Downregulation of Death-Associated Protein Kinase 1 (DAPK1) in Chronic Lymphocytic Leukemia

Department of Molecular Virology, Immunology, and Medical Genetics, Human Cancer Genetics Program, The Comprehensive Cancer Center at The Ohio State University, Columbus, OH 43214, USA.
Cell (Impact Factor: 32.24). 07/2007; 129(5):879-90. DOI: 10.1016/j.cell.2007.03.043
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The heritability of B cell chronic lymphocytic leukemia (CLL) is relatively high; however, no predisposing mutation has been convincingly identified. We show that loss or reduced expression of death-associated protein kinase 1 (DAPK1) underlies cases of heritable predisposition to CLL and the majority of sporadic CLL. Epigenetic silencing of DAPK1 by promoter methylation occurs in almost all sporadic CLL cases. Furthermore, we defined a disease haplotype, which segregates with the CLL phenotype in a large family. DAPK1 expression of the CLL allele is downregulated by 75% in germline cells due to increased HOXB7 binding. In the blood cells from affected family members, promoter methylation results in additional loss of DAPK1 expression. Thus, reduced expression of DAPK1 can result from germline predisposition, as well as epigenetic or somatic events causing or contributing to the CLL phenotype.

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Available from: Yuko Yoshinaga, Jul 10, 2014
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    • "Therefore, other mechanisms leading to TP53 malfunction may exist. In this connection, methylation of DAPK1 gene, which triggers TP53 activation upon oncogenic cellular transformation, was first reported as a TSG methylated in CLL [20], and subsequently shown to contribute to CLL progression by blocking the apoptosis of leukemia cells [10]. Moreover, since the miR-34 family is a transcriptional target of TP53, its methylation might lead to the perturbation of the TP53 tumor suppression pathway. "
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    ABSTRACT: TP53 mutation/deletion is uncommon in chronic lymphocytic leukemia (CLL). We postulated that components of TP53-centered tumor suppressor network, miR-34b/c, in addition to DAPK1 and miR-34a might be inactivated by DNA hypermethylation. Moreover, we tested if miR-34b/c methylation might correlate with miR-203 or miR-124-1 methylation in CLL. miR-34b/c, miR-34a and DAPK1 methylation was studied in 11 normal controls, 7 CLL cell lines, and 78 diagnostic CLL samples by methylation-specific polymerase chain reaction. MEC-1 cells were treated with 5-Aza-2'-deoxycytidine for reversal of methylation-associated miRNA silencing. Tumor suppressor properties of miR-34b were demonstrated by over-expression of precursor miR-34b in MEC-1 cells. miR-34b/c promoter was unmethylated in normal controls, but completely methylated in 4 CLL cell lines. miR-34b/c expression inversely correlated with miR-34b/c methylation. Different MSP statuses of miR-34b/c, including complete methylation and complete unmethylation, were verified by quantitative bisulfite pyrosequencing. 5-Aza-2'-deoxycytidine treatment resulted in promoter demethylation and miR-34b re-expression in MEC1 cells. Moreover, over-expression of miR-34b resulted in inhibition of cellular proliferation and increased cell death. In primary CLL samples, miR-34a, miR-34b/c and DAPK1 methylation was detected in 2.6%, 17.9% and 34.6% of patients at diagnosis respectively. Furthermore, 39.7%, 3.8% and 2.6% patients had methylation of one, two or all three genes respectively. Overall, 46.2% patients had methylation of at least one of these three genes. Besides, miR-34b/c methylation was associated with methylation of miR-34a (P = 0.03) and miR-203 (P = 0.012) in CLL. Taken together, miR-34b/c is a tumor suppressor miRNA frequently methylated, and hence silenced in CLL. Together with DAPK1 methylation, miR-34b/c methylation is implicated in the disruption of the TP53-centered tumor suppressor network. Moreover, the association of miRNA methylation warrants further study.
