Hypomethylation of let-7a-3 is associated with poor prognosis in myelodysplastic syndrome.

Abnormal methylation of let-7a-3 has been found in various cancers and may consequently affect their survival. In this study, real-time quantitative methylation specific PCR (RQ-MSP) was used to determine the unmethylation level of let-7a-3 in 95 patients with myelodysplastic syndrome (MDS). The hypomethylation of let-7a-3 promoter was detected in 22 of 95 (23.2%) patients with MDS compared to 4.2% (1/24) of controls (p= 0.0419). Moreover, the frequency of let-7a-3 hypomethylation was higher in older patients (≥70 years) than in younger patients (<70 years). No significant difference was observed in distribution of WHO, IPSS, and cytogenetic classification. However, hypomethylated patients had significantly shorter overall survival than those without hypomethylation (p= 0.007). Moreover both Kaplan-Meier and Multivariate Cox analyses confirmed that let-7a-3 hypomethylation was an independent prognostic risk factor in cohorts of MDS patients with lower-risk disease. Our study suggested that let-7a-3 hypomethylation may predict poor outcome in MDS.