c-MET inhibition enhances the response of the colorectal cancer cells to irradiation in vitro and in vivo

Abstract

Abstract. The aim of the present study was to investigate the effect of hepatocyte growth factor receptor (c-MET) inhibition on the viability of colon cancer cells and xenografts exposed to irradiation using short hairpin (sh)RNA or the c-MET inhibitor PHA665752. The underlying mechanisms were also investigated. Human colorectal adenocarcinoma HT-29 cells were infected with a lentivirus expressing shRNAs against c-MET and were irradiated at 0, 2, 4, 6 and 8 Gy. The viability of the cells was assessed by alamarBlue ® assays. Mice bearing human colon carcinoma SW620 xenografts were randomly selected to receive 2.5% dimethyl sulfoxide (DMSO), 25 mg/kg PHA665752 intraperitoneally once every 2 days for 3 weeks, irradiation at 10 Gy, or 25 mg/kg PHA665752 intraperitoneally once every 2 days for 3 weeks followed 24 h later by irradiation at 10 Gy. The mean tumor volume (MTV) was measured. The apoptotic rate of cells was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assays, and double stranded break marker antibody γ-H2AX and hypoxia inducible factor (HIF)-1α expression was examined by immunohistochemistry. alamarBlue assays revealed that c-MET downregulation by shRNA markedly accentuated the irradiation-induced reduction in the viability of HT-29 cells compared with HT-29 cells irradiated at the same doses (P<0.05). A combination of irradiation and PHA665752 caused an additional reduction in the MTV (382.8±42.4 mm 3 ; P<0.01 vs. irradiation and PHA665752, 998.0±180.6 and 844.8±190.0 mm 3 , respectively). TUNEL assays revealed that irradiation and PHA665752 alone caused significant apoptosis of the SW620 cells in the tumor xenografts (P<0.01 vs. DMSO). The apoptotic index in the tumor xenografts of mice treated with a combination of irradiation and PHA665752 was significantly increased compared with mice treated with either agent alone (P<0.01). The combination of irradiation and PHA665752 was also associated with a marked increase in γ-H2AX levels and a significant decrease in HIF-1α expression in the xenografts (P<0.01). In conclusion, c-MET inhibition sensitizes colorectal cancer cells to irradiation by enhancing the formation of DNA double strand breaks and possibly alleviating tumor hypoxia. IntroductionWorldwide, colorectal cancer (CRC) is the third most common cancer (1). Currently, the standard regimen for newly diagnosed patients with locally advanced rectal cancer (grade, cT3/T4 and cN + ) is surgery in combination with neoadjuvant radiochemotherapy (2,3). However, the majority of patients have mid to advanced stage CRC at the time of diagnosis. Neoadjuvant radiochemotherapy improves the survival and anus-preservation rates by shrinking tumors, decreasing the clinical stage and reducing the pathological grade (4). While patients with local CRC have a more favorable outcome, with a 5-year survival rate of 90%, patients with metastatic CRC have a poor 5-year survival rate of 12%, despite the good therapeutic regimens that are available, including surgical resection, ad...

Predictive values of FAP and HGF for tumor angiogenesis and metastasis in colorectal cancer

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“…In recent decades, the development of c-met has been increasingly recognized to play pivotal roles in promoting tumor process. 22 – 24 Jia et al 25 found that inhibiting c-MET could enhance the response of the colorectal cancer cells to irradiation in vitro and in vivo. Our study proved that knocking down ITGA7 could enhance c-met.…”

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