TGFB1 and cancer: However, the role of TGF-β during tumorigenesis is complex and somewhat paradoxical since in normal tissue and early-stage cancers it acts as a tumor suppressor by inhibiting epithelial cell cycle progression and promoting apoptosis, and only in late-stage counterparts it functions as a promoter by enhancing genomic instability, immune evasion, neoangiogenesis, cell motility, cancer invasiveness, and metastasis.