Distinct DNA Methylation Patterns of HOX Genes in Leukemia

Autor: Amanda Saraf, Samantha Lau, Rong He, Jaroslav Jelinek, Jean Pierre J. Issa
Rok vydání: 2006
Předmět:
Zdroj: Blood. 108:2238-2238
ISSN: 1528-0020
0006-4971
DOI: 10.1182/blood.v108.11.2238.2238
Popis: The HOX subset of homeobox gene family comprises 39 genes organized in 4 clusters A-D on 4 different chromosomes and in 13 paralog groups defined across the clusters. HOX genes are important regulators of development and tissue differentiation. Dysregulated expression disturbs hematopoiesis and HOX genes are frequent partners in chromosomal translocations involved in leukemia. DNA methylation of promoter-associated CpG islands is an epigenetic modification resulting in transcriptional silencing of affected genes. Methylation pattern is faithfully copied during cell replication to subsequent cell generations and hypermethylation thus represents a permanent mark functionally equivalent to a loss-of-function mutation. Epigenetic silencing of HOX genes may disrupt normal development of blood cells and thus be involved in the development of leukemia, as was recently reported for HOXA5. We performed a comprehensive DNA methylation analysis of 22 HOX genes with CpG islands in promoter to exon 1 regions: HOXA1, A4, A5, A7, A9, A10, A11; B1, B4, B5, B7, B8, B9, B13; C4, C5, C8, C9, C10, C13; D1 and D10 in 16 leukemic cell lines, 24 samples from patients with acute myelogenous leukemia (AML), 20 samples from patients with acute lymphoblastic leukemia (ALL), and 15 control samples of normal blood cells. We used bisulfite treatment of DNA, followed by PCR and pyrosequencing to quantitatively measure levels of cytosine methylation in promoter-associated CpG islands close to transcription start sites. Nonparametric tests were used for statistical analysis. Overall, lymphoblastic leukemic cell lines (TALL, Raji, ALL1, JTAg, CEM, BJAB, Jurkat) showed the highest degree of HOX genes methylation (average 60%), followed by myeloid leukemic cell lines (HL60, KG1a, ML1, HEL, TF-1, OCI-AML3, K562, TF1i, KG1, average methylation 40%), p=0.000. Analysis of ALL and AML patient samples revealed significant differences in methylation levels of several HOX genes. Consistently with their reported overexpression in leukemia, HOX A9, B4, and also HOXB5 and HOXD10 were seldom methylated in AML patients (2/24, 0/24, 1/12, 7/24, respectively), while hypermethylation over a 10% cutoff value was observed frequently in ALL patients (10/20, 6/19, 6/17, 9/19, respectively). The differences in methylation were statistically significant (p
Databáze: OpenAIRE
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