The special societal relationships existing between various cell types in bone marrow suggests that there may be a link between the adhesive characteristics of hematopoietic cells and their maturation. Egress of the developing hematopoietic cells is also a highly regulated process governed by adhesive interactions. In leukemia, immature blasts are not retained within the marrow, suggesting a breakdown of adhesive mechanisms. Recent reports suggest that E-cadherin, an epithelial adhesion molecule, is expressed on erythroid precursors and megakaryocytes, but not on other hematopoietic marrow elements.
To characterize the expression pattern of E-cadherin in normal and leukemic erythroid precursors by immunohistochemistry in paraffin-embedded tissue and bone marrow aspirate smears.
Five normal bone marrow specimens from rib resections, 15 trephine bone marrow biopsy specimens, and 6 bone marrow aspirate smears from the iliac crest of patients with no known leukemia were selected. Fourteen bone marrow biopsy specimens from patients with erythroleukemia were also studied. Immunoperoxidase staining of paraffin-embedded tissue and air-dried aspirate smears for E-cadherin (1:200 dilution, HECD-1 clone) was performed using the avidin-biotin peroxidase technique.
In paraffin-embedded bone marrow biopsy and rib specimens and in air-dried bone marrow aspirate smears, strong membrane expression of E-cadherin was seen in the normal erythroid precursors in all cases. In contrast, no membrane expression of E-cadherin was present in any of the bone marrow biopsy specimens from patients with erythroleukemia.
Immunohistochemical detection of membrane expression of E-cadherin may be a useful tool for identification of erythroid precursors. Cells of erythroleukemia lack membrane expression of E-cadherin, in contrast to their normal counterparts. Further studies are needed to define the potential role of E-cadherin in the maturation of erythroid precursors and to ascertain the significance of loss of membrane expression of E-cadherin in erythroleukemia.