[Effect of c-Met inhibitor AMG-102 on radiosensitivity in laryngeal squamous carcinoma cells]

Objective: To investigate the effect of c-Met inhibitor AMG-102 on proliferation and radiosensitivity in laryngeal squamous carcinoma cells. Methods: The effects of AMG-102 on proliferation and radiosensitivity of laryngeal squamous carcinoma cell lines Hep-2 and KBV200 were detected by 3-(4, 5-dimethy-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT) assay and colony formation assay, respectively. The apoptosis of Hep-2 and KBV200 cells was detected by flow cytometry. The expression levels of c-Met, phospho-Met (p-Met), cleaved caspase-3 and Akt/p-Akt, Erk/p-Erk were detected by Western blot. Specific small interfering RNA targeting c-Met or plasmid of c-Met were transfected into Hep-2 and KBV200 cells to investigate the cell sensitivity to AMG-102. Results: Compared with KBV200 cells, Hep-2 cells were more sensitive to AMG-102 with IC(50) of 14 and 9 μmol/L, respectively. The relative expression levels of c-Met and p-Met proteins in Hep-2 cells were 194.48±0.57 and 177.76±1.53, respectively, which were significantly higher than those in KBV200 cells (171.24±1.00 and 115.37±0.56, respectively, P<0.001 for both). Exogenous hepatocyte growth factor (HGF) was added to increase the expression level of p-Met protein in KBV200 cells. The results showed that AMG-102 significantly reduced the expression of p-Met in KBV200 cells treated with HGF (P<0.001). Compared with the dimethyl sulfoxide (DMSO) group, AMG-102 treatment combined with radiotherapy significantly increased the radiosensitivity of Hep-2 cells (SER=1.28, P<0.001). However, AMG-102 had little effect on the radiosensitivity of KBV200 cells (SER=1.18, P=0.002). Compared with the 4 Gy radiotherapy alone group and the 5 μmol/L of AMG-102 alone treatment group, the apoptosis rate of Hep-2 cells in the combined treatment group was significantly increased. Meanwhile, the expression level of cleaved caspase-3 protein was also markedly increased. However, there were no significant changes in the apoptotic rate and cleaved caspase-3 expression in each treatment group of KBV200 cells. Compared with DMSO treatment group, the expression levels of p-Met, p-Akt and p-Erk were significantly decreased in the 4 Gy radiotherapy group, 5 μmol/L of AMG-102 treatment group and combined treatment group of Hep-2 cells. And the levels of p-Met, p-Akt and p-Erk in the combined treatment group were significantly lower than those in the 4 Gy radiotherapy alone group and 5 μmol/L of AMG-102 treatment alone group. By contrast, in KBV200 cells, the expression of p-Met, p-Akt and p-Erk in each group was not changed. The relative expression of p-Met in Hep-2 cells before and after radiotherapy at 30 min, 1 h, 4 h, 8 h, 24 h were 99.89±0.61, 138.62±1.00, 163.07±5.00, 87.80±1.85, 90.67±0.65 and 94.09±1.41, respectively. The level of p-Met was slightly increased after radiotherapy at 30 min and 1 h (P<0.001 for all), whereas it was significantly decreased from 4 h to 24 h after radiotherapy (P<0.05 for all). By contrast, the expression of p-Met in KBV200 cells did not change with time after radiotherapy (P>0.05). The sensitivity of Hep-2 cells to AMG-102 was decreased after silencing of c-Met, while the sensitivity of KBV200 cells to AMG-102 was not significantly changed (P>0.05). Moreover, the radiosensitivity of Hep-2 cells in c-Met knockdown group had a slightly increasing trend (SER=1.07, P=0.068). After the treatment with 10 μmol/L of AMG-102, the proliferation rate of c-Met ectopically expressed KBV200 cells was 60.05%±3.23%, It was significantly lower than that of the blank control 90.08%±1.04% and siRNA negative control (90.12%±1.01%, P<0.001). The results suggested that the overexpression of c-Met in KBV200 cells increased the radiosensitivity to AMG-102, whereas depletion of c-Met resulted in resistance to AMG-102 in Hep-2 cells. Furthermore, the radiosensitivity of KBV200 cells that overexpressed c-Met showed a decreased trend (SER=0.7, P=0.005). Conclusions: c-Met inhibitor AMG-102 has a significant inhibitory effect on the proliferation of c-Met overexpressing laryngeal squamous carcinoma cells, leading to increased radiosensitivity. It suggests that molecular targeted therapy against c-Met receptor is more effective in c-Met overexpressed subtype of laryngeal squamous cell carcinoma.