| Abstract: | AIM: RC-RNase is a novel member of RNase A superfamily from Rana catesbeiana (bullfrog) oocytes. This study is to investigate the cytotoxic effect of RC-RNase on cancer cells. The cytotoxic mechanisms were investigated and discussed. METHODS: Cytotoxicity of RC-RNase to human cervical caner HeLa S3 cells was determined by microculture tetrazolium test and trypan blue exclusion assay. Apoptotic characteristics, such as chromatin condensation, blebbing morphology, DNA ladder, phosphatidylserine translocation, caspase activation, and poly (ADP-ribose) polymerase (PARP) cleavage, were analyzed by generally described methods. Cellcycle phases were analyzed by flow cytometry, and cellular cyclin B1/CDC2 activity was detected by in vitro histone H1 kinase assay. Western blot analyses were performed to examine the levels of Fas, FADD, TNFR1, TRADD, cyclin B1, CDC2, Wee-1, and the cleaved forms of Bid, PARP and caspases-3, 8 and 9. RESULTS: RC-RNase induced cell death with apoptotic characteristics in HeLa S3 cells. In vitro activity assays suggested that caspases-3, 8, and 9 activities were all increased in RC-RNase-treated cells. The results of Western blot analyses, including induction of FADD expression and increases of the cleaved forms of Bid, PARP and caspases-3, 8 and 9, confirmed that RC-RNase indeed induced the activation of caspases-3, 8, and 9. Although RC-RNase did not significantly affect the cell-cycle distribution, cyclin B1/CDC2 kinase activity was increased in RC-RNase-induced apoptotic cells. Cellular Wee-1 level was reduced by RC-RNase treatment, and CDC2 was kept in Tyr-15-dephosphorylated (active) form.CONCLUSION: RC-RNase was potent to induce FADD expression, caspase cascades, cyclin B1/CDC2 activation, and ultimately apoptosis in HeLa S3 cells. |
