E-cadherin expression is silenced by 5 ' CpG island methylation in acute leukemia

E-Cadherin is a transmembrane glycoprotein that mediates Ca2+-dependent int ercellular adhesion in normal epithelium, In tumors of epithelial origin, E -cadherin expression frequently is reduced, an event that contributes to tu mor invasion and metastasis, The role of E-cadherin in hematopoietic tissue s is less clear. In normal bone marrow, E-cadherin is expressed on erythroi d progenitors, CD34+ stem cells, and stromal cells, where it likely contrib utes to intercellular interactions during hematopoiesis. In this study, we used a nested-PCR approach to examine the methylation status of the E cadhe rin 5' CpG island in blood and bone marrow samples from normal donors and i n bone marrow from patients with acute leukemia. In normal peripheral blood mononuclear cells and bone marrow, E-cadherin was completely unmethylated. In peripheral blood mononuclear cells, expression was evident by reverse t ranscription-PCR, Immunoblotting confirmed E-cadherin protein expression in two lymphoblastoid cell lines derived from normal donors. In contrast, E-c adherin was aberrantly methylated in 4 of 4 (100%) leukemia cell lines, 14 of 44 (32%) acute myelogenous leukemias, and 18 of 33 (53%) acute lymphobla stic leukemias. Genomic bisulfite sequencing of primary leukemias confirmed dense methylation across the CpG island. Methylation was associated with l oss of E-cadherin RNA and protein in leukemia cell lines and primary leukem ias, Following treatment with 5-aza-2'-deoxycytidine, a methylated leukemia cell line expressed both E-cadherin transcript and protein. Our results sh ow that methylation of E-cadherin occurs commonly in acute leukemia and sug gests a hypothesis for E-cadherin downregulation in leukemogenesis.