TGFB1 and neoplasm: Despite relatively highconcentrations of TGF-β in the immediate tumor microenvironment, some malignantepithelial cells become refractory to TGF-β1-initiated proliferative arrest likely due to reductionsin either TGF-βRII and/or SMAD4 levels as well as the now recognized p21ras-dependent antagonism ofTGF-β1-mediatedgrowth inhibition/apoptosis [10–13].