TGFB1 and cancer: TGF-β itself can also have a dual role herein, depending on the cell type where signalling occurs (epithelium vs. stroma) as well as on the timing (early or late in tumour development); it can function as a tumour suppressor when activated in premalignant epithelial cells, or as a tumour promotor when activated in advanced cancer cells or the tumour microenvironment42,43.