Study on the mechanisms of alpha-linolenic acid in influencing the efficacy of immunotherapy for lung squamous cell carcinoma.

e20639 Background: Alpha Linolenic acid (ALA) has been shown to correlate with gut microbiota and plays a significant role in tumorigenesis, progression, and treatment. It also exhibits potential in modulating immune responses and promoting anti-tumor immunity. Lung squamous cell carcinoma (LUSC), a subtype of lung cancer, often faces limited immunotherapy efficacy due to an immunosuppressive microenvironment. Therefore, investigating the impact of ALA on the efficacy of LUSC immunotherapy and its underlying mechanisms holds significant clinical importance. Methods: This study begins with clinical samples, categorizing LUSC patients based on their progression-free survival (PFS) post-immunotherapy into a responder group (PFS > 6 months) R group (15 cases) and a non-responder group (PFS ≤ 6 months) NR group (8 cases). Pre-treatment fecal samples were collected for untargeted metabolomic analysis to identify differential gut metabolites affecting the efficacy of immunotherapy in LUSC. A mouse lung cancer model was employed, divided into a solvent control group, an ALA intervention group, a programmed death receptor 1 inhibitor (anti-PD-1) treatment group, and a combination therapy group (ALA + anti-PD-1), to observe changes in tumor volume across different treatment groups. Flow cytometry and immunohistochemistry were used to detect changes in CD8 + T cells within the tumors of different treatment groups. ELISA was utilized to measure the expression levels of interferon-gamma (IFN-γ) in the plasma of mice across different treatment groups. Results: Untargeted metabolomics analysis revealed that the abundance of ALA was significantly increased in the R group compared to the NR group in LUSC patients following immunotherapy. In vivo studies using a mouse model demonstrated that the combination therapy group (ALA + anti-PD-1) exhibited a markedly slower tumor growth rate compared to the anti-PD-1 monotherapy group. Flow cytometry and immunohistochemistry results indicated an increased infiltration of CD8 + T cells in the tumor tissues of the combination therapy group (ALA + anti-PD-1) relative to the anti-PD-1 monotherapy group. Concurrently, ELISA results showed an elevated proportion of IFN-γ in the peripheral blood, suggesting a systemic immunomodulatory effect of the gut metabolite ALA. Conclusions: Our findings suggest that the efficacy of immunotherapy in LUSC may be associated with the intestinal levels of ALA. ALA enhances the function of CD8 + T cells by increasing their tumor infiltration and elevating the levels of the cytokine IFN-γ, thereby demonstrating a synergistic effect when combined with anti-PD-1 therapy in improving the efficacy of LUSC immunotherapy.