title: c-MET inhibition enhances the response of the colorectal cancer cells to irradiationin vitroandin vivo.
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 mm3; P<0.01 vs. irradiation and PHA665752, 998.0±180.6 and 844.8±190.0 mm3, 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.
authors.affiliation: Third Department of Oncology, Hebei General Hospital, Shijiazhuang, Hebei 050011, P.R. China.
authors.forename: Yitao
authors.initials: Y
authors.lastname: Jia
authors.affiliation: Second Department of Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050035, P.R. China; Department of Surgery, The First Hospital of Shijiazhuang, Shijiazhuang, Hebei 050011, P.R. China.
authors.forename: Guangyao
authors.initials: G
authors.lastname: Dai
authors.affiliation: Fourth Department of General Surgery, The First Hospital of Handan, Handan, Hebei 056002, P.R. China.
authors.forename: Jinxi
authors.initials: J
authors.lastname: Wang
authors.affiliation: Second Department of Abdominal Surgery, The First Affiliated Hospital of Xingtai Medical College, Xingtai, Hebei 054001, P.R. China.
authors.forename: Xing
authors.initials: X
authors.lastname: Gao
authors.affiliation: Second Department of Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050035, P.R. China.
authors.forename: Zhaolong
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Second Department of Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050035, P.R. China.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Duan
authors.affiliation: Second Department of Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050035, P.R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Gu
authors.affiliation: Second Department of Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050035, P.R. China.
authors.forename: Weiguang
authors.initials: W
authors.lastname: Yang
authors.affiliation: Experimental Animal Center, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, P.R. China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wu
authors.affiliation: Experimental Animal Center, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, P.R. China.
authors.forename: Yingchao
authors.initials: Y
authors.lastname: Ju
authors.affiliation: Department of Pharmacy, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, P.R. China.
authors.forename: Mingxia
authors.initials: M
authors.lastname: Wang
authors.affiliation: Second Department of Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050035, P.R. China.
authors.forename: Zhongxin
authors.initials: Z
authors.lastname: Li
keywords: c-MET inhibitor; colorectal cancer; radiation; sensitivity; small interfering RNA