Abstract
BackgroundMicroRNA-200 (miR-200) suppresses the epithelial-mesenchymal transition of various cancer cells, including lung adenocarcinoma cells. We found that bone morphogenetic protein 4 (BMP4) was decreased in miR-200-overexpressing cells and epithelial-like lung cancer cells. In this study, we investigated the mechanism and role of BMP4 depletion by miR-200 in murine lung adenocarcinoma cells.MethodsBMP4 expression levels in murine lung cancer cells were measured by quantitative reverse transcription-PCR (qRT-PCR) and Western blotting. Promoter and 3′-untranslated region (UTR) luciferase reporter assays were performed to discover the mechanism of regulation of BMP4 by miR-200. Murine lung cancer cells were transfected with Bmp4 shRNAs, which were then injected into syngeneic mice to measure their tumorigenic and metastatic potential and cultured on Matrigel to study the influence of BMP4 on 3-D acinus formation.ResultsmiR-200 down-regulated BMP4 via direct targeting of the GATA4 and GATA6 transcription factors that stimulate Bmp4 transcription. BMP4 up-regulated JAG2, an upstream factor of miR-200; therefore, JAG2, miR-200, and BMP4 form a regulatory loop. Bmp4 knockdown suppressed cancer cell growth, migration, and invasion and inhibited tumorigenesis and metastasis of lung cancer cells when injected into syngeneic mice. In addition, BMP4 was required for normal acinus formation in Matrigel 3-D culture of murine lung cancer cells, which may be mediated by MYH10, a downstream target of BMP4.ConclusionBMP4 functions as a pro-tumorigenic factor in a murine lung cancer model, and its transcription is regulated by miR-200 and GATA4/6. Thus, we propose that BMP4 and its antagonists may be suitable therapeutic targets for the treatment of lung cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-015-0441-y) contains supplementary material, which is available to authorized users.
Highlights
MicroRNA-200 suppresses the epithelial-mesenchymal transition of various cancer cells, including lung adenocarcinoma cells
Among hundreds of genes downregulated by miR-200, we focused on bone morphogenetic protein 4 (BMP4), a member of the transforming growth factor β (TGF-β) superfamily, which is involved in early embryonic development and in cellular growth, Fig. 1 BMP4 is down-regulated in 344SQ_miR-200 cells. a The expression profile of immune-related genes in 344SQ_vector or 344SQ_miR-200 cells
ZEB1, a transcription suppressor of miR-200, enhanced Bmp4 expression in a low metastatic lung cancer cell line (393P), but miR-200 suppressed Bmp4 expression in 344SQ (Fig. 1c) and 531LN2 (Additional file 1: Figure S4), which was confirmed by Western blotting (Fig. 1d)
Summary
MicroRNA-200 (miR-200) suppresses the epithelial-mesenchymal transition of various cancer cells, including lung adenocarcinoma cells. We found that bone morphogenetic protein 4 (BMP4) was decreased in miR-200-overexpressing cells and epithelial-like lung cancer cells. We investigated the mechanism and role of BMP4 depletion by miR-200 in murine lung adenocarcinoma cells. Cancer cells from a primary tumor are disseminated throughout the body through sequential steps: local invasion, intravasation, survival in circulation, extravasation into distant organs, and colonization at secondary sites [3]. Local invasion begins when a subgroup of tumor cells undergoes epithelial-mesenchymal transition (EMT), characterized by the loss of cell-cell attachments and apical-basal polarity and the appearance of mesenchymal differentiation properties [3]. To prevent metastasis and cancer recurrence in patients, it is essential to identify the mechanisms triggering the EMT process.
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