    Journal of Translational Medicine 02/2014; 12(1):52. DOI:10.1186/1479-5876-12-52 · 3.93 Impact Factor
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    • "Methylation of multiple TSGs has involved in the dysregulation of signaling pathways in leukemia, lymphoma and myeloma, including cell cycle (CDKN2A/B), apoptosis (DAPK1/CDKN2A/APAF1), JAK/STAT signaling and WNT signaling; thereby indicating the importance of TSGs methylation in the pathogenesis of hematological cancers [4-6]. Of note, the DNA hypermethylation in TSGs, such as DAPK1, ID4, SFRP1, TWIST2 and ZAP70, has been identified to play a role in the pathogenesis or prognosis of chronic lymphocytic leukemia (CLL) [7-11]. "
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    ABSTRACT: The miR-9 family microRNAs have been identified as a tumor suppressor miRNA in cancers. We postulated that miR-9-1, miR-9-2 and miR-9-3 might be inactivated by DNA hypermethylation in chronic lymphocytic leukemia (CLL). Methylation of miR-9-1, miR-9-2 and miR-9-3 was studied in eight normal controls including normal bone marrow, buffy coat, and CD19-sorted peripheral blood B-cells from healthy individuals, seven CLL cell lines, and seventy-eight diagnostic CLL samples by methylation-specific polymerase chain reaction. The promoters of miR-9-3 and miR-9-1 were both unmethylated in normal controls, but methylated in five (71.4%) and one of seven CLL cell lines respectively. However, miR-9-2 promoter was methylated in normal controls including CD19 + ve B-cells, hence suggestive of a tissue-specific but not tumor-specific methylation, and thus not further studied. Different MSP statuses of miR-9-3, including complete methylation, partial methylation, and complete unmethylation, were verified by quantitative bisulfite methylation. 5-Aza-2[prime]-deoxycytidine treatment resulted in miR-9-3 promoter demethylation and re-expression of pri-miR-9-3 in I83-E95 and WAC3CD5+ cells, which were homozygously methylated for miR-9-3. Moreover, overexpression of miR-9 led to suppressed cell proliferation and enhanced apoptosis together with downregulation of NFkappaB1 in I83-E95 cells, supporting a tumor suppressor role of miR-9-3 in CLL. In primary CLL samples, miR-9-3 was detected in 17% and miR-9-1 methylation in none of the patients at diagnosis. Moreover, miR-9-3 methylation was associated with advanced Rai stage (>= stage 2) (P = 0.04). Of the miR-9 family, miR-9-3 is a tumor suppressor miRNA relatively frequently methylated, and hence silenced in CLL; whereas miR-9-1 methylation is rare in CLL. The role of miR-9-3 methylation in the constitutive activation of NFkappaB signaling pathway in CLL warrants further study.
    Molecular Cancer 12/2013; 12(1):173. DOI:10.1186/1476-4598-12-173 · 4.26 Impact Factor
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    • "Mapping eQTL target gene associations in tumors is more challenging than for other human traits or disease. Tumors acquire frequent genetic and epigenetic alterations, which can substantially affect gene expression (Raval et al. 2007; Smith et al. 2006) and consequently obscure the association between germline genetic polymorphisms and gene expression (Curtis et al. 2012). For these reasons, recent cancer studies also investigate the association between SNPs and an altered epigenetic landscape, such as promoter methylation, histone modifications or the expression of large intergenic non-coding RNAs (lincRNAs) that associate with chromatin-modifying complexes (Gibbs et al. 2010; Bell et al. 2011; Grossman et al. 2013; Ernst et al. 2011). "
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    ABSTRACT: Genome-wide association studies (GWAS) revealed genomic risk loci that potentially have an impact on disease and phenotypic traits. This extensive resource holds great promise in providing novel directions for personalized medicine, including disease risk prediction, prevention and targeted medication. One of the major challenges that researchers face on the path between the initial identification of an association and precision treatment of patients is the comprehension of the biological mechanisms that underlie these associations. Currently, the focus to solve these questions lies on the integrative analysis of system-wide data on global genome variation, gene expression, transcription factor binding, epigenetic profiles and chromatin conformation. The generation of this data mainly relies on next-generation sequencing. However, due to multiple recent developments, mass spectrometry-based proteomics now offers additional, by the GWAS field so far hardly recognized possibilities for the identification of functional genome variants and, in particular, for the identification and characterization of (differentially) bound protein complexes as well as physiological target genes. In this review, we introduce these proteomics advances and suggest how they might be integrated in post-GWAS workflows. We argue that the combination of highly complementary techniques is powerful and can provide an unbiased, detailed picture of GWAS loci and their mechanistic involvement in disease.
    Human Genetics 10/2013; 133(6). DOI:10.1007/s00439-013-1376-2 · 4.82 Impact Factor
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