Differential secretome analysis of cancer‐associated fibroblasts and bone marrow‐derived precursors to identify microenvironmental regulators of colon cancer progression

The identification of cancer‐associated fibroblast ( CAF )‐derived proteins that mediate interactions between the tumor stroma and cancer cells is a crucial step toward the discovery of new molecular targets for therapy or molecular signatures that improve tumor classification and predict clinical outcome. CAF are α‐smooth muscle actin positive, representing a myofibroblast phenotype that may differentiate from multiple precursor cells, including bone marrow‐derived mesenchymal stem cells ( MSC ). Transforming growth factor‐β1 ( TGF ‐β1 ) is a crucial inducer of α‐smooth muscle actin positive CAF s. In this study, we aimed to identify CAF ‐derived regulators of colon cancer progression by performing a high‐throughput differential secretome profiling between CAF compared to noncancer‐activated bone marrow‐derived MSC . In addition, we explored the effect of TGF ‐β1 on the secretion of proteins by bone marrow‐derived MSC in comparison with the protein secretion profile of CAF . TGF ‐β1 induced de novo secretion of 84 proteins in MSC , of which 16 proteins, including stromal‐derived factor‐1α and R antes, were also present in CAF secretome. Immunohistochemistry further validated the expression of selected candidates such as tenascin C , fibronectin ED ‐ A domain and stromal‐derived factor‐1 in clinical colon cancer specimens. In conclusion, this differential secretome approach enabled us to identify a series of candidate biomarkers for colon cancer that are associated with a CAF ‐specific phenotype.