Transforming growth factor β (TGF-β) induces normal fibroblasts to perform an inhibitory effect directed against transformed cells (P. Höfler, I. Wehrle, and G. Bauer, Int. J. Cancer, 54: 125–130, 1993). Coculture of normal fibroblasts with transformed cells, either resistant to G 418 or expressing Mx antigen detectable by specific immunofluorescence, allowed discrimination between three theoretical mechanisms of inhibition: irreversible inhibition of proliferation; reversion to the nontransformed phenotype; or elimination of transformed cells. Our data demonstrate that normal fibroblasts treated with TGF-β are able to eliminate transformed cells by induction of apoptosis. Sensitivity against TGF-β-induced elimination seems to be a general feature of in vitro-transformed cell lines. TGF-β-induced elimination of transformed fibroblasts by their untransformed counterparts is proposed as a potential potent control point in carcinogenesis, which may lead to the suppression of transformed cells.

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This work was supported by the Deutsche Forschungsgemeinschaft (Grant Ba 626-3).

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