Celastrol attenuates osteoclast-driven bone invasion in pituitary adenomas and suppresses HSP90AA1/TRAF6/NF-κB signaling.

Bone-invasive pituitary adenomas (BIPAs) are associated with skull base destruction, incomplete resection and postoperative recurrence, but pharmacological strategies targeting tumor-induced osteolysis remain limited. Here, we investigated whether celastrol, a bioactive triterpenoid from Tripterygium wilfordii, restrains BIPA progression by modulating macrophage-associated osteoclastogenesis. Clinical recurrence analysis, calvarial pituitary adenoma bone invasion models, micro-CT, histology, immunofluorescence, cell functional assays, osteoclast differentiation assays, RNA sequencing, molecular docking, biotin-celastrol pull-down, co-immunoprecipitation and ubiquitination assays were performed. BIPAs showed higher recurrence than non-BIPAs and were characterized by osteoclast activation at the tumor-bone interface. Celastrol suppressed pituitary adenoma cell proliferation, migration and invasion, reduced tumor growth and bone erosion in vivo, and inhibited macrophage-associated osteoclast activation. In vitro, celastrol blocked both RANKL- and pituitary adenoma-conditioned medium-induced osteoclast differentiation, accompanied by reduced p65 and ERK phosphorylation. Integrated target analysis and Bio-celastrol pull-down identified HSP90AA1 as a celastrol-interacting protein, with K546 contributing to this interaction and the anti-osteoclast differentiation effect of celastrol. Celastrol was also associated with reduced TRAF6 ubiquitination and NF-κB activation. These findings indicate that celastrol attenuates bone invasion by suppressing pituitary adenoma cell aggressiveness and osteoclastogenesis, with HSP90AA1/TRAF6/NF-κB signaling mainly involved in its effects on osteoclast-lineage cells.