Introduction
Gastric cancer (GC) remains one of the most lethal malignancies worldwide, with limited treatment success largely due to immune evasion and tumor heterogeneity 1. The advent of immune checkpoint inhibitors has revolutionized the treatment of solid tumors 2; however, only a subset of GC patients benefits from PD-1/PD-L1 blockade, suggesting the presence of intrinsic mechanisms regulating immune escape 3. Leukemia Inhibitory Factor (LIF), a multifunctional interleukin (IL)-6 cytokine family, plays an essential role in epithelial repair, embryonic stem cell pluripotency, and immune regulation 4. In several type of tumors, LIF is emerging as a key mediator of tumor progression and immune modulation. LIF signals through a heterodimeric receptor complex composed of LIF-receptor (LIFR) and GP130 and promotes JAK/STAT3 pathway activation 5,6. Notably, oncogenic STAT3 signaling has been shown to drive PD-L1 expression and promote immune suppression across multiple tumor types, including breast cancer 7 and NK/T-cell lymphoma, supporting the broader relevance of this axis in tumor immune escape 8. Although LIF is known to activate JAK/STAT3 signaling 4, its role in regulating PD-L1 expression and establishing an immunosuppressive microenvironment in GC is not fully defined.
Aims & Methods
We aimed to dissect the role of LIF in promoting PD-L1 expression and immune escape in GC and to explore the therapeutic potential of LIF inhibition. Neoplastic and non-neoplastic gastric mucosa from 61 GC patients were analyzed by transcriptomic profiling, immunofluorescence (IF), and tSNE analysis. Expression levels of LIF, PD-L1, and key signaling molecules were quantified. In vitro mechanistic studies, employed human gastric cancer cells (MKN45). MKN45 were exposed to recombinant LIF, with or without LRI-305, a novel LIF receptor antagonist. Western blotting, RT-qPCR, IF, and chromatin immunoprecipitation (ChIP) assays were used to evaluate downstream pathway activation and transcriptional regulation of PD-L1.
Results
Transcriptome analysis revealed a significant upregulation of LIF and PD-L1 in tumor samples, which was confirmed at the protein level by Immunofluorescence analysis. Elevated LIF expression correlated with reduced overall survival and an immunosuppressive tumor microenvironment characterized by increased infiltration of PD1⁺ T cells, Tregs, and LIF⁺ TAM. Functional assays demonstrated that LIF stimulation activated the JAK1/STAT3 pathway, leading to enhanced PD-L1 transcription. This was supported by increased phosphorylation of JAK1 and STAT3 and ChIP data confirming STAT3 recruitment to the PD-L1 promoter. LIF also promoted cell proliferation and epithelial-mesenchymal transition (EMT), indicated by upregulation of SNAIL1. Importantly, LRI-305 treatment abolished these effects, downregulating PD-L1 expression, reducing EMT markers, and restoring pro-apoptotic responses. These findings confirmed that LIF sustains tumor growth and play a pivotal role in immune resistance through STAT3-mediated PD-L1 upregulation.
Conclusion
Our data identify the LIF/STAT3/PD-L1 axis as a crucial pathway driving immune evasion in GC. LIF promotes a tolerogenic tumor microenvironment, impairs anti-tumor immunity and correlates with aggressive tumor behavior and poor prognosis. Pharmacological blockade of LIF signaling using LRI-305 effectively reverses these effects, offering a novel combinatorial strategy to enhance the efficacy of immune checkpoint inhibitors in GC patients.
References
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