Using WB and ICC detection, we observed that the protein expression levels of TGF-β1, TGF-βR1, and Smad6 in RCC xenografts of mice in group A were lower than those in groups B and C, while the protein expression levels of Smad2, Smad3, Smad4, and Smad9 in RCC xenografts of mice in groups B and C were also lower than those in group A. Compared with the results under in vitro experimental conditions (Figure 3), under in vivo experimental conditions, the mRNA expression levels of these proteins in treated Renca cells were consistent with the tends observed for the protein. Here, SMAD2 is linked to renal cell carcinoma.