Cooperative genetic defects in TLX3 rearranged pediatric T-ALL

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive neoplastic disorder, in which multiple genetic abnormalities cooperate in the malignant transformation of thymocytes. About 20% of pediatric T-ALL cases are characterized by TLX3 expression due to a cryptic translocation t(5; 14)(q35; q32). Although a number of collaborating genetic events have been identified in TLX3 rearranged T-ALL patients (NOTCH1 mutations, p15/p16 deletions, NUP214-ABL1 amplifications), further elucidation of additional genetic lesions could provide a better understanding of the pathogenesis of this specific T-ALL subtype. In this study, we used array-CGH to screen TLX3 rearranged T-ALL patients for new chromosomal imbalances. Array-CGH analysis revealed five recurrent genomic deletions in TLX3 rearranged T-ALL, including del(1)(p36.31), del(5)(q35), del(13)(q14.3), del(16)(q22.1) and del(19)(p13.2). From these, the cryptic deletion, del(5)(q35), was exclusively identified in about 25% of TLX3 rearranged T-ALL cases. In addition, 19 other genetic lesions were detected once in TLX3 rearranged T-ALL cases, including a cryptic WT1 deletion and a deletion covering the FBXW7 gene, an U3-ubiquitin ligase that mediates the degradation of NOTCH1, MYC, JUN and CyclinE. This study provides a genome-wide overview of copy number changes in TLX3 rearranged T-ALL and offers great new challenges for the identification of new target genes that may play a role in the pathogenesis of T-ALL.