The Effect Of PI3K/AKT/mTOR Signaling Pathways On Hypofractionated Radiosensitivity Of NSCLC

Objective:1. To test the radiosensitivity of the non-small cell lung cancer radioresistant cell lines that had been estibilished.2. To investigate the radiosensitivity and mechanisms caused by LY294002and Rapamycin, the inhibitors of PTEN/PI3K/AKT/mTOR cell signaling pathways, on A549R cells.Methods:1. NSCLC cell line A549、A549R2Gy-R、A549R4Gy.R cells were cultured in vitro. All cells underwent radiation exposure. The ability of cell proliferation was tested by colony formation; the24h residual yH2AX focus was detected by immunofiuorescence assay.2. NSCLC cell line A549、A549R2Gy-R、A549R4Gy-R cells were cultured in vitro. The experiment was divided into control group, LY294002group, Rapamycin group and LY294002+Rapamycin group.the effect on proliferation of A549R cells that caused by LY294002and/or Rapamycin in combination with radition was detected by colony formation. The effect on24h residual yH2AX focus that was caused by LY294002and/or Rapamycin in combination with radition was detected by immunofiuorescence assay. SPSS17.0statistical analysis software package was used, the experimental data are presented as mean±standard deviation (±S). Under the conditions of the test data normal distribution and homogeneity of variance, analysis of variance was used in multiple sets of data, and the LSD-t test was used between the two groups. Significance was accepted when P＜0.05.Results:1. The ability of proliferation of A549R2Gy-R and A549R4Gy-R cells were stronger than A549cells after radiation exposure; the A549R4Gy-R cells were the strongest. The24h residual yH2AX focus of A549R2Gy-R and A549R4Gy-R cells were less than A549cells(P<0.05); there was no difference between A549R2Gy-R and A549R4Gy-R cells. 2. Obviosly, the proliferation of A549R2Gy-R and A549R4Gy-R cells decreased when they were exposed to LY294002and/or Rapamycin in combination with radition. Of which, the proliferation of A549R2Gy-R and A549R4Gy-R cells was the same as A549cells when they were expoused to LY294002in combination with raditon. Other groups appeared lower proliferation than A549cells. The24h residual yH2AX focus apparently increased after expousing to LY294002and/or Rapamycin in combination with radition (P<0.05); there was no difference between LY294002or Rapamycin group and A549cell group. However, there was apparent difference between LY294002+Rapamycin group and A549cell group.Conclusion:1. After repeated expouse to radition, the A549radioresistant cells lines were achieved.2. LY294002and Rapamycin, the inhibitor of the PTEN/PI3K/AKT/mTOR cell signaling pathways, could inhibit the proliferiation of the radioresistant cells by delaying the repair of DNA damage. They can repair the radiosensitivity of the radioresistant cells and increase the radiosensitization of hypofractionated Radioresistant A549R4Gy-R cells.