Research of radiation resistance delivery through paracrine effects on non-small cell lung cancer

Abstract

Objective To investigate the role and possible mechanisms of paracrine in radiation tolerance of non-small cell lung cancer (NSCLC) by observing the effects of radiation-resistant NSCLC H460R cell secretion on the radiosensitivity of parental H460 cells. Methods H460 cells were inoculated and cultured, and then divided into control group, conditional culturing group, irradiation group and irradiation combined conditional culturing group. One-time irradiation with 137Cs γ-rays was conducted with a dose rate of 1.02 Gy/min. Effect of H460R conditioned media on the radiation sensitivity of H460 cells was observed by clonogenic assay. The percentage of phospho-histone histone H2AX (γH2AX) positive cells was detected by immunofluorescence staining. The cyclical changes of the cells were detected by flow cytometry. The expression of DNA damage-associated proteins γH2AX and Rad51 were detected by Western Blot. Results The results showed that compared with the single γ-rays irradiation, the number of cell clones was significantly increased in the H460R cells after γ-rays irradiation combined with conditional culturing treatment at different doses of 2, 4, and 6 Gy, and the differences were statistically significant (2,4 Gy: all P<0.05; 6 Gy: P<0.01). The results of immunofluorescence staining showed that the percentage of γH2AX positive cells in the conditional culturing group was higher than that in the control group [(39.40±2.51)% vs. (25.21±2.05)%], and the difference was statistically significant (P<0.01). This value in the irradiation combined conditional culturing group was lower than that in irradiated group [(60.48±2.79)% vs. (80.65±2.05)%], and the difference was statistically significant (P<0.001). The flow cytometry analysis showed that the percentage of cells in G2/M phase for the irradiation (4 Gy) combined conditional culturing group was higher than that of irradiated group [(26.83±1.42)% vs. (15.73±1.29)%], and the difference was statistically significant (P<0.001). The Western Blot results showed that γH2AX and Rad51 protein expression in the irradiation (4 Gy) combined conditional culturing group respectively was lower and higher than that in irradiated group. Conclusion In the tumor microenvironment, radiation-resistant H460R cells can enhance the radioresistance of H460 cells by paracrine, which may be related to the promotion of DNA repair ability after irradiation Key words: Non-small cell lung cancer; Paracrine; Radioresistance; DNA repair