Transforming growth factor β1 (TGF-β1), a potential regulator of growth of prostate cancer cells, exerts its effects through interaction with membrane receptors. In the present study, an attempt was made to establish a correlation between TGF-β1 sensitivity and TGF-β receptor expression in three prostate cancer cell lines (PC3, DU145, and LNCaP). In a dose-dependent manner, TGF-β1 inhibited the proliferation of PC3 and DU145 cells but not LNCaP cells. Since TGF-β signals through a heteromeric complex composed of TGF-β receptors type II and type I, the expression of these receptors was investigated by Western blot analysis and reverse transcriptase-PCR. These studies demonstrated that all three prostate cancer cell lines express type II receptor. In contrast, type I receptor was detected only in the TGF-β1-sensitive PC3 and DU145 cells but not in the TGF-β1-insensitive LNCaP cells. To investigate the possibility that the undetectable expression of type I receptor in LNCaP cells is due to a change in the respective gene, Southern blot analysis was performed. The result demonstrated that there was a genetic change in type I receptor gene in these cells. Subsequently, when LNCaP cells were transiently transfected with TβR-I cDNA, sensitivity to TGF-β1 was restored. These observations indicate that LNCaP cells contain a defective TβR-I gene which rendered these cells insensitive to the action of TGF-β1.
This work was supported in part by NIH Grants DK 39250, CA 69851, and CA 60553.