Abstract 1820: Circular RNAs contribute to neuroblastoma pathogenesis

• Published in: Cancer research (Chicago, Ill.) Vol. 79; no. 13_Supplement; p. 1820
• Main Authors: Klironomos, Filippos, Danssmann, Clara, Naderi, Julian, Winkler, Annika, Luz, Uschi, Hundsdoerfer, Patrick, Eggert, Angelika, Toedling, Joern, Hertwig, Falk, Schulte, Johannes H., Fuchs, Steffen
• Format: Journal Article
• Language: English
• Published: 01-07-2019
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/1538-7445.AM2019-1820

Abstract
Circular RNAs (circRNAs), a noncoding RNA class originating from alternative splicing, are highly abundant in neural tissues and can regulate gene expression by binding to and inhibiting microRNAs and RNA-binding proteins. We explored whether circRNAs influence pathogenesis in neuroblastoma, the most common solid extracranial tumor of childhood. We performed whole-transcriptome sequencing of primary neuroblastoma samples to identify candidate circRNAs, which were validated in a neuroblastoma cell line panel. Overexpression and knockdown models were created to investigate their impact on cell viability, proliferation, apoptosis and differentiation. We identified 4,482 unique circRNA backsplicing junctions involving 2,080 genes in 69 neuroblastoma samples from all risk groups. Candidate circRNA expression did not correlate with host gene expression, indicating independent regulatory mechanisms. Principal component analysis was conducted using tumor circRNA expression. MYCN-amplified tumors clustered tightly together, demonstrating that variations in circRNA expression identify MYCN-amplified neuroblastomas as do gene expression patterns. Comparing our RNA sequencing data with other cancers and healthy fetal brain tissue revealed a circRNA subset specifically upregulated in neuroblastoma that included a circRNA derived from the ARID1A tumor suppressor gene. Cell fractionization and RNA FISH localized circARID1A to the cytoplasm, where it could interact with miRNAs and RNA-binding proteins for functional consequences. Specific circARID1A knockdown reduced cell numbers and viability, and induced neurite outgrowth and differentiation markers. Neither knockdown, nor overexpression of circARID1A influenced ARID1A mRNA and protein levels. Ongoing efforts applying bioinformatics methods to investigate the mechanism of action have identified several binding sites of microRNAs and RNA-binding proteins enriched in the circARID1A sequence. We demonstrate that circRNAs are expressed in neuroblastomas unrelated to host gene expression, and that their expression can be used to cluster MYCN-amplified tumors. As one in a set of upregulated circRNAs, circARID1A acts in a tumor-promoting manner in neuroblastoma cell lines independent of the host gene.
Citation Format: Filippos Klironomos, Clara Danssmann, Julian Naderi, Annika Winkler, Uschi Luz, Patrick Hundsdoerfer, Angelika Eggert, Joern Toedling, Falk Hertwig, Johannes H. Schulte, Steffen Fuchs. Circular RNAs contribute to neuroblastoma pathogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1820.