Myelodysplastic syndromes (MDS) are a group of hematopoietic stem cell disorders characterized by refractory cytopenias and susceptibility to leukemic transformation. On a subset of MDS patients with deletion of the long arm of chromosome5 (del(5q)), lenalidomide exerts hematological and cytogenetic effects, but the underlying pharmacological mechanisms are not fully understood. In this study, we have investigated the in vitro effects of lenalidomide on an MDS-derived cell line, MDS-L, which carries del(5q) and complex chromosome abnormalities. We found that the growth of MDS-L cells was specifically suppressed mainly by apoptosis, and in addition, multinucleated cells were frequently formed and finally died out in the presence of lenalidomide. Time-lapse microscopic observation and the DNA ploidy analysis revealed that lenalidomide does not affect DNA synthesis but inhibits cytokinesis of MDS-L cells. The gene expression profile showed decreased expression of M phase-related genes such as non-muscle myosin heavy-chain 10, polo-like kinase 1, aurora kinase B, citron kinase and kinesin family member 20A(KIF20A). Interestingly, KIF20A is located at 5q31. These data contribute to the understanding of action mechanisms of lenalidomide on MDS with del(5q) and complex abnormalities.

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Chromosome 5 abnormalities, deletion of the long arm of chromosome 5 (del(5q)) or monosomy 5 (À5), arise in about 10% of myelodysplastic syndromes (MDS), either as the sole cytogenetic abnormality or as part of complicated karyotype, and has distinct clinical implications for MDS. However, the prognostic factors of MDS patients with chromosome 5 abnormalities are not determined yet. In this study, 183 Japanese MDS patients with chromosome 5 abnormalities were analyzed. Estimated incidence of del(5q) and 5q-syndrome among MDS patients was 8.4 and 1.3%, respectively. Significant shorter overall survival (OS) and leukemia-free survival (LFS) were observed in À5 patients than del(5q) patients. Among del(5q) patients, addition of monosomy 7 or complex karyotype with more than three abnormalities were significantly related to shorter OS.LFS of del(5q) patients was divided into two risk groups by international prognostic scoring system (IPSS): low/intermediate (Int)-1 and Int-2/high groups. LFS sorted by World Health Organization classification-based prognostic scoring system (WPSS) was also divided into two groups: very low/low/Int and high/very high, and WPSS was able to predict the outcome of del(5q) patients more clearly than IPSS.Together with additional cytogenetic data, WPSS might be useful for clinical decision making in MDS patients with del(5q).

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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.