Open Access

Detection of metastatic tumors after γ-irradiation using longitudinal molecular imaging and gene expression profiling of metastatic tumor nodules

  • Authors:
    • Su Jin Jang
    • Joo Hyun Kang
    • Yong Jin Lee
    • Kwang Il Kim
    • Tae Sup Lee
    • Jae Gol Choe
    • Sang Moo Lim
  • View Affiliations

  • Published online on: February 8, 2016     https://doi.org/10.3892/ijo.2016.3384
  • Pages: 1361-1368
  • Copyright: © Jang et al. This is an open access article distributed under the terms of Creative Commons Attribution License.

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Abstract

A few recent reports have indicated that metastatic growth of several human cancer cells could be promoted by radiotherapy. C6-L cells expressing the firefly luciferase (fLuc) gene were implanted subcutaneously into the right thigh of BALB/c nu/nu mice. C6-L xenograft mice were treated locally with 50-Gy γ-irradiation (γ-IR) in five 10-Gy fractions. Metastatic tumors were evaluated after γ-IR by imaging techniques. Total RNA from non-irradiated primary tumor (NRPT), γ-irradiated primary tumor (RPT), and three metastatic lung nodule was isolated and analyzed by microarray. Metastatic lung nodules were detected by BLI and PET/CT after 6-9 weeks of γ-IR in 6 (17.1%) of the 35 mice. The images clearly demonstrated high [18F]FLT and [18F]FDG uptake into metastatic lung nodules. Whole mRNA expression patterns were analyzed by microarray to elucidate the changes among NRPT, RPT and metastatic lung nodules after γ-IR. In particular, expression changes in the cancer stem cell markers were highly significant in RPT. We observed the metastatic tumors after γ-IR in a tumor-bearing animal model using molecular imaging methods and analyzed the gene expression profile to elucidate genetic changes after γ-IR.

Introduction

Glioma is the most common malignant primary brain tumor; thus, it is treated aggressively with surgery and chemotherapy and radiotherapy. The poor survival of patients with glioma reflects the prevalence of cancer recurrence after surgery, invasion into other sites, and intrinsic or acquired resistance to chemotherapy and radiotherapy (1). Ionizing irradiation (IR) is the most commonly employed treatment modality for various human cancers and regional cancer disease. IR is often used in combined treatments with chemotherapy and surgery (2). Concomitant combination therapy is used to treat patients with non-small lung, head and neck, cervical cancer, and glioblastoma (37), ~50% of cancer patients receive radio-therapy (8). The goal of radiotherapy is to provide a suitable dose to the primary tumor, while minimizing IR side-effects to surrounding normal tissues. Notably, one of the problems with lower dose (0.1–0.6 Gy) or high dose (10 Gy and higher) fractionated radiotherapy is radio-resistance and bystander factors released among treated cancer cells and in an animal model (9). Patients undergoing radiotherapy for local tumor control show better survival rates than patients with radiation-induced secondary tumors, which is attributed primarily to the observation that local treatment failure increases the probability of developing metastatic disease at distant organ sites (10,11). The first study on the effect of local tumor IR on metastatic frequency in a transplantable mouse carcinoma model was reported in 1949 by Kaplan and Murphy (12). Since then, various research groups have reported that the incidence of metastasis increases after IR of the primary tumor (13). Radio-therapeutic effects are considered because of the induction of DNA damage causing cell cycle arrest, apoptosis and senescence (14). IR induces modifications in the tumor microenvironment, which have a profound impact on tumor biology (15) and the incurred tumor hypoxic conditions can promote metastasis by recurrence in untreated hypoxic cells (16). It is now becoming evident that IR can also result in cancer cells acquiring a stemness state characterized by increased stemness gene expression and a cancer stem cell-like phenotype (17). Some studies indicate that irradiated tumors contain a stemness population and that growth of distant metastasis is driven by cancer stem-like cells. Furthermore, several studies have shown that the epithelial-mesenchymal transition (EMT) has a crucial role in IR resistance of cancer cells (18). EMT was initially recognized as an important process during the morphogenesis of epithelial tissue in embryonic development, and is now shown to be one of the key steps promoting tumor metastasis. The EMT maintains cancer stemness and is induced by various factors. Several effectors, including transforming growth factor (TGF)-β, fibronectin (Fn1), metalloproteinases (MMPs), vimentin (Vim) and cadherin, mediate the EMT. Acquisition of stemness results in metastasis along with CD24, CD133, β-catenin, Oct-4 and Sox-2 expression in non-small cell lung cancer cells (19). Although the relationships between PI3K/Akt/mTOR signaling, EMT and cancer stem cells are known, the regulation mechanisms of metastasis in irradiated tumor are still unclear.

