Acute monocytic leukemia with coexpression of minor BCR-ABL1 and PICALM-MLLT10 fusion genes along with overexpression of HOXA9

BCR-ABL-positive acute myeloid leukemia: a new entity? Analysis of clinical and molecular features

BCR-ABL-positive acute myeloid leukemia (AML) is a rare subtype of AML that is now included as a provisional entity in the 2016 revised WHO classification of myeloid malignancies. Since a clear distinction between de novo BCR-ABL+ AML and chronic myeloid leukemia (CML) blast crisis is challenging in many cases, the existence of de novo BCR-ABL+ AML has been a matter of debate for a long time. However, there is increasing evidence suggesting that BCR-ABL+ AML is in fact a distinct subgroup of AML. In this study, we analyzed all published cases since 1975 as well as cases from our institution in order to present common clinical and molecular features of this rare disease. Our analysis shows that BCR-ABL predominantly occurs in AML-NOS, CBF leukemia, and AML with myelodysplasia-related changes. The most common BCR-ABL transcripts (p190 and p210) are nearly equally distributed. Based on the analysis of published data, we provide a clinical algorithm for the initial differential diagnosis of BCR-ABL+ AML. The prognosis of BCR-ABL+ AML seems to depend on the cytogenetic and/or molecular background rather than on BCR-ABL itself. A therapy with tyrosine kinase inhibitors (TKIs) such as imatinib, dasatinib, or nilotinib is reasonable, but-due to a lack of systematic clinical data-their use cannot be routinely recommended in first-line therapy. Beyond first-line treatment of AML, the use of TKI remains an individual decision, both in combination with intensive chemotherapy and/or as a bridge to allogeneic stem cell transplantation. In each single case, potential benefits have to be weighed against potential risks.

Hox gene dysregulation in acute myeloid leukemia

ABSTRACT: 

In humans, class I homeobox genes (HOX genes) are distributed in four clusters. Upstream regulators include transcriptional activators and members of the CDX family of transcription factors. HOX genes encode proteins and need cofactor interactions, to increase their specificity and selectivity. HOX genes contribute to the organization and regulation of hematopoiesis by controlling the balance between proliferation and differentiation. Changes in HOX gene expression can be associated with chromosomal rearrangements generating fusion genes, such as those involving MLL and NUP98, or molecular defects, such as mutations in NPM1 and CEBPA for example. Several miRNAs are involved in the control of HOX gene expression and their expression correlates with HOX gene dysregulation. HOX genes dysregulation is a dominant mechanism of leukemic transformation. A better knowledge of their target genes and the mechanisms by which their dysregulated expression contributes to leukemogenesis could lead to the development of new drugs.

Translocation t(11;14) (q13;q32) and genomic imbalances in multi-ethnic multiple myeloma patients: a Malaysian study

More than 50% of myeloma cases have normal karyotypes under conventional cytogenetic analysis due to low mitotic activity and content of plasma cells in the bone marrow. We used a polymerase chain reaction (PCR)-based translocation detection assay to detect BCL1/JH t(11;14) (q13;q32) in 105 myeloma patients, and randomly selected 8 translocation positive samples for array comparative genomic hybridization (aCGH) analysis. Our findings revealed 14.3% of myeloma samples were positive for BCL1/JH t(11;14) (q13;q32) translocation (n=15 of 105). We found no significant correlation between this translocation with age (P=0.420), gender (P=0.317), ethnicity (P=0.066) or new/relapsed status of multiple myeloma (P=0.412) at 95% confidence interval level by χ²test. In addition, aCGH results showed genomic imbalances in all samples analyzed. Frequent chromosomal gains were identified at regions 1q, 2q, 3p, 3q, 4p, 4q, 5q, 7q, 9q, 11q, 13q, 15q, 21q, 22q and Xq, while chromosomal losses were detected at 4q and 14q. Copy number variations at genetic loci that contain NAMPT, IVNS1ABP and STK17B genes are new findings that have not previously been reported in myeloma patients. Besides fluorescence in situ hybridization, PCR is another rapid, sensitive and simple technique that can be used for detecting BCL1/JH t(11;14)(q13;q32) translocation in multiple myeloma patients. Genes located in the chromosomal aberration regions in our study, such as NAMPT, IVNS1ABP, IRF2BP2, PICALM, STAT1, STK17B, FBXL5, ACSL1, LAMP2, SAMSN1 and ATP8B4 might be potential prognostic markers and therapeutic targets in the treatment and management of multiple myeloma patients positive for BCL1/JH t(11;14) (q13;q32) translocation.

The vitamin D3/Hox-A10 pathway supports MafB function during the monocyte differentiation of human CD34+ hemopoietic progenitors

Although a considerable number of reports indicate an involvement of the Hox-A10 gene in the molecular control of hemopoiesis, the conclusions of such studies are quite controversial given that they support, in some cases, a role in the stimulation of stem cell self-renewal and myeloid progenitor expansion, whereas in others they implicate this transcription factor in the induction of monocyte-macrophage differentiation. To clarify this issue, we analyzed the biological effects and the transcriptome changes determined in human primary CD34(+) hemopoietic progenitors by retroviral transduction of a full-length Hox-A10 cDNA. The results obtained clearly indicated that this homeogene is an inducer of monocyte differentiation, at least partly acting through the up-regulation of the MafB gene, recently identified as the master regulator of such a maturation pathway. By using a combined approach based on computational analysis, EMSA experiments, and luciferase assays, we were able to demonstrate the presence of a Hox-A10-binding site in the promoter region of the MafB gene, which suggested the likely molecular mechanism underlying the observed effect. Stimulation of the same cells with the vitamin D(3) monocyte differentiation inducer resulted in a clear increase of Hox-A10 and MafB transcripts, indicating the existence of a precise transactivation cascade involving vitamin D(3) receptor, Hox-A10, and MafB transcription factors. Altogether, these data allow one to conclude that the vitamin D(3)/Hox-A10 pathway supports MafB function during the induction of monocyte differentiation.