CCAAT enhancer-binding protein (CEBP)transcription

PAX5 is the main target of somatic mutations in acute B lymphoblastic leukemia (B-ALL). We analyzed 153 adult and child B-ALL harboring karyotypic abnormalities at chromosome 9p, to determine the frequency and the nature of PAX5 alterations. We found PAX5 internal rearrangements in 21% of the cases. To isolate fusion partners, we used classic and innovative techniques (rolling circle amplification-rapid amplification of cDNA ends) and single nucleotide polymorphism-comparative genomic hybridization arrays. Recurrent and novel fusion partners were identified, including NCoR1, DACH2, GOLGA6, and TAOK1 genes showing the high variability of the partners. We noted that half the fusion genes can give rise to truncated PAX5 proteins. Furthermore, malignant cells carrying PAX5 fusion genes displayed a simple karyotype. These data strongly suggest that PAX5 fusion genes are early players in leukemogenesis.

To address these issues, we conducted a cytogenetic study of a large series of untreated symptomatic patients enrolled in a prospective, randomized, open-label clinical trial. The WM1 study took place in 101 centers in five countries and enrolled 339 patients with WM, 37 patients with non-MALT marginal zone lymphoma (MZL), and 38 patients with lymphoplasmacytic lymphoma, who were all randomly assigned to receive chlorambucil or fludarabine. 7Here we report our cytogenetic findings in 174 of the WM patients enrolled in this trial.

Pediatric acute myeloid leukemia (AML) is a rare disease whose prognosis is highly variable according to factors such as chromosomal abnormalities. Recurrent genomic rearrangements are detected in half of pediatric AML by karyotype. NUcleoPorin 98 (NUP98) gene is rearranged with 31 different fusion partner genes. These rearrangements are frequently undetected by conventional cytogenetics, as the NUP98 gene is located at the end of the chromosome 11 short arm (11p15). By screening a series of 574 pediatric AML, we detected a NUP98 rearrangement in 22 cases (3.8%), a frequency similar to CBFB-MYH11 fusion gene (4.0%). The most frequent NUP98 fusion gene partner is NSD1. These cases are homogeneous regarding their biological and clinical characteristics, and associated with bad prognosis only improved by bone marrow transplantation. We detailed the biological characteristics of these AML by exome sequencing which demonstrated few recurrent mutations (FLT3 ITD, WT1, CEBPA, NBPF14, BCR and ODF1). The analysis of the clonal structure in these cases suggests that the mutation order in the NUP98-rearranged pediatric AML begins with the NUP98 rearrangement leading to epigenetic dysregulations then followed by mutations of critical hematopoietic transcription factors and finally, activation of the FLT3 signaling pathway.

Adult and child B-cell progenitor acute lymphoblastic leukemia (BCP-ALL) differ in terms of incidence and prognosis. These disparities are mainly due to the molecular abnormalities associated with these two clinical entities. A genome-wide analysis using oligo SNP arrays recently demonstrated that PAX5 (paired-box domain 5) is the main target of somatic mutations in childhood BCP-ALL being altered in 38.9% of the cases. We report here the most extensive analysis of alterations of PAX5 coding sequence in 117 adult BCP-ALL patients in the unique clinical protocol GRAALL-2003/GRAAPH-2003. Our study demonstrates that PAX5 is mutated in 34% of adult BCP-ALL, mutations being partial or complete deletion, partial or complete amplification, point mutation or fusion gene. PAX5 alterations are heterogeneous consisting in complete loss in 17%, focal deletions in 10%, point mutations in 7% and translocations in 1% of the cases. PAX5 complete loss and PAX5 point mutations differ. PAX5 complete loss seems to be a secondary event and is significantly associated with BCR-ABL1 or TCF3-PBX1 fusion genes and a lower white blood cell count. Leukemia (2009Leukemia ( ) 23, 1989Leukemia ( -1998 doi:10.1038/leu.2009; published online 9 July 2009 Keywords: BCP-ALL; oncogenesis; BCR-ABL1; PAX5; TCF3-PBX1 Introduction PAX5 (paired-box domain 5) is the guardian of the B-cell identity as stated in a recent review. 1 This transcription factor belongs to the family of paired-box domain transcription factors. 2 Its expression is initiated during early stages of B-cell differentiation beginning at the pro-B stage, 3 and is turned off to allow terminal B-cell differentiation. 4 The Pax5 homozygous deletion in murine models leads to the trans-or de-differentiation of B-cells into several other hematopoietic cell lineages. [5][6][7] PAX5 is thus involved both in the maintenance of B-cell identity and in the control of terminal B-cell differentiation.Deregulations and mutations of key differentiation factors are frequently found in lymphomas and leukemias. Translocations associated with hematologic malignancies involving PAX5 exemplify PAX5 dual function. On one hand, the t(9;14)(p13;q32) translocation brings the potent enhancer of the IGH gene close to the PAX5 promoter leading to an aberrant expression of a normal PAX5 protein. 8,9 This translocation is recurrent in small plasmacytoid B-cell lymphocytic lymphomas and diffuse large B-cell lymphomas. 10 It emphasizes the importance of PAX5 downregulation during terminal B-cell differentiation. 9 On the other hand, PAX5 translocations have also been associated with a block of early B-cell differentiation because the PAX5-ETV6 chimeric protein, product of the dic(9;12)(p13;p13), is associated with B-cell progenitor acute lymphoblastic leukemia (BCP-ALL). 11 Additional PAX5 fusion partner genes have been identified as HIPK1 (chromosomal band 1p13), 12-14 LOC392027 (7p12.1), 15 AUTS2 (7q11.1), 13 POM121 (7q11), 14 ELN (7q11), 16 JAK2 (9p24), 14 SLCO1B3 (12p12), 15 DACH1 (13q21), 14 PML (15q24), 17 ZNF5...

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Thirty cases of acute myeloid leukaemia (AML) with MYST histone acetyltransferase 3 (MYST3) rearrangement were collected in a retrospective study from 14 centres in France and Belgium. The mean age at diagnosis was 59.4 years and 67% of the patients were females. Most cases (77%) were secondary to solid cancer (57%), haematological malignancy (35%) or both (8%), and appeared 25 months after the primary disease. Clinically, cutaneous localization and disseminated intravascular coagulation were present in 30 and 40% of the cases, respectively. AMLs were myelomonocytic (7%) or monocytic (93%), with erythrophagocytosis (75%) and cytoplasmic vacuoles (75%). Immunophenotype showed no particularity compared with monocytic leukaemia without MYST3 abnormality. Twenty-eight cases carried t(8;16)(p11;p13) with MYST3-CREBBP fusion, one case carried a variant t(8;22)(p11;q13) and one case carried a t(8;19)(p11;q13). Type I (MYST3 exon 16-CREBBP exon 3) was the most frequent MYST3-CREBBP fusion transcript (65%). MYST3 rearrangement was associated with a poor prognosis, as 50% of patients deceased during the first 10 months. All those particular clinical, cytologic, cytogenetic, molecular and prognostic characteristics of AML with MYST3 rearrangement may have allowed an individualization into the World Health Organization classification.

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