Regular follow-up examinations, such as imaging and tumor marker tests, may be required after radiotherapy to detect metastasis at an early stage. Therefore, many investigators utilize advance imaging techniques to monitor neoplastic progression to metastasis, such as bioluminescence imaging (BLI), computed tomography (CT) and positron emission tomography (PET) (20). These imaging modalities can evaluate progression, such as tumor growth, metabolism, or metastasis in vivo, in a longitudinal manner. A non-invasive imaging method is indispensable for detecting tumor lesions in an internal organ, such as the lungs, liver or brain, and diagnosing and determining the size of tumors in a preclinical animal model (2124). Other ways to detect cancer involved in distance metastasis include immunohistochemical staining of ex vivo biopsies; however, these often lack reproducibility and accuracy (25).

In the present study, metastatic tumors in C6-L xenografted mice were studied after local treatment with fractionated γ-IR. To accurately detect the metastatic nodules after γ-IR, we observed the effect of γ-IR on distant metastatic tumor growth using different imaging modalities, such as BLI and PET/CT. A non-invasive longitudinal imaging study with repeated measurements of metastatic nodules after γ-IR indicated extensive colonization of C6-L cells in the lungs within 6 weeks after γ-IR. We also identified and described the molecular events occurring after γ-IR through gene expression profiling to elucidate genetic changes. We identified the differentially expressed genes between the γ-IR primary tumors vs. non-γ-IR primary tumors and metastatic lung nodules vs. γ-IR primary tumors using an Agilent Expression microarray contained ~30,003 Entrez Gene RNAs. In particular, we found known cancer stem cell markers and detected EMT among the differentially expressed genes.

Materials and methods

Cell culture

C6 rat glioma cells and C6-L infected cells containing the firefly luciferase (fLuc) gene in lentiviral vectors were used with selected blasticidin treatment (5 mg/ml), as previously described by Park et al (26).

Xenograft model and local Agilent Expression microarray-IR

BALB/c nu/nu mice (females, 5–6 weeks of age) were purchased from Orient Bio, Inc. (Seoul, Korea). C6-L cells (5×105/head) were implanted subcutaneously into the right thigh of mice. When the tumors reached ≥80 mm3 (15 days after inoculation), we randomly assigned them to the C6-L γ-irradiated (γ-IR) and non-IR groups. C6-L tumor-bearing mice were treated locally with 50 Gy γ-IR in five 10-Gy fractions every day using a 60Co γ-IR source (Theratrom 780; AECL, Ltd., Mississauga, ON, Canada; n=35), but not the control group (n=5). The mice were anesthetized with an intraperitoneal injection of a mixture of zolazepam/tiletamine (50 mg/kg; Zoletil 50®; Virbac, Magnyen-Vexin, France) and xylazine (10 mg/kg; Rompun®; Bayer Healthcare, Berlin, Germany) fixed on an acryl plate. All experiments with animals were carried out according to the guidelines for the care and the use of experimental animals and were approved by the Korea Institute of Radiological and Medical Sciences.

BLI acquisition

BLI was performed with a highly sensitive, optical CCD camera mounted in a light-tight specimen chamber (IVIS200; Xenogen, Alameda, CA, USA). Animals were given the firefly substrate D-luciferin potassium salt diluted to 2.5 mg/100 μl in saline. The mice were injected intraperitoneally with 100 μl of this D-luciferin solution and were anesthetized (2% isoflurane) for in vivo imaging. The mice were placed on the stage inside the light-tight camera box with continuous exposure to 0.5% isoflurane. Image acquisition time was 10 min. Bioluminescence signals were expressed in units of photons per cm2 per second per steradian (p/cm2/s/sr). Imaging and signal quantification were controlled by the acquisition and analysis software (Living Image v. 2.50; Xenogen).

PET/CT image acquisition

Mice were imaged using a small animal PET/CT system (INVEON™; Siemens Preclinical Solutions, Knoxville, TN, USA). [18F] Fluordeoxyglucose (FDG) (7.4 MBq, 200 μCi) was injected via tail vein 1 h prior to PET/CT scanning. [18F] fluorothymidine (FLT) (same dose) was injected 2 h prior. Mice were anesthetized using 2% isoflurane. PET and CT images were acquired using small animal PET/CT scanner. The mice were moved to the PET scanner on the same bed and scanned for 30 min after CT acquisition. Tissue radioactivity was expressed as the percentage of injected radioactivity dose per gram of tissue (%ID/g). Visualization and analyses of PET images were carried out using AsiPRO™ software (Siemens Preclinical Solutions). Radioactivity concentration in the local region was calculated from the PET images using maximum pixel values.

Evaluation of fLuc expression for reverse transcription-polymerase chain reaction (RT-PCR) analysis with tissue

Total RNA was isolated from metastatic tissue and used as a template to produce cDNA using SuperScript III First-Strand Synthesis for RT-PCR (Invitrogen, Carlsbad, CA, USA). The synthesized cDNA was amplified using Taq DNA polymerase (iNtRON Biotechnology, Inc., Daejeon, Korea) with the fLuc primer: forward, 5′-CGC CTT GAT TGA CAA GGA TGG-3′, and reverse, 5′-GGC CTT TAT GAG GAT CTC TCT-3′. The forward rat GADPH primer was 5′-CAG TGC CAG CCT CGT CTC AT-3′ and the reverse primer was 5′-AGG GGC CAT CCA CAG TCT TC-3′.

Microarray analysis

Total RNA from primary tumors and IR-induced metastatic tissue for each model were used for expression profiling. Total RNA was purified using the Easy-spin Total RNA Extraction kit (iNtRON Biotechnology) according to the manufacturer's recommendations with the Agilent SurePrint G3 Rat Gene Expression 8×60K microarrays (Agilent Technologies, Inc., Santa Clara, CA, USA). The Agilent expression microarray contained ~30,003 Entrez Gene RNAs. The microarray analysis was done by Macrogen (Seoul, Korea). The arrays were scanned using the Agilent Technologies G2600D SG12494263. Array data export processing and analysis were performed using Agilent Feature Extraction software v11.0.1.1.

Results

Detection of metastatic tumors by BLI after γ-IR

The schedule for obtaining the BLI and nuclear medicine images beginning 4 weeks after γ-IR is presented in Fig. 1A. The BLI results of a longitudinal study of primary tumor growth and distant metastasis at a C6-L secondary site are shown in Fig. 1B and C. We detected metastatic tumors 6–9 weeks after γ-IR in the lungs by BLI and confirmed fLuc gene expression in the tissues (Fig. 1B and D). However, no distant metastasis was detected at the secondary site in the non-IR primary tumor (NRPT) model by BLI (Fig. 1C). Light emission of the lungs removed from sacrificed animal was examined at 9 weeks to confirm that the metastatic nodules were from the C6-L primary tumor (Fig. 1B, No. 2). This result suggests that the BLI signal from the lung originated from a γ-IR primary tumor (RPT) and was confirmed by RT-PCR (Fig. 1D). A fLuc-specific RT-PCR DNA band of 399 bp was detected in the metastatic lung nodules after γ-IR. However, survival of γ-IR treated mice was longer than that of the non-IR group because of the relatively low growth rate of the primary tumor mass after γ-IR (26).

Confirmation of metastatic tumor after γ-IR by nuclear medicine imaging

Metastatic nodules at secondary sites in the non-IR tumor model were monitored for 6 weeks by [18F]FLT-PET (Fig. 2A), however, no metastatic nodules were detected at secondary sites. Mouse (No. 4 of Fig. 1B) underwent PET/CT 6 weeks after γ-IR and the administration of 7.4 MBq [18F]FLT and [18F]FDG to confirm the metastatic lung nodules after γ-IR detected by BLI via fLuc gene expression (Fig. 2B). [18F]FLT and [18F]FDG activity in the four metastatic lung nodules was high (Fig. 2B, white arrows). The activities were re-calculated using a region of interest analysis from a three-dimensional reconstruction encompassing the [18F]FLT and [18F]FDG uptake region. The [18F]FLT and [18F]FDG uptake values into one metastatic lung nodule was 1.5±0.13 and 2.4±0.24 %ID/g, respectively (white arrowhead). Three metastatic lung nodules (blue arrow) and one metastatic spleen nodule (red arrow) were detected by [18F]FLT-PET and [18F]FLT autoradiography in another γ-IR treated C6-L bearing mouse (No. 6 of Figs. 1B and 2C). However, no splenic metastatic nodules were detected by BLI (Fig. 2C, left panel). Metastatic nodules were detected by BLI or nuclear medicine imaging in 6 (17.14%) of the 35 C6-L bearing mice from 6 weeks after γ-IR (Table I). RNA isolated from RPT, 3 meta-static lung nodules of mouse No. 6 of Fig. 1B, and NRPT of a non-irradiated mouse was analyzed by microarray.

