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

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/GFAPperiodic 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(rs = 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-2activation, thereby highlighting ATM activation as a potential target for enhancing anti-angiogenesis therapies for GBM.