Metformin Reverses Cisplatin Resistance In Ovarian Cancer Through The Downregulation Of IL-6

Background and objectivesOvarian cancer is a malignant gynecological tumor associated with the highest mortality rate among all gynecological cancers in women.Resistance to platinum-based therapy is one of the main causes of poor prognosis for ovarian cancer patients.Metformin,as a first-line drug for the treatment of type ? diabetes,has been determined that there is an association between metformin use and enhanced overall survival in ovarian cancer patients.Because resistance to platinum is the main reason for the poor prognosis of this disease,determining whether metformin alters cisplatin resistance in ovarian cancer and exploring the relevant mechanisms is a major focus in this research.Interleukin-6(IL-6)is one of the vital cytokines in the tumor microenvironment.The high expression of IL-6 in the serum and ascites of ovarian cancer patients was associated with a poor prognosis.While,whether IL-6 is the promotion factor for the establishment of cisplatin resistance in ovarian cancer still uncertain,and whether metformin could affect the expression of IL-6 to alter cisplatin resistance in ovarian cancer is worth to explore.This article aims to verify the value of serum IL-6 levels in the diagnosis of ovarian cancer,investigates the role of IL-6 in cisplatin resistance as well as how metformin regulates this process.Materials and methodsKaplan-Meier survival analysis was used to testify the correlation between serum IL-6 expression and PFS in ovarian cancer patients which are based on the information from the TOC database.Logistic regression analysis of 20 pairs of ovarian cancer patients verified the positive relation of IL-6 and ovarian cancer.ROC curves were plotted to evaluate the diagnostic value of IL-6 for ovarian cancer.The IL-6 RNA interference cell(si-IL6-SKOV3/DDP)and stabilized IL-6 overexpressed cell(exp-IL6-SKOV3/DDP)were established after the lentiviral transfection.CCK-8 method was used to analyze cell proliferation.qRT-PCR,ELISA and Western Blot were used to detect the expression of IL-6 RNA and protein in cisplatin-resistant ovarian cancer cells.The expression of STAT3 and AKT signaling pathways were detected by Western Blot.The effect of metformin on IL-6 in vivo was demonstrated by the nude mouse xenograft model which is based on cisplatin-resistance ovarian cancer cells.Results1.According to the analysis of 1104 patients in the TOC database,the PFS of ovarian cancer patients with a high level of IL-6 was significantly shorter than those patients who showed a low level of IL-6.The case-control study shows that the serum levels of IL-6,CA125,VEGF in patients with ovarian cancer are significantly higher than those in normal people.IL-6,CA125,VEGF are all considered as risk factors of ovarian cancer which has high value for diagnostic.2.The expression of IL-6 in the cisplatin-resistance ovarian cancer cell line(SKOV3/DDP)was higher than its corresponding non-resistance cell line(SKOV3)in RNA and protein level.The sensibility of cisplatin was significantly declined in SKOV3/DDP cells after the treatment of exogenous IL-6,while the knocked-down of IL-6 caused the opposite conclusion.3.After metformin treatment,the resistance of cisplatin was reversed in SKOV3/DDP cells as well as the expression of IL-6 was down-regulated.The effect of IL-6 on promoting cisplatin resistance in cisplatin resistance ovarian cancer cells could be reversed by metformin.While metformin's inhibitory effect on ovarian cancer cell proliferation was weakened in IL-6 overexpressed ovarian cancer cells.4.Metformin inhibited the phosphorylation of STAT3 and AKT in cisplatin-resistant ovarian cancer cell lines(SKOV3/DDP),reversed the promotion effect of IL-6.5.The treatment of metformin in the SKOV3/DDP cells xenograft retard the tumor growth and down-regulated the level of IL-6 both in tumor tissues and nude mice serum.ConclusionThe serum level of IL-6 in patients with ovarian cancer can be used as an independent predictor of ovarian cancer prognosis also considered as a value factor for the diagnostic of ovarian cancer.Metformin reversed cisplatin resistance in cisplatin-resistance ovarian cancer cells by down-regulating the IL-6.