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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">MCO</journal-id>
<journal-title-group>
<journal-title>Molecular and Clinical Oncology</journal-title>
</journal-title-group>
<issn pub-type="ppub">2049-9450</issn>
<issn pub-type="epub">2049-9469</issn>
<publisher>
<publisher-name>D.A. Spandidos</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="publisher-id">MCO-0-0-02413</article-id>
<article-id pub-id-type="doi">10.3892/mco.2021.2413</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Articles</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Expression of VEGF, EGF and HGF in early- and late-stage colorectal cancer</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" corresp="yes">
<name><surname>Abdulla</surname><given-names>Maha-Hamadien</given-names></name>
<xref rid="af1-MCO-0-0-02413" ref-type="aff">1</xref>
<xref rid="c1-MCO-0-0-02413" ref-type="corresp"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Shaik</surname><given-names>Asma Sultana</given-names></name>
<xref rid="af2-MCO-0-0-02413" ref-type="aff">2</xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Vaali-Mohammed</surname><given-names>Mansoor-Ali</given-names></name>
<xref rid="af1-MCO-0-0-02413" ref-type="aff">1</xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Al Khayal</surname><given-names>Khayal Abdulmalik</given-names></name>
<xref rid="af1-MCO-0-0-02413" ref-type="aff">1</xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Traiki</surname><given-names>Thamer Bin</given-names></name>
<xref rid="af1-MCO-0-0-02413" ref-type="aff">1</xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Zubaidi</surname><given-names>Ahmad Mohammed</given-names></name>
<xref rid="af1-MCO-0-0-02413" ref-type="aff">1</xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Al-Johani</surname><given-names>Tariq</given-names></name>
<xref rid="af3-MCO-0-0-02413" ref-type="aff">3</xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Shakoor</surname><given-names>Zahid</given-names></name>
<xref rid="af4-MCO-0-0-02413" ref-type="aff">4</xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Al-Obeed</surname><given-names>Omar Abdullah</given-names></name>
<xref rid="af1-MCO-0-0-02413" ref-type="aff">1</xref>
</contrib>
</contrib-group>
<aff id="af1-MCO-0-0-02413"><label>1</label>Colorectal Research Chair, Department of Surgery, King Khalid University Hospital, College of Medicine, King Saud University, Riyadh 11472, Saudi Arabia</aff>
<aff id="af2-MCO-0-0-02413"><label>2</label>Prince Naif Health Research Centre, King Saud University, Riyadh 11472, Saudi Arabia</aff>
<aff id="af3-MCO-0-0-02413"><label>3</label>Department of Pathology and Laboratory Medicine, College of Medicine, King Saud University Medical City, Riyadh 11472, Saudi Arabia</aff>
<aff id="af4-MCO-0-0-02413"><label>4</label>Department of Immunology, King Saud University Medical City, Riyadh 11472, Saudi Arabia</aff>
<author-notes>
<corresp id="c1-MCO-0-0-02413"><italic>Correspondence to:</italic> Dr Maha-Hamadien Abdulla, Colorectal Research Chair, Department of Surgery, King Khalid University Hospital, College of Medicine, King Saud University, Building 4, Exit 2, P.O. Box 7805(37), Riyadh 11472, Saudi Arabia <email>mabdulla@ksu.edu.sa</email></corresp>
<fn><p><italic>Abbreviations:</italic> CRC, colorectal cancer; EGF, epidermal growth factor; HGF, hepatocyte growth factor; VEGF, vascular endothelial growth factor</p></fn>
</author-notes>
<pub-date pub-type="ppub">
<month>12</month>
<year>2021</year></pub-date>
<pub-date pub-type="epub">
<day>08</day>
<month>10</month>
<year>2021</year></pub-date>
<volume>15</volume>
<issue>6</issue>
<elocation-id>251</elocation-id>
<history>
<date date-type="received">
<day>12</day>
<month>08</month>
<year>2020</year>
</date>
<date date-type="accepted">
<day>17</day>
<month>03</month>
<year>2021</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#x00A9; 2020, Spandidos Publications</copyright-statement>
<copyright-year>2020</copyright-year>
</permissions>
<abstract>
