TGF-beta1 influence on TNF-alpha production and sTNF-Rs shedding in a coculture of colon carcinoma cell spheroids with normal cells

Abstract

In this study, the levels of TNF-alpha and its soluble receptors sTNF-Rp55 and sTNF-Rp75 were analyzed in cocultures of human colon carcinoma cell spheroids prepared from different grades of tumors with normal human colon epithelium, myofibroblast, and endothelial cell monolayers. Additionally, the influence of exogenously added rhTGF-beta1 (2 ng/ml) on the TNF-alpha and sTNF-Rs levels was tested. Direct interactions of colon carcinoma spheroids with normal cells caused decreases in TNF-alpha levels and normal cell-dependent changes in sTNF-Rs amounts as compared to normal cells cultured alone. The addition of rhTGF-beta1 to the cocultures caused a significant increase in TNF-alpha levels with a simultaneous decrease in the amounts of both sTNF-Rs. During direct interactions of colon carcinoma cells with normal tissue, paracrine effects are very important. We showed that TGF-beta1 acts synergistically with TNF-alpha and significantly limits sTNF-Rs shedding. Therefore, TNF-Rs bound to cellular membranes, but not their soluble forms, play an important role in tumor/normal cell interactions. TGF-beta1 and sTNF-Rs, in turn, may be valuable factors in colon cancer development and metastasis.