CDKN1A and Familial prostate cancer: However, we observed increased expression of the cyclin-dependent kinase inhibitor Cdkn1b in Tg limbs, suggesting regulation of chondrocyte proliferation through regulation of this kinase inhibitor, a possibility consistent with data showing that ERRγ suppresses S-phase progression in an in vitro model of prostate cancer through transactivation of Cdkn1a and Cdkn1b[21].