Progranulin Induces Immune Escape in Breast Cancer Via Up-Regulating PD-L1 Expression on TAMS and Promoting CD8+T cell Exclusion

Abstract

Background: Progranulin (PGRN), as a multifunctional growth factor, is overexpressed in multiple tumors, but the role of PGRN on tumor immunity is still unclear. Here, we studied the effect of PGRN on breast cancer tumor immunity and its possible molecular mechanism.Methods: The changes of macrophage phenotypes after PGRN treatment were detected by western blot, quantitative PCR and flow cytometry. Western blot was used to study the signal molecular mechanism of PGRN regulating this process. The number and localization of immune cells in WT and PGRN-/- breast cancer tissues were analyzed by immunohistochemical staining and immunofluorescence techniques. The activation and proliferation of CD8+ T cells were measured by flow cytometry.Results: After being treated with PGRN, the expressions of M2 markers and PD-L1 on macrophages increased. STAT3 signaling pathway inhibitor Stattic could significantly inhibit PD-L1 expression and M2 related markers induced by PGRN. In WT group, CD8 were co-localized with macrophages and PD-L1, but not tumor cells. The number of immune cells in PGRN-/- breast cancer tissue increased, and the infiltration into tumor parenchyma also increased. Moreover, in the co-culture system, WT peritoneal macrophages not only reduced the ratio of activated CD8+T cells but also reduced the proportion of proliferating CD8+T cells. The addition of PD-1 and PD-L1 neutralizing antibodies could effectively reverse this effect and restore the immune function of CD8+T cells.Conclusion: The results show that PGRN can promote M2 polarization and PD-L1 expression by activating the STAT3 signaling pathway. Furthermore, through PD-1/PD-L1 interaction, PGRN can promote the breast tumor immune escape. Our research may provide new ideas and targets for clinical breast cancer immunotherapy.

Dying cell-released exosomal CXCL1 promotes breast cancer metastasis by activating TAM/PD-L1 signaling

“…PD-L1 signaling is an important mechanism utilized by immunosuppressive TAMs to inhibit anticancer responses. Emerging reports have suggested that TAMs represent the major cellular source for maintaining PD-L1 expression in the TME in multiple tumors, including metastatic breast cancer, and that PD-L1 is crucial for the activation and M2 polarization of macrophages 37,38 . Molecular elucidation of PD-L1 regulation in TAMs is urgently needed for the successful development of treatment strategies and targeting agents to inhibit breast cancer immune escape.…”

“…As shown in Figure 3B, CXCL1 knockdown in exo-dead or CXCL1 neutralizing antibody (NA) partially abrogated the induction effect of exo-dead on the M2 polarization of macrophages, leading to the decreased invasion of breast cancer cells in the co-culture system (Figure 3C). Increasing studies have suggested that macrophages represent the major cellular source for maintaining PD-L1 expression in the TME, while PD-L1 is crucial for the activation and M2 polarization of macrophages 37,38 . Here, western blotting revealed that exo-dead could induce PD-L1 expression in macrophages in a time-and dose-dependent manner (Figure 3D), while CXCL1 knockdown in exo-dead or CXCL1 NA administration inhibited PD-L1 expression (Figure 3E-F).…”

PD‐L1/p‐STAT3 promotes the progression of NSCLC cells by regulating TAM polarization

“…TAMs can induce the malignant progression of tumour cells by secreting tumour growth cytokines into TME. 5 Programmed death ligand 1 (PD-L1) is the natural ligand of programmed cell death-1 (PD-1) and is encoded by the CD274 gene on chromosome 9p24.1. PD-L1 is mainly expressed in activated T lymphocytes, B lymphocytes, monocytes, mesenchymal stem cell and bone marrow-derived mast cells etc.…”