Combination of MPPa-PDT and HSV1-TK/GCV gene therapy on prostate cancer

We combined pyropheophorbide-a methyl ester, photodynamic therapy (MPPa-PDT), 670 ± 10 nm, 4 mW/cm², with herpes simplex virus type 1 thymidine kinase/ganciclovir (HSV1-TK/GCV) to improve the therapeutic effect. We built HSV1-TK expression vector GV230-TK and we observed a bright green fluorescence under fluorescence microscope. It indicated the recombinant plasmid was transfected into PC-3M prostate cancer cells successfully. As the abundant glucose-regulated protein 78 (GRP78) promoter in PC-3M cells can cause active expression of HSV1-TK, cell protein was collected for western blot to determine the expression of HSV1-TK. In CCK-8 assay (n = 6), the cell survival rate of combined treatment group was about 10%, less than that of pure MPPa-PDT group (23%) and pure HSV1-TK/GCV group (35%) (t test, P < 0.05). Flow cytometry was used to measure the cytotoxicity; the apoptosis rate of combined treatment group was about 38%, higher than that of pure MPPa-PDT group (about 22%) and pure HSV1-TK/GCV group (about 19%). The results showed that the combination of the two treatments can effectively improve the cytocidal effect in PC-3M cells.