PhD Scientific Days 2021

CL_III_L: Clinical Medicine III. Lectures

Studies on Circular RNAs in Adrenocortical Tumors

Text of the abstract

Introduction. Most of the adrenocortical tumors are incidental clinical findings comprising 54% of benign adrenocortical adenomas (ACA) with excellent prognosis, rarely (0.7-2/million/year) however adrenocortical carcinoma (ACC) can be detected with a five-year survival of less than 30%. As the histological differentiation of ACA and ACC is difficult, molecular markers are of big clinicopathological relevance. Circular RNAs have been implicated as relevant factors in tumor pathogenesis, but their pathogenic relevance in adrenocortical tumors is unknown. There are also data supporting their utility as diagnostic markers of malignancy in various tumors. Based on their outstanding stability, circular RNAs can be investigated both in archived pathological samples and from blood.

Aim: to study the expression of circular RNAs in benign and malignant adrenocortical tumors.

Materials and methods. FFPE samples were selected 8-8-8 each from ACC, ACA, and normal adrenal cortex (NAC) and has been validated by pathologists. Total RNA isolation was performed with RecoverAll Total Nucleic Acid Kit for FFPE. Nanodrop 2000 and Qubit 4 were used to assess total RNA quantity. To maximize purification process for circular RNAs, we applied the RPAD method. For expression profiling of known and novel circular RNAs, MiSeq NGS platform was used. RNA-seq reads were mapped to Hg38 reference genome. CIRI2, CircExplorer2, AutoCirc were used for discovery of de novo circular RNAs.

Results. Circular RNAs were significantly differentially expressed between ACC versus ACA and ACC versus NAC cohorts. ACA versus NAC cohort did not differ significantly. Number of circular RNAs per sample by CircExplorer2 was 2700 out of which 1655 were known circular RNAs. CIRI2 found 2486 circular RNAs in total with 1679 known circular RNAs. AutoCirc total/known circular RNA ratio was 1346/578.

Conclusion. To the best of our knowledge, we are the first to describe the circular RNA patterns of adrenocortical tumors. We were also able to find novel circular RNAs in adrenocortical tissue and tumor. There is significant difference in expression of ACC versus ACA and ACC versus NAC cohorts. These expression changes need to be validated and bioinformatical analyses of novel circular RNAs for biological relevance are also warranted. These results might contribute to improved diagnosis of ACC.

University and Doctoral School

Semmelweis University, Károly Rácz Doctoral School of Clinical Medicine