RNA sequencing of T-ALL (COG study)

The clinical and cytogenetic features associated with T-cell acute lymphoblastic leukemia (T-ALL) are not predictive of early treatment failure or relapse. We investigated 213 newly diagnosed patients who were treated in the Children''s Oncology Group (COG) T-ALL Studies 9404 and 0434 and identified a cluster cases characterized by increased expression of HOX9/10. In samples with >8-fold HOXA9/10 deregulation, the presence of specific molecular lesions were confirmed through a systematic review of cytogenetic databases, FISH and PCR testing. In cases with no identifiable lesions using the methods above, RNA sequencing was performed (Illumina and Ion Proton). Fifteen cases selected for RNA sequencing met three criteria: HOXA9/10 expression =8-fold above the median, sufficient RNA, and an incomplete or absent molecular explanation for each sample’s HOXA9/10 deregulation. Three cases were confirmed to have PICALM-AF10 fusions. Two additional AF10-R cases showed DDX3X-AF10 lesions, one of which harbored a novel CASK gene fragment in a complex CASK-DDX3X-AF10 translocation. Two cases harbored NUP98 fusions46 and one case each was identified for MLL-AF6, MLL-PICALM, HOXA10-(3’UTR)TRBC45, STAG2-LMO2, LOC338817-CCDC91. We could not identify fusion transcripts in 3 cases. Overall design: Identification of novel fusion transcripts in HOXA9/10-deregulated T-ALL