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Natural killer cell depletion confounds the antitumor mechanism of endogenous IL‐12 overexpression
Author(s) -
Miller George,
Bleier Joshua I.,
Antonescu Cristina,
Pillarisetty Venu G.,
Shah Alaap B.,
Lahrs Svenja,
DeMatteo Ronald P.
Publication year - 2004
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.20131
Subject(s) - transgene , genetically modified mouse , endogeny , adoptive cell transfer , biology , interleukin 12 , natural killer cell , immunology , cancer research , interleukin 21 , t cell , cytotoxicity , immune system , in vitro , endocrinology , cytotoxic t cell , gene , biochemistry
IL‐12 gene transfer to hepatocytes using a recombinant adenovirus vector (AdIL‐12) has been shown to protect against primary and metastatic liver tumors in mice. However, the mechanism of protection has been elusive and studies using depleting monoclonal antibodies or transgenic mice have purported it to be independent of T and NK cells. We postulated that depletion of NK cells may distort the experimental model and misrepresent the antitumor mechanism by altering the magnitude and duration of transgene expression. We show in mice treated with AdIL‐12 that NK depletion increased serum IL‐12 levels by more than 250‐fold and prolonged transgene expression by nearly 2 weeks compared to nondepleted mice. To determine the contribution of NK cells to tumor protection after AdIL‐12 treatment, we analyzed NK cells from treated animals. Isolated NK cells were markedly activated in terms of their lytic activity and IFN‐γ secretion. Adoptive transfer of NK cells from mice that had been treated with AdIL‐12 to naive mice was sufficient to confer protection against colorectal hepatic metastases. This protection was mediated in part by NK‐cell production of IFN‐γ. Our findings indicate that NK‐cell depletion distorts the model of systemic AdIL‐12 administration by markedly altering transgene expression, which then may potentiate other antitumor mechanisms, and that endogenous IL‐12 overexpression activates NK cells, rendering them sufficient to protect against liver metastases. These data have critical implications for investigating the immunologic mechanisms of experimental models that utilize gene transfer. © 2004 Wiley‐Liss, Inc.