<p>The heterogenous nature of colorectal cancer (CRC) highlights the need for a better understanding of the growth factors that affect tumour growth and cancer progression. The aim of the present study was to evaluate the role of epidermal growth factor (EGF), vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) in the early (I and II) and late (III and IV) stages of CRC. The serum levels and mRNA expression (n=30) of the aforementioned growth factors were measured and immunohistochemistry (n=20) was performed in patients with CRC. Histological examination revealed comparable distribution of early-stage &#x005B;I: 8 (26.7&#x0025;) and II: 7 (23.3&#x0025;)&#x005D; and late-stage &#x005B;III: 8 (26.7&#x0025;) and IV: 7 (23.3&#x0025;)&#x005D; CRC. The mean serum concentrations of VEGF during the early (152.9&#x00B1;14.5 vs. 88.39&#x00B1;3.99 pg/ml; P=0.001) and late (182.7&#x00B1;25.8 vs. 88.39&#x00B1;3.99 pg/ml; P=0.002) stages were significantly higher compared with those in controls. Similarly, the mean serum concentrations of EGF in the early (409.4&#x00B1;7.96 vs. 153.7&#x00B1;13.8 pg/ml; P=0.05) and HGF in the late (90.4&#x00B1;17.4 vs. 56.9&#x00B1;4.97 pg/ml; P=0.05) stages were significantly higher compared with those in controls. The serum concentrations of VEGF, EGF and HGF were comparable between the early and late stages of CRC. Compared to normal tissues, the mRNA expression of both VEGF (P&#x003C;0.001) and HGF (P&#x003C;0.01) was upregulated in early-stage and downregulated in late-stage CRC. The expression of EGF remained significantly elevated during both the early and late stages of CRC (P&#x003C;0.01). Histopathological analyses confirmed increased expression of VEGF in cancerous tissues compared with that in normal tissues. The present study emphasized the need for monitoring the serum levels and tissue expression of growth factors to fully elucidate their role in patients with CRC.</p>
</abstract>
<kwd-group>
<kwd>colorectal cancer</kwd>
<kwd>early stage</kwd>
<kwd>late stage</kwd>
<kwd>VEGF</kwd>
<kwd>EGF</kwd>
<kwd>HGF</kwd>
<kwd>expression</kwd>
</kwd-group>
</article-meta>
</front>
<body>
<sec sec-type="intro">
<title>Introduction</title>
<p>Colorectal cancer (CRC) is the third most frequent among all types of cancer, comprising an estimated 8-9&#x0025; of all cancer cases reported in 2020 worldwide (<xref rid="b1-MCO-0-0-02413" ref-type="bibr">1</xref>). In Saudi Arabia, CRC accounts for 14.1&#x0025; of all cancer-related deaths (<xref rid="b2-MCO-0-0-02413" ref-type="bibr">2</xref>). The local incidence of CRC is on the rise, affecting men more frequently than women (<xref rid="b3-MCO-0-0-02413" ref-type="bibr">3</xref>) and being more frequently diagnosed in young adults (<xref rid="b4-MCO-0-0-02413" ref-type="bibr">4</xref>).</p>
<p>The heterogenous nature of CRC emphasizes the need for a better understanding the of cellular and molecular factors in the tumour microenvironment that regulate tumour cell proliferation and metastasis (<xref rid="b5-MCO-0-0-02413" ref-type="bibr">5</xref>). Alterations in the expression of growth factors and their receptors profoundly affect the proliferation of cancer cells, development of vasculature (angiogenesis) and spread to other organs (<xref rid="b6-MCO-0-0-02413" ref-type="bibr">6</xref>). Signals generated by growth factors modify the tumour microenvironment at various stages of cancer progression (<xref rid="b7-MCO-0-0-02413" ref-type="bibr">7</xref>,<xref rid="b8-MCO-0-0-02413" ref-type="bibr">8</xref>). Low levels of growth factors in biological fluids during the initial stages of cancer development tend to increase rapidly as cancer progresses (<xref rid="b9-MCO-0-0-02413" ref-type="bibr">9</xref>). Certain growth factors, such as epidermal growth factor (EGF), hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF), exhibit a robust association with cancer progression (<xref rid="b10-MCO-0-0-02413" ref-type="bibr">10</xref>).</p>
<p>Overexpression of EGF receptor (EGFR) in 60-80&#x0025; of colonic tumours has been associated with poor prognosis (<xref rid="b11-MCO-0-0-02413" ref-type="bibr">11</xref>). The interaction of EGFR with EGF and TGF&#x03B1; promotes tumourigenesis by dysregulation of the cell cycle, resulting in enhanced tumour cell survival (<xref rid="b12-MCO-0-0-02413" ref-type="bibr">12</xref>). Furthermore, TGF&#x03B1; interaction with EGFR has been shown to promote the expression of VEGF (<xref rid="b12-MCO-0-0-02413" ref-type="bibr">12</xref>), and elevated serum levels of VEGF have been associated with shorter disease-free survival among patients with CRC (<xref rid="b13-MCO-0-0-02413" ref-type="bibr">13</xref>); this may be due to VEGF-mediated angiogenesis through the proliferation, differentiation and migration of vascular endothelial cells (<xref rid="b14-MCO-0-0-02413" ref-type="bibr">14</xref>). Increased serum levels of HGF among patients with cancer, including patients with CRC, have been associated with disease progression (<xref rid="b15-MCO-0-0-02413 b16-MCO-0-0-02413 b17-MCO-0-0-02413" ref-type="bibr">15-17</xref>), most likely due to its ability to promote angiogenesis in tumours (<xref rid="b18-MCO-0-0-02413" ref-type="bibr">18</xref>).</p>
