In pancreatic cancer cells [35] and normal human mammary epithelial cells (HMEC) [46], RAC1B acts as a negative regulator of the TGF-β1-induced cell cycle inhibitor p21WAF1 which supports proliferative effects of RAC1B on cell cycle progression (see Section 5.7). This evidence concerns the gene TGFB1 and pancreatic neoplasm.