Staurosporine-induced Growth Inhibition of Glioma Cells is Accompanied by Altered Expression of Cyclins, CDKs and CDK Inhibitors

Staurosporine was found to bring about complete growth inhibition of human glioma cell lines. U87 MG cells were arrested in S phase while U373 MG cells in G2/M phase on staurosporine treatment. Consistent with this observation, no change in G1 phase regulators viz., Cyclin D1, D3 and CDK4 was seen on staurosporine treatment. The levels of CDK2, CDC2, Cyclin A and Cyclin B proteins decreased, while the levels of CDK inhibitors viz., p21 and p27 were found to increase on staurosporine treatment. The mRNA levels of CDK2 and CDC2 genes were also found to decrease on staurosporine treatment. Thus apart from staurosporine’s known direct inhibitory effect on CDK2 and CDC2 activities, staurosporine was found to down-regulate activities of these two kinases by modulating the expression of the kinases themselves as well that of their activating partners (Cyclins) and their inhibitors.