Donor lymphocyte-derived natural killer cells control MHC class i-negative melanoma

Abstract

Natural killer (NK) cells provide a natural defense against MHC-I-negative tumors, such as melanoma. Donor lymphocyte infusion (DLI) containing NK cells, a form of adoptive immunotherapy used after allogenic bone marrow transplantation (allo-BMT), promotes antitumor immune responses but is often associated with life-threatening complications such as graftversus- host disease (GvHD). Here, we showed that without prior allo-BMT, DLI provoked melanoma control associated with the infiltration and persistence of the transferred NK cells. This allograft acceptance did not correlate with an increase of GvHD; instead it correlated with the expansion and activation of tumorinfiltrating NK cells that expressed the cytotoxic molecules (e.g., IFNg and granzyme B) and maturation signatures (e.g., CD11bhiCD27loand KLRGhi/CD43hi). The development of beneficial tumor-infiltrating NK cells of DLI origin required host CD4+T-cell help in part by producing IL2, as well as by limiting regulatory CD4+T cells (Treg). IL2 blockade impaired the NK-dependent melanoma control, which could not be rescued by IL2 administration beyond CD4+T-cell help. Our findings linked NK allograft acceptance-CD4+T-cell help crosstalk to melanoma development without the need of allo-BMT. We thereby helped define that tumor-infiltrating NK cells of DLI origin may serve as effective therapeutic targets for controlling melanoma.