Establishment of a radioresistant human lung cancer cell subline and its mechanism of radioresistance / 中华放射医学与防护杂志

ABSTRACT

Objective To establish a radioresistant cell subline from a human A549 lung cancer cell line and investigate the mechanism of radioresistance. Methods Two proposals were applied for the non-small cell lung cancer A549 cells irradiated with X-raysA group of A549 cell line was irradiated five times, the fractionated dose was 600 cGy, and the other group was exposed 15 times, the fractionated dose was 200 cGy. After the completion of irradiation, two monoclones were obtained from the survival of cells and named the subline A549-S1 and A549-S2. The radiosensitivity and cell cycle distribution of these two clones,together with its parental A549 cells were measured by clone formation assay and flow cytometry.The mRNA and protein levels of Notch1 in A549 cell line and the sublines were determined by RT-PCR and Western-blots. Results Compared with the parental A549 cells, A549-S1 cells showed significant resistance to radiation with D0, Dq and N values increased, and a broader initial shoulder as well as 1.38-fold increased value of SF2. The A549-S1 subline also showed higher percentage of cells in S phase and G2/M phase, but lower percentages in G0/G1 phase (P<0.05). The expression of Notch1 in A549-S1 was enhanced obviously than in A549 cells. But for A549-S2 the radioseasitivity was slightly increased compared with the parental cells with D0, Dq and N values decreased and a curve initial shoulder. The ratio of cells in S and G0/G1 phase ratio was lower than that in parental A549 cells, but that in G2/M phase ratio was higher significantly (P<0.05) .The expression of Notch1 had no marked change compared to A549 cell. Conclusions The radioresistance of the A549 cell subline is correlated with the irradiation program. The cell subline shows a different cell cycle distribution from their parental line. The cell cycle distribution has a close correlation with the expression of Notch1.