Endothelial Agrin Is Dispensable for Normal and Tumor Angiogenesis.

Peng Ye,Zelong Fu,Patrick Ming-Kuen Tang,Ho Ko,Jeff Yat-Fai Chung,Xiao Yu Tian,Kathy O Lui,Xiaoyun Cao

doi:10.3389/fcvm.2021.810477

Abstract

Recently, the extracellular matrix protein agrin has been reported to promote tumor angiogenesis that supports tumorigenesis and metastasis; however, there is a lack of in vivo genetic evidence to prove whether agrin derived from the tumors or endothelial cells (ECs) systemically should be the therapeutic target. To date, the physiological role of endothelial agrin has also not been investigated. In the EC-specific agrin knockout mice, we observed normal endothelial and haematopoietic cell development during embryogenesis. Moreover, these mice develop normal vascular barrier integrity and vasoreactivity at the adult stage. Importantly, the growth of localized or metastatic cancer cells was not affected after implantation into endothelial agrin depleted mice. Mechanistically, agrin did not regulate endothelial ERK1/2, YAP or p53 activation in vivo that is central to support endothelial proliferation, survival and invasion. Cumulatively, our findings may suggest that agrin could play a redundant role in endothelial development during physiological and tumor angiogenesis. Targeting the endothelial derived agrin might not be effective in inhibiting tumor angiogenesis.

Highlights

The extracellular matrix (ECM) is a network of secreted macromolecules that forms a non-cellular microenvironment essential in modulating cell behavior during multiple biological processes including development [1], repair and regeneration [2], as well as tumorigenesis and metastasis [3]
Agrin has been demonstrated to recruit blood vessels within a growing tumor as xenotransplantation of Matrigel plugs containing agrin-depleted human liver cancer cells in immunodeficient mice shows reduced infiltration of murine CD31+ endothelial cells (ECs) compared to that of the control [14]. These findings suggest that agrin promotes tumor angiogenesis, and is likely a therapeutic target for cancer therapy. shRNA-mediated agrin knockdown in human umbilical vein ECs (HUVEC) significantly reduces in vitro angiogenesis, proliferation and migration through reduced vascular endothelial growth factor receptor 2 (VEGFR2) expression; and impedes the activation of extracellular signal regulated kinase (ERK)1/2, protein kinase B (Akt), and endothelial nitric oxide synthase signaling downstream of VEGFR2 [14]
Our results indicated that agrin might not control endothelial barrier function; or the loss of endothelial agrin was compensated by other mediators to maintain the barrier integrity

Summary

INTRODUCTION

The extracellular matrix (ECM) is a network of secreted macromolecules that forms a non-cellular microenvironment essential in modulating cell behavior during multiple biological processes including development [1], repair and regeneration [2], as well as tumorigenesis and metastasis [3]. Agrin has been demonstrated to recruit blood vessels within a growing tumor as xenotransplantation of Matrigel plugs containing agrin-depleted human liver cancer cells in immunodeficient mice shows reduced infiltration of murine CD31+ ECs compared to that of the control [14]. These findings suggest that agrin promotes tumor angiogenesis, and is likely a therapeutic target for cancer therapy. Our results suggested that endothelial agrin was dispensable for embryonic and adult endothelial and haematopoietic development, respectively

RESULTS

DISCUSSION

ETHICS STATEMENT