Up-regulation of miR-335 predicts a favorable prognosis in esophageal squamous cell carcinoma

Introduction: MicroRNAs (miRNAs) are noncoding RNAs that regulate multiple cellular processes during cancer progression. MiR-335 has recently been identified to be involved in tumorigenesis of several cancers such as ovarian cancer and gastric cancer. However, the regulation of miR-335 in esophageal squamous cell carcinoma (ESCC) has not been reported yet. Methods: Expression of miR-335 in tumor and their normal matched tissues was determined by quantitative real-time PCR in 67 ESCC patients and its association with overall survival of patients was analyzed by statistical analysis. Results: The expression level of miR-335 was reduced in malignant tissue samples in comparison to normal matched tissue (P < 0.05). It was also proved that miR-335 expression was associated with ESCC histological grade, lymph node metastasis, tumor stage and clinical stage (P < 0.05). In addition, the Kaplan-Meier survival curves revealed that low miR-335 expression was associated with poor prognosis in ESCC patients. Multivariate analysis showed that miR-335 expression was an independent prognostic marker of overall survival of ESCC patients. Conclusions: The study proves for the first time that miR-335 is down regulated in a majority of ESCC patients. Our results indicate that miR-335 expression is an independent prognostic factor for patients with esophageal cancer, which might be a potential valuable biomarker for ESCC.