Radiosensitivity of different non-small cell lung cancer cell lines to carbon ion irradiation

Abstract

Objective To study the sensitivities of different NSCLC cells irradiated with carbon ion beam and the underlying molecular mechanism. Methods Adenocarcinoma A549 cells, squamous carcinoma H520 cells and large cell carcinoma PGCL3 cells were exposed to carbon ions with different doses (0, 2, 4, 6 Gy). Cell survival fraction, apoptosis and cell cycle distribution were analyzed by colony formation assay, Hoechst33258 staining and flow cytometry assay, respectivily. DNA-PKcs mRNA expression was detected by real time RT-PCR. Results With the increasing of radiation dose, the survival of H520, PGCL3 and A549 cells were markedly reduced in order. G2/M phase arreast and apoptosis were also induced in these cells(t=4.813, 20.738, 25.654; t=2.790, 2.977, P<0.05). The G2/M phase arreast rates in the irradiated H520 and PGCL3 cells were higher than that in A549 cells. The apoptosis rates in H520 and PGCL3 cells were also much higher than that in A549 cells (t=8.579, 14.289, 15.244; t=3.785, 5.098, 8.105, P<0.05). The DNA-PKcs expression levels were upregulated in three cell lines but declined along with the increasing dose, while those in H520 and PGCL3 cells at 2 and 4 Gy were much lower than those in A549 cells (t=7.782, 3.689; t=3.889, 2.814, P<0.05). Conclusions Among these three cell lines, the squamous carcinoma H520 cells have the highest radiosensitivity. Adenocarcinoma A549 cells have the lowest radiosensitivity, which may due to the high expression of DNA-PKcs corresponding to NHEJ-mediated DSBs repair. Key words: Carbon ion irradiation; Non-small cell lung cancer (NSCLC); Radiosensitivity; DNA-PKcs