Fusobacterium nucleatum promotes bladder cancer progression and immune escape by activating the IL22/STAT3/PD-L1 signaling cascade.

OBJECTIVE

This study investigates the mechanism by which Fusobacterium nucleatum (Fn) promotes bladder cancer (BC) progression and immune escape through the interleukin 22 (IL22)/signal transducer and activator of transcription 3 (STAT3)/programmed death-ligand 1 (PD-L1) cascade signaling.

METHODS

Fecal samples from BC patients (n = 73) and healthy controls (n = 39) were analyzed for Fn abundance using qRT-PCR. IL-22, p-STAT3, STAT3, and PD-L1 levels were determined by qRT-PCR and western blot. The in vitro cultured human BC cell line (T24) were co-cultured with Fn, followed by CCK-8, colony formation, and Transwell assays to assess cell viability, proliferation, and invasion and migration, respectively. A co-culture system of T24 and CD8-positive T lymphocytes (CD8+ T) cells was established. Immune responses were assessed by determining tumor necrosis factor alpha (TNF-α), interferon gamma (INF-γ), granzyme B (GZMB), and pore-forming protein (Perforin) levels in supernatants. In vivo studies using a BC mouse model examined tumor progression and immune markers through flow cytometry, focusing on CD8+ T cells and regulatory T cell (Treg) populations. Immunohistochemical assay was conducted to measure ki67 levels in tumor tissues.

RESULTS

Fn levels were significantly elevated in BC patients' feces. Fn treatment enhanced cancer cell viability, proliferation, invasion, and migration. Fn activated the IL22/STAT3/PD-L1 pathway and showed positive correlations with these markers in BC tissues. In the co-culture system, Fn reduced CD8+ T cell function and increased Treg proportions in tumor tissues. The in vivo experiments confirmed that Fn promoted IL22/STAT3/PD-L1 expression, altered immune cell ratios, and increased ki67 expression levels.

CONCLUSION

Fn promotes the IL22/STAT3/PD-L1 cascade signaling, thereby facilitating in vivo progression and immune evasion of BC.