Targeting FGFR1-regulated SPP1 signaling repolarizes immunosuppressive macrophages and sensitizes Hepatocellular Carcinoma to anti-PD-1 therapy.

The response rate to immune checkpoint blockade (ICB) in hepatocellular carcinoma (HCC) remains unsatisfactory, and the mechanisms of resistance are not fully understood. Here, we investigated the role of fibroblast growth factor receptor 1 (FGFR1) in shaping the tumor microenvironment (TME) and mediating ICB resistance. An anti-PD-1-resistant HCC model was established in mice, followed by single-cell RNA sequencing to profile TME alterations. We observed that ICB resistance was associated with FGFR1 upregulation, which activated MAPK signaling and induced SPP1 expression. This cascade promotes macrophage infiltration and M2-type polarization, while simultaneously suppressing T cell recruitment and cytotoxic function, thereby fostering an immunosuppressive microenvironment. SPP1 knockdown or neutralization significantly reduced macrophage accumulation and restored intratumoral T cell infiltration. Importantly, pharmacological inhibition of FGFR1 using BGJ398 synergized with anti-PD-1 therapy, resulting in enhanced antitumor efficacy in preclinical models. Analysis of clinical datasets further revealed that high FGFR1 expression correlated with poor responses to ICB of HCC patients. Collectively, these findings identify FGFR1 as a key mediator of ICB resistance in HCC. Targeting FGFR1 represents a promising strategy to reprogram the immunosuppressive TME and enhance response to immunotherapy, with potential additional value as a predictive biomarker.