Effects of DNA methyltransferase inhibitors (DNMTIs) on MDS-derived cell lines.

DNA methyltransferase inhibitors (DNMTIs), including decitabine (DAC) and azacitidine (AZA), have recently been highlighted for the treatment of high-risk myelodysplastic syndrome (MDS); however, their action mechanisms have not been clearly defined. Therefore, we investigated the effects of DNMTIs on MDS-derived cell lines in vitro. An MDS-derived cell line MDS92 and its blastic subline MDS-L and HL-60 were used. All three cell lines were sensitive to DNMTIs, but MDS-L was the most susceptible. DAC-induced cell death in MDS-L was preceded by DNA damage-induced G2 arrest via a p53-independent pathway. AZA did not influence the pattern of cell cycle, although it induced DNA damage response. The IC(50) of DAC or AZA on MDS-L cells was associated with the dose inducing the maximal hypomethylation in long interspersed nuclear elements-1 (LINE-1) methylation assay. AZA suppressed the level of methylation in a time-dependent manner (days 4, 7, and 10), whereas DAC maintained the level of methylation from day 4 to 11. The protein expression of DNMT1 and DNMT3a decreased with the suppression of growth and methylation. We conclude that this study provides in vitro models for understanding the effects of DNMTIs on cell growth and gene regulation, including differences in the possible action mechanism of DAC and AZA.

Validation of the revised 2008 WHO diagnostic criteria in 75 suspected cases of myeloproliferative neoplasm.

The objective of this study was to validate the recently revised 2008 WHO diagnostic criteria of myeloproliferative neoplasms (MPN) together with the analysis of correlation of JAK2 (Janus kinase 2)-V617F mutant allele burden with clinical/laboratory findings on each patient. We made a diagnosis of 75 suspected MPN patients based on both diagnostic criteria of the 2001 WHO classification and the revised 2008 WHO classification, and found that both criteria show a quite similar diagnostic power except for two patients (idiopathic erythrocytosis (IE) and thrombocytosis) who were diagnosed as essential thrombocythemia by the 2008 WHO criteria. From JAK2-V617F analysis, hemoglobin and hematocrit values were significantly higher and platelet count was lower in JAK2-V617F high allele burden group than JAK2-V617F middle allele burden group. Mutant allele burden of polycythemia vera (PV) group was higher than that of essential thrombocythemia group. Therefore, the amount of mutant allele seemed to define the disease phenotypes. We further found a PV case presenting a rare type of JAK2-exon12 mutation. In contrast, IE presented a good prognosis unlike MPN. Hereafter, the 2008 WHO criteria with JAK2 gene analysis are useful for precise diagnosis of MPN and the patients with erythrocytosis.

DNA ploidy and cell cycle analyses in the bone marrow cells of patients with megaloblastic anemia using laser scanning cytometry.

BACKGROUND: Megaloblastic anemias are characterized by several hematopoietic cells with dysplastic nuclear morphology. The analyses of DNA ploidy and cell cycle of these cells are important to understand the property of such diseases. METHODS: As laser scanning cytometry (LSC) is a useful tool to evaluate the morphology of the cells fixed on the slide glass together with the quantitative analysis of the fluorescence information of each cell by rapid scanning of the specimens, the authors examined the DNA ploidy and cell cycle of six cases with megaloblastic anemia using LSC. RESULTS: Giant neutrophilic series such as giant metamyelocytes and giant band cells were found to have extraordinarily higher DNA ploidy, while hypersegmented neutrophils represented the normal diploid pattern like normal neutrophils. As to megaloblasts, cell cycle analysis showed that the proportion of the cells in S phase was increased as compared with the case of normal erythroblasts. CONCLUSIONS: The present study clearly demonstrates the abnormal aspects of the hematopoietic cells with megaloblastic anemia from the viewpoint of the DNA ploidy and cell cycle analyzed by the use of LSC.