TGFB1 and neoplasm: In mice studies targeting TGF-β1 transgene, primarily in the suprabasal/differentiated layers of the epidermis in transgenic, overexpression of TGF-β1 inhibits papilloma formation at early stages but promotes tumour aggressiveness via epithelial–mesenchymal transition at later stages of skin carcinogenesis (Weeks et al, 2001).