TGF-BETA INDUCES AN INHIBITORY EFFECT OF NORMAL-CELLS DIRECTED AGAINST TRANSFORMED-CELLS

Co-cultivation of normal and transformed fibroblasts in the presence o f exogenously added transforming growth factor type beta1 (TGF-beta1) leads to a drastic reduction of colony-forming transformed cells. This inhibitory effect is dependent both on the dose of TGF-beta applied a nd the density of normal cells. It does not reflect a direct action of TGF-beta on transformed cells, but is rather induced by TGF-beta in n ormal cells. In the absence of exogenously added TGF-beta, normal cell s exhibit a basal inhibitory activity, which can be abrogated by anti- TGF-beta. TGF-beta-mediated inhibition of transformed cells by normal cells may be considered as a novel potent controlling step in carcinog enesis.