Tumor development and therapeutic resistance are linked with tumor-associated macrophage (TAM) and myeloid-derived suppressor cell (MDSC) infiltration in
tumors via
chemokine axis.
Chemokine expression, which determines the pro or anti-inflammatory status of myeloid cells, are partly regulated by the
nuclear factor-kappa B (NF-κB) pathway. Here, we identified that conditional deletion of canonical NF-κB signaling (p65) in myeloid cells inhibited syngeneic
glioblastoma (GBM) through decreased CD45 infiltration in
tumors, as characterized by decreased TAMs (CD206+) and MDSCs (Gr1+ CD11b+), increased dendritic cells (CD86+) and cytotoxic T cells (CD8+) in the p65 knockout (KO) mice. Proinflammatory
cytokines (IFNγ, MCP1, MIP1α, and TNFα) and myeloid differentiation factor (
Endoglin) were increased in myeloid cells from p65 KO
tumor, which demonstrated an influence on CD8+T cell proliferation. In contrast, p65KO athymic chimeric mice with human GBM, failed to inhibit
tumor growth, confirming the contribution of T cells in an immune competent model. The analysis of human datasets and GBM
tumors revealed higher expression of p65 in GBM-associated CD68+ macrophages compared to neighboring stroma. Thus, canonical NF-κB signaling has an anti-inflammatory role and is required for macrophage polarization, immune suppression, and GBM growth. Combining an NF-κB inhibitor with standard
therapy could improve antitumor immunity in GBM.