Diagnostic Validation of a Clinical Laboratory-Oriented Targeted RNA Sequencing System for Detecting Gene Fusions in Hematologic Malignancies.

Targeted RNA sequencing (RNA-seq) is a highly accurate method for sequencing transcripts of interest with a high resolution and throughput. However, RNA-seq has not been widely performed in clinical molecular laboratories because of the complexity of data processing and interpretation. We developed and validated a customized RNA-seq panel and data processing protocol for fusion detection using 4 analytical validation samples and 51 clinical samples, covering seven types of hematologic malignancies. Analytical validation showed that the results for target gene coverage and between- and within-run precision and linearity tests were reliable. Using clinical samples, RNA-seq based on filtering and prioritization strategies detected all 25 known fusions previously found by multiplex reverse transcriptase-PCR and fluorescence in situ hybridization. It also detected nine novel fusions. Known fusions detected by RNA-seq included two IGH rearrangements supported by expression analysis. Novel fusions included six that targeted just one partner gene. In addition, 18 disease- and drug resistance-associated transcript variants in ABL1, GATA2, IKZF1, JAK2, RUNX1, and WT1 were designated simultaneously. Expression analysis showed distinct clustering according to subtype and lineage. In conclusion, this study showed that our customized RNA-seq system had a reliable and stable performance for fusion detection, with enhanced diagnostic yield for hematologic malignancies in a clinical diagnostic setting.