TY - JOUR A1 - Smid, Marcel A1 - Wilting, Saskia A1 - Uhr, Katharina A1 - Rodriguez-Gonzalez, Germán A1 - de Weerd, Vanja A1 - Prager-Van der Smissen, Wendy A1 - van der Vlugt -Daane, Michelle A1 - van Galen, Anne A1 - Nik-Zainal, Serena A1 - Butler, Adam A1 - Martin, Sancha A1 - Davies, Helen A1 - Staaf, Johan A1 - van de Vijver, Marc A1 - Richardson, Andrea A1 - MacGrogan, Gaeten A1 - Salgado, Roberto A1 - van den Eynden, Gert A1 - Purdie, Colin A1 - Thompson, Alastair A1 - Caldas, Carlos A1 - Span, Paul A1 - Sweep, Fred A1 - Simpson, Peter A1 - Lakhani, Sunil A1 - van Laere, Steven A1 - Desmedt, Christine A1 - Paradiso, Angelo A1 - Eyfjord, Jorunn A1 - Broeks, Annegien A1 - Vincent-Solomon, Anne A1 - Futreal, Andrew A1 - Knappskog, Stian A1 - King, Tara A1 - Viari, Alain A1 - Børresen-Dale, Anne-Lise A1 - Stunnenberg, Hendrik A1 - Stratton, Mike A1 - Foekens, John A1 - Sieuwerts, Anieta A1 - Martens, John T1 - The circular RNome of primary breast cancer Y1 - 2019/01/28 JF - Genome Research JO - Genome Research DO - 10.1101/gr.238121.118 SP - gr.238121.118 UR - http://genome.cshlp.org/content/early/2019/01/28/gr.238121.118.abstract N2 - Circular RNAs (circRNAs) are a class of RNA that is under increasing scrutiny, although their functional roles are debated. We analyzed RNA-seq data of 348 primary breast cancers and developed a method to identify circRNAs that does not rely on unmapped reads or known splice-junctions. We identified 95,843 circRNAs, of which 20,441 were found recurrently. Of the circRNAs that match exon-boundaries of the same gene, 668 showed a poor or even negative (R<0.2) correlation with the expression level of the linear gene. In silico analysis showed only a minority (8.5%) of circRNAs could be explained by known splicing events. Both these observations suggest that specific regulatory processes for circRNAs exist. We confirmed the presence of circRNAs of CNOT2, CREBBP and RERE in an independent pool of primary breast cancers. We identified circRNA profiles associated with subgroups of breast cancers and with biological and clinical features such as amount of tumor lymphocytic infiltrate and proliferation index. siRNA-mediated knockdown of circCNOT2 was shown to significantly reduce viability of breast cancer cell lines MCF-7 and BT-474, further underlining the biological relevance of circRNAs. Furthermore, we found that circular and not linear CNOT2 levels are predictive for progression-free survival time to aromatase inhibitor (AI) therapy in advanced breast cancer patients and found that circCNOT2 is detectable in cell-free RNA from plasma. We showed that circRNAs are abundantly present, show characteristics of being specifically regulated, are associated with clinical and biological properties, and thus are relevant in breast cancer. ER -