Knockdown of P4HA1 inhibits neovascularization via targeting glioma stem cell-endothelial cell transdifferentiation and disrupting vascular basement membrane.

Yiqiang Zhou,Junwen Zhang,Hengzhou Xu,Ruifang Mi,Wenjie Song,Fusheng Liu,Yunsheng Zhang,Guishan Jin,Sen Cheng,Jin Zhang

doi:10.18632/oncotarget.16270

Abstract

Emerging evidence has demonstrated transdifferentiation process of glioma stem cells (GSCs) into endothelial cells (ECs) in glioma neovascularization. Herein, we focused on screening for genes that were differentially expressed in the transdifferentiation process using microarray analysis. Bioinformatics analysis revealed differential expression of the prolyl 4-hydroxylase subunit alpha-1 (P4HA1) gene. We determined that P4HA1 expression was correlated with histological grade, the level of Ki67 and microvessel density (MVD) in human glioma specimens. Knockdown of P4HA1 inhibited the proliferation, migration and tube formation of GSCs in vitro. In vivo studies revealed that the downregulation of P4HA1 inhibited intracranial tumor growth, prolonged the overall survival time of xenograft mice and suppressed the neovascularization in brain tumors. Moreover, P4HA1 regulates the expression of vascular endothelial growth factor A (VEGF-A), especially an anti-angiogenic isoform-VEGF165b. Additionally, knockdown of P4HA1 inhibited the synthesis of collagen IV, and hence disrupted the structures of vascular basement membranes (BMs) in gliomas. Our study indicates that P4HA1 plays a pivotal role in the process of GSC-EC transdifferentiation and the structural formation of vascular BMs.

Highlights

Glioblastomas (GBMs) are the most aggressive brain tumors and account for 70% of the malignant primary brain tumors in adults [1]
We found that the prolyl 4-hydroxylase subunit alpha-1 (P4HA1) was overexpressed in high-grade gliomas, and that P4HA1 expression was correlated with tumor microvessel density (MVD)
IF-double staining showed the co-expression of human CD34 (hCD34) and luciferase in microvessels (Figure 1F). These results are supported by the results of previous studies [7, 8, 10], which suggested that CD133+ glioma stem cells (GSCs) could transdifferentiate into endothelial cells (ECs) in vitro under hypoxia but could form functional microvessels in vivo

Summary

Introduction

Glioblastomas (GBMs) are the most aggressive brain tumors and account for 70% of the malignant primary brain tumors in adults [1]. There are currently at least five known mechanisms of tumor neovascularization in GBMs: sprouting angiogenesis, vasculogenesis, vascular co-option, vascular mimicry (VM) and transdifferentiation of glioblastoma stem-like cells (GSCs) or GBM cells into endothelial cells (ECs) [4, 5]. The former three processes have been extensively described and are well recognized, and the latter two mechanisms are only beginning to be explored. The transdifferentiation mechanism may be suspected to be involved in the failure of anti-angiogenic therapy for glioma

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