<p>The literature indicates that the growth factors EGF, VEGF and HGF may play important roles in determining cancer progression. Since EGF induces VEGF production and HGF regulates EGF expression (<xref rid="b11-MCO-0-0-02413 b12-MCO-0-0-02413 b13-MCO-0-0-02413 b14-MCO-0-0-02413 b15-MCO-0-0-02413 b16-MCO-0-0-02413 b17-MCO-0-0-02413" ref-type="bibr">11-17</xref>), simultaneous assessment of these three growth factors may indicate how they vary at different stages of CRC. Therefore, the present study was performed to assess the serum levels of EGF, VEGF and HGF, along with their mRNA and protein expression, in patients with early- and late-stage CRC.</p>
</sec>
<sec sec-type="Materials|methods">
<title>Materials and methods</title>
<sec>
<title/>
<sec>
<title>Study population</title>
<p>The present study was performed between March 2015 and September 2016 at King Khalid University Hospital, King Saud University (Riyadh, Saudi Arabia). The study protocol was approved by the Institutional Review Board of the College of Medicine, King Saud University. After obtaining written informed consent, blood samples and tissue specimens were collected from a total of 30 patients &#x005B;14 men (46.7&#x0025;) and 16 women (53.3&#x0025;); mean age, 60 years; range, 38-80 years&#x005D;. Early-stage CRC was defined as stages I and II, whereas late-stage CRC was defined as stages III and IV. Patient demographic and clinical characteristics, including the tumour site and type, were recorded. Tumour staging was performed according to the Union for International Cancer Control (UICC)-TNM staging system; tumour localization, UICC stage and tumour grade were classified as described previously (<xref rid="b19-MCO-0-0-02413" ref-type="bibr">19</xref>). Patients receiving neoadjuvant or adjuvant therapy were excluded from the study.</p>
</sec>
<sec>
<title>Blood and tissue samples</title>
<p>A 5-ml venous blood sample was obtained under aseptic conditions from each patient and from age- and sex-matched healthy controls (n=30). Healthy blood samples were obtained from Blood Bank Unit, King Khalid University Hospital (Riyadh, Saudi Arabia). The blood samples were allowed to clot for 1 h at room temperature and were centrifuged at 1,000 x g for 10 min at room temperature to collect the serum. All serum samples were then stored at -80&#x02DA;C until further use. Cancer and adjacent normal tissue samples (at least 10 cm away from the tumour site) were obtained from the patients, freeze-dried in liquid nitrogen and stored at -80&#x02DA;C until histological examination.</p>
</sec>
<sec>
<title>Measurement of serum concentrations of VEGF, EGF and HGF</title>
<p>The serum concentrations of VEGF, EGF and HGF in patients and controls were quantified using a Human Cytokine multiplex panel (LHC6003, Novex, Invitrogen; Thermo Fisher Scientific, Inc.) and the plates were read using Milliplex&#x2122; Luminex xMAP technology (EMD Millipore). The assay was performed in accordance with the manufacturer&#x0027;s instructions. Assessments of standards, internal controls and samples were performed in duplicates and the results are expressed in pg/ml.</p>
</sec>
<sec>
<title>Preparation of total RNA and reverse transcription (RT)</title>
<p>RNA was extracted from paired tumour and adjacent healthy tissues using PARIS&#x2122; kit (Ambion; Thermo Fisher Scientific, Inc.). Reverse transcription was performed as per the manufacturer&#x0027;s instructions using a high-capacity cDNA kit (cat. no. 4368814; Applied Biosystems; Thermo Fisher Scientific, Inc.). The quality of RNA was evaluated by calculating the A260/280 ratio (1.8-2.0).</p>
</sec>
<sec>
<title>Quantitative (q)PCR) analysis</title>
<p>qPCR was performed on ViiA&#x2122; 7 Real-Time PCR system (Thermo Fisher Scientific, Inc.) using the SYBR Green PCR Master Mix (cat. no. 4385612; Thermo Fisher Scientific, Inc.). The relative mRNA levels of EGF, HGF and VEGF were normalized to GAPDH in order to estimate their expression in tumour and adjacent normal tissues. The qPCR conditions were 95&#x02DA;C for 15 min, 40 cycles of 94&#x02DA;C for 15 sec, and 57&#x02DA;C for 30 sec. The following primers were used: Human EGF, 5&#x0027;-GGAATTCTACTTGTGTGGGTCCT-3&#x0027; (sense) and 5&#x0027;-TCACTGAGACACCAGCATCC-3&#x0027; (antisense); human HGF, 5&#x0027;-GACGCAGCTACAAGGGAACA-3&#x0027; (sense) and 5&#x0027;-GCTCGAAGGCAAAAAGCTG-3&#x0027; (antisense); human VEGF, 5&#x0027;-TGTGAATGCAGACCAAAGAAAGAT-3&#x0027; (sense) and 5&#x0027;-GCTCCAGGGCATTAGACAGC-3&#x0027; (antisense); and human GAPDH, 5&#x0027;-ACCCATCACCATCTTCCAGGAG-3&#x0027; (sense) and 5&#x0027;-GAAGGGGCGGAGATGATGAC-3&#x0027; (antisense). The results were normalized to GAPDH levels and the relative expression was calculated with the 2<sup>-&#x2206;&#x2206;Cq</sup> method (<xref rid="b20-MCO-0-0-02413" ref-type="bibr">20</xref>).</p>
