Abstract 4996: Co-stimulation of IL-12 gene delivery plus doxorubicin induces NKG2D-dependent CD8+T cell infiltration to tumors and inhibition of tumor progression.
Authors: Hu Jiemiao , Zhu Shiguo , Xia Xueqing , Kleinerman Eugenie , Li Shulin 
Published: August 2014

Chemotherapeutic agents were conventionally viewed as agents that can only eradicate tumor cells and have no impact on the immune system. However, recent work has identified a novel function of chemotherapeutic agents, which is to prevent an immunosuppressive effect in the tumor microenvironment and even facilitate the infiltration of immune effector cells into tumors and sensitize tumor cells to immune cell attack. In fact, immune response induced by chemotherapeutic agents may become a predictor of therapeutic outcome in cancer patients. In agreement with these observations, some chemotherapeutic agents when combined with immunotherapy promote anti-tumor immune response, resulting in an improved anti-tumor efficacy. Despite these progress, it remains unclear how to properly and effectively combine immune stimulatory gene therapy and chemotherapy to boost anti-tumor efficacy.

This study reveals upregulation of NKG2D in CD8+T cells may serve as a valuable end point for selecting such a proper immune- and chemo-therapy combination. This conclusion is based on the fact that IL-12 immunogene therapy plus doxorubicin-induced expression of natural killer group 2, member D (NKG2D) in CD8+T cells, increases NKG2D-dependent CD8+T cell localization into tumors and anti-tumor efficacy. This NKG2D upregulation and localization into tumors after the co-stimulation of IL-12 plus doxorubicin is CD8+T cell specific because this observation occurs in wild-type mice and NK deficient mice, but not in T cell deficient mice. The depletion study confirmed this statement because depletion of NK cells did not affect the detection of NKG2D upregulation and NKG2D positive CD8+T cell localization in tumors by the co-stimulation, but depletion of CD8+T cells completely abolish the detection of CD8+T cells in tumor microenvironment subjected to the same stimulation. Consistent with these result, blocking NKG2D receptor using a neutralizing antibody impaired doxorubicin plus IL-12 gene delivery-mediated tumor eradication in vivo and reduced cytolytic activity in vitro.

In summary, we have shown in vivo evidence that Dox plus IL-12 gene delivery induces CD8+T cell-specific NKG2D upregulation. This upregulation facilitates the infiltration of these NKG2D-expressing CD8+T cells into the tumor site. The significance of this study is to elucidate that doxorubicin plus IL-12-induced CD8+T cells infiltrating into tumors is dependent on NKG2D expression and this NKG2D upregulation can be used as an end point for this combination therapy for measuring anti-tumor immune response. Our study is also significant for CAR-based T cell therapy, because our data suggests that IL-12 plus doxorubicin treatment may promote NKG2D-based CAR-T cell therapy by possibly causing tumor specific infiltration.

Citation Format: Jiemiao Hu, Shiguo Zhu, Xueqing Xia, Eugenie Kleinerman, Shulin Li. Co-stimulation of IL-12 gene delivery plus doxorubicin induces NKG2D-dependent CD8+T cell infiltration to tumors and inhibition of tumor progression. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4996. doi:10.1158/1538-7445.AM2013-4996