title: Hypermethylation of let-7a-3 in epithelial ovarian cancer is associated with low insulin-like growth factor-II expression and favorable prognosis.
abstract: MicroRNAs (miRNA) are endogenous noncoding small RNAs that regulate the activity of mRNAs. Many miRNA genes, including let-7a-3, are located in CpG islands, suggesting possible epigenetic regulation of their expression. Promoter CpG island methylation of tumor suppressor genes is involved in cancer development and progression. Using real-time methylation-specific PCR and real-time reverse transcription-PCR, we analyzed DNA methylation in the let-7a-3 gene and miRNA expression of let-7a in 214 patients with epithelial ovarian cancer to assess the effect of let-7a-3 methylation on the expressions of let-7a as well as a possible target of let-7 regulation, insulin-like growth factor-II (IGF-II). The association of let-7a-3 methylation with patient survival outcomes was also evaluated. let-7a-3 methylation was detected in epithelial ovarian cancer, and the expression of let-7a was slightly affected by the methylation, but the effect was not substantial. The methylation of let-7a-3, however, was inversely correlated with IGF-II expression and positively with insulin-like growth factor binding protein-3 (IGFBP-3) expression. Patients with methylated let-7a-3 seemed to have reduced risk for death compared with those without, and the association was independent of patient age at surgery, tumor grade, disease stage, and IGF-II or IGFBP-3 expression. No association was found for let-7a-3 methylation and disease progression. These results suggest that the let-7a-3 gene is methylated and the methylation may affect IGF-II expression and the survival of ovarian cancer patients. Further investigation of the role of miRNAs and their regulation in cancer is warranted.
authors.affiliation: Department of Epidemiology and Public Health, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520-8034, USA.
authors.forename: Lingeng
authors.initials: L
authors.lastname: Lu
authors.forename: Dionyssios
authors.initials: D
authors.lastname: Katsaros
authors.forename: Irene A Rigault
authors.initials: IA
authors.lastname: de la Longrais
authors.forename: Olga
authors.initials: O
authors.lastname: Sochirca
authors.forename: Herbert
authors.initials: H
authors.lastname: Yu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019175:DNA Methylation; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics*; D008875:Middle Aged; D009375:Neoplasms, Glandular and Epithelial / Q000235:genetics* / Q000401:mortality; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000401:mortality; D011379:Prognosis; D012333:RNA, Messenger / Q000032:analysis
chemical_list: C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D035683:MicroRNAs; D012333:RNA, Messenger; C487931:mirnlet7 microRNA, human; D007335:Insulin-Like Growth Factor II