SMAD2 and renal cell carcinoma: TGF-β signaling, elevated in advanced (stage III and IV) RCC tumors, has been shown to repress PAX2 mRNA transcription through Mothers against decapentaplegic homolog 2, or 3 (SMAD2/3)-mediated mechanisms, potentially contributing to the reduced PAX2 expression observed in advanced stages of RCC [16,40].