Membrane Fluidity and Adherence to Extracellular Matrix Components Are Related to Blast Cell Count in Acute Myeloid Leukemia

The level of blast cells in peripheral blood in acute myeloid leukemia (AML) varies in individual patients. The bone marrow egress of hematopoietic cells is an unclear phenomenon in which cell deformability and cytoadhesion to the extracellular matrix are involved. One component of deformability is the membrane fluidity. Using fluorescence polarization, we have studied the fluidity of blast cell membranes from 22 AML patients. This membrane was found to be highly fluid and a statistically significant correlation was found between the increase in membrane fluidity and the number of blast cells in the blood. Studying interaction between blast cells and several components of bone marrow stroma, we found adhesion to fibronectin and fibroblastic extracellular matrix. Adhesion to the extracellular matrix was inversally correlated to the level of blast cells in the blood. The observed increase in membrane fluidity and reduction of adhesion to bone marrow stroma may result in an increase of blast cells egress in AML.