BACKGROUND: Immune checkpoint inhibitors (ICIs), particularly PD-1 antibodies, represent a breakthrough in colorectal cancer (CRC) treatment. However, their clinical efficacy remains limited by tumour-induced immunosuppression. Traditional Chinese medicine (TCM) has attracted growing interest as a potential adjuvant to immunotherapy. Zhenqi Fuzheng Granule (ZQFZ) is a clinically approved herbal prescription widely used as an adjuvant therapy for CRC, yet its mechanistic underpinnings remain elusive.
OBJECTIVE: To investigate how ZQFZ improves the efficacy in CRC, with emphasis on gut microbiota modulation, SCFAs production, and downstream immunometabolic pathways involving GPR109A, and confirms that butyrate plays an important role in colorectal cancer inhibition.
METHODS: Phytochemical analysis of ZQFZ was conducted using LC-MS/MS and UPLC-MS/MS, identifying and quantifying seven major compounds. In vivo experiments, AOM/DSS-induced CRC mouse models were treated with ZQFZ, PD-1 antibody, or their combination. Tumour progression, body weight, and survival were monitored. Gut microbial composition and colonic SCFAs levels were assessed via 16S rRNA sequencing and gas chromatography. RT-qPCR was employed to validate the expression of key genes associated with the GPR109A/AKT/mTOR/HIF-1α signaling pathway. Molecular changes in the GPR109A/AKT/mTOR/HIF-1α pathway were evaluated through Western blotting, transcriptomic, and proteomic analyses. Immune cell infiltration and phenotypes were analyzed by flow cytometry. Molecular docking and molecular dynamics simulations were conducted to predict the binding affinity and structural stability between GPR109A and AKT1. The interactions between GPR109A and AKT1, as well as between butyrate and GPR109A, were further validated in vitro using microscale thermophoresis (MST) assays. To evaluate the microbial basis of ZQFZ activity, antibiotic-pretreated mice received ZQFZ-derived fecal microbiota transplantation (FMT). In vitro experiments, to investigate the mechanism by which sodium butyrate (NaB), the major gut microbial metabolite of ZQFZ, inhibits glycolysis in colorectal cancer under hypoxic conditions, CCK-8 assays, flow cytometry, lactate measurements, and Western blotting were performed to assess cell viability, apoptosis, lactate production, and the expression of AKT/mTOR/HIF-1α and glycolysis-related proteins.
RESULTS: LC-MS/MS profiling identified multiple bioactive constituents in ZQFZ. Targeted UPLC-MS/MS quantification revealed that the formulation contained Adenosine (0.87mg/g), Salidroside (0.11 mg/g), Astragaloside IV (0.07 mg/g), Calycosin (0.03 mg/g), Formononetin (6.7 μg /g), Chlorogenic acid (1.4 μg/g), Apigenin (0.5 μg/g). In vivo studies, both ZQFZ and PD-1 antibody inhibited tumour growth, with the combination treatment exerting the most pronounced antitumour effects. ZQFZ reshaped the gut microbiota, increased the levels of short-chain fatty acids (SCFAs), particularly butyrate, and activated the GPR109A pathway, leading to downregulation of the AKT/mTOR/HIF-1α signaling axis, suppression of HK2 expression and lactate production, and consequent inhibition of glycolysis. Immune remodeling was also observed, including reduced infiltration of myeloid-derived suppressor cells (MDSCs), polarization of macrophages toward the M1 phenotype, restoration of the CD4⁺/CD8⁺ T cell ratio, and modulation of serum cytokines including upregulation of IL-2, IL-12, and IFN-γ, along with downregulation of IL-4 and IL-10. ZQFZ-derived FMT significantly inhibited tumour growth, suppressed glycolysis-related markers (PKM2, GLUT1, HIF-1α, LDHA), and remodeled the immune microenvironment by reducing MDSCs and enhancing M1 macrophages and CD8⁺ T cell infiltration. In hypoxia-mimicking in vitro experiments, sodium butyrate (NaB), the principal gut microbial metabolite of ZQFZ, suppressed colorectal cancer cell viability and induced apoptosis. Through activation of GPR109A, NaB inhibited the AKT/mTOR/HIF-1α pathway and glycolysis-related enzymes, reduced lactate production, and further suppressed glycolysis. Molecular docking and dynamics simulations suggested a stable interaction between GPR109A and AKT1, which was confirmed in vitro by MST showing high-affinity binding (Kd=74.5 ± 20.8 nM); MST also verified moderate-affinity binding between GPR109A and sodium butyrate (Kd=43.3 ± 6.5 μM), supporting a dual interaction model wherein butyrate activates GPR109A, which in turn directly binds AKT1 to inhibit downstream glycolytic signaling.
CONCLUSION: This study uncovers a novel integrated mechanism whereby ZQFZ enhances PD-1 antibody efficacy via the gut microbiota-SCFAs-GPR109A axis, and NaB-mediated glycolysis inhibition under hypoxia further confirms its immunometabolic mechanism against CRC.
