DNAM-1/CD155 Interactions Promote Cytokine and NK Cell-Mediated Suppression of Poorly Immunogenic Melanoma Metastases

A role for NK cells in therapeutic intervention for hematologic malignancies, such as acute myeloid leukemia and multiple myeloma, and nonhematologic malignancies, such as melanoma, is becoming more apparent. DNAM-I is an NK cell receptor whose importance in facilitating activation signals received by NK cells in natural and cytokine-driven responses to tumor metastases in vivo is poorly explored. In this study, we used matched tumor lines expressing a variety of relevant ligands, neutralizing monoclonal Abs, and DNAM-1 gene-targeted mice to determine the relative importance of DNAM-1-ligand interactions in controlling tumor metastases. Our results demonstrate that NK cells require DNAM-1 for natural or cytokine (IL-2, IL-12, or IL-21) suppression of tumor metastases or their variants expressing CD70 or CD80. In contrast, DNAM-1 was dispensable when tumor cells were targets of Ab-dependent cellular cytotoxicity or presented ligands for NKG2D. CD155 appeared to be a key ligand recognized by DNAM-I in NK cell-mediated suppression of metastases, and DNAM-1-mediated suppression coincided with perforin activity. Overall, these data implied a general role for DNAM-1-CD155 interactions in NK cell-mediated killing of tumors, even in the presence of tumor CD70 or CD80 expression, and further defined the optimal efficacy requirements of cytokines that directly activate NK cells. The Journal of Immunology, 2010, 184: 902-911.