The ability of Obatoclax to inhibit multiple pro-survival members of the Bcl-2 family, including Bcl-2, Bcl-xL, and Mcl-1, as well as cyclin D1 and Cdk4/6, is important clinically because a comparison of MI-BC patient studies reveals that they differ with regards to which pro-survival Bcl-2 family members are overexpressed [7,50]. This evidence concerns the gene CDK4 and breast cancer.