Table I

Summary of the incidence of metastatic nodules after γ-irradiation (IR).

Table I

Summary of the incidence of metastatic nodules after γ-irradiation (IR).

No.ImagesDetection time (weeks)
1WB BLI, nuclear imaging (FDG)8
2WB BLI, ex vivo BLI9
3WB BLI, nuclear imaging (FDG)9
4WB BLI, nuclear imaging (FDG, FLT), ex vivo BLI6
5WB BLI, nuclear imaging (FLT)7
6aWB BLI, nuclear imaging (FLT), autoradiography6

{ label (or @symbol) needed for fn[@id='tfn1-ijo-48-04-1361'] } WB, whole body;

a microarray sample mouse.

Overview of metastatic tumors after γ-IR-related gene expression

The expression patterns of whole mRNAs were analyzed by microarray to elucidate the changes in NRPT, RPT and metastatic lung nodules. A hierarchical clustering analysis of 3,881 genes (≥2-fold change, P-value <0.05) indicated differentially expressed genes between the NRPT, RPT and three metastatic lung nodules (Fig. 3A). RPT and NRPT are closely clustered together and showed a similar heat map pattern of mRNA expression, which is different from that of the meta-static lung nodules. As shown in Fig. 3B, the biological process terms differ between the RPT vs. NRPT and the metastatic lung nodules vs. RPT that reflects their known functions. The RPT enriched genes have linked biological process terms: hypoxia (3%), immune response (4%), inflammatory (3%) and signal transduction (8%). In contrast, transcription factor (4%) and glucose metabolism (2%) are linked by biological process terms for the metastatic lung nodules. Gene Ontology (GO) analysis was performed using DAVID to gain a comprehensive understanding of the gene classes that were differentially regulated in the RPT vs. NRPT and the metastatic lung nodules vs. RPT (Fig. 3C). We found upregulated expression of angiogenesis, migration, and proliferation-related genes in RPT but downregulated expression in glucose metabolism-related genes and apoptosis in the metastatic lung nodules. The molecular mechanisms and therapeutic targets underlying metastatic tumors after γ-IR remain unclear. Identifying metastatic tumors using γ-IR-related molecular target will be helpful to identify useful therapeutic targets, developing novel treatment approaches, and overcome recurrence after γ-IR in patients with glioma. We present novel insight into the EMT and enhanced stemness in RPT based on our total gene expression analysis in γ-IR tumor tissue and metastatic lung nodules of the genes of interest. Our findings are summarized in Fig. 4. In particular, expression changes in RPT with cancer stem cell markers were highly significant. For example, aldehyde dehydrogenases 1A1 and 3A1 (ALDH1A1 and ALDH3A1), which are members of the human aldehyde dehydrogenase superfamily, constitute novel candidate cancer stem cell markers in various solid tumors in the testis, brain, lens, liver, lung and retina (27). These cytoplasmic enzymes act during the oxidative stress response (28), differentiation (29) and drug resistance (30). ALDH1A1 has been reported as a novel marker for glioblastoma cells with stem cell characteristics (31) and showed the highest level change (72.18-fold higher in RPT than in NRPT) in the present study. The cancer stem cell marker CD24 was also differentially expressed (5.5-fold higher in RPT than in NRPT). In contrast to the finding on RPT and NRPT, expression of cancer stem cell markers, such as ALDH1A1, ALDH3A1, CD24, CXCL1 and IL-6 was mostly downregulated in metastatic lung nodules after γ-IR compared to RPT (Fig. 4).

Discussion

In the present study, we observed distant metastasis after local γ-IR using BLI of fLuc gene expressing rat glioma and [18F]FLT and [18F]FDG-PET. Next, we observed that γ-IR, particularly fractionated local γ-IR, increased stem cell marker expression in γ-IR primary tumors by microarray. We used the γ-IR dose and schedule for C6-L tumor-bearing mice as described by Camphausen et al (32), who used Lewis lung carcinoma cells to confirm that γ-IR promotes metastasis in a mouse model.

