The miR-19a/Cylindromatosis Axis Regulates Pituitary Adenoma Bone Invasion by Promoting Osteoclast Differentiation

Simple Summary In this study, we demonstrate that miR-19a promotes the progression of bone invasion of pituitary adenoma and reveal the specific mechanism. miR-19a is released from pituitary adenoma cells into the tumor microenvironment and enters the osteoclasts to exert its effects. miR-19a reduces cylindromatosis (CYLD) expression, thereby preventing the K63 deubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6). k63 ubiquitinated TRAF6 acts as a key downstream node of RANK and can activate downstream NF-kB and mitogen-activated protein kinase (MAPK) pathways to promote osteoclastogenesis. Through a combination of molecular biology and cytology, as well as in vivo experiments, we verified the specific mechanism by which miR-19a promotes bone invasion in pituitary tumors.Abstract Background: The presence of bone invasion in aggressive pituitary adenoma (PA) was found in our previous study, suggesting that PA cells may be involved in the process of osteoclastogenesis. miR-19a (as a key member of the miR-17-92 cluster) has been reported to activate the nuclear factor-kB (NF-kB) pathway and promote inflammation, which could be involved in the process of the bone invasion of pituitary adenoma. Methods: In this work, FISH was applied to detect miR-19a distribution in tissues from patients with PA. A model of bone invasion in PA was established, GH3 cells were transfected with miR-19a mimic, and the grade of osteoclastosis was detected by HE staining. qPCR was performed to determine the expression of miR-19a throughout the course of RANKL-induced osteoclastogenesis. After transfected with a miR-19a mimic, BMMs were treated with RANKL for the indicated time, and the osteoclast marker genes were detected by qPCR and Western Blot. Pit formation and F-actin ring assay were used to evaluate the function of osteoclast. The TargetScan database and GSEA were used to find the potential downstream of miR-19a, which was verified by Co-IP, Western Blot, and EMSA. Results: Here, we found that miR-19a expression levels were significantly correlated with the bone invasion of PA, both in clinical samples and animal models. The osteoclast formation prior to bone resorption was dramatically enhanced by miR-19, which was mediated by decreased cylindromatosis (CYLD) expression, increasing the K63 ubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6). Consequently, miR-19a promotes osteoclastogenesis by the activation of the downstream NF-kB and mitogen-activated protein kinase (MAPK) pathways. Conclusions: To summarize, the results of this study indicate that PA-derived miR-19a promotes osteoclastogenesis by inhibiting CYLD expression and enhancing the activation of the NF-kB and MAPK pathways.