Abberant expression of adhesion molecules on CD34+ cells of acute leukemia

The expression of adhesion molecules on CD34+ cells in acute myeloid leukemia (AML) and B-lineage acute lymphoblastic leukemia (B-ALL) was compared with that on the myeloid and B-lymphoid CD34+ cells in normal bone marrow. Bone marrow aspirates of 10 patients with AML, 8 patients with B-ALL and of 6 healthy volunteers were examined. The phenotype of the CD34+ cells was determined with a double immunofluorescence method and flow cytometry. Myeloid and B-lymphoid CD34+ cells in normal bone marrow were distinguished by their forward scatter. CD34+ cells in AML and B-ALL generally had VLA-4, VLA-5, PECAM-1, ICAM-1 and LFA-3 on their surface membrane. AML CD34+ cells more frequently expressed b2 integrins than B-ALL CD34+ cells. Aswell in AML as in B-ALL the CD34+ cells showed a lower expression of VLA-2 and VLA-3 and a higher expression of ICAM-1 than their normal bone marrow counterparts. AML CD34+ cells also had less L-selectin on the surface membrane than normal myeloid CD34+ cells. Whether these systematic differences in expression of adhesion molecules between normal and leukemic cells could explain the higher tendency of the latter to migrate tothe peripheral blood is not clear. Abnormally low or high expression of VLA-5 PECAM-1, HCAM, ICAM-1 and L-selectin in individual patients also occurred. These phenotypic characteristics might be useful for the detection of minimal residual leukemia in these patients.