Hirsutella sinensis Fungus Enhances CD8(+) T Cell Anti-Tumor Activity in NSCLC via Modulating the IL-10/STAT3/STAT1 Axis.

PURPOSE: The tumor microenvironment (TME) has been shown to have a significant impact on lung cancer. Previously, Hirsutella sinensis fungus (HSF) may greatly boost T cell infiltration in the TME. In this study, we aimed to investigate HSF-mediated immunomodulation via IL-10 signaling in TME of non-small cell lung cancer (NSCLC). METHODS: An lung cancer mouse model was generated by subcutaneous injection of LLC cells with or without IL-10 knockdown in C57BL/6 mice or nude mice. HSF was orally administered once to the model mice daily for 15 days. Tumor growth was measured using in vivo imaging technology and vernier calipers. Hematoxylin and eosin (H&E) and Enzyme-linked immunosorbent assay (ELISA) were employed to estimate the cytotoxicity and immunological factors of the HSF treatment. Immune profiles, proliferation, apoptosis, the function of CD8(+) T cells, and the primary source of IL-10 in tumor tissue were detected by flow cytometry. RT-qPCR and Western blotting were performed to detect IL-10/STAT3/STAT1-related proteins in tumor tissues and CD8(+) T cells. RESULTS: HSF could inhibit tumor growth in LLC tumor model mice. Significantly, HSF reduced F4/80(+) CD11b(+) macrophages and regulatory T cells, as well as increased the percentage of Naïve T cells (CD44(Low)CD62L(High)) and central memory T cells (T(CM), CD44(High)CD62L(High)) populations in tumor tissues. Importantly, HSF inhibited apoptosis, and promoted cell proliferation and secretion of interferon (IFN)-γ and granzyme B in CD8(+) T cells, which were attenuated by IL-10. Western blot analysis of tumor tissues and CD8(+) T cells demonstrated that IL-10R, phosphorylation of STAT3 and STAT1 were significantly decreased upon HSF treatment. Flow cytometry identified B cells as the primary IL-10 source in tumor tissues. CONCLUSION: HSF displayed antitumor immune activity by increasing the infiltration of CD8(+) T cells in vivo, which might be made feasible by down-regulation of the IL-10/STAT3/STAT1 signaling pathway.