BLI has relatively low cost and high throughput capability, but the depth dependence of the signal is a major disadvantage in small animals. The other major limitation is that BLI does not provide anatomical information. Therefore, metastatic tumors in lung and spleen after γ-IR were confirmed by small-animal PET/CT. [18F]FDG is the most widely used PET tracer and is indispensable for diagnosing and staging PET tracer for a variety of cancers. Several research groups have suggested that [18F]FLT is useful as a PET tracer to monitor proliferation and other biological response of tumors to chemotherapy and radiotherapy (3336).

In the present study, we evaluated [18F]FDG and [18F] FLT-PET as a potential diagnostic tool for monitoring the response to metastatic tumors after γ-IR in a tumor-bearing mouse model. We found high uptake of [18F]FLT and [18F] FDG in metastatic lung nodules after γ-IR. The four nodules that were discriminated by [18F]FLT and [18F]FDG-PET were detected as one spot on BLI (Fig. 2B). The other limitation of BLI is that it does not discriminate focal signals due to spill-over. Three metastatic lung nodules and one metastatic splenic nodule in another γ-IR C6-L bearing mouse were detected by [18F]FLT-PET and autoradiography, but the splenic nodule was not detected by BLI due to a light penetration problem into deep tissue (Fig. 2C). Therefore, BLI and nuclear medicine imaging may be suitable for metastatic tumor screening after γ-IR and to more precisely locate metastatic tumors, respectively.

Recent studies have shown that a decreased cellular proliferation capacity is an early event in response to 20-Gy IR (37). We wondered whether proliferation had recovered in IR primary tumor lesions at 6 weeks γ-IR. Cancer stem cell markers were upregulated in γ-IR primary tumor lesions compared to that in non-IR primary tumors. We also found downregulation in a proportion of cancer stem cell markers in metastatic lung nodules. The proportion of cancer cell markers, particularly the ALDH family and CD24, increasing in γ-IR primary tumors may be important for distant metastasis in glioma. In particular, we revealed that upregulation of ALDH1A1 in γ-IR C6-L primary tumors may be a cancer stemness property. ALDH1A1 is a predominant isoform of the ALD family located in the cytoplasm (38) and has gained attention as a putative cancer stem cell and progenitor cell marker (39). Our data show that the small number of C6-L cells that survived in γ-IR C6-L primary tumors may have high ALDH1A1 expression, suggesting that cells surviving γ-IR are a source for distant metastasis. CD44 and CD90 have also been proposed as cancer stem-like cell markers in esophageal squamous cell carcinoma but cell heterogeneity limits their application (40,41).

We evaluated the metastatic tumors after γ-IR and found invasive/migration ability after local treatment of C6-L xeno-graft mice, suggesting that the small number of C6-L cells that survived in locally γ-IR treated tumors have more potential to metastasize, which is the main reason for recurrence of glioma after radiotherapy. The microarray study revealed more surviving cancer cells with cancer stem cell markers in the γ-IR primary tumors compared with those in the non-IR primary tumors. After formation of metastatic lung nodules in our experiments, expression of cancer stem cell markers may be downregulated as shown in our microarray data (Fig. 4). Recent studies in patients with glioma observed that the EMT may affect the ability of biomarkers to predict radio-resistant glioma (42). We observed downregulation of TGF-β and Smad5 and upregulation of MMPs, Fn1 and Snail2 in RPT compared with NRPT.

In summary, metastatic tumors were detected after fractionated γ-IR with 60Co by non-invasive longitudinal imaging and repeated measurements of the metastatic tumors after γ-IR. We demonstrated that metastatic tumors after γ-IR are associated with several genes, including the EMT and enhanced cancer stem cell markers which result in cancer cell growth, survival, invasion and proliferation.

Acknowledgements

The present study was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MEST) (NRF-2012M2A2A7013480).

References

1 

Dirks PB: Brain tumor stem cells: Bringing order to the chaos of brain cancer. J Clin Oncol. 26:2916–2924. 2008. View Article : Google Scholar : PubMed/NCBI

2 

Lawrence TS, Haffty BG and Harris JR: Milestones in the use of combined-modality radiation therapy and chemotherapy. J Clin Oncol. 32:1173–1179. 2014. View Article : Google Scholar : PubMed/NCBI

3 

Govindan R, Bogart J and Vokes EE: Locally advanced non-small cell lung cancer: The past, present, and future. J Thorac Oncol. 3:917–928. 2008. View Article : Google Scholar : PubMed/NCBI

