Interferon gamma inhibits CXCL8–CXCR2 axis mediated tumor-associated macrophages tumor trafficking and enhances anti-PD1 efficacy in pancreatic cancer

<jats:sec> <jats:title>Background</jats:title> <jats:p>Pancreatic cancer (PC) is a common malignancy of the digestive system and is characterized by poor prognosis and early metastasis. Tumor immune escape plays an important role in PC progression. Programmed death 1 (PD1) blockade therapy is a promising treatment for patients with PC, but is yet to achieve significant clinical effects so far. Interferon gamma (IFN-γ) is a soluble dimeric cytokine that is closely associated with tumor immune surveillance and cytotoxicity. IFN-γ suppresses a variety of tumor-derived cytokines in PC, such as CXCL8. In the present study, we investigated the therapeutic efficacy of combined anti-PD1 and IFN-γ treatment in PC.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>BxPC-3 and Panc-1 human PC cell lines were used to construct a murine PC model. Blood samples (n=44) and surgical resection specimens (n=36) from human patients with PC were also collected. χ<jats:sup>2</jats:sup> test, two-tailed unpaired t-test or Kaplan-Meier survival analysis was used to calculate p values.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>PD1/PD-L1 signaling was overexpressed in PC tumor-bearing mice. Anti-PD1 prevented tumor growth if initiated early after tumor inoculation; however, delayed anti-PD1 treatment showed limited benefit. Murine PC model had a preferential expansion of CXCR2<jats:sup>+</jats:sup>CD68<jats:sup>+</jats:sup> macrophages, and these cells showed an immunosuppressive nature (M2 polarization). PC tumors overexpressed CXCL8 and tumor-derived CXCL8 deficiency prohibited the trafficking of CXCR2<jats:sup>+</jats:sup>CD68<jats:sup>+</jats:sup> macrophages. IFN-γ suppressed the expression of tumor-derived CXCL8, and combined with IFN-γ treatment, delayed anti-PD1 treatment showed significant antitumor effects. Thus, we conclude that murine CXCR2<jats:sup>+</jats:sup>CD68<jats:sup>+</jats:sup> macrophages traffic to PC tumors by tumor-derived CXCL8 and mediate local immunosuppression, which limits the efficacy of PD1 blockade therapy. IFN-γ suppresses tumor-derived CXCL8 and inhibits the tumor trafficking of CXCR2<jats:sup>+</jats:sup>CD68<jats:sup>+</jats:sup> macrophages by blocking the CXCL8–CXCR2 axis to enhance anti-PD1 efficacy. Human PC also produces high levels of CXCL8. Patients with PC present elevated CXCR2 expression on peripheral and tumor-infiltrating CD68<jats:sup>+</jats:sup> macrophages, which are associated with advanced tumor stage and poor prognosis.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Our findings suggest that IFN-γ is a translatable, therapeutic option to improve the efficacy of PD1 blockade therapy by preventing trafficking of CXCR2<jats:sup>+</jats:sup>CD68<jats:sup>+</jats:sup> macrophages via blocking the CXCL8–CXCR2 axis.</jats:p> </jats:sec>