An interaction between human colon carcinoma cells and hepatocytes activates transforming growth factor-β1 in vitro

We established in vitro heterotypic co-cultures of a human colon carcinoma cell line, HT-29, and a human hepatocyte line, tPH5CH, using transwells to investigate possible interactions between colon carcinoma cells and hepatocytes during the metastatic process. Co-culture, but not HT-29 conditioned medium, inhibited tPH5CH cell proliferation, and this inhibition was blocked by an anti-TGF-β1 antibody. Significantly more activated TGF-β1 was released by co-culture than by each cell line cultured alone, whereas there were no significant differences between the total TGF-β1 released by the individual cultured cell lines and that released by co-culture. These data indicate that an interaction between human colon carcinoma cells and hepatocytes activates TGF-β1 in vitro.