Role of Novel Gene Clusters in Pathogenesis of Adrenocorticotropic Hormone-Secreting Pituitary Neuroendocrine Tumor

Background: Cushing's disease (CD) is a rare disease caused by exposure to excessive amount of endogenous glucocorticoids due to adrenocorticotropic hormone-secreting pituitary neuroendocrine tumor (ACTH-PitNET). In this study, we investigated the expression of cell cycle regulator, deubiquitinating enzyme, transcription factor, and cell signaling genes, as well as the methylation of CDKN2A and USP8 genes, which are likely to play a role in the development of ACTH-PitNET. Methods: Formalin-fixed paraffin embedded (FFPE) pituitary tumor tissue samples from thirty-two patients with corticotroph adenomas and fifteen anterior pituitary tissue samples were investigated. Gene expression analysis of USP8, CABLES1, USP2, STAM2, VPS28, HDAC2, IL-6, SMARCA4, EGFR, WEE1, CDKN2A, CCND1, NR4A1, NEUROD1 and RIPK1 was performed by qRT-PCR, and methylation analysis was performed by MS-PCR. All data were analyzed using the IBM SPSS Statistics 21 program and Principal Component Analysis (PCA). Results: Expression of CABLES1, NR4A1, CCND1, NEUROD1, USP2 and WEE1 genes changed significantly between the patient group and the control group. There was a significant correlation between RIPK1, SMARCA4 and USP2 expression and pre-op cortisol levels; WEE1 expression and pre-op ACTH levels; CDKN2A expression and urinary cortisol levels; CABLES1, NEUROD1, SMARCA4 and STAM2 expression and post-op 48 h cortisol levels; CCND1 expression and adenoma size, and finally WEE1 expression and remission status. The CDKN2A gene was partially methylated, and the USP8 gene was fully unmethylated. Conclusion: We demonstrated that the altered expression of USP2, CABLES1, CDKN2A and WEE1 genes and ACTH-PitNET development were related. WEE1 can be used as a target gene for predicting remission of CD.