Differential expression of transforming growth factors-β1, -β2 and -β3 in human colon carcinoma

Transforming growth factor (TGF)-β is a protein family which affects multiple cellular functions including survival, proliferation, differentiation and adhesion. Among the three known isoforms, TGF-β1 is commonly overexpressed in solid malignancies. Recent studies in knock-out mice demonstrated non-redundant roles of different TGF-β isoforms in development. The present study was performed to assess tumour-associated expression of the three TGF-β isoforms in colon carcinoma. We report that colon carcinoma progression is associated with gradual and significant increases in expression of TGF-β1 and TGF-β2 mRNA and proteins. By contrast, TGF-β3 expression was detected in normal colonic mucosa and, at slightly higher levels, in tumour tissues. In addition, plasma levels of both TGF-β1 and TGF-β2 were significantly higher in cancer patients when compared with unaffected individuals. Taken together, our results indicate distinct expression patterns of the three TGF-β isoforms in colon carcinoma cells and possible systemic effects of TGF-β1 and TGF-β2 in tumour patients.