Radiosensitizing effect of c-Met kinase inhibitor BPI-9016M in esophageal squamous cell carcinoma cells in vitro and in vivo

Background: c-Met is the receptor of hepatocyte growth factor (HGF) which plays a key role in inhibiting apoptosis. BPI-9016M is a small-molecule c-Met inhibitor that can promote apoptosis and enhance the cytotoxicity of various DNA-damaging agents. Here, we evaluated the radiosensitizing potential of BPI9016M in Eca109 human esophageal squamous cell carcinoma (ESCC) cells in vitro and in vivo. Methods: Cell Counting Kit-8 (CCK-8) assay was used to measure cell viability. Clonogenic survival assay and a murine tumor xenograft in male nude mice were used to evaluate the radiosensitizing effect of BPI9016M. Apoptosis was determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and flow cytometry experiment. Apoptosis-related proteins were detected by western blot. By evaluating the activation of the ATR-Chk1/ATM-Chk2 pathway to detect radiation-induced DNA double-strand break and homologous recombination repair. BPI-9016M induced a radiosensitizing effect in Eca109 cells and reduced the survival rate of clone formation in vitro. Results: The combination of BPI-9016M with irradiation (IR) significantly delayed the growth of ESCC tumor xenografts than treatment alone (P<0.05). The radiosensitizing effects of BPI-9016M were due to increased apoptosis, such as the up-regulation of cleaved-caspase 3 and 9, down-regulation of mutant P53 and Bcl-2, the decreased of phosphorylation of ATR and ATM, and the inhibition of gamma-H2AX accumulation in vitro and in vivo. Conclusions: These findings indicated that BPI-9016M exerts a radiosensitizing effect and enhances apoptosis by inhibiting homologous recombination DNA repair in irradiated ESCC cells.