Gamma-IFN induced cell adhesion in chronic myelogenous leukemia cells.

Both gamma- and alpha-interferons (IFNs) have been shown to induce clinical responses in chronic myelogenous leukemia (CML). The mechanisms behind these effects are not known. In chronic phase CML, granulocytic progenitors normally found in the bone marrow only, are found extramedullary. A defect in the adhesion of CML cells, that may be responsible for this finding, has been described earlier. In this study, we have investigated whether IFN can restore the defect in CML cell adhesion. It was found that gamma-, but not alpha-IFN, strongly induced the adhesion of CML cells to other cells and to plastic in a majority of the patients. In parallel, an induction in the expression of the adhesion molecules ICAM-1 and LFA-1 was found, and blocking of these molecules by antibodies abolished the effect. The ability of gamma-IFN to restore the adhesive property of CML cells may add to the antitumor effects observed with gamma-IFN therapy in CML.