Figure 2. Cdk2 activity compensates for loss of cdk4 activity in PD resistant MCF7 cells.

(A) Proliferation of MCF7 cells treated with DMSO or PD. Media with DMSO or drug is refreshed every two days starting at day 2 (arrowhead). (B) Immunoblot analysis with treated MCF7 lysates. (N≥3). (C) Cdk4 activity [(RbS780/RB ratio)/cdk4] determined by densitometry (bottom) of in vitro kinase assay immunoblots (top) (N=5). (D) Cdk2 activity [(RbS7807/811/RB ratio)/cdk2] determined by densitometry (bottom) of in vitro kinase assay immunoblots in (top) (N=5). (E) p27 immunoprecipitated, followed by pY88 immunoblot (top). pY88/p27 ratio determined by densitometry (bottom) (N=3). (F) Cdk2 immunoprecipitated, followed by p27 immunoblot (top). p27 association with cdk2 determined by densitometry (bottom) (N=6).