</sec>
<sec>
<title>Construction of tissue microarrays (TMAs) and immunohistochemistry</title>
<p>TMAs were constructed and immunohistochemistry was performed as described previously (<xref rid="b21-MCO-0-0-02413" ref-type="bibr">21</xref>). VEGF expression was detected using streptavidin-biotinylated horseradish peroxidase (S-ABC) kit cat. no. 65306; NovoLink Max Polymer Detection System; Leica Microsystems, Ltd.) as per the manufacturer&#x0027;s instructions. Negative controls without the primary antibody were also included. The expression of VEGF in tumour and normal tissue was analyzed with the eSlide capture device (ScanScope CS; Aperio Technologies, Inc.). VEGF staining intensity was evaluated as negative, weak or strong and a semi-quantitative analysis was performed based on the categorization of patient samples by staining intensity (<xref rid="b22-MCO-0-0-02413" ref-type="bibr">22</xref>).</p>
</sec>
<sec>
<title>Statistical analysis</title>
<p>Statistical analyses were performed using GraphPad Prism 6 (GraphPad Software, Inc.). Data are presented as mean &#x00B1; standard error. A paired t-test was used to compare growth factor serum and mRNA levels between early- and late-stage CRC. P&#x003C;0.05 was considered to indicate statistically significant differences.</p>
</sec>
</sec>
</sec>
<sec sec-type="Results">
<title>Results</title>
<sec>
<title/>
<sec>
<title>Patients</title>
<p>A total of 30 patients with CRC &#x005B;14 men (46.7&#x0025;) and 16 women (53.3&#x0025;); mean age, 60 years; range, 38-80 years&#x005D; were included in the study. Histological examination indicated comparable distribution of early-stage &#x005B;I: n=8 (26.7&#x0025;) and II: n=7 (23.3&#x0025;)&#x005D; and late-stage &#x005B;III: n=8 (26.7&#x0025;) and IV: n=7 (23.3&#x0025;)&#x005D; CRC. The characteristics of the patients and clinicopathological data are summarised in <xref rid="tI-MCO-0-0-02413" ref-type="table">Table I</xref>.</p>
</sec>
<sec>
<title>Serum levels of VEGF, EGF and HGF</title>
<p>The serum concentrations of VEGF, EGF and HGF were compared between patients with early- and those with late-stage CRC and between patients and controls (<xref rid="tII-MCO-0-0-02413" ref-type="table">Table II</xref>). Among patients with CRC, the mean serum concentrations of VEGF during the early (152.9&#x00B1;14.5 vs. 88.39&#x00B1;3.99 pg/ml; P=0.001) and late (182.7&#x00B1;25.8 vs. 88.39&#x00B1;3.99 pg/ml; P=0.002) stages of the disease were significantly higher compared with those in controls. Similarly, the mean serum concentrations of EGF among patients with early-stage (409.4&#x00B1;7.96 vs. 153.7&#x00B1;13.8 pg/ml; P=0.05) and late-stage (669.5&#x00B1;13.1 vs. 153.7&#x00B1;13.8 pg/ml) CRC were higher compared with those controls. The mean serum concentrations of HGF did not differ significantly between patients with early-stage CRC and controls (83.54&#x00B1;14.4 vs. 56.9&#x00B1;4.97 pg/ml; P=0.13); however, the levels of HGF were higher in patients with late-stage CRC compared with controls (90.4&#x00B1;17.4 vs. 56.9&#x00B1;4.97 pg/ml; P=0.05). There was no statistically significant difference in the mean serum concentrations of VEGF, EGF and HGF between early- and late-stage CRC.</p>
</sec>
<sec>
<title>Gene expression of VEGF, EGF and HGF in patients with CRC</title>
<p>Relative quantification of growth factor expression in early-stage cancer indicated a substantial upregulation in the levels of VEGF (P&#x003C;0.001), EGF (P&#x003C;0.05) and HGF (P&#x003C;0.01) in early-stage CRC compared to adjacent normal tissues (<xref rid="f1-MCO-0-0-02413" ref-type="fig">Fig. 1A</xref>). However, decreased expression levels of VEGF and HGF were observed in late-stage CRC compared with the levels observed in the early stages, whereas the levels of EGF remained significantly elevated during both the early and late stages of CRC (P&#x003C;0.01 vs. control; <xref rid="f1-MCO-0-0-02413" ref-type="fig">Fig. 1B</xref>).</p>
</sec>
<sec>
<title>Protein expression of VEGF in patients with CRC</title>
<p>Immunohistochemical analysis of VEGF expression was performed on TMAs of paired tumour and adjacent normal specimens (n=20). Increased expression of VEGF (brown staining) was confirmed in cancerous tissues compared with that in normal tissues (<xref rid="f2-MCO-0-0-02413" ref-type="fig">Fig. 2A-C</xref>). Early-stage (I and II) tumour tissues exhibited a higher number of VEGF-positive tumour cells (<xref rid="f2-MCO-0-0-02413" ref-type="fig">Fig. 2A</xref>) compared with late-stage (III and IV) tumour tissues (<xref rid="f2-MCO-0-0-02413" ref-type="fig">Fig. 2B</xref>). A semi-quantitative analysis was also performed based on the staining intensity of VEGF as negative, weak or strong. Strong staining was observed in 47&#x0025; of late-stage CRC samples, whereas 53&#x0025; of the early-stage samples exhibited strong staining. While all tumours displayed VEGF positivity, the intensity of staining varied from weak to strong between early and late cancer stages, and also within the same stage, demonstrating heterogeneous expression.</p>
