum</italic> and <italic>Taxus baccata</italic></article-title><source>Pharm Biol</source><volume>39</volume><fpage>236</fpage><lpage>238</lpage><year>2001</year></element-citation></ref>
<ref id="b70-ijo-45-04-1329"><label>70</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Adams</surname><given-names>DJ</given-names></name><name><surname>Dai</surname><given-names>M</given-names></name><name><surname>Pellegrino</surname><given-names>G</given-names></name><name><surname>Wagner</surname><given-names>BK</given-names></name><etal/></person-group><article-title>Synthesis, cellular evaluation and mechanism of action of piperlongumine anlogs</article-title><source>Proc Natl Acad Sci USA</source><volume>109</volume><fpage>15115</fpage><lpage>15120</lpage><year>2012</year></element-citation></ref>
<ref id="b71-ijo-45-04-1329"><label>71</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Wang</surname><given-names>Y</given-names></name><name><surname>Wang</surname><given-names>JW</given-names></name><name><surname>Xiao</surname><given-names>X</given-names></name><name><surname>Shan</surname><given-names>Y</given-names></name><name><surname>Xue</surname><given-names>B</given-names></name><name><surname>Jiang</surname><given-names>G</given-names></name><name><surname>He</surname><given-names>Q</given-names></name><name><surname>Chen</surname><given-names>J</given-names></name><name><surname>Xu</surname><given-names>HG</given-names></name><name><surname>Zhao</surname><given-names>RX</given-names></name><name><surname>Werle</surname><given-names>KD</given-names></name><name><surname>Cui</surname><given-names>R</given-names></name><name><surname>Liang</surname><given-names>J</given-names></name><name><surname>Li</surname><given-names>YL</given-names></name><name><surname>Xu</surname><given-names>ZX</given-names></name></person-group><article-title>Piperlongumine induces autophagy by targeting p38</article-title><source>Cell Death Dis</source><volume>4</volume><fpage>e824</fpage><year>2013</year></element-citation></ref>
<ref id="b72-ijo-45-04-1329"><label>72</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Ginzburg</surname><given-names>S</given-names></name><name><surname>Golovine</surname><given-names>KV</given-names></name><name><surname>Makhov</surname><given-names>PB</given-names></name><name><surname>Uzzo</surname><given-names>RG</given-names></name><name><surname>Kutikov</surname><given-names>A</given-names></name><name><surname>Kolenko</surname><given-names>VM</given-names></name></person-group><article-title>Piperlongumine inhibits NFkappaB activity and attenuates aggressive growth characteristics of prostate cancer cells</article-title><source>Prostate</source><volume>73</volume><fpage>1</fpage><lpage>10</lpage><year>2013</year></element-citation></ref></ref-list></back>
<floats-group>
<fig id="f1-ijo-45-04-1329" position="float">
<label>Figure 1</label>
<caption>
<p>The proposed antineoplastic action of Taurolidine. By increasing ROS, Taurolidine induces cytotoxicity in tumor cells largely by induction of apoptosis, but also autophagy and necroptosis. The degree to which these processes are involved may vary with the type of tumor cell. Reducing agents such as N-acetylcysteine (NAC) or glutathione (GSH) inhibit cytotoxicity, which supports the mechanism of redox-directed antineoplastic activity.</p></caption>
<graphic xlink:href="IJO-45-04-1329-g00.gif"/></fig>
<fig id="f2-ijo-45-04-1329" position="float">
<label>Figure 2</label>
<caption>
<p>Initiation of the mitochondrial response pathway by Taurolidine (<xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>). (A) Confocal microscopy images demonstrating Taurolidine-induced loss of mitochondrial membrane potential (red, visualized by MitoTracker) and translocation of Apoptosis-Inducing-Factor (AIF, green) from mitochondria to the nucleus in LN229 glioma cells after 2 h of Taurolidine treatment with 100 &#x003BC;g/ml. In contrast, cytochrome <italic>c</italic> (represented by the green punctate immunostaining) was not released. (B) Time dependency of the Taurolidine effect. AIF translocation, cell shrinkage, and nuclear condensation (chromatin stained red with PI) are detectable within 10 min after Taurolidine (100 &#x003BC;g/ml) treatment. For details see ref. <xref rid="b19-ijo-45-04-1329" ref-type="bibr">19</xref>.</p></caption>
<graphic xlink:href="IJO-45-04-1329-g01.gif"/></fig>
<fig id="f3-ijo-45-04-1329" position="float">
<label>Figure 3</label>
<caption>
<p>(A) Ultrastructural evidence of Taurolidine (100 &#x003BC;g/ml, 12 h of treatment)-induced apoptosis in LN229 glioma cells and SW-480 colon adenocarcinoma cells as shown by blebbing of the plasma membrane and chromatin condensation. (B) Dose response of Taurolidine-induced cell death as shown for the human LN229 glioma and SW-480 colon adenocarcinoma cell lines. Electron microscopy and cytotoxicity were performed as described in ref. <xref rid="b20-ijo-45-04-1329" ref-type="bibr">20</xref>.</p></caption>
<graphic xlink:href="IJO-45-04-1329-g02.gif"/></fig>
<fig id="f4-ijo-45-04-1329" position="float">
<label>Figure 4</label>
<caption>
<p>Piperlongumine treatment induces cell death in cancer cells but not in normal cells. Normal human cells (N), including aortic endothelial cells (PAE), breast epithelial cells (76N), keratinocytes (HKC) and skin fibroblasts (HDF), as well as two immortalized breast epithelial cell lines (184B5 and MCF 10A), were grown in 12-well or 24-well plates and treated with piperlongumine at 1&#x02013;15 &#x003BC;M for 24 h. A variety of human cancer cell lines (Tu) were also treated with piperlongumine or DMSO (control) for 24 h. Cytotoxicity was measured by trypan blue exclusion staining (average of three independent experiments) (reproduced with permission from ref. <xref rid="b14-ijo-45-04-1329" ref-type="bibr">14</xref>).</p></caption>
<graphic xlink:href="IJO-45-04-1329-g03.gif"/></fig></floats-group></article>