4 

Cognetti DM, Weber RS and Lai SY: Head and neck cancer: An evolving treatment paradigm. Cancer. 113(Suppl): 1911–1932. 2008. View Article : Google Scholar : PubMed/NCBI

5 

Gold KA, Lee HY and Kim ES: Targeted therapies in squamous cell carcinoma of the head and neck. Cancer. 115:922–935. 2009. View Article : Google Scholar : PubMed/NCBI

6 

Stupp R, Mason WP, van den Bent MJ, Weller M, Fisher B, Taphoorn MJ, Belanger K, Brandes AA, Marosi C, Bogdahn U, et al; European Organisation for Research and Treatment of Cancer Brain Tumor and Radiotherapy Groups; National Cancer Institute of Canada Clinical Trials Group. Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. N Engl J Med. 352:987–996. 2005. View Article : Google Scholar : PubMed/NCBI

7 

Eifel PJ, Winter K, Morris M, Levenback C, Grigsby PW, Cooper J, Rotman M, Gershenson D and Mutch DG: Pelvic irradiation with concurrent chemotherapy versus pelvic and para-aortic irradiation for high-risk cervical cancer: An update of radiation therapy oncology group trial (RTOG) 90-01. J Clin Oncol. 22:872–880. 2004. View Article : Google Scholar : PubMed/NCBI

8 

Baskar R, Lee KA, Yeo R and Yeoh KW: Cancer and radiation therapy: Current advances and future directions. Int J Med Sci. 9:193–199. 2012. View Article : Google Scholar : PubMed/NCBI

9 

Prasanna A, Ahmed MM, Mohiuddin M and Coleman CN: Exploiting sensitization windows of opportunity in hyper and hypo-fractionated radiation therapy. J Thorac Dis. 6:287–302. 2014.PubMed/NCBI

10 

Suit HD: Local control and patient survival. Int J Radiat Oncol Biol Phys. 23:653–660. 1992. View Article : Google Scholar : PubMed/NCBI

11 

Balasubramaniam A, Shannon P, Hodaie M, Laperriere N, Michaels H and Guha A: Glioblastoma multiforme after stereo-tactic radiotherapy for acoustic neuroma: Case report and review of the literature. Neuro Oncol. 9:447–453. 2007. View Article : Google Scholar : PubMed/NCBI

12 

Kaplan HS and Murphy ED: The effect of local roentgen irradiation on the biological behavior of a transplantable mouse carcinoma; increased frequency of pulmonary metastasis. J Natl Cancer Inst. 9:407–413. 1949.PubMed/NCBI

13 

von Essen CF: Radiation enhancement of metastasis: A review. Clin Exp Metastasis. 9:77–104. 1991. View Article : Google Scholar : PubMed/NCBI

14 

Núñez MI, McMillan TJ, Valenzuela MT, Ruiz de Almodóvar JM and Pedraza V: Relationship between DNA damage, rejoining and cell killing by radiation in mammalian cells. Radiother Oncol. 39:155–165. 1996. View Article : Google Scholar : PubMed/NCBI

15 

Barcellos-Hoff MH, Park C and Wright EG: Radiation and the microenvironment - tumorigenesis and therapy. Nat Rev Cancer. 5:867–875. 2005. View Article : Google Scholar : PubMed/NCBI

16 

Moulder JE and Rockwell S: Hypoxic fractions of solid tumors: Experimental techniques, methods of analysis, and a survey of existing data. Int J Radiat Oncol Biol Phys. 10:695–712. 1984. View Article : Google Scholar : PubMed/NCBI

17 

Ghisolfi L, Keates AC, Hu X, Lee DK and Li CJ: Ionizing radiation induces stemness in cancer cells. PLoS One. 7:e436282012. View Article : Google Scholar : PubMed/NCBI

18 

Zhou YC, Liu JY, Li J, Zhang J, Xu YQ, Zhang HW, Qiu LB, Ding GR, Su XM, Mei-Shi, et al: Ionizing radiation promotes migration and invasion of cancer cells through transforming growth factor-beta-mediated epithelial-mesenchymal transition. Int J Radiat Oncol Biol Phys. 81:1530–1537. 2011. View Article : Google Scholar : PubMed/NCBI

19 

Gomez-Casal R, Bhattacharya C, Ganesh N, Bailey L, Basse P, Gibson M, Epperly M and Levina V: Non-small cell lung cancer cells survived ionizing radiation treatment display cancer stem cell and epithelial-mesenchymal transition phenotypes. Mol Cancer. 12:942013. View Article : Google Scholar : PubMed/NCBI

20 

Adseshaiah PP, Patel NL, Ileva LV, Kalen JD, Haines DC and McNeil SE: Longitudinal imaging of cancer cell metastases in two preclinical models: A correlation of noninvasive imaging to histopathology. Int J Mol Imaging. 102702:20142014.