</sec>
</sec>
</sec>
<sec sec-type="Discussion">
<title>Discussion</title>
<p>Growth factors in cancer are well known to stimulate cellular proliferation, tumour progression, angiogenesis and subsequent metastasis (<xref rid="b6-MCO-0-0-02413" ref-type="bibr">6</xref>). Increased expression of growth factors is frequently encountered in neoplastic/cancerous cells (<xref rid="b23-MCO-0-0-02413" ref-type="bibr">23</xref>). This may have potential clinical implications in the management and outcome of CRC, as a number of growth factors have been shown to serve as prognostic markers in monitoring the response to therapeutic interventions (<xref rid="b24-MCO-0-0-02413" ref-type="bibr">24</xref>). Elevated serum levels of tumour growth factors, such as EGF, VEGF and HGF, have been reported among patients with CRC, whereas these levels tend to decline following effective treatment (<xref rid="b25-MCO-0-0-02413" ref-type="bibr">25</xref>). Moreover, higher preoperative levels of VEGF and HGF have been reported to be associated with recurrence of CRC after therapy (<xref rid="b26-MCO-0-0-02413" ref-type="bibr">26</xref>). Targeting these angiogenic factors with biological agents may counteract the tumour-promoting effects of these circulating factors. In the present study, significantly higher serum concentrations of EGF, VEGF and HGF were found among patients with early- and late-stage CRC compared to controls.</p>
<p>Owing to its angiogenic potential, the role of VEGF is considered to be critical in CRC. Significantly higher expression of VEGF has been reported in 50&#x0025; of patients with CRC compared to its expression in healthy tissues (<xref rid="b27-MCO-0-0-02413" ref-type="bibr">27</xref>). Enhanced expression of VEGF is considered as a poor prognostic marker in CRC (<xref rid="b28-MCO-0-0-02413" ref-type="bibr">28</xref>,<xref rid="b29-MCO-0-0-02413" ref-type="bibr">29</xref>) and is also associated with poor overall survival among affected patients (<xref rid="b30-MCO-0-0-02413" ref-type="bibr">30</xref>). Furthermore, elevated serum levels of VEGF are positively correlated with tumour stage, with significantly higher levels of circulating VEGF observed in advanced stages of CRC compared to early stages (<xref rid="b31-MCO-0-0-02413" ref-type="bibr">31</xref>,<xref rid="b32-MCO-0-0-02413" ref-type="bibr">32</xref>). The results of the present study were consistent with these observations, and the intense expression of VEGF in the later stages of the disease suggested a possible role of VEGF in disease progression. Despite the convincing data linking VEGF with disease progression among patients with CRC, there is however evidence refuting these claims and stating that VEGF has no prognostic significance as a risk factor for CRC progression (<xref rid="b33-MCO-0-0-02413" ref-type="bibr">33</xref>). Moreover, no difference in the serum concentrations of VEGF between patients with CRC and healthy controls has been reported (<xref rid="b34-MCO-0-0-02413" ref-type="bibr">34</xref>). Due to the conflicting reports, investigations of factors, such as the involvement of other members of the VEGF family of growth factors (<xref rid="b29-MCO-0-0-02413" ref-type="bibr">29</xref>,<xref rid="b35-MCO-0-0-02413" ref-type="bibr">35</xref>), the extent of inflammation and the number of tumour-infiltrating lymphocytes in CRC, may be useful in gaining a better understanding of the pathogenesis of CRC.</p>
<p>The serum levels of EGF were found to be significantly elevated in patients with early- and late-stage CRC compared to healthy controls in the present study. Data for EGF among patients with CRC are scarce and, to the best of our knowledge, no previous study has compared EGF levels between the early and late stages of CRC. Elevated serum levels of EGF have been shown to exhibit 80&#x0025; sensitivity and 65&#x0025; specificity in the detection of ovarian cancers (<xref rid="b36-MCO-0-0-02413" ref-type="bibr">36</xref>). Increased expression of EGF has not only been associated with various types of cancer, but is also considered to be a poor prognostic marker in terms of adverse clinical outcomes (<xref rid="b37-MCO-0-0-02413 b38-MCO-0-0-02413 b39-MCO-0-0-02413 b40-MCO-0-0-02413 b41-MCO-0-0-02413" ref-type="bibr">37-41</xref>). By