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

F. Chasseloup^a (Dr), E. Lefevre^b (Dr), N. Ladurelle^b (Ms), A. Dormoy^b (Dr), C. Janot^b (Dr), M. Hage^b (Dr), S. Viengchareun^c (Dr), P. Zizzari^d (Dr), P. Chanson^e (Prof), M. Buchfelder*^f (Prof), P. Kamenicky^e (Prof)

^a Université Paris Saclay, Inserm, Physiologie et Physiopathologie Endocriniennes, Le Kremlin Bicêtre Cedex, FRANCE ; ^b Université Paris Saclay, Inserm, Physiologie et Physiopathologie Endocriniennes, Le Kremlin Bicêtre, FRANCE ; ^c Université Paris Saclay, Inserm, Physiologie et Physiopathologie Endocriniennes, Le Kremlin Bicetre, FRANCE ; ^d Université de Bordeaux, INSERM U1215, Neurocentre Magendie, Bordeaux, FRANCE ; ^e Université Paris-Saclay, INSERM U1185 « Physiologie et Physiopathologie Endocriniennes », AP-HP, Hôpital de Bicêtre, Service d'Endocrinologie et des Maladies de la Reproduction, Centre de Référence des Maladies Rares de l’Hypophyse, Le Kremlin Bicêtre, FRANCE ; ^f Universitätsklinikum Erlangen, Erlangen, GERMANY

* michael.buchfelder@uk-erlangen.de

Context: Surgical removal is the primary treatment option for pituitary adenomas, however, pituitary surgery is frequently incomplete because of cavernous sinus invasion. Our objective was to study the molecular mechanisms of the cavernous sinus invasion by pituitary adenomas.

Methods: We obtained a 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 transcriptome analysis to compare the gene expression profiles of the invading and intrasellar portions. The implication of one up-regulated candidate gene in the invasive phenotype was first analyzed in vitro using Transwell Assay and both murine lactosomatotroph GH3 cells and gonadotroph LbT2 cells. Further, we studied tumor growth and behavior in vivo, by elaborating a model of invasive pituitary adenomas using stereotaxic injection of murine somatotroph GC cells into the pituitary gland of female Wistar Furth rats. After surgery, rats were monitored weekly, tumor development was assessed fortnightly by 3 successive 7Tesla MRIs. Half of the 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 portion of the adenomas. 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 cells (p=0.0345 and p=0.0131). Amongst the 26 injected animals, 23 (88%) rats developed invasive pituitary tumors. Tumor growth was rapid, causing death from intracranial hypertension. Pharmacological inhibition decreased per-protocol mortality in treated animals (p=0.06) and in a pilot experience, tended to slow tumor growth from 30.3 mm³/week to 7.8 mm³/week (p=0.12, n=12).

Conclusion: We described the molecular signature associated with the invasive behavior of pituitary adenomas and identified a therapeutic target related to pituitary cell migration and invasion in functional in vitro studies. Pharmacologic inhibition of this target tended to decrease tumor growth and mortality in vivo, further experiences are ongoing and will be presented at the congress. Our approach of orthotopic cell injection into rat pituitaries resulting in tumor development provides a new tool for pituitary tumorigenesis studies.

The author has declared no conflict of interest.