After treatment with lathyrol and paraplatin, the expression of cyclinD1, cyclinB1, cyclinE1, CDK4, CDK6, CDK2, and CDK1 in group A RCC xenografts was greater than that in groups B and Cwhereas the expression of P16, P21, and P27 in groups B and C was greater than that in group A. However, lathyrol and paraplatin had a negligible effect on the expression of cyclin A1 protein in Renca cells in vivo, and the cell cycle might be blocked in the G1 phase. This evidence concerns the gene CDK4 and renal cell carcinoma.