Abstract 1993: Acidic tumor microenvironment stimulation of GPR4 alters cytoskeletal dynamics and migration of vascular endothelial cells

Abstract

Abstract The acidic tumor microenvironment results from aberrant vasculature, insufficient oxygen delivery and aerobic glycolysis of cancer cells. As cancer progresses, the acidic microenvironment can lead to structural changes of endothelial cells (ECs) resulting in increased vascular permeability which may increase metastasis. Extracellular acidification can activate cellular signaling molecules, including G-protein coupled receptor 4 (GPR4), which is prominently expressed in ECs. We have previously reported that acidic activation of GPR4 induces the transcription of several pro-inflammatory and ER-stress related genes in ECs. The purpose of the study is to identify the functional response of acidosis-induced GPR4 activity using Human Umbilical Vein Endothelial Cells (HUVECs) as a model system. The expression of GPR4 was overexpressed (HUVEC/GPR4) or knocked down (GPR4 shRNA) using several genetic constructs. HUVECs were treated with media buffered to pH 6.4 or to physiological pH 7.4. Permeability of a HUVEC cell monolayer was assessed by quantifying gap formation as one indicator. Cell migration was assessed through wound-healing assays. Cytoskeletal dynamics were also investigated using Rhodamine Phalloidin to investigate actin stress fiber formation and immunocytochemistry to investigate focal adhesion dynamics. Our results showed acidic pH induced GPR4 activation changed the cytoskeletal phenotype, decreased cellular migration, and proliferation in HUVECs compared to the physiological pH treatment. There was also a further increase in gap area of a HUVEC/GPR4 monolayer and formation of actin stress fibers in response to acidic conditions. Additionally, altering expression of phosphorylated paxillin and focal adhesion kinase were observed under acidosis/GPR4 mediated stress. In conclusion, the proton sensor GPR4 induces cytoskeletal variations, reduces cellular migration, and proliferation in response to an acidic tumor microenvironment. Citation Format: Elizabeth A. Krewson, Li V. Yang, Lixue Dong. Acidic tumor microenvironment stimulation of GPR4 alters cytoskeletal dynamics and migration of vascular endothelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1993. doi:10.1158/1538-7445.AM2017-1993