Influence Of Small Interfering RNA(siRNA) Targeting Hypoxia Inducible Factor-1α(HIF-1α) On The Radiosensitivity Of PC3 Cell Lines

Objective To evaluate the influence of silencing hypoxia inducible factor-1α(HIF-1α) expression by small interfering RNA(siRNA) targeting HIF-1αon the radiosensitivity of PC3 cell line, which is an androgen independent human prostate cancer cell line.Methods In this study, PC3 cell was divided into three groups:PC3 group, PC3+ NC siRNA group (negative control group), PC3+HIF-1αsiRNA group (HIF-1αsilence group) and transfect with NC siRNA and HIF-1αsiRNA confirmed by the preceding study using cationic liposome Lipofectamine2000. HIF-1αsiRNA's radiosensitization was measured by clongenic assay through different doses of 6MV X-ray. We calculated D0, Dq, SF2, N, SER and delineated dose-survival curve using single-target multi-hit model. CCK-8 Determination was used to evaluate proliferation of PC3 cell after single dose irradiation of 6Gy. Apoptotic rate of PC3 cells at 72 hours after single dose irradiation of 6Gy X-ray and cycle distribution of PC3 cell before or 72 hours after 6Gy X-ray was analyzed by flow cytometry.Results (1) Analysis of clongenic assay showed radiosensitizing effect in PC3+ HIF-1αsiRNA group. The values of D0, SF2, Dq, N in PC3+HIF-1αsiRNA group decreased and SER is 1.24. (2) The outcomes of CCK-8 tests showed that the proliferation of PC3 cell transfect with HIF-1αsiRNA was delayed compared with control groups after single dose irradiation of 6Gy (24h:F= 139.74,P<0.01;48h:F= 495.49,P<0.01;72h:F= 426.89,P<0.01; 96h:F= 471.11, P< 0.01). There was no statistic difference between two control groups (P>0.05). (3) Apoptotic rate of PC3 group, PC3+NC siRNA group, PC3+HIF-1αgroup 72 hours after radiotherapy was 1.65%, 18.6±1.37%,29.1±2.16%, respectively. HIF-1αsiRNA enhanced apoptotic rate of PC3 cell compared with control groups 72 hours after radiotherapy. (P<0.01). (4) Flow cytometry analysis showed there was less G0/G1 phase arrest in PC3+HIF-1αsiRNA group than control groups.Conclusion (1) HIF-1αsiRNA can enhance radiosensitivity of PC3 cell line in vitro by inhibition HIF-1αexpression. (2) The possible mechanisms involved in radiosensitization of HIF-1αsiRNA include enhancement of injury after radiotherapy, decreased capability of repair, increased apoptosis rate and released cell cycle arrest of G0/G1.