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Phorbol myristate acetate induces both high affinity and low affinity interleukin 2-receptors on a pre-B leukemic
M Allouche1, V Georgoulias, Y Augery-Bourget
1Unité d'Oncogénèse Appliquée, INSERM U. 268, Hôpital Paul Brousse, Villejuif, France.
Insights
Phorbol Myristate Acetate (PMA) induces functional interleukin 2-receptor (IL2-R) expression on Reh6 pre-B leukemia cells. This IL2-R enables IL2-dependent proliferation, suggesting a novel therapeutic target for B-cell leukemia.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- The Tac molecule (p55), a component of the interleukin 2-receptor (IL2-R), is not constitutively expressed in Reh6 human pre-B leukemic cells.
- Phorbol Myristate Acetate (PMA) is a known inducer of cellular activation and gene expression.
Purpose of the Study:
- To investigate the induction and functionality of IL2-R on PMA-stimulated Reh6 pre-B leukemic cells.
- To determine if IL2 can mediate proliferation in these leukemia cells.
Main Methods:
- Reh6 cells were treated with PMA to induce Tac molecule expression.
- Binding experiments using radiolabeled recombinant IL2 (rIL2) were performed to characterize IL2-R affinity and expression levels.
- Western blotting identified the polypeptide chains of the IL2-R.
- Functional assays assessed rIL2-mediated proliferation in vitro.
Main Results:
- PMA treatment dose- and time-dependently induced Tac molecule expression on Reh6 cells.
- Both high and low affinity IL2-R were detected on PMA-stimulated cells, with high affinity receptors showing partial internalization.
- PMA-induced IL2-R on Reh6 cells were functional, as rIL2 specifically enhanced proliferation in semi-solid cultures.
Conclusions:
- PMA induces the expression of functional, high-affinity IL2-R on Reh6 pre-B leukemic cells.
- These findings demonstrate an IL2-dependent proliferation mechanism in PMA-treated pre-B leukemic cells, highlighting a potential therapeutic target.
Abstract:
The human pre-B leukemic cell line Reh6 does not constitutively express the Tac molecule (p55), which is one of the two polypeptide chains of the interleukin 2-receptor (IL2-R). Cell incubation with Phorbol Myristate Acetate (PMA) induces expression of the Tac molecule in a dose and time-dependent manner. Binding experiments with radiolabelled recombinant IL2 (rIL2) revealed both high and low affinity IL2-R (225 +/- 105 sites/cell with a Kd of 130 +/- 51 pM and 24060 sites/cell with a Kd of 17.3 nM respectively), whereas unstimulated Reh6 cells only expressed intermediate affinity Reh6 cells revealed the presence of two polypeptide chains of mol. wts 55,000 (Tac molecule) and 70,000, as in normal activated T cells, while the 70,000 mol. wt chain alone was observed in unstimulated Reh6 cells. IL2-R-bearing Reh6 cells could absorb rIL2 in a dose-dependent manner and this absorption was inhibited by a monoclonal antibody against the Tac molecule (anti-Tac). Moreover, partial internalization of IL2 bound under high affinity conditions occurred at 37 degrees C. IL2-R expressed on PMA-induced cells were functional since rIL2 specifically enhanced the proliferation in vitro of PMA-treated cells in semi-solid but not liquid cultures. These findings thus demonstrate an IL2-dependent mechanism of proliferation in vitro of pre-B leukemic cells induced by PMA, which can express high affinity, functional IL2-R.
