Abstract 4815: Aberrant DNA hypermethylation of the ITIH5 tumor suppressor gene in acute myeloid leukemia

Acute myeloid leukemia (AML) is a clonal disorder resulting from uncontrolled proliferation of hematopoietic stem cells. Important genetic findings in AML comprise chromosomal translocations involving different transcription factors and activating point mutations in multiple signal transduction pathways. Hypermethylation of CpG islands within gene promoter regions in collaboration with deacetylation and other modifications of histone amino acids is associated with transcriptional inactivation and represents, in addition to genetic aberrations, an important mechanism of gene silencing in the pathogenesis of human cancer. Inter-alpha-trypsine inhibitors (ITIs) are proteases consisting of one light chain (bikunin) and two heavy chains (ITIHs), which stabilize the extracellular matrix (ECM). The putative tumor suppressor gene ITIH5 has previously been reported to be downregulated in association with aberrant DNA methylation in breast cancer. In this study, we determined the methylation status of the promoter-associated CpG island of ITIH5 in hematopoietic cell lines and primary AML patient samples. Methylation specific polymerase chain reaction (MSP) analysis revealed that the ITIH5 promoter region was hypermethylated in the AML cell lines HL60 and KG1a. Treatment of cell lines that carry a hypermethylated ITIH5 gene with the demethylating agent 5-aza-2’-deoxycytidine resulted in partial promoter demethylation. We then analyzed the ITIH5 methylation status in primary mononuclear cells obtained from 110 patients with newly diagnosed AML. The frequency of aberrant methylation among the primary patient samples was 14.5 % (16/110). Among clinical prognostic parameters, we found a significant positive correlation between hypermethylation of ITIH5 and elevated serum levels of lactate dehydrogenase (LDH, p=0.013) in univariate analysis, whereas no correlation was found for cytogenetics, FAB subtype, age, white blood cell count and overall survival. We conclude that promoter hypermethylation of ITIH5 is a novel epigenetic event in AML that may contribute to leukemogenesis by interfering with the interaction between the ECM and the leukemic clone. Further studies are warranted to elucidate the functional consequences of epigenetic dysregulation of ITIH5 in leukemogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR