Cancer-associated fibroblasts in digestive tumors

The significant influence of tumor stroma on malignant cells has been extensively investigated in this era of targeted therapy.The tumor microenvironment,as a dynamic system,is orchestrated by various cells including tumor vascular composing cells,inflammatory cells and fibroblasts.As a major and important component in tumor stroma,increasing evidence has shown that spindle-shaped cancer-associated fibroblasts(CAFs)are a significant modifier of cancer evolution,and promote tumorigenesis,tumor invasion and metastasis by stimulating angiogenesis,malignant cell survival,epithelial-mesenchymal transition(EMT)and proliferation via direct cell-to-cell contact or secretion of soluble factors in most digestive solid tumors.CAFs are thought to be activated,characterized bythe expression ofα-smooth muscle actin,fibroblast activated protein,fibroblast specific protein,vimentin,fibronectin,etc.They are hypothesized to originate from normal or aged fibroblasts,bone marrow-derived mesenchymal cells,or vascular endothelial cells.EMT may also be an important process generating CAFs,and most probably,CAFs may originate from multiple cells.A close link exists between EMT,tumor stem cells,and chemo-resistance of tumor cells,which is largely orchestrated by CAFs.CAFs significantly induce immunosuppression,and may be a prognostic marker in various malignancies.Targeted therapy toward CAFs has displayed promising anticancer efficacy,which further reinforces the necessity to explore the relationship between CAFs and their hosts.