Combined Downregulation of MicroRNA-133a and MicroRNA-133b Predicts Chemosensitivity of Patients with Esophageal Squamous Cell Carcinoma Undergoing Paclitaxel-based Chemotherapy

microRNA-133a (miR-133a) and miR-133b, located on chromosome 18 in the same bicistronic unit, have been commonly identified as being downregulated in esophageal squamous cell carcinoma (ESCC). The aim of this study was to investigate the correlation of miR-133a/b expression with efficacy of paclitaxel-based chemotherapy and clinical outcome of ESCC patients. miR-133a expression and miR-133b expression were examined in 100 newly diagnosed ESCC patients prior to treatment by quantitative real-time PCR. Then, the patients received four cycles of paclitaxel-based chemotherapy, the short-term treatment efficacy was evaluated, and a 3-year follow-up was performed. Expression levels of miR-133a and miR-133b were both significantly lower in ESCC tissues compared to adjacent noncancerous tissues (both P < 0.001). In addition, combined miR-133a/b downregulation was found to be closely correlated with advanced tumor stage (P = 0.02) and poor differentiation (P = 0.01). Moreover, the response rate of ESCC patients to paclitaxel-based chemotherapy was significantly higher in combined miR-133a/b downregulation group compared with other groups (P = 0.02). Furthermore, univariate and multivariate Cox analyses revealed that tumor stage and combined expression of miR-133a/b were independent prognosis factors in ESCC patients. Our data offer the convincing evidence that combined expression of miR-133a and miR-133b may predict chemosensitivity of patients with ESCC undergoing paclitaxel-based chemotherapy, implying its importance in applying 'personalized cancer medicine' in the clinical treatment of ESCC. We also identified combined expression of miR-133a and miR-133b as an effective prognostic marker of this malignancy.