21 

Kang JH and Chung JK: Molecular-genetic imaging based on reporter gene expression. J Nucl Med. 49(Suppl 2): 164S–179S. 2008. View Article : Google Scholar : PubMed/NCBI

22 

Park JH, Kim KI, Lee YJ, Lee TS, Kim KM, Nahm SS, Park YS, Cheon GJ, Lim SM and Kang JH: Non-invasive monitoring of hepatocellular carcinoma in transgenic mouse with bioluminescent imaging. Cancer Lett. 310:53–60. 2011.PubMed/NCBI

23 

Kim KI, Park JH, Lee YJ, Lee TS, Park JJ, Song I, Nahm SS, Cheon GJ, Lim SM, Chung JK, et al: In vivo bioluminescent imaging of α-fetoprotein-producing hepatocellular carcinoma in the diethylnitrosamine-treated mouse using recombinant adeno-viral vector. J Gene Med. 14:513–520. 2012. View Article : Google Scholar : PubMed/NCBI

24 

Park JH, Kang JH, Lee YJ, Kim KI, Lee TS, Kim KM, Park JA, Ko YO, Yu DY, Nahm SS, et al: Evaluation of diethylnitrosamine- or hepatitis B virus X gene-induced hepatocellular carcinoma with 18F-FDG PET/CT: A preclinical study. Oncol Rep. 33:347–353. 2015.

25 

Gown AM: Current issues in ER and HER2 testing by IHC in breast cancer. Mod Pathol. 21(Suppl 2): S8–S15. 2008. View Article : Google Scholar : PubMed/NCBI

26 

Park JK, Jang SJ, Kang SW, Park S, Hwang SG, Kim WJ, Kang JH and Um HD: Establishment of animal model for the analysis of cancer cell metastasis during radiotherapy. Radiat Oncol. 7:153–163. 2012. View Article : Google Scholar : PubMed/NCBI

27 

Vasiliou V, Thompson DC, Smith C, Fujita M and Chen Y: Aldehyde dehydrogenases: From eye crystallins to metabolic disease and cancer stem cells. Chem Biol Interact. 202:2–10. 2013. View Article : Google Scholar

28 

Marchitti SA, Brocker C, Stagos D and Vasiliou V: Non-P450 aldehyde oxidizing enzymes: The aldehyde dehydrogenase superfamily. Expert Opin Drug Metab Toxicol. 4:697–720. 2008. View Article : Google Scholar : PubMed/NCBI

29 

Chute JP, Muramoto GG, Whitesides J, Colvin M, Safi R, Chao NJ and McDonnell DP: Inhibition of aldehyde dehydrogenase and retinoid signaling induces the expansion of human hematopoietic stem cells. Proc Natl Acad Sci USA. 103:11707–11712. 2006. View Article : Google Scholar : PubMed/NCBI

30 

Muramoto GG, Russell JL, Safi R, Salter AB, Himburg HA, Daher P, Meadows SK, Doan P, Storms RW, Chao NJ, et al: Inhibition of aldehyde dehydrogenase expands hematopoietic stem cells with radioprotective capacity. Stem Cells. 28:523–534. 2010.PubMed/NCBI

31 

Rasper M, Schäfer A, Piontek G, Teufel J, Brockhoff G, Ringel F, Heindl S, Zimmer C and Schlegel J: Aldehyde dehydrogenase 1 positive glioblastoma cells show brain tumor stem cell capacity. Neuro Oncol. 12:1024–1033. 2010. View Article : Google Scholar : PubMed/NCBI

32 

Camphausen K, Moses MA, Beecken WD, Khan MK, Folkman J and O'Reilly MS: Radiation therapy to a primary tumor accelerates metastatic growth in mice. Cancer Res. 61:2207–2211. 2001.PubMed/NCBI

33 

Murayama C, Harada N, Kakiuchi T, Fukumoto D, Kamijo A, Kawaguchi AT and Tsukada H: Evaluation of D-18F-FMT, 18F-FDG, L-11C-MET, and 18F-FLT for monitoring the response of tumors to radiotherapy in mice. J Nucl Med. 50:290–295. 2009. View Article : Google Scholar : PubMed/NCBI

