Abstract 160: CD8+T cell-specific induction of NKG2D receptor by doxorubicin plus interleukin-12 requires the engagement of CD80 and CD28
Authors: Hu Jiemiao , Xia Xueqing , Zhang Liangfang , Kleinerman Eugenie S. , Li Shulin 
Published: May 2015

Abstract
Background: Increased infiltration of CD8+T cells into tumors inhibits tumor progression, in which natural killer group 2, member D receptor (NKG2D) plays a key role. At previous meetings, we have presented data showing that NKG2D can be induced on CD8+T through treatment with interleukin (IL)-12 plus doxorubicin (Dox), and that infiltration of this subpopulation of effector cells into tumors is associated with increased antitumor efficacy of treatment with IL-12 plus Dox. The mechanisms of both NKG2D induction and the tumor-specific infiltration were unknown. This year, we reveal the mechanism of NKG2D positive CD8+T infiltration into the tumor microenvironment.
Methods: We administered Dox, IL-12 plasmid DNA, or both via intraperitoneal injection or intramuscular electroporation into tumor-bearing wild-type C57bl/6 mice or CD28 knockout mice. Control siRNA or CD80 siRNA were administered via intratumoral injection followed by electroporation. Induction of NKG2D in CD8+T cells was analyzed using flow cytometry. Cell death in tumors after each treatment was examined using the TUNEL assay. Antitumor cytolytic activity of CD8+T cells was examined using the CTL assay. NKG2D-positive CD8+T cell-specific localization in tumors was examined using immunofluorescence staining.
Results: Treatment with Dox plus IL-12 specifically increased expression of NKG2D in CD8+T cells. This induced NKG2D expression in CD8+T cells was associated with increased accumulation of NKG2D-positive CD8+T cells in murine tumors, as well as with increased antitumor cytotoxicity in vitro and tumor cell death in vivo. Administration of NKG2D-blocking antibody completely abrogated the antitumor immune response. Knocking down CD80 in tumor cells or using CD28 knockout mice not only abolished the induction of NKG2D in CD8+T cells, but also abrogated the accumulation of NKG2D-positive CD8+T cells in tumors. Accumulation of NKG2D-positive CD8+T cells in tumors was dependent on the engagement of CD28 in CD8+T cells and CD80 in tumor cells.
Conclusion: We conclude that treatment with IL-12 plus Dox induces NKG2D in CD8+T cells in vivo and boosts NKG2D+CD8+T-dependent antitumor immune surveillance. Induction of NKG2D and accumulation of NKG2D-positive CD8+T cells in tumors is dependent on the engagement of CD28 in CD8+T cells and CD80 in tumor cells. This discovery reveals a novel mechanism showing how chemo-immune therapy synergistically promotes T-cell-mediated antitumor immune surveillance.
Citation Format: Jiemiao Hu, Xueqing Xia, Liangfang Zhang, Eugenie S. Kleinerman, Shulin Li. CD8+T cell-specific induction of NKG2D receptor by doxorubicin plus interleukin-12 requires the engagement of CD80 and CD28. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 160. doi:10.1158/1538-7445.AM2014-160