The clinical and biological roles of transforming growth factor beta in colon cancer stem cells: A systematic review

Background: Transforming growth factor beta (TGF-beta) is a multipurpose cytokine, which plays a role in many cellular functions such as proliferation, differentiation, migration, apoptosis, cell adhesion and regulation of epithelial to mesenchymal transition. Despite many studies having observed the effect that TGF-beta plays in colorectal cancer, its role in the colorectal stem cell population has not been widely observed. Method: This systematic review will analyse the role of TGF-beta in the stem cell population of colorectal cancer. Results: The effects on the stem cell phenotype are through the downstream proteins involved in activation of the TGF-beta pathway. Its involvement in the initiation of the epithelial to mesenchymal transition (EMT), the effect of colorectal invasion and metastasis regulated through the Smad protein involvement in the EMT, initiation of angiogenesis, promotion of metastasis of colorectal cancer to the liver and its ability to cross-talk with other pathways. Conclusion: TGF-beta is a key player in angiogenesis, tumour growth and metastasis in colon cancer.