Autocrine IL-2-dependent growth of a newly established CD3⁺, CD16⁻, CD56⁺, CD57⁺, J_H⁻, TCRβ⁻, TCRγ⁻ leukemia cell line (NOI-90)

Abstract

Leukemic cells from a 45-year-old male patient with a CD3⁺, CD56⁺, CD57⁺, CD7⁺ acute lymphoblastic leukemia were cultured in vitro in the absence of any added growth factor for up to 6 years and a continuous lymphoblastoid cell line (NOI-90) was established. NOI-90 cells have the same phenotype and karyotype as initial leukemic cells. Southern blot of DNA from NOI-90 cells showed that TCRβ, TCRγ, and J_H were in germ line. Two and 25% of NOI-90 cells were positive when stained with the IOT14 and 7G7/B6 moAbs, which recognize the CD25 molecule (IL-2Rα chain); moreover, 4% and 13% of the cells were positive when stained with the TU-27 and mikβ3 moAbs which recognize the CD122 molecule (IL-2Rβ chain). Equilibrium binding experiments with radiolabelled IL-2 revealed the presence of a small number of high affinity IL-2R on both fresh and continuously growing cells. Media conditioned by NOI-90 cells could induce proliferation of an IL-2-dependent cell line and this IL-2 activity could be detected by a sensitive immunoenzymatic assay using antibodies recognizing distinct epitopes of IL-2. Moreover, IL-2 activity could be adsorbed by immunoaffinity on anti-IL-2 polyclonal purified IgG and the retained molecule displayed a m.w. of 14.5 kDa in SDS-PAGE. In addition, IL-2 immunoreactive molecules could be revealed in the cytoplasm of the cells. Finally, IL-2 fixed on the cell membrane could be detected by indirect immunofluorescence. Although added IL-2 could not induce cell proliferation, monoclonal antibodies against CD25, CD122 and IL-2 could specifically inhibit spontaneous cell proliferation in a dose-dependent manner. NOI-90 cells failed to demonstrate any cytotoxic activity against the K-562, Raji or Daudi cells. These findings indicate that NOI-90 cells are of non-T, non-B, origin lacking NK activity but proliferate under an autocrine pathway which involves, at least partly, the IL-2/IL-2R system.