ABSTRACT
Objective To study the radiosensitization of histone deaeetylases inhibitor(HDACI) panobinistat in prostate cancer cells in vitro,as well as the possible mechanisms.Methods IC20 of two prostate cancer cell lines(LNCaP and PC-3)was determined using MTI assay.Cells received a single dose irradiation of 0,2,4,6,or 8 Gy using 6 MV X-ray for radiosensitivity experiment,but only 2 Gy for western blot and flow cytometry.Radiosensitization of panobinostat was investigated with clonogenic assay,and sensitizing enhancement ratio(SER)was calculated with single-hit multi-target model.Western blot was used to compare γH2AX expression.Flowcytomctry was used to detect the cell cycle distribution.Results IC20 of LNCaP and PC-3 was 2.5 and 10.0 μmol/L,respectively.SER of panobinostat at IC20 was 1.37(D0 ratio)and 1.11(Dq ratio)for LNCaP cells,and 1.78(D0 ratio)and 1.17(Dq ratio)for PC-3 cells.Expression of γH2AX gradually decreased in the 2 Gy irradiation-alone cells standing for the DSB repair,while γH2AX expression was persistent in the combination group.Irradiation triggered a G2/M arrest 6-12 hours after irradiation in LNCaP and PC-3 cells.G2/M arrest was observed when cells were treated with panobinostat for 24 hours,however,no significant change concerning cell cycle distribution was showed when cells received further irradiation.Conclusions Panobinostat Call radiosensitize prostate cancer cells,which may be related with increased DNA DSB,inhibition of DSB repair and attenuation of cell cycle modulation after irradiation.