Comparative adhesion of human haemopoietic cell lines to extracellular matrix components, bone marrow stromal and endothelial cultures

We used flow cytometry to characterize cell adhesion molecule expression of the human haemopoietic cell lines KG1a, K562, HL-60, NALM-6 and CEM. A ⁵¹chromium labelling assay was used to study the adhesion of these cell lines to extracellular matrix components and to bone marrow stromal and endothelial cultures. Both adhesion molecule expression and functional binding behaviour varied between cell lines. All five cell lines expressed the integrins α₄β₁ and α₅β₁ and all adhered to fibronectin. However, differences in intensity of expression of these integrins failed to correlate with extent of fibronectin adhesion. Inhibition experiments demonstrated that adhesion of KG1a to fibronectin was completely inhibited by divalent cation chelation and partially inhibited by RGDS peptides and chondroitinase ABC, suggesting that both α₄β₁ and α₅β₁ as well as CD44 were responsible for this interaction. Adhesion to bone marrow stromal and endothelial layers was superior to that to purified extracellular matrix components and was partially inhibited by divalent cation chelation. RGD peptides and anti-α₄ monoclonal antibody also partially inhibited KG1a adhesion to bone marrow endothelium. Discordance between cell adhesion molecule expression and adhesive behaviour suggest that current phenotypic descriptions remain incomplete and reinforce the need for complementary functional binding studies.