IL-2 Receptor (IL-2R) Alpha, Beta, and Gamma Chains Expressed on Blasts of Acute Myelocytic Leukemia May Not Be Functional

Abstract

Preliminary clinical studies including IL-2 in chemotherapeutic strategies for treatment of acute myelocytic leukemia suggest that IL-2 may improve the overall outcome of the patients [1, 2]. To date, the mechanisms of eradication of blast cells are still unclear. Cytotoxic T and NK cells or secondary cytokines released after administration of IL-2 have been discussed to contribute to the elimination of leukemic cells [3–5]. However, it is important to know, whether IL-2 may directly influence AML blasts [6]. In initial sudies, using flow cytometry, we found expression of considerable levels of the IL-2R alpha chain on blast cells in a low proportion of patients with AML. However, the IL-2R beta chain was more frequently expressed ranging from 0% to 98%. To confirm these results on a transcriptional level, we studied the expression of RNA of the IL-2R α, β, and γ chains by RT PCR in the bone marrow of 39 newly diagnosed patients with AML and in three AML derived cell lines. RNA for all three IL-2R chains was expressed in lines KG1, HEL 92.1.7 and K562. Surface expression of the IL-2R β chain was observed in all three lines, but of the α chain only in KG1 cells. In comparison with unstimulated cell lines incubation of the three lines with various amounts of IL-2 over 3 and 14 days did not influence their growth, measured by cell numbers and 3H-thymidin incorporation. RNA for the α chain was detectable in 12/39 patients, of the β chain in 10/39 patients and the γ chain in 29/39 patients with AML. Altogether the data suggest that the IL-2R expressed on AML blast cells may be incomplete and not functional. In future studies, functional properties of IL-2 R on blast cells obtained from newly diagnosed patients with AML will have to be investigated.