Glioma cells enhance angiogenesis and inhibit endothelial cell apoptosis through the release of exosomes that contain long non-coding RNA CCAT2

Oncol Rep. 2017 Aug;38(2):785-798. doi: 10.3892/or.2017.5742. Epub 2017 Jun 22.

Abstract

Angiogenesis is a key event in the progression of gliomas. Exosomes, as signaling extracellular organelles, modulate the tumor microenvironment and promote angiogenesis and tumor progression. We previously demonstrated that long intergenic non-coding RNA CCAT2 (linc-CCAT2) was overexpressed in glioma tissues and functioned to promote glioma progression. Therefore, this study aimed to explore an underlying mechanism of glioma cell-affected angiogenesis. First, qRT-PCR was used to determine the expression level of linc-CCAT2 in 4 glioma cell lines and 293T cells, and the results revealed that the U87-MG cells exhibited the highest expression level. Subsequently, the pro-angiogenesis function of exosomes that were derived from negative control shRNA-treated U87-MG cells (ncU87-Exo) and linc-CCAT2 shRNA-treated U87-MG cells (shU87-Exo) was evaluated in vitro and in vivo. We found that ncU87-Exo, which was enriched in linc-CCAT2, could be taken up by HUVECs. ncU87-Exo improved the linc-CCAT2 expression level in HUVECs and more strongly promoted HUVEC migration, proliferation, tubular-like structure formation in vitro and arteriole formation in vivo as well as inhibited HUVEC apoptosis induced by hypoxia. Further mechanistic studies revealed that ncU87-Exo could upregulate VEGFA and TGFβ expression in HUVECs as well as promote Bcl-2 expression and inhibit Bax and caspase-3 expression. Finally, gain-/loss-of-function studies revealed that the overexpression of linc-CCAT2 in HUVECs activated VEGFA and TGFβ, promoted angiogenesis, promoted Bcl-2 expression and inhibited Bax and caspase-3 expression, thus decreasing apoptosis. Downregulation of linc-CCAT2 revealed the opposite effect. Thus, our results revealed a new exosome‑mediated mechanism by which glioma cells could promote angiogenesis through the transfer of linc-CCAT2 by exosomes to endothelial cells. Moreover, we suggest that exosomes and linc-CCAT2 are putative therapeutic targets in glioma.

MeSH terms

  • Apoptosis / genetics
  • Cell Line, Tumor
  • Cell Proliferation / genetics
  • Endothelial Cells / pathology
  • Exosomes / genetics
  • Gene Expression Regulation, Neoplastic
  • Glioma / genetics*
  • Glioma / pathology
  • Human Umbilical Vein Endothelial Cells
  • Humans
  • Neovascularization, Pathologic / genetics*
  • Neovascularization, Pathologic / pathology
  • RNA, Long Noncoding / antagonists & inhibitors
  • RNA, Long Noncoding / genetics*
  • RNA, Small Interfering / genetics
  • Tumor Microenvironment / genetics*

Substances

  • RNA, Long Noncoding
  • RNA, Small Interfering
  • long non-coding RNA CCAT2, human