Discovery and validation of Hsa-microRNA-3665 promoter methylation as a potential biomarker for the prognosis of esophageal squaous cell carcinoma.

BACKGROUND: Methylation of microRNA (miRNA) promoters associated with diseases is a common epigenetic mechanism in the development of various human cancers. However, its relationship with prognosis in esophageal squamous cell carcinoma (ESCC) remains unclear. This study aims to explore the association between the methylation level of has-miR-3665 promoter and prognosis in ESCC. METHODS: Human miRNA data were downloaded from miRbase, and we identified CpG islands of these human miRNAs by genomics browser analysis. MiRNA methylation levels were detected by methylation-specific high-resolution melting. Gene ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used to explore the molecular mechanism of hsa-miR-3665. Cox regression analysis was used to investigate prognostic factors. The overall survival rate was predicted by a nomogram. RESULTS: We found that 88 human miRNAs had promoter methylatio, of which 15 miRNAs were found to be epigenetically regulated in ESCC cells compared with their normal counterparts, including hsa-miR-3665. Meanwhile, hsa-miR-3665 expression was significantly lower in ESCC tumour tissue than in adjacent tissue (P = 0.03). GO and KEGG analyses demonstrated that the target genes are involved in protein transport, transcription regulator activity, MAPK and RAS signaling pathway. High hsa-miR-3665 promoter methylation levels were associated with a poor prognosis (HR = 3.89, 95% CI 1.11 ~ 13.55). Moreover, a nomogram incorporating the hsa-miR-3665 methylation level and clinical factors presented a good performance for predicting survival in the training and validation tests, with C-indices of 0.748 and 0.751, respectively. CONCLUSIONS: High hsa-miR-3665 promoter methylation levels may be a potential biomarker for the progression of ESCC.