The effect of differentiation inducers on the integrin expression of K562 erythroleukemia cells.

We studied the effects of differentiation-inducers on the integrin profile and adhesive properties of K562 leukemia cells. The fibronectin (Fn) receptor integrin, α₅β₁, was the only integrin expressed in suspension cultured K562 cells. When the cells were exposed to 12-O-tetradecanoylphorbol-13-acetate (TPA) immunoreactivity for the β₁ integrin subunit was slightly enhanced. TPA exposure also induced the appearance of the α₂, α₃, α_v and β₃ integrin subunits, but the platelet integrin subunit α_IIb was not detected. On the other hand, hemin chloride-induced erythroid differentiation of K562 cells diminished the expression of the α₅β₁ integrin on the surface of the cells. Adhesion experiments with TPA-exposed K562 cells indicated that although the adherence to the extracellular matrix (ECM) proteins as a rule was low a few cells spread on these proteins. The present results specify the effects of differentiation inducers on the integrin profile of K562 cells and excludes the comprehension that TPA would induce expression of the platelet integrin α_IIb on their surface. Our results also show, that an increased expression of a certain integrin does not necessarily lead to a comparable adhesion ability on its ligand in vitro.