Connection between inflammation and carcinogenesis in gastrointestinal tract: Focus on TGF-β signaling

Figure 3 Role of transforming growth factor (TGF)-β in cancer progression. TGF-β is a secreted polypeptide that signals via receptor serine/threonine kinases and intracellular Smad effectors. TGF-β inhibits proliferation and induces apoptosis in various cell types. Accumulation of loss-of-function mutations in the TGF-β receptor or Smad genes classifies the pathway as a tumor suppressor in humans. In addition, various oncogenic pathways directly inactivate the TGF-β receptor-Smad pathway, thus favoring tumor growth. On the other hand, all human tumors overproduce TGF-β whose autocrine and paracrine actions promote tumor cell invasiveness and metastasis. Accordingly, TGF-β induces epithelial to mesenchymal transition (EMT).