PO-003 Metformin restores nickel-reduced glutathione S-transferase Mu2 expression by promoter methylated alteration

Abstract

IntroductionGlutathione S-transferases M2 (GST-M2) is a family of inducible enzymes that are important in carcinogen detoxification. GST-M2 has been reported as a great potential tumour suppressor and low expression of GST-M2 has associated with promoter hypermethylation in lung cancer cells. Nickel compounds have been identified as human carcinogens. Our objective is to clarify the expression of GST-M2 in lung cells under nickel exposure. Moreover, we attempted to investigate the effects of the antidiabetic drug metformin on GST-M2 expression and lung cancer chemoprevention.Material and methodsGST-M2 mRNA level and transcription activity were measured by real-time PCR and reporter assay. CHIP assay, bisulfite sequencing and methylation specific PCR (MSP) and site-directed reporter assay were used to evaluate the effects of nickel and metformin co-treatments, including silencing of Sp1 by shRNA, on promoter epigenetic alteration in BEAS-2B cells.Results and discussionsGST-M2 mRNA level but not GST-M1 was significantly reduced in lung bronchial epithelial cells BEAS-2B and fibroblast WI-38 after nickel treatment. Metformin restored nickel-decreased GST-M2 mRNA expression and promoter activity in BEAS-2B cellsGST-M2 exhibited high frequency of promoter hypermethylation in nickel-exposure cells and metformin reversed. After nickel and metformin co-treatment, the methylation of specificity protein 1 (Sp1) was revealed binding to GST-M2 promoter and regulating gene transcription.ConclusionOur results demonstrated that metformin rescues nickel-inhibited GST-M2 expression via Sp1-binding and promoter methylated status alteration.