The Proton-Sensing G-Protein Coupled Receptor GPR4 Promotes Angiogenesis in Head and Neck Cancer

Abstract

Squamous cell carcinoma of the head and neck (SCCHN) is an aggressive disease with poor survival and is the sixth most common cancer worldwide. Gastroesophageal reflux is a common event in SCCHN patients. GPR4 is a proton-sensing G-protein coupled receptor, which can be activated by acidosis. The objective of this study was to explore the role of GPR4 in acid exposure and tumor angiogenesis in SCCHN. In this study, we confirmed that overexpressing GPR4 in SCCHN cells could increase the expression and secretion of IL6, IL8 and VEGFA at pH 5.9. This effect could be inhibited by SB203580 (a p38 inhibitor). Western blot analysis indicated that phosphorylation of p38 increased in GPR4 infected cells at pH 5.9, which could be inhibited by SB203580. In tube formation assay, HMEC-1 cells were incubated with conditioned medium (CM, pH 5.9, 6.5, 7.4) derived from control and GPR4 infected SCCHN cells. Tube length was significantly increased in HMEC-1 cells incubated with CM from GPR4 infected cells compared with control cells at pH5.9, which indicated the pro-angiogenic effect of GPR4 in acidic pH. The neutralizing antibodies of IL6, IL8 and VEGFA could inhibit tube formation of HMEC-1 cells. In vivo, the effect of GPR4 on angiogenesis was investigated with the chick chorioallantoic membrane (CAM) model. Control and GPR4 infected SCCHN cells were seeded onto the upper CAM surface (n = 5 in each group) and 5 μL DMEM/F12 (pH 5.9, 6.5, 7.4) was added to the surface of the cell every 24 h. Four days later, the upper CAM were harvested and the ratio of the vascular area to the CAM area was quantified using Image-Pro Plus 6.0 software. GPR4 infected cells could recruit more vascular than control cells at pH5.9. In conclusion, we suggested that GPR4 induces angiogenesis via GPR4-induced p38-mediated IL6, IL8 and VEGFA secretion at acidic extracellular pH in SCCHN.

Propranolol inhibits the proliferation, migration and tube formation of hemangioma cells through HIF-1α dependent mechanisms

“…Trypsinized hemangioma cells were harvested and resuspended (1×10 4 cells/100 µL medium), seeded into matrigel, then incubated at 37°C for 6 h. Tube structures were inspected under an inverted light microscope (200× magnification). The images were quantified using the Image-Pro Plus 6.0 software from Media Cybernetics (USA), as previously described ( 13 ). The quantified values are reported as the fold of control.…”

On a structured multiscale model for acid-mediated tumor invasion: The effects of adhesion and proliferation

“…nonlinear and possibly degenerate diffusion 7 by a slight abuse of definition we will call y an internal variable, which stresses out the fact that its dynamics is acting on the faster, subcellular scale 8 usually proton dynamics refers to their shuttling across the cell membrane by several transporters like NHE (Na + and H + exchanger), NDBCE (Na + dependent Cl-HCO 3 exchanger), MCTs (monocarboxylate transporters) and AE (Cl-HCO 3 anion exchanger), however there have also been investigated cell receptors -so-called proton sensing-which can be activated by acidosis, see e.g., [14,34,55] …”

Association between G‑protein coupled receptor 4 expression and microvessel density, clinicopathological characteristics and survival in hepatocellular carcinoma

“…Certain studies have demonstrated the role of GPR4 in the process of angiogenesis. Jing et al (9) revealed the promotion of angiogenesis by GPR4 in head and neck cancer, and Ren et al (10) reported that the overexpression of GPR4 may be required for angiogenesis in epithelial ovarian carcinomas. The expression of VEGFR2 and the angiogenic response to VEGF was found to be decreased in GPR4-deficient mice (11).…”

“…These findings suggest that GPR4 plays an important role in angiogenesis. Furthermore, certain studies have demonstrated the ability of GPR4 to induce angiogenesis in ovarian cancer and squamous cell carcinoma of the head and neck (SCCHN) (9,10). In ovarian cancer, the expression level of GPR4 is positively correlated with the microvessel density (MVD) of vascular ECs, which is not observed in benign ovarian tissues (10).…”

“…In ovarian cancer, the expression level of GPR4 is positively correlated with the microvessel density (MVD) of vascular ECs, which is not observed in benign ovarian tissues (10). In SCCHN, GPR4 promotes angiogenesis by inducing p38, which mediates secretion of vascular endothelial growth factor A, interleukin (IL)-6 and IL-8 (9). In mice with conditional loss of GPR4 expression, the expression level of vascular endothelial growth factor (VEGF) receptor 2 was decreased, with suppressed angiogenesis that remained low following re-expression of VEGF (11).…”