Alizadeh D, Zhang L, Brown CE, Farrukh O, Jensen MC, Badie B. Induction of anti-glioma natural killer cell response following multiple low-dose intracerebral CpG therapy.
Clin Cancer Res 2010;
16:3399-408. [PMID:
20570924 DOI:
10.1158/1078-0432.ccr-09-3087]
[Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
PURPOSE
Stimulation of toll-like receptor-9 by CpG oligodeoxynucleotides (CpG-ODN) has been shown to counteract the immunosuppressive microenvironment and to inhibit tumor growth in glioma models. These studies, however, have used high doses of CpG-ODN, which can induce toxicity in a clinical setting. The goal of this study was to evaluate the antitumor efficacy of multiple low-dose intratumoral CpG-ODN in a glioma model.
EXPERIMENTAL DESIGN
Mice bearing 4-day-old intracranial GL261 gliomas received a single or multiple (two or four) intratumoral injections of CpG-ODN (3 microg) every 4 days. Tumor growth was measured by bioluminescent imaging, brain histology, and animal survival. Flow cytometry and cytotoxicity assays were used to assess anti-glioma immune response.
RESULTS
Two and four intracranial injections of low-dose CpG-ODN, but not a single injection, eradicated gliomas in 70% of mice. Moreover, surviving animals exhibited durable tumor-free remission (> 3 months) and were protected from intracranial rechallenge with GL261 gliomas, showing the capacity for long-term antitumor immunity. Although most inflammatory cells seemed to increase, activated natural killer (NK) cells (i.e., NK(+)CD107a(+)) were more frequent than CD8(+)CD107a(+) in the brains of rechallenged CpG-ODN-treated animals and showed a stronger in vitro cytotoxicity against GL261 target cells. Leukocyte depletion studies confirmed that NK cells played an important role in the initial CpG-ODN antitumor response, but both CD8 and NK cells were equally important in long-term immunity against gliomas.
CONCLUSIONS
These findings suggest that multiple low-dose intratumoral injections of CpG-ODN can eradicate intracranial gliomas possibly through mechanisms involving NK-mediated effector function.
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