CDK4 and prostate carcinoma: Silibinin has been reported to inhibit cell growth and induce G1 arrest in cell cycle progression of human prostate carcinoma, which was associated with decreased levels of cyclin D1, CDK4, and CDK6 and induction of Cip1/p21 and Kip1/p27, followed by increased binding with CDK2 [36, 37].