Calcified pituitary adenomas: First comprehensive characterization of a distinct clinical entity driven by...

Calcification in pituitary adenomas is a rare phenomenon, observed in only 0.2% to 8% of imaging studies and 5.4% to 25% of histopathological analyses, which complicates diagnosis and surgical intervention, yet its molecular underpinnings remain largely unknown. In this study, we retrospectively analyzed 115 patients with calcified pituitary adenomas, focusing on 36 cases with radiologically visible calcifications that we classified into four distinct subtypes, and performed molecular profiling via single-cell RNA sequencing and transcriptome sequencing. Our results identified a unique tumor cell subpopulation in calcified samples, which was enriched in pathways related to metal ion response and extracellular matrix reorganization but not osteogenic differentiation. We pinpointed GNAQ as a key gene, with its expression significantly elevated in calcified tissues. Functional experiments demonstrated that overexpressing GNAQ in GH3 pituitary adenoma cells induced calcium overload through the IP3R/CaMKII pathway, leading to mitochondrial dysfunction, increased reactive oxygen species, apoptosis, and ultimately extracellular calcium salt deposition, as confirmed by Alizarin Red staining. The calcium channel blocker verapamil was found to partially mitigate GNAQ-induced cytotoxicity. Furthermore, in mouse xenograft models, GNAQ overexpression promoted calcification and suppressed tumor proliferation. Collectively, our findings establish GNAQ as a critical driver of pituitary adenoma calcification, unveiling a unique "GNAQ-IP3/Ca2 + -mitochondrial apoptosis-calcification" axis that is distinct from the classical osteogenic pathway seen in tumors like craniopharyngioma, thereby providing new insights into the pathogenesis and potential therapeutic targeting of this condition.