Activated natural killer cell-mediated immunity is required for the inhibition of tumor metastasis by dendritic cell vaccination

Aeyung Kim,Yong Suk Jang,Jong-Seok Lim,Young-Woock Noh,Kwang Dong Kim,Yong-Kyung Choe

doi:10.1038/emm.2004.55

Abstract

Immunization with dendritic cells (DCs) pulsed with tumor antigen can activate tumor-specific cytotoxic T lymphocytes (CTL), which is responsible for tumor protection and regression. In this study, we examined whether DCs pulsed with necrotic tumor lysates can efficiently prevent malignant melanoma tumor cell metastasis to the lung. DCs derived from mouse bone marrow were found to produce remarkably elevated levels of IL-12 after being pulsed with the tumor lysates. Moreover, immunization with these DCs induced CTL activation and protected mice from metastasis development by intravenously inoculated tumor cells. In addition, these DCs activated NK cells in vitro in a contact-dependent manner, and induced NK activities in vivo. Furthermore, NK cell depletion before DC vaccination significantly reduced the tumor-specific CTL activity, IFN-gamma production, and IFN-gamma- inducible gene expression, and eventually interfered with the antitumor effect of tumor-pulsed DCs. Finally, similar findings with respect to NK cell dependency were obtained in the C57BL/ 6J-bg/bg mice, which have severe deficiency in cytolytic activity of NK cells. These data suggest that the antitumor effect elicited by DC vaccination, at least in a B16 melanoma model, requires the participation of both cytolytic NK and CD8(+) T cells. The findings of this study would provide important data for the effective design of DC vaccines for cancer immunotherapy.

Highlights

Dendritic cells (DCs) are highly effective antigenpresenting cells with the unique ability of inducing primary immune responses against tumor-associated antigens (Banchereau et al, 2000), and have important roles in both early and late adaptive immune responses
Given that the induction of stronger cytotoxic T lym phocytes (CTL) responses is a major goal of current cancer vaccine strategies, tumor lysate-loaded DCs containing multiple known and unknown antigens that can be presented to T cells by both MHC class I- and class II-pathways provide the potential to induce efficient antitumor immune responses (Nouri-Shirazi et al, 2000; Sauter et al, 2000; Kotera et al, 2001)
NK cells are the major lymphocytes of innate immune response and are able to kill tumor cells in vitro (Trinchieri, 1989)

Summary

Introduction

Dendritic cells (DCs) are highly effective antigenpresenting cells with the unique ability of inducing primary immune responses against tumor-associated antigens (Banchereau et al, 2000), and have important roles in both early and late adaptive immune responses. NK cells are the major lymphocytes of innate immune response and are able to kill tumor cells in vitro (Trinchieri, 1989) They have been shown to kill circulating tumor cells in vivo, and in this way participate in the defense against establishment of metastasis (Salup et al, 1985; Wiltrout et al, 1985), it is the current paradigm that NK cells do not attack and destroy established solid tumors. We and other groups have previously reported that the injection of DC cocultured with tumor cells can activate NK cells in vivo (Kim et al, 1999), and that the in vivo depletion of NK cells results in a marked reduction in tumorspecific CTL activity (Kim et al, 2001; Nakamura et al, 2004) Overall, these findings suggest that the initiation of innate immune responses by NK cells in cooperation with DCs facilitates CTL developments. Our data suggest that the antitumor effect elicited by DC vaccination requires, at least in a B16 melanoma model, the participation of both cytolytic NK and CD8+ T cells

Mice and tumor cell lines

Generation of dendritic cells from mouse bone marrow cells

Immunization of mice and lung metastasis identificaiton

In vivo NK cell depletion

Determination of cytotoxic activity

Statistical analysis