Genetic deletion or tyrosine phosphatase inhibition of PTPRZ1 activates c‐Met to up‐regulate angiogenesis and lung adenocarcinoma growth

Abstract

AbstractProtein tyrosine phosphatase receptor zeta 1 (PTPRZ1) is a transmembrane tyrosine phosphatase (TP) expressed in endothelial cells and required for stimulation of cell migration by vascular endothelial growth factor A165 (VEGFA165) and pleiotrophin (PTN). It is also over or under‐expressed in various tumor types. In this study, we used genetically engineered Ptprz1−/− and Ptprz1+/+ mice to study mechanistic aspects of PTPRZ1 involvement in angiogenesis and investigate its role in lung adenocarcinoma (LUAD) growth. Ptprz1−/− lung microvascular endothelial cells (LMVEC) have increased angiogenic features compared with Ptprz1+/+ LMVEC, in line with the increased lung angiogenesis and the enhanced chemically induced LUAD growth in Ptprz1−/− compared with Ptprz1+/+ mice. In LUAD cells isolated from the lungs of urethane‐treated mice, PTPRZ1 TP inhibition also enhanced proliferation and migration. Expression of beta 3 (β3) integrin is decreased in Ptprz1−/− LMVEC, linked to enhanced VEGF receptor 2 (VEGFR2), c‐Met tyrosine kinase (TK) and Akt kinase activities. However, only c‐Met and Akt seem responsible for the enhanced endothelial cell activation in vitro and LUAD growth and angiogenesis in vivo in Ptprz1−/− mice. A selective PTPRZ1 TP inhibitor, VEGFA165 and PTN also activate c‐Met and Akt in a PTPRZ1‐dependent manner in endothelial cells, and their stimulatory effects are abolished by the c‐Met TK inhibitor (TKI) crizotinib. Altogether, our data suggest that low PTPRZ1 expression is linked to worse LUAD prognosis and response to c‐Met TKIs and uncover for the first time the role of PTPRZ1 in mediating c‐Met activation by VEGFA and PTN.