Clostridium Butyricum and butyrate enhance PD-1 inhibitor therapy in non-small cell lung cancer by regulating the HDAC1/ID2/IL-12R pathway

Background PD-1 blockade has become an important immunotherapeutic strategy, its clinical efficacy in non-small cell lung cancer (NSCLC) remains suboptimal. This study explores the effect and mechanism of sodium butyrate (NaB) and Clostridium butyricum ( C. butyricum ) combined with PD-1 inhibitors in NSCLC. Methods We established an NSCLC mouse model and evaluated tumor size, histopathology, apoptosis, cell proliferation, inflammatory factors, immune cell populations, and proteins of the HDAC1/ID2/IL-12R axis in the tumor, along with gut microbiome profiling. Results A combination of NaB or C. butyricum with PD-1 inhibitors significantly inhibited tumor growth and increased spleen and thymus indices. The combinations promoted tumor cell apoptosis, reduced the number of Ki67-positive proliferating cells, and increased IL-2, IL-6, IL-12, TNF-α, and IFN-γ levels in tumor tissues and serum. Additionally, the infiltration of CD4 + and CD8 + T cells in the tumor increased, while the Treg cells decreased. Importantly, the expressions of HDAC1 were markedly decreased, whereas ID2 and IL-12R levels increased in tumor tissues from NaB or C. butyricum with PD-1 inhibitor groups. Meanwhile, the combination of NaB or C. butyricum with PD‑1 inhibitors could alleviate the disturbance of gut microbiota by decreasing the Gordonibacter and increasing the WCHB1-32 . Significantly, the anti-CD8 antibody attenuated the inhibition of tumor growth conferred by NaB and PD‑1 inhibitors in vivo. Conclusions Collectively, NaB and C. butyricum enhanced the therapeutic action of PD‑1 inhibitors in murine models of NSCLC, possibly by modulating the HDAC1/ID2/IL-12R pathway, impacting intestinal microbiota and immune microenvironment.