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Cleveland, OH, United States

Patel B.,Cleveland Clinic | Hirsch C.,Cleveland Clinic | Clemente M.,Cleveland Clinic | Sekeres M.,Cleveland Clinic | And 3 more authors.
International Journal of Hematology | Year: 2015

Whole exome next generation sequencing systematically applied as a discovery tool in myelodysplastic syndromes (MDS) has led to the identification of a large number of novel mutations. Despite hundreds of patients studied, mutational saturation has not been reached and it is expected that new driver mutations will be discovered in this very heterogeneous condition. Serial samples and deep sequencing of the identified alterations has allowed for a dynamic/chronologic analysis of clonal architecture and identification of a subset of ancestral and secondary molecular lesions. Chromosomal gains and losses have been incorporated into the mutational analyses because they can either cooperate with mutations or produce a functional phenocopy. In addition to the search for somatic defects in MDS, similar discovery studies have been also performed to identify germ line mutations/alterations. Clinical analysis showed applicability of multiplexed somatic mutational panels that would complement current pathomorphologic diagnosis, allow for subclassification of nosologic entities, and enhance predictive power of current prognostic algorithms. Overall, comprehensive genomic analysis in MDS has revealed a tremendous heterogeneity of somatic lesions and their combinations further enhanced by the heterogeneity of clonal architecture and chromosomal lesions. © 2015, The Japanese Society of Hematology.

Khan S.N.,Taussig Cancer Institute R40 | Jankowska A.M.,Taussig Cancer Institute R40 | Mahfouz R.,Taussig Cancer Institute R40 | Dunbar A.J.,Taussig Cancer Institute R40 | And 18 more authors.
Leukemia | Year: 2013

Polycomb repressive complex 2 (PRC2) is involved in trimethylation of histone H3 lysine 27 (H3K27), chromatin condensation and transcriptional repression. The silencing function of PRC2 complex is mostly attributed to its intrinsic activity for methylating H3K27. Unlike in B-cell lymphomas, enhancer of zeste homolog 2 (EZH2) mutations in myeloid malignancies are inactivating/hypomorphic. When we assessed the mutational status in myeloid malignancies (N=469 cases examined), we found EZH2 and EED/SUZ12 mutations in 8% and 3.3% of cases, respectively. In addition to mutant cases, reduced EZH2 expression was also found in 78% cases with hemizygous deletion (-7/del7q cases involving EZH2 locus) and 41% of cases with diploid chromosome 7, most interestingly cases with spliceosomal mutations (U2AF1/SRSF2 mutations; 63% of cases). EZH2 mutations were characterized by decreased H3K27 trimethylation and increased chromatin relaxation at specific gene loci accompanied by higher transcriptional activity. One of the major downstream target is HOX gene family, involved in the regulation of stem cell self-renewal. HOXA9 was found to be overexpressed in cases with decreased EZH2 expression either by EZH2/spliceosomal mutations or because of -7/del7q. In summary, our results suggest that loss of gene repression through a variety of mutations resulting in reduced H3K27 trimethylation may contribute to leukemogenesis. © 2013 Macmillan Publishers Limited.

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