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NK cell HMGB1 mediates IL-2-induced “systemic autophagic” toxicity
© Li et al; licensee BioMed Central Ltd. 2013
Published: 7 November 2013
Background and objectives
High dose Interleukin 2 (HDIL-2) treatment has durable antitumor effects in 5-10% of patients with metastatic melanoma and RCC. The application and efficacy of HDIL-2 treatment is limited due to substantial toxicity. We have previously shown that the toxicity results from cytokine-induce autophagy, which we term a “systemic autophagic syndrome”. Depletion of individual induced cytokines or B or T cells can’t rescue murine mortality with IL-2/IL-12 administration, but only NK cell depletion. Here, we hypothesize that the “systemic autophagic” toxicity is critically mediated by NK cells.
Immunodeficient mice (RAG1-/- and NSG mice), hepatic metastases model, flow cytometry, ELISA, immunofluorescence and western blotting, transmission electron microscopy.
RAG1-/- mice containing an exaggerated NK cell population and function but no T or B cells die unlike wild type (WT) mice with HDIL-2 alone. Systemic autophagy was detected by autophagosome (TEM) and LC3-II (Immunofluorescence and western blot) in the lung, liver and kidney. Pre-treatment with the autophagy inhibitor chloroquine (CQ) mediated a modest protective effect, while NK elimination completely abrogates toxicity, associated with dramatically reduced serum HMGB1 and IL-6 levels. Adoptive transfer of WT B6 splenocytes with NK depletion can partially rescue the effects, with an enhanced population of CD3+CD4+CD25+ Tregs. Additionally, NSG mice adoptively transferred with RAG1-/- mice splenocytes display dose-dependent toxicity, assessed by relative lung weight and edema(H&E staining), serum HMGB1 and sRAGE (a novel indicator of toxicity and cancer prognosis) level and LC3 punctae formation. IL-2/18 combination which kills WT B6 mice, but NK elimination allows survival. NK cells generated from precursors show similar activated status but less mature phenotypes. Notably, anti-HMGB1 neutralizing antibodies can partly abrogate the severe syndrome of RAG mice, suggesting that HMGB1 may be essential to IL-2 toxicity. NKH mice lacking HMGB1 using floxed HMGB1 mice backcrossed into NKp46-cre mice specifically are viable, demonstrating that NK HMGB1 is required for systemic toxicity.
IL-2 immunotherapy induces a “systemic autophagic” toxicity. The autophagy inhibitor, chloroquine, as well as administration of the HMGB1 neutralizing antibody, NK abolishment, or depletion of HMGB1 solely in NK cells promotes protection from IL-2 lethality. Thus, HMGB1 mediates the toxicity of IL-2 administration and possibly other immunotherapies.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.