ABSTRACT
BACKGROUND: Oral submucous fibrosis (OSF) is a potentially malignant lesion characterized by epithelial-mesenchymal transition (EMT). Bone morphogenetic protein 4 (BMP4) promotes EMT in fibrotic diseases, but the underlying mechanisms and its potential role in OSF are unclear. This study investigates whether BMP4 plays a role in the pathogenesis of OSF and explores the underlying mechanisms. METHODS: The expression of BMP4 and the EMT proteins E-cadherin and vimentin was investigated in OSF specimens by immunohistochemical staining. Pearson's correlation analysis was conducted to explore the correlation between BMP4 and the EMT markers. Western blotting and RT-PCR assays were used to analyze the effect of arecoline (a known EMT-promoting pathogenic factor in OSF) on BMP4 and identify the transcription factor involved. Confocal microscopy was used to observe the intracellular sublocalization of the identified transcription factor, Yes-associated protein 1 (YAP1). Finally, siRNA silencing of BMP4 was used to determine its effect on YAP1 activation and arecoline-induced EMT. RESULTS: BMP4 is overexpressed in OSF and plays a role in EMT, as its expression correlates with the expression of E-cadherin and vimentin. Arecoline induces BMP4 expression via the activation of YAP1 (through its nuclear translocation). Furthermore, the YAP1/BMP4 mechanism is the main molecular event in arecoline-induced EMT, as knockdown of BMP4 expression affects expression of the EMT markers and inhibits extracellular matrix accumulation. CONCLUSIONS: Arecoline induces EMT in OSF via the YAP1/BMP4 pathway. Thus, BMP4 could be considered as a potential therapeutic target for the treatment of OSF.
