CDK4 and neoplasm: Analysis of tumor specimens confirmed that the antitumor activity of selumetinib+AZD8186 was associated with a significant reduction in protein expression of the Cyclin D1/CDK4/CDK6 proliferation complex, thereby inducing cell cycle arrest at the G1/S checkpoint (Figure 4E) as well as with a decrease in Bcl-2 antiapoptotic protein expression (Figure 4F).