The therapeutic efficacy of tea polyphenols (TP) has been demonstrated in various tumor types, and research has indicated its potential role in modulating the intestinal microbiota. However, the impact of it on tumor microbiota remains uncertain. The research aimed to investigate how TP treatment affects microorganisms in breast tumors (4T1) and explore their potential influence on the TP's therapeutic efficacy. The TP significantly inhibited the growth of 4T1 tumors, and DOX-TP significantly enhanced the efficacy of TP against the tumors, whereas DOX alone did not show similar effects. The results of 16 S rDNA sequences indicated that Herbaspirillum, Herminiimonas, Stenotrophomonas exhibited a remarkable increase (regulation rate≥99.72% and the abundance up-regulation by 7.91%, 5.17% and 5.77%, respectively), transitioning from absence to presence in the TP group to the DOX-TP group. Conversely, Halomonas, ZOR0006, Hydrogenophilus, Rhodococcus, Vibrio were significantly decreased (regulation rate≥99.91% and the abundance down-regulation by 3.16%, 2.78%, 3.15%, 12.92% and 16.03%, respectively) after DOX-TP treatment, resulting in a shift from presence to absence. Compared to the TP group, DOX-TP group demonstrated enhanced infiltration of CD4+ T and CD8+ T cells, while exhibiting significantly elevated expression levels of IL-2, IFN-α, IFN-γ and TNF-α. Additionally, Rhodococcus and Halomonas were observed to be negatively correlated with IFN-α expression. The co-administration of TP and antibiotics further modified the tumor microbiota composition, influencing the tumor immune microenvironment. The study demonstrated that DOX-TP can enhance TP's anticancer effect by modulating the tumor microbiota.
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