GBP2 Suppresses PD-L1 Dependent T-Cell Immune Responses via the STAT3-NF-κB Signaling Pathway in Gastric Cancer

Abstract

Background: Gastric cancer presents a significant global health burden, with existing therapies exhibiting limited efficacy and potential side effects. Molecular-targeted therapy has emerged as a promising approach. This study aimed to explore the role of guanylate binding protein 2 (GBP2) in programmed death 1 ligand (PD-L1)-related immune response in gastric cancer and to elucidate the underlying molecular regulatory mechanisms. Methods: The gastric adenocarcinoma cell line AGS, the human immortalized gastric epithelium cell line GES-1, and the peripheral blood mononuclear cells (PBMCs) obtained from healthy donors were utilized. Lentiviral plasmids, small interfering (si)RNAs, and the signal transducer and activator of transcription 3 (STAT3) inhibitor BP-1-102 were used to modulate targeted protein expression. Differential expression of GBP2 in gastric cancer cells was assessed, and the impact of GBP2 levels on STAT3, nuclear factor-kappa B (NF-κB), CD8, PD-L1, T-cell response-related cytokines of interleukin-2 (IL-2), interferon-γ (IFN-γ), tumor necrosis factor-alpha (TNF-α), and cell viability was determined. Immunofluorescence and gene expression analyses were conducted using Enzyme-Linked Immunosorbent Assay (ELISA), the RT-qPCR, Western Blot, and flow cytometry. Results: GBP2 was upregulated in gastric cancer cells, positively regulating PD-L1 expression and activating the STAT3-NF-κB pathway while negatively regulating CD8 expression. GBP2 overexpression enhanced the STAT3-NF-κB pathway activation and PD-L1 expression, which was reversed upon suppressing of the STAT3-NF-κB signaling pathway. Moreover, GBP2 knockdown in AGS cells cultured alone or with activated T-cells resulted in increased cell proliferation and invasion, and reduced cell apoptosis. Additionally, the increased/decreased GBP2 inhibited/promoted the expressions of interleukin-2 (IL-2), interferon-γ (IFN-γ) and tumor necrosis factor-alpha (TNF-α). Conclusion: GBP2 positively regulates PD-L1 expression through the STAT3-NF-κB signaling pathway and subsequently causes a suppression on T-cell immune responses, thus suggesting GBP2 as a potential immunotherapeutic target in gastric cancer.