A growth-promoting effect of aTGFβ1 has been described previously in MDA-MB-231 cells [47] and in colon carcinoma cells [18,19] with aTGFβ regulating the cell cycle through a pathway different from exogenous TGFβ with respect to sensitivity of p21WAF1 and CDK4 [18]. This evidence concerns the gene CDK4 and colon carcinoma.