Alteration of hMLH1 protein expression and promoter CpG island methylation of hMLH1 gene in eutopic endometria of women with endometriosis

Objective To study the hMLH1 protein expression and promoter CpG island methylation of hMLH1 gene in endometriosis(EMs).Methods Immunohistochemistry were used to detect the expression of hMLH1 protein of 52 cases(with 9,16,12,15 cases of Ⅰ,Ⅱ,Ⅲ,Ⅳ stage) with EMs and 30 cases healthy controls.Methylation specific polymerase chain reaction(MSP) were used to detect eutopic endometrium hMLH1 promoter CpG island methylation.Glandular cells and stromal cells in endometrial glandular of hMLH1 promoter CpG island methylation abnormalities with eutopic were separated,hMLH1 promoter methylation status of CpG islands in two types of cells were detected by MSP.Results In EMs group,1 stage Ⅲ case and 5 stage Ⅳ cases showed reduced expression of hMLH1 protein,and 3 stage Ⅳ cases showed hypermethylation of hMLH1 promoter CpG island,while the rest EMs cases and all the normal cases showed no aberrant of hMLH1.Stage Ⅳ EMs cases compared with stage Ⅰ,Ⅱ,Ⅲ and normal group,all P0.05.Expression of hMLH1 protein in the 3 cases which showed hypermethylation of hMLH1 promoter CpG island were all reduced,and promoter hypermethylation shows mainly in epithelial cells.Conclusions The expression of hMLH1 protein is decreased and hMLH1 promoter CpG island with some methylation is found in eutopic endometrial tissue of EMs patients,and mainly in glandular cells.hMLH1 abnormalities maybe related with pathogenesis of severe EMs.