“…Additionally, loss of TGF-b expression in benign skin papillomas is correlated with a high risk for malignant conversion (Missero et al, 1991;Glick et al, 1993;Cui et al, 1994;Glick et al, 1994). On the other hand, TGF-b can also stimulate malignant progression, possibly by its action on cell-matrix interaction, by its immunosuppressive activities or by enhancing angiogenesis (Roberts et al, 1986;Torre-Amione et al, 1990;Arrick et al, 1992;Glick et al, 1994;Cui et al, 1996). TGF-b conveys signals via two serine/threonine kinase receptors, type I and type II, both of which are necessary for signal transduction Derynck, 1994).…”