Adoptive transfer of immature myeloid cells lacking NF-κB p50 (p50-IMC) impedes the growth of MHC-matched high-risk neuroblastoma.

High-risk neuroblastomas harbor abundant myeloid cells that suppress antitumor immunity and support tumor growth. Macrophages lacking the inhibitory NF-κB p50 subunit adopt a pro-inflammatory phenotype. We now report that murine 9464D neuroblastoma cells, which express high levels of exogenous MYCN, grow slower in syngeneic p50(f/f);Lys-Cre mice that lack p50 in macrophages and neutrophils, compared with p50(f/f) littermates. Tumors in p50(f/f);Lys-Cre mice possess increased numbers of total and activated CD4 and CD8 T cells, and depletion of both of these T-cell populations accelerates tumor growth. Anti-PD-1 T-cell checkpoint blockade, or DNA methyltransferase and histone deacetylase inhibition, further slows tumor growth. In addition, adoptive transfer of immature myeloid cells lacking NF-κB p50 (p50-IMC), generated either from the bone marrow of p50 mice or via nucleofection of a p50 sgRNA:Cas9 complex into wild-type hematopoietic progenitors, also slowed growth of MHC-matched 9464D tumors but not of MHC-mismatched Neuro2A tumors. These findings further validate the utility of targeting myeloid NF-κB p50 as a strategy for cancer therapy and demonstrate activity of p50-IMC generated by gene editing of syngeneic marrow cells, a cell product relevant to clinical translation.