The VE‐cadherin binding domain of fibrinogen induces endothelial barrier permeability and enhances transendothelial migration of malignant breast epithelial cells

Abstract

Fibrin deposition and exudation of plasma fibrinogen (Fg) have long been recognized as hallmarks of inflammation, cardiovascular disease and neoplasia. The Fg-b 15-42 domain binds to the endothelial cell adhesion molecule, VE-cadherin, promoting endothelial cell proliferation, angiogenesis and leukocyte diapedesis. Furthermore, spontaneous blood-borne and lymphatic metastasis of some types of tumor emboli requires plasma fibrin(ogen); however, the molecular mechanisms by which this occurs are poorly understood. We sought to determine whether Fg-b 15-42 and VEcadherin binding interactions promote endothelial barrier permeability and breast cancer cell transendothelial migration (TEM) using transwell insert culture systems. Synthetic peptides containing/missing residues b 15-17 critical for In 1865, Armand Trousseau reported the observation that patients with an increased incidence of coagulopathies would later manifest visceral malignancies, which became known as Trousseau's syndrome. Ironically, Trousseau diagnosed himself with his own syndrome in 1866 and died of gastric cancer the following year. Causal factors linked to the prothrombotic state of Trousseau's syndrome also facilitate cancer metastasis, including thrombin, tissue factor, selectins, platelets, endothelial cells (EC) and fibrin. 1 Deposition of fibrinogen (Fg) 5 and fibrin commonly occurs within the stroma of most solid tumors, 2 and elevated levels of plasma Fg and fibrin degradation products (FDPs) correlate positively with lymph node involvement and metastasis of colon, ovarian, lung and breast cancers. 1 Studies by Degen and co-workers 3-5 have firmly established that plasma fibrin(ogen) and platelets play critical roles in spontaneous cancer metastasis through both the circulation and lymphatic systems, in part by protecting tumor cells from natural killer cell-mediated lysis.Expression of interleukin (IL)-6 during systemic inflammation upregulates expression of specific plasma proteins in the liver, including Fg. 6 Excessive fibrin deposition is accompanied by local expression of proinflammatory mediators, vascular leakage, and inflammatory cell recruitment and activation leading to amplification of the inflammatory response. 2,7,8 Residues 15-42 on the b chain of Fg have been implicated in functional attributes ascribed to fibrin(ogen). Although the primary structure of fibrinopeptide B (FPB) is poorly conserved across species, the fibrin b 15-42 domain is highly conserved, implying evolutionary conservation of function. 9 The b 15-42 region constitutes a cryptic domain in soluble Fg that is exposed in fibrin after thrombin cleavage. 10 Newly exposed residues, b15-GHRP-18, promote lateral aggregation of fibrin monomers during polymerization and insoluble clot formation in secondary hemostasis. 10 Furthermore, exposure of the b 15-42 domain mediates fibrin binding to EC surfaces, 11 promotes EC adhesion and spreading, 12 and stimulates proliferation of EC, fibroblasts and cancer cells. 13,14 Cadherins mediate homophilic cell-cell adhesion...

The Role of Fibrin(ogen) in Transendothelial Cell Migration During Breast Cancer Metastasis

“…Using transwell insert culture systems, we showed that Fg  15-42 and VEcadherin binding interactions promote endothelial cell barrier permeability (Sahni et al, 2009) (Fig. 6).…”

“…Although Fg is known for its hemostatic role, we showed that Fg, not fibrin, is a component of the insoluble fibrillar ECM of fibroblasts, alveolar epithelial cells, endothelial cells and breast epithelial cells (Guadiz et al, 1997;Pereira et al, 2002;Sahni et al, 2009;SimpsonHaidaris et al, 2010;Simpson-Haidaris & Sahni, 2010). Upon assembly into matrix fibrils, Fg undergoes conformational changes exposing the cryptic  15-42 epitope in the absence of thrombin cleavage or covalent crosslinking (Guadiz et al, 1997;Simpson-Haidaris & Sahni, 2010).…”

“…In most cases, cancers exploit pro-inflammatory mediators and recruited inflammatory cells to benefit their own survival (Lorusso & Ruegg, 2008) (also as reviewed in ). Fg and fibrin deposition is found within the stroma of most solid tumors (Simpson-Haidaris & Rybarczyk, 2001), and elevated levels of plasma Fg and fibrin degradation products (FDPs) correlate positively with lymph node involvement and metastatic spread of colorectal, ovarian, lung and breast cancers (Sahni et al, 2009;Varki, 2007). Fibrin deposition at the tumor-normal host cell interface as well as in the stroma of primary tumors is well documented, and is thought to protect tumors from infiltrating inflammatory cells by acting as a barrier thereby preventing inflammatory reactions directed towards the tumor cells (reviewed in (Simpson-Haidaris & Rybarczyk, 2001)).…”

“…VE-cadherin mediates homophilic cell-cell adhesion critical for the maintenance of barrier integrity of the endothelium. Disruption of VE-cadherin-mediated endothelial barrier function leads to altered vascular permeability found in a number of diseases including ischemia-reperfusion (IR) injury, inflammation, angiogenesis, and cancer growth and metastasis (discussed in (Sahni et al, 2009)). Exposure of  15-42 and binding by VE-cadherin is also required for endothelial capillary tube formation in fibrin gels (Bach et al, 1998a;Chalupowicz et al, 1995); portions of the third extracellular domain (EC3) of VE-cadherin constitute a fibrin  15-42 receptor (Bach et al, 1998b;Yakovlev & Medved, 2009).…”

“…In a recent report (Sahni et al, 2009), we sought to determine whether fibrin(ogen)  15-42 binding to VE-cadherin induced endothelial cell permeability, and whether fibrinogeninduced cancer metastasis involves binding interactions between VE-cadherin and fibrin(ogen)  15-42 . Using transwell insert culture systems, we showed that Fg  15-42 and VEcadherin binding interactions promote endothelial cell barrier permeability (Sahni et al, 2009) (Fig.…”