Renal cell carcinoma (RCC) is a major health issue. Whereas localized disease can be cured surgically, there is no effective therapy for metastatic disease. The development of an effective therapy will require an understanding of the pathways that are important in RCC carcinogenesis and progression. Using genomic profiling of patientmatched tissue, we have identified aberrations in the transforming growth factor b (TGFb) signaling pathway in RCC. We observed loss of type III TGFb receptor (TBR3) expression in all RCC samples. This suggests that TBR3 loss is an early event in RCC carcinogenesis and plays a sentinel role in the acquisition of a tumorigenic phenotype. We also observed subsequent loss of type II TGFb receptor (TBR2) expression in metastatic RCCs. We propose that loss of TBR3 is necessary for RCC carcinogenesis, and that loss of TBR2 leads to acquisition of a metastatic phenotype. To this end, we have identified a human renal cell carcinoma line (UMRC6) that is representative of localized, nonmetastatic RCC, reflecting a loss of TBR3, but not TBR2 expression. Another cell line, UMRC3, is highly metastatic, having lost TBR3 and TBR2 expression. We demonstrate functional loss of TGFb responsiveness in these cell lines as observed through phenotypic and transcriptional responsiveness to exogenous TGFb. Restoring TBR2 and TBR3 expression in UMRC3 cells attenuates cell proliferation, completely restores TGFb-mediated transcriptional responses, and completely blocks anchorage independent-growth: while restoration of TBR2 partially restores TGFb-mediated signaling. Based on these data, we propose that dysregulation in TGFb signaling, through stepwise loss in receptor expression, plays a prominent role in RCC carcinogenesis and progression. In addition, these studies unequivocably demonstrate a link between loss of TBR3 and a human disease.