Pharmaceutical compositions including an effective amount of an antiandrogen or androgen antagonist in combination with a Plk inhibitor and methods of use thereof for treating cancer are disclosed. Administration of the combination of the active agents can be effective to reduce cancer cell proliferation or viability in a subject with cancer to the same degree, or a greater degree than administering to the subject the same amount of either active agent alone. The active agents can be administered together or separately. Methods of selecting and treating subjects with cancers, particular prostate cancers including castration resistant prostate cancer, breast cancers, particularly androgen receptor positive breast cancers, and pancreatic cancers are also provided.
