PFOS exposure at environmentally relevant concentrations promote papillary thyroid carcinoma progression through PI3K/AKT/mTOR-mediated epithelial-mesenchymal transition.

Perfluorooctane sulfonate (PFOS), a pervasive and persistent environmental pollutant, has been epidemiologically linked to thyroid disorders, but its toxic effects on papillary thyroid carcinoma (PTC) remain unclear. This study provides the clinical evidence that PFOS accumulates at significantly higher levels in human PTC tumor tissues compared to adjacent normal tissues (p = 0.037), indicating tissue-specific bioaccumulation. To investigate its health impact, we modeled chronic environmental exposure by treating human PTC cells with low, environmentally relevant concentrations of PFOS (0.01, 0.05 μM). Chronic exposure markedly enhanced malignant phenotypes, including proliferation, migration, and invasion. Mechanistically, PFOS activated the PI3K/AKT/mTOR signaling pathway, which subsequently drove epithelial-mesenchymal transition (EMT), as evidenced by upregulation of β-catenin and SNAI1, and increased expression of matrix metalloproteinase (MMP-2 and MMP-9). These pro-tumor effects were partially reversed by the pharmacological inhibitor BEZ235, which targets PI3K/mTOR. In vivo validation using a mouse xenograft model confirmed that PFOS exposure promotes tumor growth and upregulates the same pathway and effector molecules. This study provides integrated clinical and experimental evidence that PFOS exposure at environmentally relevant concentrations promotes PTC progression by inducing PI3K/AKT/mTOR-mediated EMT and associated enzyme secretion. These findings offer crucial experimental insight into the toxic role of PFOS as an environmental contaminant in thyroid tumors and underscore the urgent need for enhanced environmental health risk assessment and regulatory action.