IFN-γ-mediated suppression of ANGPT2-Tie2 in endothelial cells facilitates tumor vascular normalization during immunotherapy.

INTRODUCTION

Tumor angiogenesis is a critical biological hallmark of cancer, which involves multiple molecularly regulated signaling pathways, including the angiopoietin (ANGPT)-Tie2 and the vascular endothelial growth factor (VEGF) signaling pathways. Despite initial optimism, targeting tumor angiogenesis in the treatment of lung adenocarcinoma (LUAD) has been unsatisfactory. Currently, monotherapy with PD-1/PD-L1 inhibitors, or their combination with bevacizumab, is considered the standard therapeutic approach for LUAD. Recent studies have shown that immunotherapy suppresses tumor angiogenesis and facilitates vascular normalization. However, whether and how anti-PD-L1 therapy influences tumor vasculature remains unclear.

METHODS

To investigate the impact of immunotherapy on the vasculature of LUAD, a mouse model of lung adenocarcinoma was established by subcutaneous implantation of Lewis lung carcinoma cells . The effects of different treatments on microvessel density and pericyte coverage were explored, and the expression of angiogenesis-related factors was analyzed. Furthermore, to explore the molecular mechanisms through which IFN-γ regulates tumor blood vessels during immunotherapy, we elucidated the specific mechanisms by means of techniques such as siRNA, ChIP, RT-qPCR, Western blot, and immunofluorescence. Finally, the effects of IFN-γ on the proliferation, migration, and angiogenic function of endothelial cells (ECs) were evaluated through CCK-8, Transwell, and HUVEC tube formation assays.

RESULTS

Employing a mouse model of LUAD, we demonstrated that PD-L1 blockade therapy inhibits tumor angiogenesis and normalizes vasculature in an IFN-γ-signaling-dependent manner. Notably, anti-PD-L1 therapy reduced Tie2 and ANGPT2 expression, and these effects were reversed by the JAK1/2 inhibitor. Mechanistically, we demonstrated that IFN-γ inhibited Tie2 and ANGPT2 expression in ECs, and suppressed gene transcription through the AKT-FOXO1 signaling pathway. Interestingly, IFN-γ-mediated activation of STAT1 exerts negative regulation by directly binding to the promoter regions of the and genes. Functionally, IFN-γ limits the migration, proliferation, and tube formation of ECs.

DISCUSSION

In conclusion, our results revealed a novel mechanism wherein IFN-γ-mediated inhibition of ANGPT2-Tie2 facilitates vascular normalization during immunotherapy in LUAD, which performs an essential function in the antitumor efficacy of immunotherapy.