Background & objective: Rapamycin, isolated from Streptomyces hygroscopicus, is recently reported to have immunosuppressive and antitumor effects on a large variety of cancers. This study was to investigate the role of Caspase-3 in rapamycin-induced apoptosis of hepatocellular carcinoma BEL-7402 cells.
Methods: BEL-7402 cells were treated with different concentrations (5, 10, 20, 30, 40, 50 nmol/L) of rapamycin. Cell viability was detected by MTT assay; cell apoptosis was observed by flow cytometry (FCM) and Hoechst 33258 staining. The activity of Caspase-3 was determined by Caspase colorimetric assay kit and Western blot.
Results: Rapamycin inhibited the growth of BEL-7402 cells and induced apoptosis significantly in time- and dose-dependent manners. Marked morphologic changes of cell apoptosis, such as chromatin condensation and nuclear fragmentation, were observed clearly at 48 h after exposion to rapamycin; Caspase-3 was activated by the loss of Caspase-3 proenzyme (32-ku) and its 20-ku subunit appeared at 24 h after incubation. Caspase-3 inhibitor z-DEVD-FMK could block the apoptosis induced by rapamycin.
Conclusions: Rapamycin can inhibit growth and induce apoptosis of BEL-7402 cells. The activation of Caspase-3 may play an important role in cell apoptosis.