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. 2026 Mar 25;17:1740257. doi: 10.3389/fimmu.2026.1740257

Figure 13.

Diagram showing Terrisporobacter bacteria producing metabolites that activate M2 macrophages and NTRK1 expression in PTC cells, leading to cell proliferation, while inhibiting CD8 positive T cell activity.

Proposed mechanistic model of the Terrisporobacter-NTRK1 axis in PTC progression. Dysbiosis of the gut microbiota leads to an increased abundance of Terrisporobacter. This bacterium promotes Papillary Thyroid Carcinoma (PTC) through two key pathways: (1) secretion of metabolites that directly upregulate the oncogene NTRK1 in PTC cells, enhancing cell proliferation; and (2) remodeling of the tumor immune microenvironment by recruiting M2 macrophages and suppressing CD8+ T cells. Green arrows indicate promotion/activation; red T-bars indicate inhibition.