Fig. 2.

Biology and dynamics supporting the biomarker approach to quantify tumor fibrosis non-invasively. Cancer associated fibroblasts (CAFs) synthesize excess amount of fibrillar collagens such as type III collagen upon activation by for example transforming growth factor beta (TGF-β). These fibrillar collagens contain pro-peptides that are released into circulation when the collagens are deposited as collagen fibrils in the tissue. It is the excess accumulation of bundles of collagen fibrils that make up excess of collagens fibers that ultimately result in tumor fibrosis. In the blood, the pro-peptides are quantifiable biomarkers of tumor fibrosis