NF-κB p50-deficient immature myeloid cell (p50-IMC) adoptive transfer slows the growth of murine prostate and pancreatic ductal carcinoma

background Macrophages and dendritic cells lacking the transcription factor nuclear factor kappa B p50 are skewed toward a proinflammatory phenotype, with increased cytokine expression and enhanced T cell activation; additionally, murine melanoma, fibrosarcoma, colon carcinoma, and glioblastoma grow slower in p50^−/− mice. We therefore evaluated the efficacy of p50-negative immature myeloid cells (p50-IMCs) adoptively transferred into tumor-bearing hosts. Immature cells were used to maximize tumor localization, and pretreatment with 5-fluorouracil (5FU) was examined due to its potential to impair marrow production of myeloid cells, to target tumor myeloid cells and to release tumor neoantigens. Methods Wild-type (WT)-IMC or p50-IMC were generated by culturing lineage-negative marrow cells from WT or p50^−/− mice in media containing thrombopoietin, stem cell factor and Flt3 ligand for 6 days followed by monocyte colony-stimulating factor for 1 day on ultralow attachment plates. Mice inoculated with Hi-Myc prostate cancer (PCa) cells or K-Ras^G12D pancreatic ductal carcinoma (PDC)luciferase cells received 5FU followed 5 days later by three doses of 10⁷ immature myeloid cells (IMC) every 3–4 days. results PCa cells grew slower in p50^−/− mice, and absence of host p50 prolonged the survival of mice inoculated orthotopically with PDC cells. IMC from Cytomegalovirus (CMV)-luciferase mice localized to tumor, nodes, spleen, marrow, and lung. 5FU followed by p50-IMC slowed PCa and PDC tumor growth, ~3-fold on average, in contrast to 5FU followed by WT-IMC, 5FU alone or p50-IMC alone. Slowed tumor growth was evident for 93% of PCa but only 53% of PDC tumors; we therefore focused on PCa for additional IMC analyses. In PCa, p50-IMC matured into F4/80⁺ macrophages, as well as CD11b⁺F4/80⁻CD11c⁺ conventional dendritic cells (cDCs). In both tumor and draining lymph nodes, p50-IMC generated more macrophages and cDCs than WT-IMC. Activated tumor CD8⁺ T cells were increased fivefold by p50-IMC compared with WT-IMC, and antibody-mediated CD8⁺ T cell depletion obviated slower tumor growth induced by 5FU followed by p50-IMC. Conclusions 5FU followed by p50-IMC slows the growth of murine prostate and pancreatic carcinoma and depends on CD8⁺ T cell activation. Deletion of p50 in patient-derived marrow CD34⁺ cells and subsequent production of IMC for adoptive transfer may contribute to the therapy of these and additional cancers.