Interleukin-6–mediated epigenetic control of the VEGFR2 gene induces disorganized angiogenesis in human breast tumors

Abstract

<jats:p>Disorganized vessels in the tumor vasculature lead to impaired perfusion, resulting in reduced accessibility to immune cells and chemotherapeutic drugs. In the breast tumor–stroma interplay, paracrine factors such as interleukin-6 (IL-6) often facilitate disordered angiogenesis. We show here that epigenetic mechanisms regulate the cross-talk between IL-6 and vascular endothelial growth factor receptor 2 (VEGFR2) signaling pathways in myoepithelial (CD10+) and endothelial (CD31+, CD105+, CD146+, and CD133-) cells isolated from malignant and non-malignant tissues of clinically characterized human breast tumors. Tumor endothelial (Endo-T) cells in 3D cultures exhibited higher VEGFR2 expression levels, accelerated migration, invasion, and disorganized sprout formation in response to elevated IL-6 levels secreted by tumor myoepithelial (Epi-T) cells. Constitutively, compared with normal endothelial (Endo-N) cells, Endo-T cells differentially expressed DNA methyltransferase isoforms and had increased levels of IL-6 signaling intermediates such as IL-6R and signal transducer and activator of transcription 3 (STAT3). Upon IL-6 treatment, Endo-N and Endo-T cells displayed altered expression of the DNA methyltransferase 1 (DNMT1) isoform. Mechanistic studies revealed that IL-6 induced proteasomal degradation of DNMT1, but not of DNMT3A and DNMT3B and subsequently led to promoter hypomethylation and expression/activation of VEGFR2. IL-6 induced VEGFR2 up-regulation was inhibited by overexpression of DNMT1. Transfection of a dominant-negative STAT3 mutant, but not of STAT1, abrogated VEGFR2 expression. Our results indicate that in the breast tumor microenvironment, IL-6 secreted from myoepithelial cells influences DNMT1 stability, induces the expression of VEGFR2 in endothelial cells via a promoter methylation-dependent mechanism, and leads to disordered angiogenesis.</jats:p>

Heterotypic Tumor Spheroids in Agitation-Based Cultures: A Scaffold-Free Cell Model That Sustains Long-Term Survival of Endothelial Cells

“…Statistical analysis was performed by one-way ANOVA followed by a post hoc Tukey's multiple-comparison test; *p < 0.05; **p < 0.01; for each ratio, no statistical significance was found between conditions with and without VEGF supplementation at each cell ratio. cytokine secreted by tumor cells and fibroblasts, involved in angiogenesis (Nagasaki et al, 2014;Hegde et al, 2020). IL-6 appeared to be secreted by tumor cells and by fibroblasts and consumed by ECs (Supplementary Figure 8); although further studies will be required to conclude on the role of IL-6, its concentration was not correlated with EC maintenance.…”

Epigenetic underpinnings of inflammation: Connecting the dots between pulmonary diseases, lung cancer and COVID-19

“…IL-6 in turn, can epigenetically regulate other molecular factors. Its inhibition of methyltransferases DNMT1 [ 222 ] and DNMT3B [ 223 ] can possibly impact expression and activity of multiple genes. Not only a direct but even some indirect epigenetic regulation of IL-6 has been suggested.…”

Comprehensive analysis of regulation of DNA methyltransferase isoforms in human breast tumors

“…IL-6 via IL-6R/STAT3 pathway regulates DNMT1 expression in tumor cells (Huang et al 2016 ). Our recent studies in clinically characterized human breast tumor tissues, we demonstrated IL-6 induced proteasomal degradation of DNMT1 which led to promoter DNA hypomethylation of VEGFR2 promoter and subsequently to disorganized sprout formation in endothelial cells isolated from malignant part of breast tissue (Hegde et al 2020 ).…”