Macrophage-BMP5 Signaling Mediates Carcinogenesis in Oral Leukoplakia

Background and aims: Oral leukoplakia (OLK) is a potentially malignant disorder of the oral cavity, and the risk of malignant transformation correlates positively with the severity of epithelial dysplasia. The aim of this study was to investigate the critical role of the macrophage-BMP5 axis in OLK carcinogenesis.Methods: We established macrophage-depleted OLK model and the oral lesions were assessed through macroscopic and histopathological examination, immunostaining, and TUNEL staining. The target genes were identified through comparative analysis of RNA-sequencing data. The association between macrophage infiltration and BMP5 expression was examined by integrating experimental datasets with RNA-sequencing data. Leuk1 cells were transfected with lentiviral vectors to induce BMP5 overexpression and knockdown, and cellular proliferation, apoptosis were analyzed by standard in vitro functional assays. For in vivo functional validation, recombinant BMP5 protein was directly injected into the submucosa of the tongue in OLK model. For BMP5 function in macrophage axis, BMP5-specific siRNA was directly injected into the tongue submucosa of OLK model with macrophage depletion.Results: Macrophage depletion markedly inhibited OLK carcinogenesis in model, and was accompanied by a significant upregulation of BMP5. Furthermore, overexpression of BMP5 in the OLK model inhibited carcinogenic progression of oral lesions even when the macrophage population was intact. BMP5 up-regulation in the Leuk1 cells inhibited their proliferationn and induced apoptosis. Knocking down BMP5 in the tongue lesions of OLK model lacking macrophages reversed the protective effect associated with macrophage depletion.Conclusion: Our findings confirm that the macrophage-BMP5 axis is involved in the carcinogenesis of OLK.