{
  "abstract": "Background Glioblastoma (GBM), the most common malignant primary brain tumor, remains incurable despite aggressive multi-modal therapies. Immunotherapy, while effective for many solid tumors, has not shown benefits against GBM. Limited T cell infiltration and an immunosuppressive tumor microenvironment (TME) are among the main barriers to successful immunotherapy. Evidence from extracranial solid tumors suggests that the chemokine CXCL-12 regulates immune cell trafficking and promotes an immunosuppressive TME. 1–7 We hypothesized that the brain’s unique tissue environment creates a distinct immune response compared to extracranial tissues. This work aimed to test whether blocking CXCL12, using the spiegelmer NOX-A12, modulates the immune TME to enhance immunotherapy response in GBM, and whether the immune response differs between intracranial and extracranial environments.Methods Using B6 immunocompetent mice, we established a subcutaneous (s.c.) SB28 GBM model representing an extracranial tissue environment and compared it to orthotopic (intracranial) SB28. Tumor-bearing mice were treated with either vehicle, NOX-A12, anti-PD1 and anti-CTLA4 (immune-check-point blockade, ICB), or NOX-A12 + ICB (combination). Immune cells from tumor and blood were analyzed using high-dimensional flow cytometry. Statistical analysis used ANOVA with post-hoc Tuckey`s multiple comparison test. Survival was analyzed using the log-rank test.Results Treatment with ICB increased overall survival in s.c. SB28, but not in intracranial (i.c.) SB28 model. While ICB increased circulating CD8 and CD4 T cell subsets in both s.c. and i.c. models, it increased antigen-experienced CD8 and CD4 T cells only in the TME of the s.c. tumors. To enhance T cell migration into i.c. tumors, we targeted CXCL12 with NOX-A12. As expected, combining NOX-A12 with ICB significantly increased antigen-experienced CD8 T cells in i.c. and s.c. SB28 compared to ICB or NOX-A12 monotherapy. Additionally, the combination treatment increased antigen-experienced CD4 T cells only in the i.c tumor, indicating a tissue-specific treatment effect. These treatment effects were not evident in the blood, indicating a local mechanism of action within the TME. However, the increase in intra-tumoral T-cells induced by the combination treatment was not translated into increased median overall survival.Conclusions The distinct survival benefit of s.c. SB28 tumors in response to ICB was consistent with an increase in T cell subsets, which was absent in i.c SB28 tumors. However, an increase in T cells by CXCL12 inhibition was not translated into increased survival, suggesting that additional factors in the brain tissue contribute to treatment resistance. Elucidating those factors is imperative for the development of innovative strategies to augment immunotherapy efficacy in GBM.Acknowledgements We acknowledge TME Pharma AG for providing of Nox-A12References De Filippo K, Rankin SM, CXCR4, the master regulator of neutrophil trafficking in homeostasis and disease. Eur J Clin Invest, 2018;48(Suppl 2):e12949.Mercurio L, et al. Targeting CXCR4 by a selective peptide antagonist modulates tumor microenvironment and microglia reactivity in a human glioblastoma model. J Exp Clin Cancer Res. 2016;35:55.Wang Z, et al. Carcinomas assemble a filamentous CXCL12-keratin-19 coating that suppresses T cell-mediated immune attack. Proc Natl Acad Sci U S A, 2022;119(4).Seo YD, et al. Mobilization of CD8(+) T cells via CXCR4 blockade facilitates PD-1 checkpoint therapy in human pancreatic cancer. Clin Cancer Res. 2019;25(13):3934–3945.Fearon DT. The carcinoma-associated fibroblast expressing fibroblast activation protein and escape from immune surveillance. Cancer Immunol Res. 2014;2(3):187–93.Feig C, et al. Targeting CXCL12 from FAP-expressing carcinoma-associated fibroblasts synergizes with anti-PD-L1 immunotherapy in pancreatic cancer. Proc Natl Acad Sci U S A. 2013;110(50):20212–7.Yang J, et al. Loss of CXCR4 in myeloid cells enhances antitumor immunity and reduces melanoma growth through NK cell and FASL mechanisms. Cancer Immunol Res. 2018;6(10):1186–1198.Ethics Approval All animal experiments and protocols were reviewed and approved by National Cancer Institute",
  "authors": [
    {
      "affiliations": [
        "Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Chen Cam-El Makranz"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Brita Anderson"
    },
    {
      "affiliations": [
        "Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Tuesday Haynes"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Jo Spurgeon"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Ayaka Hara"
    },
    {
      "affiliations": [
        "National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Nicole Briceno"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Meili Zhang"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Dionne Davis"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Hua Song"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Wei Zhang"
    },
    {
      "affiliations": [
        "Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Masashi Watanabe"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Mark Gilbert"
    },
    {
      "affiliations": [
        "National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Masaki Terabe"
    },
    {
      "affiliations": [
        "Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA"
      ],
      "name": "Caitlin Huguely"
    }
  ],
  "title": "448 The brain tissue environment contributes to a unique response of glioblastoma against immunotherapy",
  "uid": "eb491f9a-96a7-5564-9ccf-8b1c4fe1411a"
}