contrast, low levels of EGF have been reported among patients with non-small cell lung cancer and head and neck cancer compared with healthy controls (<xref rid="b42-MCO-0-0-02413" ref-type="bibr">42</xref>). In the present study, however, EGF was found to be markedly elevated in both the early and late stages of CRC, indicating the potential clinical role of this marker. Although studies ascertaining the clinical significance of this finding in CRC are currently lacking, the evidence reported by studies performed on patients with ovarian (<xref rid="b36-MCO-0-0-02413" ref-type="bibr">36</xref>), lung, and head and neck cancers (<xref rid="b42-MCO-0-0-02413" ref-type="bibr">42</xref>) indicate that EGF expression may be of substantial diagnostic value. Further studies are therefore needed to evaluate the diagnostic and/or prognostic significance of this marker in CRC.</p>
<p>HGF and its receptor, c-Met (tyrosine-protein kinase Met or hepatocyte growth factor receptor), are involved in a number of important biological processes (<xref rid="b43-MCO-0-0-02413" ref-type="bibr">43</xref>). HGF/c-Met interaction has been implicated in HGF-activated colonic fibroblast-mediated carcinogenesis of colonic epithelial cancer cells (<xref rid="b44-MCO-0-0-02413" ref-type="bibr">44</xref>,<xref rid="b45-MCO-0-0-02413" ref-type="bibr">45</xref>). The higher levels of c-Met mRNA and protein in CRC liver metastasis, the positive correlation between c-Met expression and liver metastasis, and the association of the downregulation of HGF/c-Met signalling with the reduction in cell proliferation, invasion and metastasis of liver cancer, indicate a potentially crucial role of HGF in CRC (<xref rid="b46-MCO-0-0-02413" ref-type="bibr">46</xref>). Moreover, increased expression of HGF among patients with CRC has been shown to exhibit a positive correlation with disease progression (<xref rid="b25-MCO-0-0-02413" ref-type="bibr">25</xref>). The serum concentration of HGF was found to be higher in the early stages of CRC in the present study, whereas its levels normalized in the late stages. These observations suggest an involvement of HGF in disease pathogenesis in the early stages of CRC, thus highlighting it as a promising target for therapeutic interventions. Furthermore, there appears to be a need for further investigations to elucidate the role of HGF in cancer development, lymphatic invasion and survival in CRC (<xref rid="b17-MCO-0-0-02413" ref-type="bibr">17</xref>).</p>
<p>It is evident that tumour progression from early to late stage involves a number of cellular, biochemical and molecular events, including altered expression of several growth factors (<xref rid="b46-MCO-0-0-02413" ref-type="bibr">46</xref>). However, mRNA expression levels may not be reflective of serum concentrations, possibly owing to post-transcriptional, translational and post-translational modifications, which may determine protein degradation and its regulation (<xref rid="b47-MCO-0-0-02413" ref-type="bibr">47</xref>). Further studies are needed to understand this perspective. Moreover, an increase in the concentrations of growth factors may be associated with an increase in the numbers of cancer niche cells during carcinogenesis, which also needs additional supportive evidence (<xref rid="b48-MCO-0-0-02413" ref-type="bibr">48</xref>). The growth factor expression profile observed in the present study during the early and late stages of CRC offers an opportunity for further investigations to identify targets for predicting the prognosis and establishing therapeutic interventions for the containment of CRC progression.</p>
<p>In conclusion, the elevated levels of growth factors during the early and late stages of CRC observed in the present study highlight the importance of growth factor expression in CRC. However, a major limitation of the present study was its small sample size. Large scale studies are recommended to validate the findings of the present study and to gain a better understanding of the exact role of growth factors in the pathogenesis of CRC.</p>
</sec>
</body>
<back>
<ack>
<title>Acknowledgements</title>
<p>Not applicable.</p>
</ack>
<sec>
<title>Funding</title>
<p>The present study was supported and funded by Researchers Supporting Project number (grant no. RSP-2021/344), King Saud University, Riyadh, Saudi Arabia.</p>
</sec>
<sec>
<title>Availability of data and materials</title>
<p>The datasets used and/or analysed during the present study are available from the corresponding author upon reasonable request.</p>
</sec>
<sec>
<title>Authors&#x0027; contributions</title>
