TGFB1 and neoplasm: TGFβ suppresses the cell cycle progression of epithelial cells and inhibits tumor growth; however, in later stages of tumor development, tumor cells generally develop resistance to TGFβ1-mediated growth inhibition, and TGFβ ceases to function in tumor suppression and consequently adopts the converse role of inducing distal metastatic spread [14, 15].