CDK4 and benign prostatic hyperplasia: Our preliminary study in a rat model of BPH showed that QC significantly decreased prostatic volume and weight, inhibited prostatic hyperplasia, attenuated abnormal serum levels of estrogen and androgen, regulated the expression of estrogen receptor (ER), androgen receptor (AR), and related mRNA, inhibited the EGF/STAT3 pathway, and reduced expression of proproliferative PCNA, cyclin D1, and CDK4 proteins [15–19].