Yi-Fei-San-Jie Chinese medicine formula reverses immune escape by regulating deoxycholic acid metabolism to inhibit TGR5/STAT3/PD-L1 axis in lung cancer.

Background: Yi-Fei-San-Jie Formula (YFSJF), a proprietary medicine of the First Affiliated Hospital of Guangzhou University of Chinese Medicine, has been widely used in clinical practice for several years and is currently being tested in randomized controlled trials for early-stage lung cancer in China. However, the mechanisms by which YFSJF affects lung cancer biology, particularly the immune microenvironment and metabolic processes, remain poorly understood.

Purpose: This study aims to explore how YFSJF modulates the immune microenvironment and metabolism in lung cancer, specifically its unique role in inhibiting immune evasion by targeting the TGR5/STAT3/PD-L1 pathway, which has not previously been reported.

Methods: Computed Tomography (CT) scan was used to assess YFSJF efficacy in patients with lung cancer and a mouse model of urethane-induced lung cancer. Histopathological evaluation, flow cytometry, and metabolomic analysis were used to assess lung tissue structure, immune cell subset changes, and metabolism modulation, respectively. Western blotting and immunohistochemistry were used to detect Ki67, TTF-1, TGR5, STAT3, p-STAT3, and PD-L1 protein expression. Serum cytokines were detected by ELISA.

Results: YFSJF effectively reduced the size of human lung cancer lesions and decreased the tumor burden and improved survival rates in mice. Lung tissue structure was also improved after YFSJF treatment. YFSJF regulated T-cell subsets, particularly by downregulating cells with PD-1-positive expression of CD3⁺, CD4⁺, and CD8⁺, and elevated serum TNF-α, IFN-γ, and GzmB levels. In addition, YFSJF modulated bile acid metabolism, particularly by inhibiting deoxycholic acid metabolism, which participates in immune regulation in lung cancer by acting on the G protein-coupled bile acid receptor TGR5.

Conclusion: Finally, YFSJF inhibited immune evasion by blocking the TGR5-mediated STAT3/PD-L1 pathway, weakening PD-L1 and PD-1 binding and reviving T-cell immune activity, thereby countering lung cancer immune evasion and exerting anti-tumor effects.