The Role And Mechanism Of Calcium-sensing Receptor In Chemotherapy Resistance Of Tumor Cells

Chemotherapy is one of the major approaches in the comprehensive treatment of malignancies.However,along with the chemotherapeutic drug administration,cancer patients will develop drug resistance to the certain anti-tumor drugs and to other anti-tumor drugs that have different structures and mechanisms,which is also called multidrug resistance(MDR).Drug resistance is the main reason to cause treatment failure.The mechanisms of drug resistance remain unclear,which are complex and involving a variety of factors.Thus,the discovery of the new molecular markers and the underlying of the molecular mechanism in tumor drug resistance are very important for the improvement of tumor chemotherapy.It is well known that calcium ions are essential factors for the human body and influence various cellular activities.The calcium-sensing receptors(CaSR)belong to the C-protein family of the receptor-type superfamily G-protein couple receptors(GPCRs),and they are widely distributed in various cells,tissues,and organs.A large number of studies have indicated that the dysregulation of calcium-sensing receptors is involved in numerous diseases such as cancer.To investigate the expression and the function of calcium-sensing receptors in cancer drug-resistant cells and to explore the relationship between calcium-sensitive receptors and tumor chemoresistance and to elucidate molecular mechanisms,we used western-blot to detect the expression of CaSR in parental cancer cells and chemotherapy-resistant cancer cells.The expression of CaSR in lung cancer cisplatin-resistant cells was down-regulated by transient transfection of siRNA,and the transfection efficiency was confirmed by western-blot and qPCR.MTS assay was used to detect the sensitivity to chemotherapeutic drugs before and after siRNA transfection in cisplatin-resistant tumor cells.The clone formation ability of drug-resistant cancer cells was also measured by down-regulation of CaSR.And the mechanism of how CaSR influences chemotherapy-resistance was preliminarily explored.Our results demonstrated that the expression level of the calcium-sensing receptor in tumor drug-resistant cells was much higher than parental tumor cells.The down-regulation of CaSR in tumor drug-resistant cells made it more sensitive to chemotherapeutic drugs.Also,the down-regulation of CaSR influences the cell cycle-related proteins such as AKT,p-AKT,P62,and p27,which indicated that CaSR may contribute to the drug-resistance by mediating these proteins and signaling pathways.Taken together,all these data indicated that CaSR plays an important role in the formation of drug resistance in tumor cells.Targeted drugs for calcium-sensing receptors may be a promising way to improve the efficiency of current chemotherapy drugs.Our preliminary investigation on the function and mechanism of calcium-sensitive receptors in tumor chemotherapy resistance provided a new perspective for reversing the drug resistance of tumor cells in clinics and improving the therapeutic effects of chemotherapy drugs.