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.