Differential microRNA Expression in USP8-Mutated and Wild-Type Corticotroph Pituitary Tumors Reflect the Difference in Protein Ubiquitination Processes
Expression profiling by high throughput sequencing
Summary
Background: USP8 mutations are the most common driver changes in corticotroph pituitary tumors. They have direct effect on cells’ proteome through disturbance of ubiquitination process and also influence gene expression. The aim of this study was to compare microRNA profiles in USP8- mutated and wild-type tumors and determine the probable role of differential microRNA expression by integrative microRNA and mRNA analysis. Methods: Patients with Cushing’s disease (n = 28) and silent corticotroph tumors (n = 20) were included. USP8 mutations were identified with Sanger sequencing. MicroRNA and gene expression was determined with next-generation sequencing. Results: USP8-mutated patients with Cushing’s disease showed higher rate of clinical remission and trend towards lower tumor volume than wild-type patients. Comparison of microRNA profiles of USP8-mutated and wild-type tumors revealed 68 differentially expressed microRNAs. Their target genes were determined by in silico prediction and microRNA/mRNA correlation analysis. GeneSet Enrichment analysis of putative targets showed that the most significantly overrepresented genes are involved in protein ubiquitination-related processes. Only few microRNAs influence the expression of genes differentially expressed between USP8-mutated and wild-type tumors. Conclusions: Differences in microRNA expression in corticotropinomas stratified according to USP8 status reflect disturbed ubiquitination processes, but do not correspond to differences in gene expression between these tumors.
Overall design
Pituitary tumor samples were collected during transsphenoidal surgery and fixed in formalin for routine diagnostic procedures, including immunohistochemical and ultrastruc- tural evaluation. Archival formalin-fixed paraffin-embedded (FFPE) tissue samples from 48 patients, including 28 samples from patients with Cushing’s disease and 20 samples from patients with SCA, were included.
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