Transforming growth factor-β1 (TGF-β1) inhibits the proliferation of many cancer cells. However, tumor cells frequently become resistant to this inhibitory effect due to the absence of TGF-β receptor (TβR) expression. This study reports the nature of TGF-β sensitivity in an aggressive murine renal carcinoma cell line, Renca, investigated in a series of experiments. The growth of Renca cells, in tissue culture, was not sensitive to the inhibitory effect of TGF-β1 with doses ranging from 0.1 to 10 ng./ml., nor was this cell line sensitive to the effect of TGF-β1 in inducing the expression of plasminogen activator inhibitor-I. Renca cells expressed TGF- β1 mRNA and protein, as determined by RT-PCR and ELISA, respectively. The level of TGF-β1 production by Renca cells was moderate, thus eliminating the possibility that endogenous TGF-β1 production might be masking the effect of TGF-β sensitivity. Furthermore, Renca cells expressed TβR-I mRNA, but did not express TβR-II mRNA, suggesting that the absence of this receptor may be the cause of TGF-β insensitivity. Additionally, a vector containing the TβR-II cDNA was transiently transfected into Renca cells. The inhibitory effect of TGF-β1 was introduced in Renca cells after transfection with this receptor. At the same time, the growth rate of these cells diminished significantly when compared with that of the wild type Renca cells, as judged by the rate of [3H]-thymidine incorporation in the absence of any exogenous TGF-β1. These observations demonstrated that Renca cells lack the functional TβR-II and suggest that their aggressive growth pattern is due, at least in part, to their insensitivity to TGF-β.
All Science Journal Classification (ASJC) codes
- Murine tumor system
- Renal cell carcinoma
- TGF-β receptor