miR-135b reverses chemoresistance of non-small cell lung cancer cells by downregulation of FZD1

Background: Non-small cell lung cancer (NSCLC) chemoresistance usually limits the clinical efficacy of chemotherapeutic approaches. However, few reports have revealed the regulation of miR-135b and Frizzled-1 (FZD1) involved in NSCLC chemoresistance. Methods: To identify the mechanism of miR-135b and FZD1 in NSCLC chemoresistance and to observe their biological functions, we detected the expression levels of miR-135b and FZD1 by conducting quantitative real-time polymerase chain reaction (RT-qPCR) and modified the expressions of miR-135b and FZD1 by transiently transfecting cells with miR-135b mimics or FZD1-siRNA. The 3'-untranslated region (3'-UTR) of FZD1 combined with miR-135b was verified through dual-luciferase reporter assay. Results: Compared with that in A549 parental cell lines, the miR-135b expression in drug-resistant lung cancer cell lines (A549/DDP) was decreased and their FZD1 expression was increased. The increased miR135b expression and silenced FZD1 expression enhanced the sensitivity of resistant cells to cisplatin treatment. The high expression of miR-135b in A549/DDP cells remarkably decreased the mRNA levels of FZD1. FZD1 was further identified as the functional downstream target of miR-135b by directly targeting the 3'-UTR of FZD1. Conclusion: The amplification of miR-135b suppressed NSCLC chemoresistance by directly mediating the FZD1 downregulation. (C) 2016 Elsevier Masson SAS. All rights reserved.