Restoration of expression of transforming growth factor-β Type II receptor in murine renal cell carcinoma (renca) cells by 5-Aza-2′-deoxycytidine

The murine renal cell carcinoma (Renca) cells are insensitive to TGF-β due to a lack of TGF-β type II receptor (TβR-II). The objective of the present study is to determine the mechanism of this loss of sensitivity to TGF-β in Renca cells. Renca cells were cultured and treated with 5-Aza-2′-Deoxycytidine (5-Aza), a specific inhibitor of methylation. Expression of TGF-β type I receptor (TβRI) and TβRII was determined by RT-PCR and Western blot analysis before and after the treatment of Renca cells with 5-Aza. The expression of phosphorylated Smad2 (P-Smad2) was determined by Western blot analysis. TGF-β levels in the conditioned medium were measured by ELISA. Renca cells did not express TβR-II prior to 5-Aza treatment. After 5-Aza treatment, these cells expressed TβR-II at both mRNA and protein levels, which corresponded to the restoration of sensitivity to TGF-β by an increase in P-Smad2. Levels of TGF-β1 were similar before and after 5-Aza treatment. Results of the present study indicated that, in Renca cells, the loss of sensitivity to TGF-β is likely due to a promoter hypermethylation in the TβR-II gene.