CDK4 and prostate cancer: Forinstance, WIN55,212-2 (WIN), a synthetic cannabinoid receptor agonist,induced cell cycle arrest in prostate cancer cells, accompanied byincreased p27 expression and reduced expression of CDK4 and phosphorylatedretinoblastoma protein.19 Investigationsinto the in vivo antitumor activity of cannabinoidsin prostate cancer have also focused primarily on synthetic cannabinoids.20 For example, WIN inhibited tumor growth in PC-3,DU145, and LNCaP xenograft mouse models.19,21 Meanwhile, limited evidence exists regarding the antiproliferativeeffects of plant-derived cannabinoids in prostate cancer.