ATM Activation is Key in Vasculogenic Mimicry Formation by Glioma Stem-like Cells.

Abstract

Objective: Vasculogenic mimicry (VM) is a novel vasculogenic process integral to glioma stem cells (GSCs) in glioblastoma (GBM). However, the relationship between VM and ataxia-telangiectasia mutated (ATM) serine/threonine kinase activation, which confers chemoradiotherapy resistance, remains unclear.

Methods: We investigated VM formation and phosphorylated ATM (pATM) levels by CD31/GFAP-periodic acid-Schiff dual staining and immunohistochemical staining in 145 GBM specimens. Glioma stem-like cells (GSLCs) derived from the formatted spheres of U87 and U251 cell lines and their pATM level and VM formation ability were examined using western blot and three-dimensional culture. For the examination of the function of pATM in VM formation by GSLCs, ATM knockdown by shRNAs and deactivated via ATM phosphorylation inhibitor KU55933 were studied.

Results: VM and high pATM expression occurred in 38.5% and 41.8% of tumors, respectively, and were significantly associated with reduced progression-free and overall survival. Patients with VM-positive GBMs exhibited higher pATM levels ( r _s = 0.425, P = 0.01). The multivariate analysis established VM as an independent negative prognostic factor ( P = 0.002). Furthermore, GSLCs expressed high levels of pATM and formed vascular-like networks in vitro. ATM inactivation or knockdown hindered VM-like network formation concomitant with the downregulation of pVEGFR-2, VE-cadherin, and laminin B2.

Conclusion: VM may predict a poor GBM prognosis and is associated with pATM expression. We propose that pATM promotes VM through extracellular matrix modulation and VE-Cadherin / pVEGFR-2 activation, thereby highlighting ATM activation as a potential target for enhancing anti-angiogenesis therapies for GBM.