Bhavna Verma, PhD, Jon Weidanz, PhD, Amy Wesa, PhD
Harnessing NK cell anti-cancer cytotoxicity has gained interest as a therapeutic strategy, and
consequently improved preclinical models supporting the translation of NK cell–mediated therapies to the clinic are desired. Reproducible models with human NK engraftment into immunodeficient mice co-engrafted with cell line-derived xenograft or patient-derived xenograft tumor models have been lacking due to an inability to support NK cell engraftment and persistence. Here we evaluated IL-15-NOG mice for the engraftment and sustained survival of both ex vivo expanded and primary human NK cell isolates for establishing models that engraft effectively with both human NK cells and a PDX or CDX tumor.
Materials and Methods
NK cells from normal adult peripheral blood mononuclear cells (PBMC) donors (N=3) were expanded using two different commercially available kits and evaluated for NK phenotype, expansion rates and yields. Ex vivo expanded NK cells were tested for antibody dependent cell cytotoxicity (ADCC). Titrated doses of ex vivo expanded NK cells were adoptively transferred into IL-15-NOG mice for human chimerism, and the persistence and survival of NK cells and their immunophenotype were assessed. In separate studies, naïve NK cells enriched from PBMC were also evaluated for NK cell persistence and expansion in vivo. To establish an NK ImmunoGraft, NK cells were engrafted in xenograft tumor bearing mice (CDX or PDX) and tumor growth kinetics and infiltrating NK cells phenotype were characterized.
Donor dependent NK expansion was observed ex vivo, with 28 to 50-fold expansion by two weeks. NK cells expanded ex vivo were CD3-CD16+CD56± and varied based on the expansion kit utilized. ADCC mediated lysis was observed with ex vivo expanded NK cells. Nearly all CD45+ cells in circulation were NK cells, and these peaked by week 2, and were maintained for up to 10 weeks in IL-15-NOG mice. Primary NK cells engrafted with slower kinetics, with peak abundance at 3-4 weeks. NK cells expressed granzyme B, and further functional studies are in progress. For all NK cell populations, cell density-dependent engraftment was observed with a largely stable NK phenotype observed across the study. In the absence of any therapeutic treatment, NK cell persistence and expansion in vivo did not inhibit tumor xenograft growth kinetics in IL-15-NOG mice.
IL-15-NOG mice support the survival and persistence of human NK cells from both ex vivo expanded and naïve NK cells, suggesting the universality of this platform for human NK engraftment. Our preliminary studies support IL-15 NOG mouse model as a suitable system for evaluation of NK cellular therapies or NK cell-modulating therapies in the context of patient-derived or cell-line derived xenograft (PDX or CDX) mouse models.