The Functional Aspects And Signaling Mechanisms Of Lactate Receptor GPR81 In Tumor

Under the condition of sufficient or insufficient oxygen,tumor cells increase glucose uptake and accumulation of lactate,which is called metabolic reprogramming effect.To prevent acidosis,lactate is transported by monocarboxylate transporters to the extracellular space in tumor cells,making the tumor microenvironment acidic.This acidic environment is a kind of stress to most cells,but tumor cells have strong acid resistance ability,which can improve the immune evasion activity of tumor cells.In recent years,the G-protein-coupled receptor GPR81 has been identified as a lactate receptor and found to be widely expressed in a variety of tumors,but the functions and mechanisms of GPR81 sensing lactate in tumors are not very clear.Therefore,we investigated the lactate receptor GPR81,and uncovered the mysterious veil of its roles in tumor development with valuable clues and theoretical basis,and provide a new argument for breaking through the tumor acid barrier and tumor inhibition strategy.First of all,through big-data analysis,we found that the expression of GPR81 was related to the survival of breast cancer patients.Therefore,in this study,breast cancer cell lines MCF-7 and Bcap-37 were used as cell models,and breast epithelial cell line MCF-10A as control,to clarify the functions and mechanisms of GPR81 in tumor,and to explore whether GPR81 could be a valuable target in tumor control and treatment.In this study,it was found that GPR81 was variably expressed in breast cancer cells Bacp-37 and MCF-7.Lactate can promote the proliferation and migration of breast cancer cells MCF-7 and Bacp-37.In order to further probe the functions of GPR81 at cellular and animal level,GPR81overexpression and interference plasmids were constructed and lentivirus transfection was used to establish breast cancer cells MCF-7 and breast epithelial cells MCF-10A with overexpression of GPR81(OV-GPR81-MCF-7 and OV-GPR81-MCF-10A)and breast cancer cells Bacp-37 with interference of GPR81(sh GPR81-3-Bcap-37).In the stable cell lines experiment,it was found that GPR81 promoted the migration,proliferation and clone formation of breast cancer cells.The results of tumor-bearing experiment in nude mice showed that GPR81 had tumorigenicity in vivo.The signaling mechanisms of GPR81 was elucidated by pharmacological methods,Lactate/GPR81/G_i protein-MAPK-p-38/ERK1/2-NF-KB signal pathway mediated the proliferation of breast cancer cells.The transcriptome results of GPR81 overexpressed stable cell lines showed that there were 1378 differential genes,including 715 up-regulated genes and663 down-regulated genes.Differential genes were mainly enriched in biological processes and pathways related to cancer survival.In this study,through biological experimental studies combined with big-data analysis,we preliminarily determined that lactate receptor GPR81is a cancer-promoting factor and the possible mechanisms.Our results provide a new argument for breaking the acidic adaptability of tumors mediated by lactate receptor GPR81 and how to control tumor biological behavior in acidic pathological environment.