Fibroblast Activation Protein-Alpha, a Serine Protease that Facilitates Metastasis by Modification of Diverse Microenvironments

Abstract

Our overarching hypothesis is that FAP functions with other proteases in an extracellular communication network to digest certain proteins, thereby exposing signals stored in peptide regions that enable breast cancer cells to thrive in diverse microenvironments. FAP likely has important functions in two parts of the metastatic cascade: 1) FAP and proteases such as MMP-1 and MMP-9 cooperate to produce fragments of ECM proteins during adjacent tissue remodeling and these derivative peptides promote fibroblast growth, ECM deposition and angiogenesis; 2) cancer cell membrane FAP cleaves precursive A2AP to generate the more effective derivative for protecting and stabilizing fibrin within ECM margins of the expanding neoplastic cell mass as well as fibrin within cancer cell/fibrin/platelet emboli that lead to hematogenous metastasis. We believe that peptides that target and inhibit FAP on FAP-expressing cells can be produced by taking advantage of the substrate/active-site binding specificity of FAP.