Metabolism profiles of tannins in Phyllanthus emblica L. and its immunotherapeutic potential against hepatocellular carcinoma by re-educating tumor microenvironment.

Purpose: Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality worldwide. Tumor-associated macrophages (TAMs) are key components of the immunosuppressive tumor microenvironment and represent significant obstacles to effective immunotherapy. Phyllanthus emblica L. (PE), a medicinal plant traditionally used in Tibet, has shown therapeutic promise. This study investigates the effects of the tannin fraction of PE (PE-TF) on HCC and its ability to modulate the tumor immunosuppressive microenvironment.

Methods: We evaluated the antitumor efficacy of PE-TF using H22 xenografts and Hepa1-6 orthotopic mouse models. Transcriptomic analysis was performed to identify molecular targets underlying PE-TF suppression of HCC growth. Additionally, UPLC-MS/MS analysis identified the prototypic and metabolic components of PE-TF present in serum, tumor tissues, and adjacent normal liver tissues in the orthotopic HCC model.

Results: PE-TF significantly suppressed tumor growth in both subcutaneous and orthotopic HCC models and promoted reprogramming of TAMs toward an antitumor M1 phenotype in vivo. Furthermore, PE-TF counteracted the protumoral effects mediated by bone marrow-derived macrophages (BMDMs) exposed to Hepa1-6-derived conditioned medium (HCM). Although TBH promoted macrophage M2 polarization, the reactive oxygen species (ROS)-scavenging activity of PE-TF effectively inhibited this process. Modulation of the tumor microenvironment by PE-TF-enhanced CD8T cell infiltration and bolstered their antitumor response, as evidenced by increased transcription of perforin, IFN-γ, and IL-2. Transcriptomic analysis further revealed that T-cell receptor and cytotoxic T-cell signaling pathways are critical mediators of PE-TF' therapeutic effects. Moreover, we preliminarily characterized 79 components across serum, liver, and tumor tissues, and identified metabolic pathways for PE-TF ingredients-including methylation and glycosylation modifications of tumor-enriched constituents. Notably, seven components, such as corilagin and urolithin D, are hypothesized to possess immunomodulatory properties.

Conclusion: Our findings underscore the potential of PE-TF as an adjuvant immunotherapy for HCC. By scavenging ROS, PE-TF reverses the immunosuppressive M2-TAM phenotype and remodels the tumor microenvironment, thereby enhancing antitumor immunity. Additionally, integrating chemical and metabolic profiling offers a promising strategy for refining candidate selection in future drug discovery endeavors.