Clinical, cytogenetic and molecular characteristics of 14 T-ALL patients carrying the TCR beta-HOXA rearrangement: a study of the Groupe Francophone de Cytogenetique Hematologique

Recently, we and others described a new chromosomal rearrangement, that is, inv( 7)( p15q34) and t( 7; 7)( p15; q34) involving the T-cell receptor beta ( TCR beta) ( 7q34) and the HOXA gene locus ( 7p15) in 5% of T-cell acute lymphoblastic leukemia ( T-ALL) patients leading to transcriptional activation of especially HOXA10. To further address the clinical, immunophenotypical and molecular genetic findings of this chromosomal aberration, we studied 330 additional T-ALLs. This revealed TCR beta-HOXA rearrangements in five additional patients, which brings the total to 14 cases in 424 patients ( 3.3%). Real-time quantitative PCR analysis for HOXA10 gene expression was performed in 170 T-ALL patients and detected HOXA10 overexpression in 25.2% of cases including all the cases with a TCR beta-HOXA rearrangement ( 8.2%). In contrast, expression of the short HOXA10 transcript, HOXA10b, was almost exclusively found in the TCR beta-HOXA rearranged cases, suggesting a specific role for the HOXA10b short transcript in TCR beta-HOXA-mediated oncogenesis. Other molecular and/or cytogenetic aberrations frequently found in subtypes of T-ALL ( SIL-TAL1, CALM-AF10, HOX11, HOX11L2) were not detected in the TCRb- HOXA rearranged cases except for deletion 9p21 and NOTCH1 activating mutations, which were present in 64 and 67%, respectively. In conclusion, this study defines TCR beta-HOXA rearranged T-ALLs as a distinct cytogenetic subgroup by clinical, immunophenotypical and molecular genetic characteristics.