Fluorescence in situ hybridization and conventional cytogenetics for the diagnosis of 11q23+/MLL+ translocation in leukaemia

Epigenetic balance ensures mechanistic control of MLL amplification and rearrangement

MLL/KMT2A amplifications and translocations are prevalent in infant, adult, and therapy-induced leukemia. However, the molecular contributor(s) to these alterations are unclear. Here, we demonstrate that histone H3 lysine 9 mono- and di-methylation (H3K9me1/2) balance at the MLL/KMT2A locus regulates these amplifications and rearrangements. This balance is controlled by the crosstalk between lysine demethylase KDM3B and methyltransferase G9a/EHMT2. KDM3B depletion increases H3K9me1/2 levels and reduces CTCF occupancy at the MLL/KMT2A locus, in turn promoting amplification and rearrangements. Depleting CTCF is also sufficient to generate these focal alterations. Furthermore, the chemotherapy doxorubicin (Dox), which associates with therapy-induced leukemia and promotes MLL/KMT2A amplifications and rearrangements, suppresses KDM3B and CTCF protein levels. KDM3B and CTCF overexpression rescues Dox-induced MLL/KMT2A alterations. G9a inhibition in human cells or mice also suppresses MLL/KMT2A events accompanying Dox treatment. Therefore, MLL/KMT2A amplifications and rearrangements are controlled by epigenetic regulators that are tractable drug targets, which has clinical implications.

t(4;11) translocation in hyperdiploid de novo adult acute myeloid leukemia: A case report

BACKGROUND

MLL gene rearrangement is a common genetic abnormality of acute myeloid leukemia (AML), which predicts poor prognosis and is important in clinical diagnosis. MLL rearrangement involves many chromosomes, among which, t(4;11) translocation is rare in AML. The present case was t(4;11) AML, accompanied by a hyperdiploid karyotype. Such cases have not been reported previously.

CASE SUMMARY

An adult male with self-reported symptoms of fatigue, febrility and hyperleukocytosis was diagnosed with AML by morphology and confirmed by immunophenotype analysis. Uncommonly, chromosomal and fluorescence in situ hybridization (FISH) analysis showed a hyperdiploid karyotype with t(4;11) translocation and MLL rearrangement, and a negative MLL–AF4 fusion gene result. The patient died of respiratory and circulatory failure 5 days after diagnosis.

CONCLUSION

t(4;11) AML with hyperdiploid karyotype has not been reported. In this case, t(4;11) was only detected by karyotype analysis and FISH, suggesting their importance in MLL rearrangement detection.

The Superiority of Allogeneic Hematopoietic Stem Cell Transplantation Over Chemotherapy Alone in the Treatment of Acute Myeloid Leukemia Patients with Mixed Lineage Leukemia (MLL) Rearrangements

BACKGROUND Acute myeloid leukemia (AML) patients with mixed lineage leukemia (MLL) gene rearrangements always had a very poor prognosis. In this study, we report the incidence of MLL rearrangements in AML patients using gene analysis, as well as the clinical significance and prognostic features of these rearrangements. MATERIAL AND METHODS This retrospective study took place from April 2008 to November 2011 in the People's Liberation Army General Hospital. A total 433 AML patients were screened by multiple nested reverse transcription polymerase chain reaction (RT-PCR) to determine the incidence of the 11 MLL gene rearrangements. There were 68 cases of MLL gene rearrangements, for a positive rate of 15.7%. A total of 24 patients underwent allogeneic hematopoietic stem cell transplantation (Allo-HSCT), and 34 patients received at least 4 cycles of chemotherapy. Ten patients were lost to follow-up. RESULTS The median follow-up was 29 months. The complete remission (CR) rate was 85.4%. The overall survival (OS) was 57.4±5.9 months for the Allo-HSCT group and 21.0±2.1 months for the chemotherapy group. The Allo-HSCT group had superior survival compared with the chemotherapy group (5-year OS: 59±17% vs. 13±8%, P<0.01; 5-year disease-free survival [DFS]: 65±10% vs. 40±16%, P>0.05). Multivariate analysis showed that transplantation, platelets >50×10^9/L at onset, and CR are associated with a better OS in MLL rearranged AML patients. Patients with thrombocytopenia and extramedullary involvement were prone to relapse. CONCLUSIONS Our results suggest that Allo-HSCT is superior to chemotherapy alone for treating MLL rearranged AML patients. Patients treated with Allo-HSCT have a better prognosis and a longer survival. CR is an independent prognostic factor for OS, and extramedullary involvement is an independent prognostic factor for DFS. MLL rearranged AML patients with thrombocytopenia at onset <50×10^9 had very bad OS and DFS.

Clinical significance of microRNA-34b expression in pediatric acute leukemia

The present study aimed to explore the function of miR‑34b promoter methylation in cell proliferation in children's acute leukemia. Quantitative PCR and methylation‑specific PCR were performed to measure the levels of miR‑34b and its promoter methylation in normal cells, eight leukemia cell lines as well as primary leukemic cells isolated from patients newly diagnosed with acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML) and mixed lymphocytic lymphoma. miR‑34b levels in leukemia cell lines and primary leukemic cells were significantly lower than those in normal cells. The miR‑34b promoter was found to be methylated in all leukemia cell lines, 24 of 31 ALL patients and 8 of 19 AML patients, but not in the 23 normal controls. miR‑34b expression and methylation of its promoter were not associated with most clinical parameters assessed; however, miR‑34b levels in prednisone‑sensitive ALL were significantly different from those in insensitive ALL. A cell counting kit‑8 assay showed that transfection of miR‑34b mimics into K562 cells inhibited their proliferation. Furthermore, treatment with the demethylating agent 5‑aza‑2‑deoxycytidine significantly enhanced miR‑34b expression levels and decreased the methylation status of its promoter in HL‑60 and K562 cells. In conclusion, the results of the present study indicated that in pediatric leukemia cells and leukemia cell lines, the expression of miR‑34b is inhibited by methylation of its promoter, which impairs the restraining effects of miR‑34b on cell proliferation. It was also indicated that the expression of miR‑34b in ALL patients may affect their response to early treatments.

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.

Screening by fluorescence in situ hybridization for MLL status at diagnosis in 239 unselected patients with acute myeloblastic leukemia

A large number of abnormalities involving the MLL gene have been associated with hematological malignancies, including acute myeloblastic leukemias (AML). Given the overall unfavorable prognosis of AML with an MLL abnormality, its reliable and accurate detection is needed for informed treatment decision. We therefore investigated the occurrence of MLL abnormalities in 239 unselected consecutive AML patients, using conventional cytogenetic and fluorescent in situ hybridization (FISH) analyses. FISH analysis for MLL was performed using a commercial dual-color probe. Of the 239 patients, 30 (12.6%) showed MLL abnormalities under FISH analysis, 10 (4.2%) showed a split signal indicating the disruption of the MLL gene by translocation or insertion, and 20 (8.4%) showed overrepresentation of the MLL gene without evidence of rearrangement. MLL abnormalities were more frequently found in AML-M5 and M4, mainly as rearrangements, and in AML-M2, mainly as overrepresentation. Our results are in agreement with those reported in other studies. All M2, M4, and M5 AML patients without known recurrent translocations, such as t(8;21) and inv(16), should be investigated by FISH with an MLL probe because it allows the detection of MLL rearrangement that would go undetected by conventional cytogenetics and because it has the ability of detecting multiple copies of the MLL gene in, for example, marker chromosomes and double minutes.