CELL-CYCLE CONTROL WITH MINIMAL PARTICIPATION OF CDK2 IN A MURINE FIBROSARCOMA CLONE CULTURED IN PROTEIN-FREE MEDIUM

The differences in the protein expression of cyclins, cyclin-dependent kinases (cdks), and their inhibitors and cdk kinase activities were e xamined in serum dependent (SD) and independent (PF) clones of the mur ine fibrosarcoma cell line, Gc-4. The expression of cyclin A in SD was minimal in contrast to PF, Furthermore, cdk2 kinase activity in PF wa s remarkably lower than that in SD, yet the G1/S transition in PF appe ared normal, PF was also resistant against the selective inhibitor of cdk2, butyrolactone I. These findings suggest that tumor cell prolifer ation and tumor progression can be promoted by the activation of a mol ecule(s) downstream of cdk2. (C) 1997 Academic Press.