Lequn Li

Growth factor-independent-1 transcription repressor (GFI1) is crucial for determining the differentiation and fate of exhausted CD8⁺ T cells and affects immunotherapy outcomes. However, the effects of tumor cell-intrinsic GFI1 on antitumor immunity and the response to immunotherapy remain unknown. The tumor cell-intrinsic expression of GFI1 was examined via RT‒qPCR and Western blotting. Immunohistochemical staining of tumor tissues was performed to assess the relationships among GFI1, CD8, and MHC I expression. A syngeneic mouse model and clinical tumor samples from NSCLC patients undergoing immunochemotherapy were used to evaluate how tumor cell-intrinsic GFI1 affects the response to immunotherapy. Additionally, techniques such as flow cytometry, immunoprecipitation, ChIP-qPCR, immunofluorescence, and both loss- and gain-of-function approaches were employed to investigate the underlying mechanisms involved. Tumor-intrinsic GFI1 expression was positively associated with MHC I expression and the infiltration of CD8⁺ T cells. Tumors with higher GFI1 levels showed a significantly better response to immunotherapy. The overexpression of GFI1 in tumor cells increases MHC-I expression in a STAT1-dependent manner. Mechanistic analysis revealed that GFI1 inhibits HDAC1 activity in tumor cells by promoting its export to the cytoplasm, thereby increasing H3K9 acetylation and the transcription of STAT1 and MHC-I. Additionally, phenformin, an AMPK activator, increases GFI1 levels by downregulating EZH2 expression. Compared with anti-PD-L1 therapy alone, combining phenformin with anti-PD-L1 therapy enhances antitumor effects. This study demonstrated the crucial role of tumor-intrinsic GFI1 in enhancing antitumor immune responses, suggesting a new target for increasing the effectiveness of PD-1/PD-L1 blockade.

IFNγ-mediated signaling in tumor cells can induce immunosuppressive responses and cause tumor resistance to immunotherapy. Blocking TGFβ promotes T lymphocyte infiltration and turns immunologically cold tumors into hot tumors, thereby improving the efficacy of immunotherapy. Several studies have shown that TGFβ inhibits IFNγ signaling in immune cells. We thus sought to determine whether TGFβ affects IFNγ signaling in tumor cells and plays a role in the development of acquired resistance to immunotherapy. TGFβ stimulation of tumor cells increased SHP1 phosphatase activity in an AKT–Smad3-dependent manner, decreased IFNγ-mediated tyrosine phosphorylation of JAK1/2 and STAT1, and suppressed the expression of STAT1-dependent immune evasion–related molecules, e.g., PD-L1, IDO1, herpes virus entry mediator (HVEM), and galectin-9 (Gal-9). In a lung cancer mouse model, dual blockade of TGFβ and PD-L1 led to superior antitumor activity and prolonged survival compared with anti–PD-L1 therapy alone. However, prolonged combined treatment resulted in tumor resistance to immunotherapy and increased expression of PD-L1, IDO1, HVEM, and Gal-9. Interestingly, after initial anti–PD-L1 monotherapy, dual TGFβ and PD-L1 blockade promoted both immune evasion gene expression and tumor growth compared with that in tumors treated with continuous PD-L1 monotherapy. Alternatively, treatment with JAK1/2 inhibitor following initial anti–PD-L1 therapy effectively suppressed tumor growth and downregulated immune evasion gene expression in tumors, indicating the involvement of IFNγ signaling in immunotherapy resistance development. These results demonstrate an unappreciated effect of TGFβ on the development of IFNγ-mediated tumor resistance to immunotherapy.Significance:Blocking TGFβ facilitates IFNγ-mediated resistance to anti–PD-L1 therapy due to the role of TGFβ in inhibiting IFNγ-induced immunoevasion by increasing SHP1 phosphatase activity in tumor cells.

Parameters for orthotopic OVA+ metastasis model

Tumor reactive OT-I T cells are more cytotoxic in blood than in tumor draining lymph nodes

Direct injection does not damage the LN anti-tumor immune response

Metastatic patterns of colon cancer differ by MSI status