Abstract 2707: Targeted RNA sequencing reveals thus far unknown diagnostically relevant fusion partners confirming its diagnostic potential

Abstract

Abstract Introduction: The genomic landscape of hematological malignancies has been resolved mainly based on whole exome and whole genome sequencing, primarily targeting gene mutations. In addition to mutations, gene fusions have also been identified as therapeutic targets, impressively shown e.g. for BCR-ABL1 and ETV6-PDGFRB. Even though fluorescence in situ hybridization (FISH) is the current gold standard in fusion detection, it is by concept limited to the selected genes it is applied to. In contrast, targeted RNA sequencing is a valuable hypothesis-free approach to discover all possible fusion junctions in a single reaction. Aim: Explore the value of targeted RNA sequencing in a routine diagnostic work up. Patients and Methods: We sequenced 134 cases in parallel to our routine diagnostics workflow using chromosome banding analysis (CBA), FISH and real-time quantitative (RQ-PCR). Targeted RNA sequencing was performed on the NextSeq 500 using the TruSight RNA Fusion panel (Illumina, San Diego, CA) consisting of 7690 probes covering 507 genes known to be involved in gene fusions. Analysis was performed with the RNA-Seq Alignment App v1.2.0 (BaseSpace Sequence Hub) using Star for Alignment and Manta for gene fusion calling with default parameters (Illumina, San Diego, CA). Results: In 127 of 134 (95%) cases the results of FISH, subsequently confirmed with RT-PCR were also picked up by RNA Seq. This included diagnostically highly relevant fusions like BCR-ABL1 (n=8), KMT2A rearrangements (n=7), PML-RARA (n=4), and ETV6 and NPM1 rearrangements. In addition to the confirmation of orthogonal results, we were able to identify novel rare gene fusions, which we subsequently confirmed by RQ-PCR. This included immediately targetable fusions like TNIP1-PDGFRB and ETV6-EFL1, ETV6-FOXO1, IRF2PB1-RARA, RARA-SAE1). Conclusion: 1) In the vast majority of instances targeted RNA sequencing confirmed results obtained by FISH/RT-PCR and in addition discovered new rare gene fusions 2) Targetable genetic aberrations were identified, which were not identifiable by chromosome banding analysis but would now lead to more individualized treatment. 3) Thus, targeted RNA sequencing may be a valuable tool in routine diagnostics and for patients with rearrangements unresolved by standard techniques, also paving the way to precision medicine in a considerable number of patients. Citation Format: Niroshan Nadarajah, Manja Meggendorfer, Torsten Haferlach, Wolfgang Kern, Claudia Haferlach. Targeted RNA sequencing reveals thus far unknown diagnostically relevant fusion partners confirming its diagnostic potential [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2707. doi:10.1158/1538-7445.AM2017-2707