Induction of lymphokine-activated killing with reduced secretion of interleukin-1 beta, tumor necrosis factor-alpha, and interferon-gamma by interleukin-2 analogs.
BACKGROUND
Interleukin-2 (IL-2)-based immunotherapy has been shown to effect clinical responses in 15-35% of patients with metastatic renal cell carcinoma or melanoma. Despite its clinical efficacy, many clinicians refrain from using IL-2 because of the associated toxicity. This toxicity is believed to be mediated by such secondary cytokines as IL-1, tumor necrosis factor (TNF), and interferon (IFN)-gamma, which are produced by the patient's IL-2-stimulated peripheral blood mononuclear cells (PBMCs).


METHODS
Human PBMCs were stimulated with 1 nM wild-type recombinant IL-2 (rIL-2) or IL-2 analogs (R38A or F42K) that preferentially bind to the intermediate affinity IL-2 receptor (IL-2R). PBMCs were activated for lymphokine-activated killer (LAK) activity in 4-h 51Cr-release assays, using Daudi target cells. Cytokine content in the culture supernatants was determined by enzyme-linked immunosorbent assay.


RESULTS
Both R38A and F42K were capable of generating substantial LAK activity. Maximal specific lysis was 54% for PBMCs activated by R38A and 52% for F42K-stimulated cells, in contrast to 64% for rIL-2. In addition, analog-stimulated PBMCs secreted 59% of the IL-1 beta, 25% of the TNF-alpha, and only 8% of the IFN-gamma produced in response to rIL-2 (all p < 0.01 compared with rIL-2-stimulated secretion; one-way ANOVA).


CONCLUSIONS
IL-2 analogs that preferentially bind the intermediate-affinity IL-2R retain the capacity to induce substantial LAK activity despite a greatly reduced secondary cytokine production. Therefore, such IL-2 analogs may provide an effective, yet less toxic means of cancer immunotherapy.
Department of Tumor Biology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
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Heaton
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Grimm
D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic / Q000502:physiology*; D006801:Humans; D016219:Immunotherapy, Adoptive; D007371:Interferon-gamma / Q000378:metabolism*; D007375:Interleukin-1 / Q000378:metabolism*; D007376:Interleukin-2 / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015979:Killer Cells, Lymphokine-Activated / Q000187:drug effects* / Q000502:physiology; D007963:Leukocytes, Mononuclear / Q000502:physiology; D009369:Neoplasms / Q000276:immunology / Q000628:therapy; D011994:Recombinant Proteins / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D007375:Interleukin-1; D007376:Interleukin-2; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma