Expression Status of Proton Sensing Receptor GPR68 in Various Breast Cancer Molecular Subtypes

Abstract

Background and aimBreast cancer has become the most diagnosed cancer and the leading cause of global cancer incidence in 2020. It is quite known that highly malignant and invasive cancers have disrupted metabolism that leads to the creation of an acidic milieu of the tumor microenvironment (TME). Among the acid sensing G protein‐coupled receptors is GPR68/OGR1. In this study, we aimed to investigate the expression of GPR68 in breast cancer patients and cell lines in order to understand its role in the breast cancer TME.Patients, Materials and MethodsIn silico tools such as TNMplot and UALCAN were used to assess the expression of GPR68 in breast cancer patients. The expression pattern was validated in fresh and formalin‐fixed paraffin‐embedded tissues obtained from breast cancer patients using qPCR and immunohistochemistry (IHC), respectively. Also, in silico tool EMBEL‐EBI was used to assess GPR68 expression in different breast cancer cell lines. Validation of GPR68 expression was done on the mRNA and protein levels using qPCR and immunofluorescence techniques in four different breast cancer cell lines (MCF‐7, MDA‐MB‐231, BT‐549 and SkBr3).ResultsGPR68 expression was found to be significantly increased in breast cancer patients using the in silico tools and upon validation using qPCR and IHC (figure 1). Additionally, upon classification according to molecular subtypes, the luminal subtype showed highest GPR68 expression followed by triple negative and HER2 enriched classes. Also, in silicoanalysis revealed that the triple negative breast cancer cell line MDA‐MB‐231 showed the highest expression of GPR68, followed by the luminal A, MCF‐7 and Her2+ SkBr3, and lastly BT‐549. Quantitative PCR and immunofluorescence were used to validate this pattern of expression (figure 2), where all four cell lines showed cytoplasmic and membranous expression indicating possible internalization of GPR68 receptor that might be due to its excessive activation.ConclusionGPR68 plays a critical role in the TME of breast cancer and its different molecular subtypes. Such a marker could be a potential diagnostic marker and therapeutic target in breast cancer.