Using a human prostate cancer cell model, Johnson et al. 31 indicated that due to its structure, α-mangostin, the major xanthone of MPP, inhibited cyclin/cyclin-dependent kinase 4 (CDK4), and treating mice with α-mangostin (100 mg/kg) by oral gavage significantly decreased the average tumor volume in an in vivo 22Rv1 tumor xenograft model. This evidence concerns the gene CDK4 and Familial prostate cancer.