Clinicopathological significance of microRNA-9 and microRNA-34 methylation in non-small cell lung cancer

DNA methylation is a key epigenetic mechanism involved in lung carcinogenesis. MicroRNAs (miRs) regulate gene expression and cellular processes, and their aberrant methylation may contribute to dysregulation in non-small cell lung cancer (NSCLC). This retrospective study aimed to characterize the methylation profiles of the miR-9 (miR-9-2, miR-9-3) and miR-34 (miR-34a, miR-34b/c) families in NSCLC and to evaluate their clinicopathological significance. Promoter methylation status was assessed by methylation-specific PCR following bisulfite conversion of DNA isolated from 68 primary tumor specimens and 11 adjacent normal lung tissues. No promoter methylation of miR-9 or miR-34 family members was detected in normal tissues. Methylation of at least one miR-9 locus was observed in 50% of tumors, with miR-9-2 and miR-9-3 methylated in 41.2% and 38.2% of cases, respectively. miR-34 family methylation was detected in 69.1% of tumors, including miR-34a in 60.3% and miR-34b/c in 47.1%, with concurrent methylation of both miR-34 loci in 38.2%. miR-9-3 methylation was significantly associated with male sex (p = 0.046) and smaller tumor size (p = 0.035). miR-34a methylation was significantly associated with histological subtype (p = 0.041). Overall, the frequent of miR-9 and miR-34 family members supports their potential involvement in NSCLC epigenetic dysregulation and warrants further validation in larger, independent cohorts exploring their clinical relevance in personalized cancer management.