Cytokine and Natural Killing Regulation of Growth of a Hairy Cell Leukemia-Like Cell Line

Abstract

Hairy cell leukemia (HCL) is a lymphoproliferative disorder of B-lymphocytes, with pathological manifestations usually including splenomegaly and pancytopenia. Naturally occurring and recombinant interferons (IFNs), specifically of the alpha subtype, have shown a significant anti-tumor effect in HCL patients, with improvement of hematologic parameters within the first few months of treatment. The mechanisms responsible for the beneficial action of IFN-alpha in HCL patients are unclear, but several hypotheses have been suggested. Recently, a continuous line of cells (Eskol) from a patient diagnosed with hairy cell leukemia was established and shown to have several properties of a leukemic hairy cell. In the present study, we investigated the direct effect of IFN-alpha and interleukin (IL-2) on the Eskol cell line, and lymphokine regulation of natural killing (NK) activity against these cells. It was found that IFN-alpha has a direct antiproliferative effect on Eskol cells. Furthermore, Eskol cells were found to be completely resistant to NK-cell mediated cytotoxicity (CMC) but were somewhat sensitive to either IFN-alpha-primed NK or lymphokine-activated killer (LAK) cells-CMC. The resistance of Eskol cells to NK-CMC is due to a low binding ability to effector cells. Moreover, it was found that like IFN, IL-2 can protect Eskol cells from activated NK-CMC. Both cytokines reduced the ability of Eskol cells to induce NK-cytotoxic factor (NKCF) release from NK cells following conjugate formation between Eskol cells and effector cells. Moreover, cycloheximide treatment abolished the protective effect against NK-CMC induced by IFN-alpha or by IL-2. Therefore, it seems that the protective effect against NK-CMC induced by both cytokines is mediated via the same mechanism.