34 

Molthoff CF, Klabbers BM, Berkhof J, Felten JT, van Gelder M, Windhorst AD, Slotman BJ and Lammertsma AA: Monitoring response to radiotherapy in human squamous cell cancer bearing nude mice: comparison of 2′-deoxy-2′-[18F]fluoro-D-glucose (FDG) and 3′-[18F]fluoro-3′-deoxythymidine (FLT). Mol Imaging Biol. 9:340–347. 2007. View Article : Google Scholar : PubMed/NCBI

35 

Yang YJ, Ryu JS, Kim SY, Oh SJ, Im KC, Lee H, Lee SW, Cho KJ, Cheon GJ and Moon DH: Use of 3′-deoxy-3′-[18F]fluo-rothymidine PET to monitor early responses to radiation therapy in murine SCCVII tumors. Eur J Nucl Med Mol Imaging. 33:412–419. 2006. View Article : Google Scholar : PubMed/NCBI

36 

Sugiyama M, Sakahara H, Sato K, Harada N, Fukumoto D, Kakiuchi T, Hirano T, Kohno E and Tsukada H: Evaluation of 3′-deoxy-3′-18F-fluorothymidine for monitoring tumor response to radiotherapy and photodynamic therapy in mice. J Nucl Med. 45:1754–1758. 2004.PubMed/NCBI

37 

Wang H, Liu B, Tian J, Xu B, Zhang J, Qu B and Chen Y: Evaluation of 18F-FDG and 18F-FLT for monitoring therapeutic responses of colorectal cancer cells to radiotherapy. Eur J Radiol. 82:e484–e491. 2013. View Article : Google Scholar : PubMed/NCBI

38 

Hess DA, Craft TP, Wirthlin L, Hohm S, Zhou P, Eades WC, Creer MH, Sands MS and Nolta JA: Widespread nonhematopoietic tissue distribution by transplanted human progenitor cells with high aldehyde dehydrogenase activity. Stem Cells. 26:611–620. 2008. View Article : Google Scholar

39 

Douville J, Beaulieu R and Balicki D: ALDH1 as a functional marker of cancer stem and progenitor cells. Stem Cells Dev. 18:17–25. 2009. View Article : Google Scholar

40 

Zhao JS, Li WJ, Ge D, Zhang PJ, Li JJ, Lu CL, Ji XD, Guan DX, Gao H, Xu LY, et al: Tumor initiating cells in esophageal squamous cell carcinomas express high levels of CD44. PLoS One. 6:e214192011. View Article : Google Scholar : PubMed/NCBI

41 

Zhao R, Quaroni L and Casson AG: Identification and characterization of stemlike cells in human esophageal adenocarcinoma and normal epithelial cell lines. J Thorac Cardiovasc Surg. 144:1192–1199. 2012. View Article : Google Scholar : PubMed/NCBI

42 

Meng J, Li P, Zhang Q, Yang Z and Fu S: A radiosensitivity gene signature in predicting glioma prognostic via EMT pathway. Oncotarget. 5:4683–4693. 2014. View Article : Google Scholar : PubMed/NCBI

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April 2016
Volume 48 Issue 4

Print ISSN: 1019-6439
Online ISSN:1791-2423

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APA
Jang, S.J., Kang, J.H., Lee, Y.J., Kim, K.I., Lee, T.S., Choe, J.G., & Lim, S.M. (2016). Detection of metastatic tumors after γ-irradiation using longitudinal molecular imaging and gene expression profiling of metastatic tumor nodules. International Journal of Oncology, 48, 1361-1368. https://doi.org/10.3892/ijo.2016.3384
MLA
Jang, S. J., Kang, J. H., Lee, Y. J., Kim, K. I., Lee, T. S., Choe, J. G., Lim, S. M."Detection of metastatic tumors after γ-irradiation using longitudinal molecular imaging and gene expression profiling of metastatic tumor nodules". International Journal of Oncology 48.4 (2016): 1361-1368.
Chicago
Jang, S. J., Kang, J. H., Lee, Y. J., Kim, K. I., Lee, T. S., Choe, J. G., Lim, S. M."Detection of metastatic tumors after γ-irradiation using longitudinal molecular imaging and gene expression profiling of metastatic tumor nodules". International Journal of Oncology 48, no. 4 (2016): 1361-1368. https://doi.org/10.3892/ijo.2016.3384