RF13 | PMON146 Molecular determinants of cavernous sinus invasion by pituitary adenomas: functional in vitro studies and in vivo investigations in a rat model of invasive pituitary tumorigenesis obtained by stereotactic pituitary GC cells injection

CONTEXT: Surgical removal is the primary treatment option for pituitary adenomas. However, pituitary surgery is frequently incomplete because of invasion of extrasellar cerebral structures. In particular, the vicinity with the carotid artery hinders the radical surgical excision of the adenoma portion invading the cavernous sinus. Our objective was to study the molecular bases of the cavernous sinus invasion by pituitary adenomas. METHODS: We obtained a unique tissue collection of 19 invasive pituitary adenomas with a sample from the intrasellar portion and a sample from the portion invading the cavernous sinus for each adenoma. We used RNA-sequencing to compare the gene expression patterns of the invading and intrasellar portions. The implication of one differentially expressed candidate gene in the invasive behavior was first analyzed in vitro using Transwell Assay to study the impact of its pharmacologic inhibition on cell migration and invasion. These experiments were conducted in murine lactosomatotroph GH3 cells and gonadotroph LbT2 cell. To further study the role of this gene on tumor growth and behavior in vivo, we elaborated a model of invasive pituitary adenomas by stereotactic injection of murine somatotroph GC cell into the lobes of the pituitary gland of female Wistar Furth rats. Twelve rats (10-12 week-old) received 20.000 GC cells in each pituitary lobe. After surgery, rats were monitored weekly, tumor development was assessed fortnightly by 3 successive 7Tesla MRI and analyzed by Horos software. Rats were sacrificed 7 weeks after GC cells injection. Six of the 12 rats were treated during this period with the pharmacological inhibitor of the candidate gene. RESULTS: RNA-sequencing identified 159 up-regulated genes and 11 down-regulated genes in the invasive adenoma portion. In vitro pharmacological inhibition of the candidate gene decreased cell migration and invasion in GH3 cells (p=0.0205 and p=0.0038) and LbT2 cell (p=0.0345 and p=0.0131). Amongst the 12 injected animals, 11 (92%) rats developed invasive pituitary tumors. Tumor growth was rapid, causing death from intracranial hypertensions before the theoretical end of the study protocol in 7 animals. Pharmacological inhibition tended to slow tumor growth from 30.3 mm(3)/week to 7.8 mm(3)/week (p=0.12) and decreased cumulative mortality (83% in untreated animals versus 33% in treated animals, p=0.08). CONCLUSION: We described the molecular signature associated with the invasive behavior of pituitary adenomas and identified a therapeutic target, which is related to pituitary cells migration and invasion in functional in vitro studies. Pharmacologic inhibition of this target tended to decrease tumor growth and mortality from intracranial hypertension in vivo, however larger numbers of animals are necessary to confirm this observation. Our original approach of orthotopic cell injection into rat pituitaries resulting in tumor development provides a new tool for molecular studies of pituitary tumorigenesis and for the screening of new therapeutic agents. Presentation: Sunday, June 12, 2022 1:06 p.m. - 1:11 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.