Using a human prostate cancer cell model, Johnson et al. [13] indicated that due to its structure, α-mangostin, the major xanthone of Mangosteen pericarp powder, inhibited cyclin/cyclin-dependent kinase 4 (CDK4), and treating mice with α-mangostin (100 mg/kg) via oral gavage significantly decreased the average tumor volume in an in vivo 22Rv1 tumor xenograft model. This evidence concerns the gene CDK4 and neoplasm.