OBJECTIVETo investigate the radiosensitizing effect and its mechanism of 3-MA in human hypopharynx cancer cells.

METHODS5 mmol/L of 3-MA combined with 2 Gy or 4 Gy of X-ray was utilized to deal with Fadu cells, and the cell livability (cloning efficiency) and DNA lesion severity (tail moment) of each groups was examined by clonogenic survival assay and comet assay, then differences were compared between groups by independent-sample T test. Fadu cells were then treated with different dose of 3-MA (1, 2, 5, 10 mmol/L), the alteration of cell cycle distribution was detected by flow cytometer, and differences among groups were analyzed through one-way analysis of variance. The expression of p62 and cyclinB1 in each group was examined by western blot.

RESULTSThe livability and DNA lesion severity of cells treated with 3-MA alone showed no notable variation. Compared with non-3-MA groups, the cloning efficiency of cells treated with 3-MA decreased much more after irradiated with 2 Gy or 4 Gy of X-ray (t = 13.41 or 13.98, P < 0.001), and the cells showed a more serious DNA lesion (t = 7.07 or 6.91, P < 0.001). The G2/M percentages of cells in the control group and groups treated with 1, 2, 5, 10 mmol/L of 3-MA were 17.10 ± 1.20, 23.30 ± 2.3, 39.90 ± 3.12, 58.47 ± 1.65, 76.13 ± 3.51 and differences among groups were statistically significant (F = 278.4, P < 0.05). The expression of p62 in cells treated with 3-MA showed a dose-dependent increase, while cyclinB1 showed a dose-dependent decrease.

CONCLUSIONSThe autophagy inhibitor 3-MA could enhance radiosensitivity of human hypopharynx cancer cells by inducing G2/M arrest and enhancing irradiation-induced DNA damage.