High-affinity interleukin 2 receptors on B cell chronic lymphocytic leukemia cells are induced by phorbol myristate acetate but not by calcium ionophore

The role of phorbol myristate acetate (PMA: a protein kinase-C (PKC) activator) and calcium ionophore A23187 in the induction mechanism of the interleukin 2 receptor (IL2R) on B-cell chronic lymphocytic leukemia (B-CLL) cells was studied. B-CLL cells from five patients were cultured with PMA or A23187 for 72 h and used for the following experiments. Interleukin 2 (IL2) cross-linking assays showed that PMA induced the expression of IL2R subunits (p55 and p70/75) in all cases examined, but that A23187 induced neither subunit. Radiolabeled IL2 binding assays also demonstrated that PMA induced both high-affinity IL2R (HA-IL2R) and low-affinity IL2R (LA-IL2R) on B-CLL cells, but that A23187 did not. After treatment with PMA, three of five cases did not respond to IL2 even though they expressed HA-IL2R, suggesting impaired signal transduction. No cases responded to IL2 after treatment with A23187. In conclusion, PMA but not A23187 stimulates B-CLL cells to induce the expression of p55 and p70/75, indicating that the PKC pathway plays a more important role than the calcium pathway in the induction of IL2R subunits in B-CLL cells.