PD0332991 is a potent inhibitor of CDK4/6 but does not inhibit Flt3 ITD. (A) Structure of PD0332991. (B) MV4-11 cells were incubated with DMSO (vehicle control), THRX-165724 (500 nM), and PD0332991 (500 nM) for 30 minutes. The cells were lysed, Flt3 ITD was immunoprecipitated, and an immunoblot was performed with an anti-phosphotyrosine antibody. The blot was subsequently stripped and reprobed with anti-Flt3. (C) Western blot. MV4-11 and MOLM13 cells were incubated with increasing concentrations of PD0332991 for 16 hours. Lysates were resolved by SDS-PAGE followed by immunoblotting with anti-pRb.