Effect of protein kinase C alpha, caspase-3, and survivin on apoptosis of oral cancer cells induced by staurosporine

Aim: To elucidate inhibition of protein kinase C alpha(PKC alpha) activity by staurosporine on apoptosis of oral cancer cell line tongue squamous cell carcinoma (TSCCa) cells and to clarify the role of survivin and caspase-3 in mediating apoptosis. Methods: TSCCa cell viability was measured by MTT assay after 100 nmol/L staurosporine treatment. Apoptotic cells were identified by using phase contrast acridine orange/ethidium bromide staining, and flow cytometry. Level microscopy, of PKC alpha and its subcellular location were investigated using Western blot analysis. Expression of survivin and caspase-3 were evaluated using immunocytochemistry. Results: Staurosporine significantly inhibited the cell viability of TSCCa cells in a dose- and time-dependent manner. Marked cell accumulation in G(2)/M phase was observed after 100 nmol/L staurosporine exposure for 6 h and 12 h. In addition, the percentage of apoptosis increased in a time-dependent manner, from 2.9% in control cultures to approximately 27.4% at 100 nmol/L staurosporine treatment for 24 h. Staurosporine displayed difference in inhibitory efficacy between cytosolic and membrane-derived PKC alpha. The content of PKC alpha in membrane versus cytosol decreased quickly, from 0.45 in ethanol-treated control cultures to 0.18 after staurosporine exposure for 24 h (P < 0.01). After treatment with staurosporine, a time-dependent reduction of survivin and an activation of caspase-3 were observed in TSCCa cells. Conclusion: Staurosporine inhibited cell viability and promoted apoptosis in TSCCa cells. Inhibition of PKC alpha activity might be a potential mechanism for staurosporine to induce apoptosis in this cell line. The cleavage of survivin and activation of caspase-3 signaling pathway might contribute to PKC alpha inhibition-induced apoptosis.