EFFECT OF SURAMIN ON P34(CDC2) KINASE IN-VITRO AND IN EXTRACTS FROM HUMAN H69 CELLS - EVIDENCE FOR A DOUBLE MECHANISM OF ACTION

We examined the effect of suramin, an anticancer agent and a functiona l analog of naturally occuring glycosaminoglycans, on p34(cdc2) kinase . We find that suramin strongly inhibits the catalytic activity of pur ified p(34cdc2) kinase (IC(50)similar to 4 mu M), whereas it only weak ly inhibits the p13-agarose precipitated kinase activity from nuclear and cytoplasmic extracts of the asynchronous H69 human small cell lung cancer cells. We also find that the tyrosine phosphorylation of p34(c dc2) kinase in the nuclear extract is increased about twice when the e xtracts are preincubated with 50 mu M of suramin prior to the p13-agar ose precipitation. We propose that this increase might result from the inhibitory effect of suramin towards p34(cdc2)-specific tyrosine phos phatases. These results suggest both a direct and an indirect effect o f suramin on p34(cdc2) kinase. We also find that heparin is a potent i nhibitor of purified cdc2 kinase (IC(50)similar to 3.5 mu g/ml). There fore, glycosaminoglycans might be physiological regulators of p34(cdc2 ) kinase in vivo. (C) 1994 Academic Press, Inc.