CDK6 and renal cell carcinoma: In vivo, lathyrol suppressed the mRNA and protein expression of TGF-β1, TGF-βR1, Smad2, Smad3, Smad4, and Smad9 in RCC xenografts; promoted the protein expression of Smad6; and decreased the protein expression of cyclin D1, cyclin B1, cyclin A1, cyclin E1, CDK6, CDK4, and CDK1 while increasing the expression of P16, P21, and P27.