Project description:T-cell acute lymphoblastic leukemia (T-ALL) is mostly characterized by specific chromosomal abnormalities, some occurring in a mutually exclusive manner possibly delineating specific T-ALL subgroups. One subgroup, including MLL-rearranged, CALM-AF10 or inv(7)(p15q34) cases, is characterized by elevated expression of HOXA genes. Using a gene expression based clustering analysis of 67 T-ALL cases with recurrent molecular genetic abnormalities and 25 samples lacking apparent aberrations, we identified 5 new cases with elevated HOXA levels. Using array-CGH, a cryptic and recurrent deletion, del(9)(q34.11q34.13), was exclusively identified in 3 of these 5 cases. This deletion results in a conserved SET-NUP214 fusion product, that was also identified in the T-ALL cell line LOUCY. SET-NUP214 binds in the promoter regions of specific HOXA genes, where it may interact with CRM1 and DOT1L leading to the transcriptional activation of HOXA genes. Targeted inhibition of SET-NUP214 by siRNA abolished expression of HOXA genes, inhibited proliferation and induced differentiation in LOUCY but not in other T-ALL lines. We conclude that SET-NUP214 may contribute to the pathogenesis of T-ALL by enforcing T-cell differentiation arrest. We combined gene expression profiling and array-CGH analysis to detect a new and recurrent molecular cytogenetic abnormality in T-ALL patients that co-clustered with 5 well-defined HOXA-activated T-ALL samples. We describe the cloning of a recurrent SET-NUP214 fusion product in these samples, and identified a potential mechanism by which SET-NUP214 may activate the HOXA gene cluster as potential leukemogenic event in T-ALL. Experiment Overall Design: For 67 T-ALL patients having one of the major molecular cytogenetic abnormalities (i.e. TAL1 (n=24), LMO2 (n=9), HOXA (n=5), HOX11/TLX1 (n=7), and HOX11L2/TLX3 (n=22)), differentially expressed probesets were calculated from Affymetrix U133plus2.0 data based upon a Wilcoxon analysis and corrected for multiple testing for each probeset. Significant and differentially expressed probesets were obtained for the TAL1, HOX11 and HOX11L2 subgroups. No significant probesets were obtained for the HOXA subgroup or the LMO2 subgroup . As TAL1 and LMO2 both participate in the same transcriptional complex, activation of these genes may both lead to a highly similar expression profile. Combined analysis of TAL1 and LMO2 rearranged cases revealed significant and differentially expressed probesets that, as expected, almost entirely overlapped with the gene signature obtained for the TAL1-subgroup only. Next, we clustered 92 T-ALL cases, that besides the 67 cases as described above further included 25 T-ALL that lacked any of these recurrent abnormalities. Cluster analysis was performed based upon the top 25, 50 or 100 most significant probesets for the TAL1, TAL1/LMO2, HOX11 and HOX11L2 subgroups combined with 15 HOXA probesets identified by Soulier et al (2005)

Project description:A "Cartes d'Identite des Tumeurs" (CIT) project from the french Ligue Nationale Contre le Cancer (http://cit.ligue-cancer.net). 104 samples; Affymetrix U133A micro-arrays. Ninety two patients with T-ALL were diagnosed and treated at Saint-Louis hospital, Paris. Seven patients were studied at diagnosis and relapse (total 99 T-ALL samples). There were 56 children (median age 9 years old; range 1 to 16), and 36 adults (median age 27; range 17 to 66). Informed consent was obtained from the patients and/or relatives. T-ALL diagnosis was based on morphological and immunophenotypical criteria using flow cytometry and an extended monoclonal antibody panel. Using a combination of molecular cytogenetic and large-scale expression analysis in human T-ALL, we identified and characterized a new recurrent chromosomal translocation, targeting the major homeobox gene cluster HOXA and the TCRB locus. Specific quantitative PCR analysis showed that the expression of the whole HOXA gene cluster was dramatically dysregulated in the HOXA-rearranged cases, and also in MLL and CALM-AF10-related T-ALL cases, strongly suggesting that HOXA genes are oncogenic in these leukemias. Inclusion of HOXA-translocated cases in a general molecular portrait of 92 T-ALL based on large-scale expression analysis shows that this rearrangement defines a new homogeneous subgroup, which shares common biological networks with the TLX1 and TLX3-related cases. Since T-ALLs derive from T-cell progenitors, expression profiles of the distinct T-ALL subgroups were analyzed with respect to those of normal human thymic sub-populations. Inappropriate utilization or perturbation of specific molecular networks involved in thymic differentiation was detected. Moreover, we found a significant association between T-ALL oncogenic subgroups and ectopic expression of a limited set of genes, including several developmental genes, namely HOXA, TLX1, TLX3, NKX3-1, SIX6 and TFAP2C. These data strongly support the view that the abnormal expression of developmental genes, including the prototypical homeobox genes HOXA, is critical in T-ALL oncogenesis. Project Leader: FranC'ois Sigaux Institut Universitaire d'Hematologie Hopital Saint Louis, Paris, France Data submission: Fabien Petel

Dataset Information

Homo sapiens

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets