Abstract 1556: α-mannosylceramide, a new NKT cell agonist, induces tumor immunity without anergy induction in NKT cells

NKT cells are CD1d-restricted T cells recognizing lipid antigens. When NKT cells are activated with a prototypic antigen, α-galactosylceramide (α-GalCer), they induce strong tumor immunity. Strong preclinical evidence for α-GalCer's ability to induce tumor immunity through NKT cell-activation led to translation into therapy of cancer patients. However, so far minimal success has been achieved in patients. We reasoned that having an α-linked sugar moiety in the structure of α-GalCer can be a target for anti-α-linked galactose natural antibodies, which are a cause of acute xenograft rejection, and which might abrogate the biological activity of α-GalCer. After testing multiple glycosylceramides with potential agonistic activity for NKT cells, we discovered that α-mannosylceramide (α-ManCer) has strong activity to induce tumor immunity through a TNF-α- and NOS-dependent mechanism that is distinct from the IFN-γ dependent protection induced by α-GalCer. Another downside of α-GalCer treatment is induction of long-lasting anergy in activated NKT cells. Since we did not observe massive cytokine production with α-ManCer, in contrast to α-GalCer, we asked whether this new compound activates NKT cells without inducing long-lasting anergy in vivo. In contrast to α-GalCer, α-ManCer did not induce long-lasting anergy of activated NKT cells. This was correlated with the observation that α-ManCer induced only a short term expression of PD-1 on activated NKT cells, which has been reported to be responsible for α-GalCer-induced long-term anergy. Furthermore, while prior treatment with α-GalCer abrogated the protective effect of either α-GalCer or α-ManCer against CT26 colon carcinoma tumor challenge for at least two months, the pre-treatment with α-ManCer had no effect on the protection induced by either NKT cell agonist. Since α-ManCer can activate human NKT cells, this new NKT cell agonist may provide a better opportunity for NKT cell targeted immunotherapy in cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1556. doi:1538-7445.AM2012-1556

Abstract 4746: Type I NKT cells mediate anti-tumor immunity through a TNF-α- and NOS-dependent pathway when stimulated with β-ManCer

CD1d-restricted type I NKT cells have been shown to play a critical role in the induction of tumor immunity by producing IFN-γ, which activates effector arms such as NK cells and CD8+ T cells. It has been considered that IFN-γ is necessary for type I NKT cell-induced tumor immunity. In this study, we show that type I NKT cells can induce strong tumor immunity through an IFN-γ-independent pathway when activated with a new type of agonistic antigen, β-mannosylceramide (β-ManCer). The protection induced by β-ManCer treatment was completely abrogated in type I NKT cell deficient Jα18 KO mice. With the observations that in vitro activation of type I NKT cells by β-ManCer was blocked by anti-CD1d blocking monoclonal antibody and that β-ManCer-loaded CD1d dimers bind to type I NKT cells and stimulate type I NKT cell hybridomas in an APC-free system, we concluded that recognition of CD1d presented β-ManCer by a TCR of type I NKT cells is necessary for the protection. Surprisingly β-ManCer-induced protection was not abrogated in IFN-γ deficient mice, which is in contrast with the protection induced by a prototypic agonist α-galactosylceramide (α-GalCer). Instead, β-ManCer-induced protection was dependent on nitric oxide synthase (NOS) and TNF-α since blockade of either completely abrogated the protection while the blockade did not affect protection induced by α-GalCer. The conclusion that NKT cells activated with β-ManCer utilize a different pathway from that used by the cells activated with α-GalCer to enhance tumor immunity was confirmed with the observation that the combination of both antigens synergistically enhanced tumor immunity when suboptimal doses of each were used. These data demonstrate that NKT cells mediate tumor immunity through a TNF-α- and NOS-dependent pathway when stimulated with β-ManCer and that β-ManCer represents a new class of type I NKT cell agonist. Since we observed that human type I NKT cells also can be activated by β-ManCer, β-ManCer may provide a new intervention against cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4746. doi:10.1158/1538-7445.AM2011-4746