<p>MHA, OAAO and MAVM conceived and designed the study, and drafted the manuscript; MHA, SAS and MAVM performed the statistical data analysis; MAVM, MHA, SAS and TBT have seen and can confirm the authenticity of the raw data; KAAK, TBT, TAJ, ZS and AMZ were involved in data acquisition and interpretation, and critically revised the manuscript for important intellectual content. All the authors have read and approved the final manuscript.</p>
</sec>
<sec>
<title>Ethics approval and consent to participate</title>
<p>The study was approved by the Institutional Review Board of College of Medicine (approval no. 15/0482), King Saud University, and all the participants provided their written informed consent prior to enrolment.</p>
</sec>
<sec>
<title>Patient consent for publication</title>
<p>Not applicable.</p>
</sec>
<sec>
<title>Competing interests</title>
<p>The authors declare that they have no competing interests.</p>
</sec>
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<fig id="f1-MCO-0-0-02413" position="float">
<label>Figure 1</label>
<caption><p>Relative quantification of growth factor expression normalized to GAPDH in (A) early-stage and (B) late-stage colorectal cancer. <sup>&#x002A;</sup>P&#x003C;0.05, <sup>&#x002A;&#x002A;</sup>P&#x003C;0.01 and <sup>&#x002A;&#x002A;&#x002A;</sup>P&#x003C;0.001 vs. control. EGF, epidermal growth factor; VEGF, vascular endothelial growth factor; HGF, hepatocyte growth factor.</p></caption>
<graphic xlink:href="mco-15-06-02413-g00.tif" />
</fig>
<fig id="f2-MCO-0-0-02413" position="float">
<label>Figure 2</label>
<caption><p>Immunohistochemistry staining for VEGF. (A) Photomicrograph showing normal mucosa with negative staining for VEGF. (B) Colonic adenocarcinoma exhibiting strong positive epithelial neoplastic luminal staining for VEGF in a patient with early-stage disease. (C) Colonic adenocarcinoma exhibiting weak staining for VEGF in a patient with late-stage disease. Magnification, x600.</p></caption>
<graphic xlink:href="mco-15-06-02413-g01.tif" />
</fig>
<table-wrap id="tI-MCO-0-0-02413" position="float">
<label>Table I</label>
<caption><p>Clinicopathological characteristics of patients with colorectal cancer.</p></caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th align="left" valign="middle">Variables</th>
<th align="center" valign="middle">Number of patients</th>
<th align="center" valign="middle">Percentage</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left" valign="middle">Mean age (years)</td>
<td align="center" valign="middle">&#x00A0;</td>
<td align="center" valign="middle">&#x00A0;</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x2264;60</td>
<td align="center" valign="middle">17</td>
<td align="center" valign="middle">56.7</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x003E;60</td>
<td align="center" valign="middle">13</td>
<td align="center" valign="middle">33.3</td>
</tr>
<tr>
<td align="left" valign="middle">Sex</td>
<td align="center" valign="middle">&#x00A0;</td>
<td align="center" valign="middle">&#x00A0;</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;Male</td>
<td align="center" valign="middle">14</td>
<td align="center" valign="middle">46.7</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;Female</td>
<td align="center" valign="middle">16</td>
<td align="center" valign="middle">53.3</td>
</tr>
<tr>
<td align="left" valign="middle">Primary tumour</td>
<td align="center" valign="middle">&#x00A0;</td>
<td align="center" valign="middle">&#x00A0;</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;Colon</td>
<td align="center" valign="middle">27</td>
<td align="center" valign="middle">90</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;Rectum</td>
<td align="center" valign="middle">3</td>
<td align="center" valign="middle">10</td>
</tr>
<tr>
<td align="left" valign="middle">Tumour stage (UICC 2010)</td>
<td align="center" valign="middle">&#x00A0;</td>
<td align="center" valign="middle">&#x00A0;</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;pT1</td>
<td align="center" valign="middle">4</td>
<td align="center" valign="middle">13.3</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;pT2</td>
<td align="center" valign="middle">8</td>
<td align="center" valign="middle">26.7</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;pT3</td>
<td align="center" valign="middle">15</td>
<td align="center" valign="middle">50</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;pT4</td>
<td align="center" valign="middle">3</td>
<td align="center" valign="middle">10</td>
</tr>
<tr>
<td align="left" valign="middle">Lymph node status (UICC 2010)</td>
<td align="center" valign="middle">&#x00A0;</td>
<td align="center" valign="middle">&#x00A0;</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;pN0</td>
