Circulating miRNA sequencing in serum of patients with Cushing's syndrome and related controls

Cushing's syndrome (CS) is a rare disease with high morbidity and mortality. Diagnosis and subtyping are complex and challenging. Circulating microRNAs were described to be useful as minimally invasive diagnostic markers. Our aim was to determine and compare the circulating microRNA expression profiles of patients with CS and controls. We included three groups of patients of the German Cushing's registry: A.) patients with florid adrenal dependent CS scheduled for adrenalectomy (CPA); B.) patients with florid pituitary dependent CS scheduled for surgery (CD); and C.) patients in whom CS had been ruled out (controls). Next-generation sequencing was performed in the 30 CS serum samples before and after curative surgery, respectively, and in 10 baseline samples of controls. No significant differential expression was observed between all the CS samples and controls by NGS as well as by QPCR. The sequencing of the preoperative samples revealed a significant differential expression of miR-182-5p (p=0.02) between CD and controls. The differential expression was validated by QPCR in the discovery cohort and in an independent validation cohort. MiR-96-5p, miR-146b-5p, miR-183-5p, miR-185-5p, miR-616-5p and miR-629-5p were found to be significantly upregulated in CPA samples in comparison to CD group of the preoperative group in NGS. However, similar upregulation pattern could not be observed by QPCR in the discovery and validation cohorts. Additionally, miR-96-5p and miR-185-5p were found to be modulated by dexamethasone in controls. Thus, our study reports miR-182-5p as a possible biomarker for CD, which has to be validated in a prospective cohort. Overall design: Circulating miRNA profile in patient serum samples for identifcation of potential biomarkers