Cushing's Disease Pituitary Adenomas Suppress Pro-apoptotic Noxa to Evade Cell Death. (16th November 2020)

• Record Type: Journal Article
• Authors: Alvarez, Reinier; Mandal, Debjani; Ray-Chaudhury, Abhik; Edwards, Nancy A; Johnson, Kory; Elkahloun, Abdel; Wu, Weiwei; Chittiboina, Prashant
• Is Part Of: Neurosurgery. Volume 67(2010)Supplement 1
• Publication Date: 2020-11-16
• Subjects: Nervous system -- Surgery -- Periodicals; 617.48005
• DOI: 10.1093/neuros/nyaa447_824
• Languages: English
• ISSNs: 0148-396X

Abstract

Abstract: INTRODUCTION: Mechanisms underlying tumorigenesis in pituitary adenomas causing Cushing's disease (CD) remain unknown. Malignant and benign tumors in humans often have dysregulated apoptosis. Noxa is a BH3 proapoptotic protein frequently downregulated in malignant human tumors. Noxa gene (PMAIP1) expression is suppressed in non-functioning pituitary adenomas (NFPA) and gonadotrope adenomas, compared to autopsy derived normal pituitary gland. In surgery derived en-route normal pituitary gland during microadenoma resection, we found significant differences in gene expression compared to CD adenomas including in PMAIP1. Here, we describe our findings of PMAIP1 overexpression, and mechanism of escape from the pro-apoptotic effects of noxa in CD adenomas. METHODS: Surgically derived syngeneic pairs composed of adenoma and adjacent normal pituitary gland for Cushing's disease (n = 5), NFPA (n = 1), and a prolactinoma (n = 1) underwent pairwise RNAseq. Immunohistochemical (IHC) analysis of 12 surgically resected adenomas (10 CD, 1 NFPA, 1 GH) for noxa expression were interpreted by quantitative digital image analysis and by a neuropathologist. Primary cell cultures of 8 CD, 2 GH-secreting, and 1 NFPA that were surgically resected were used for in - vitro protein and functional assays. RESULTS: Noxa gene (PMAIP1) mRNA expression was elevated 4 fold in CD adenomas compared to adjacent normal pituitary.PMAIP1 gene expression was suppressed (1.15 fold decrease) in NFPA and prolactinoma. Despite elevated mRNA, noxa protein expression was suppressed in CD adenomas compared to normal gland but not in other tumor types. This suggested post-translational degradation of noxa. We then treated adenoma primary cell cultures with proteasomal inhibitors to modulate post-translational degradation of noxa. Bortezomib (5nM) and Orlistat (7.5uM) produced a robust increase in noxa protein expression in CD adenoma cells and increased apoptosis in CD tumor cells. CONCLUSION: We found surprising elevation of pro-apoptotic PMAIP1 gene expression in CD adenomas compared to adjacent normal gland. We also found evidence of proteasomal post-translational degradation of noxa in CD tumors. These findings suggest that inhibtion of the proteasomal machinery with targeted drugs may elevate noxa protein and induce apoptosis in CD adenomas.