CDK4 and benign prostatic hyperplasia: In addition, in tests with experimental animals, QC significantly decreased the prostatic volume and weight, inhibited prostatic hyperplasia, attenuated the abnormal serum levels of estrogen and androgen, regulated the expression of estrogen receptor (ER), androgen receptor (AR) and related mRNA, and inhibited the expression of pro-proliferative PCNA, cyclin D1 and CDK4 in the prostatic tissues of BPH rats (26–30).