<td align="center" valign="middle">15</td>
<td align="center" valign="middle">50</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;pN1</td>
<td align="center" valign="middle">13</td>
<td align="center" valign="middle">43.3</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;pN2</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">6.7</td>
</tr>
<tr>
<td align="left" valign="middle">Clinical stage (UICC 2010)</td>
<td align="center" valign="middle">&#x00A0;</td>
<td align="center" valign="middle">&#x00A0;</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;I</td>
<td align="center" valign="middle">8</td>
<td align="center" valign="middle">26.7</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;II</td>
<td align="center" valign="middle">7</td>
<td align="center" valign="middle">23.3</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;III</td>
<td align="center" valign="middle">8</td>
<td align="center" valign="middle">26.7</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;IV</td>
<td align="center" valign="middle">7</td>
<td align="center" valign="middle">23.3</td>
</tr>
<tr>
<td align="left" valign="middle">Histological grade (UICC 2010)</td>
<td align="center" valign="middle">&#x00A0;</td>
<td align="center" valign="middle">&#x00A0;</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;G1</td>
<td align="center" valign="middle">0</td>
<td align="center" valign="middle">0</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;G2</td>
<td align="center" valign="middle">28</td>
<td align="center" valign="middle">93.3</td>
</tr>
<tr>
<td align="left" valign="middle">&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;G3</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">6.7</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn><p>UICC, Union for International Cancer Control.</p></fn>
</table-wrap-foot>
</table-wrap>
<table-wrap id="tII-MCO-0-0-02413" position="float">
<label>Table II</label>
<caption><p>Comparison of serum levels of growth factors between patients with CRC and healthy controls.</p></caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th align="left" valign="middle" colspan="2">&#x00A0;</th>
<th align="center" valign="middle" colspan="2">CRC</th>
<th align="center" valign="middle" colspan="3">P-value</th>
</tr>
<tr>
<th align="left" valign="middle">Growth factors</th>
<th align="center" valign="middle">Controls</th>
<th align="center" valign="middle">Early-stage</th>
<th align="center" valign="middle">Late-stage</th>
<th align="center" valign="middle">Control vs. early-stage CRC</th>
<th align="center" valign="middle">Control vs. late-stage CRC</th>
<th align="center" valign="middle">Early- vs. late-stage CRC</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left" valign="middle">VEGF</td>
<td align="center" valign="middle">88.39&#x00B1;3.99</td>
<td align="center" valign="middle">152.9&#x00B1;14.5</td>
<td align="center" valign="middle">182.7&#x00B1;25.8</td>
<td align="center" valign="middle">0.0012<sup><xref rid="tfnc-MCO-0-0-02413" ref-type="table-fn">c</xref></sup></td>
<td align="center" valign="middle">0.002<sup><xref rid="tfnb-MCO-0-0-02413" ref-type="table-fn">b</xref></sup></td>
<td align="center" valign="middle">0.291</td>
</tr>
<tr>
<td align="left" valign="middle">EGF</td>
<td align="center" valign="middle">153.7&#x00B1;13.8</td>
<td align="center" valign="middle">409.4&#x00B1;7.96</td>
<td align="center" valign="middle">669.5&#x00B1;13.1</td>
<td align="center" valign="middle">0.05<sup><xref rid="tfna-MCO-0-0-02413" ref-type="table-fn">a</xref></sup></td>
<td align="center" valign="middle">0.01<sup><xref rid="tfnb-MCO-0-0-02413" ref-type="table-fn">b</xref></sup></td>
<td align="center" valign="middle">0.08</td>
</tr>
<tr>
<td align="left" valign="middle">HGF</td>
<td align="center" valign="middle">56.9&#x00B1;4.97</td>
<td align="center" valign="middle">83.54&#x00B1;14.4</td>
<td align="center" valign="middle">90.4&#x00B1;17.4</td>
<td align="center" valign="middle">0.13</td>
<td align="center" valign="middle">0.05<sup><xref rid="tfna-MCO-0-0-02413" ref-type="table-fn">a</xref></sup></td>
<td align="center" valign="middle">0.762</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn><p>Values are provided in pg/ml and are presented as mean &#x00B1; SD.</p></fn>
<fn id="tfna-MCO-0-0-02413"><p><sup>a</sup>P&#x2264;0.05;</p></fn>
<fn id="tfnb-MCO-0-0-02413"><p><sup>b</sup>P&#x2264;0.01;</p></fn>
<fn id="tfnc-MCO-0-0-02413"><p><sup>c</sup>P&#x2264;0.001. EGF, epidermal growth factor; VEGF, vascular endothelial growth factor; HGF, hepatocyte growth factor; CRC, colorectal cancer.</p></fn>
</table-wrap-foot>
</table-wrap>
</floats-group>
</article>
