Restoration of BRG1 inhibits proliferation and metastasis of lung cancer by regulating tumor suppressor miR-148b

BACKGROUND Brahma-related gene 1 (BRG1) has been implicated in a variety of biological processes, and it has been found to be mutated or silenced in numerous cancers, including lung cancer. Recent reports have proposed BRG1 as a tumor suppressor, but its roles in cell proliferation and metastasis remain unknown. miR-148b functions as a tumor suppressor in non-small-cell lung cancer. However, the mechanism responsible for the downregulation of miR-148b in lung cancer is still elusive. METHODS The expression of BRG1 and miR-148b was evaluated in lung cancer tissues and cells using quantitative real-time polymerase chain reaction. The effect of BRG1 on proliferation of lung cancer cells was investigated using MTT assay. Transwell and Western blot assays were used to analyze the effect of BRG1 on invasion and epithelial-mesenchymal transition (EMT), respectively. The target of miR-148b was ascertained using luciferase reporter assay. Chromatin immunoprecipitation (ChIP) assay was performed to analyze the relation of BRG1 and the promoter region of miR-148b. RESULTS Restoration of BRG1 was demonstrated to inhibit cell proliferation, metastasis, and EMT in lung cancer cell lines. Furthermore, we found that miR-148b was positively regulated by BRG1. Additionally, we suggested that miR-148b suppressed cell proliferation, metastasis, and EMT in lung cancer cells by directly binging to 3'-untranslated region of WNT1, blocking the WNT1/β-catenin signaling pathway. ChIP assay showed that BRG1 bound to the promoter of miR-148b in A549 cells. CONCLUSION BRG1 positively regulated the expression of miR-148b, leading to inhibition of cell proliferation, metastasis, restraint of EMT, and inactivation of the WNT/β-catenin signaling pathway, which highlights potential therapeutic possibilities for the treatment of lung cancer.