S which includes checkpoint inhibitors. Updated information might be presented. Trial Registration ClinicalTrials.gov identifier NCT02869295. P370 NF-kB p50 promotes the suppressive M2 phenotype of tumorassociated macrophages within a mouse model of glioma Theresa Barberi, Allison Martin, Rahul Suresh, David Barakat, Sarah Harris-Bookman, Charles Drake, Alan Friedman Johns Hopkins University, Baltimore, MD, USA Correspondence: Theresa Barberi ([email protected]) Journal for ImmunoTherapy of Cancer 2016, four(Suppl 1):P370 Background Glioblastoma multiforme (GBM) brain tumors are nearly uniformly fatal. The GBM microenvironment involves abundant tumor-associated macrophages (TAMs) that predominantly assume a pro-tumor “M2” phenotype instead of a pro-inflammatory “M1” phenotype. The inhibitory p50 subunit from the NF-kB transcription issue exhibits markedly improved nuclear expression in TAMs and M2-polarized macrophages, and p50 knockdown/deletion suppresses expression of M2-associated factors [1, 2]. We hypothesize that absence of p50 will convert TAMs to an M1 phenotype that could lessen glioma development and prolong survival. Methods GL261-Luc cells have been intracranially implanted into mice. Tumor development was monitored by IVIS imaging. Brains had been removed 136 days soon after implantation for flow cytometry (FC) or RT-qPCR analysis. Depleting antibodies were administered by i.p. injection; clodronate by tail vein injection. Na e T cells had been enriched from spleens, skewed in vitro with cytokines and blocking antibodies, expanded in IL-2, then stimulated with PMA/ionomycin. Cells were assessed for Th or Tc1 skewing by FC or ELISA. Outcomes p50(-/-) mice exhibit drastically slower GL261-Luc tumor growth and prolonged survival. p50(-/-) tumor CD11b + myeloid cells express enhanced M1-associated and decreased M2-associated mRNAs relative to WT mice. FC indicates glioma-bearing p50(-/-) brains contain fewer TAMs expressing the M2 marker CD206/MRC1, at the same time as fewer Tregs, improved IFNg-producing CD4+ T cells, and improved granzyme B+ CD8+ T cells. Transplant of p50(-/-) bone marrow into lethally-irradiated WT recipients confers a Glycoprotein 130 (gp130) Proteins Formulation important survival benefit upon tumor inoculation. Clodronate-mediated macrophage IL-25/IL-17E Proteins medchemexpress depletion decreases survival of tumor-bearing p50(-/-) mice but has no effect on WT mice. Depletion of CD4+ T cells markedly reduces survival in tumor-bearing p50(-/-) mice whereas depletion of CD8+ T cells has no effect. We observe no intrinsic defect in the capability of p50(-/-) na e splenic CD4+ T cells to differentiate into Tregs, Th1, Th17, or Th2 subsets; nevertheless, p50(-/-) na e splenic CD8+ T cells exhibit enhanced capability to make IFNg, TNFa, and granzyme B. Conclusions NF-kB p50 is definitely an essential modulator from the suppressive immune phenotype in GBM. Both TAM and T cells are extra activated and much less tumorpermissive when p50 is absent. Targeted deletion of p50 from TAMs and/or T cells may serve as a viable therapeutic for individuals with GBM.References 1. Saccani A, et al.: p50 nuclear factor-B overexpression in tumorassociated macrophages inhibits M1 inflammatory responses and antitumor resistance. Cancer Res 2006, 66(23):114321440. 2. Porta C, et al.: Tolerance and M2 (alternative) macrophage polarization are associated processes orchestrated by p50 nuclear element B. Proc Natl Acad Sci 2009, 106(35):149784983.P369 A CD122-biased agonist increases CD8 + T Cells and all-natural killer cells in the tumor microenvironment; making cold tumors hot with NKTR-214 Chantal.