In vitro evaluation of the carcinogenic potential of perfluorinated chemicals
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Abstract
Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are the major components of long-chain per- and polyfluorinated alkyl substances (PFAS), known for their chemical stability and environmental persistence. Even if PFOA and PFOS have been phased out or are limited in use, they still represent a concern for human and environmental health. Several studies have been performed to highlight the toxicological behavior of these chemicals and their mode of action (MoA). Data have suggested a causal association between PFOA or PFOS exposure and carcinogenicity in humans, but the outcomes of epidemiological studies showed some inconsistency. Moreover, the hypothesized MoA based on animal studies is considered not relevant for human cancer. To improve the knowledge on PFAS toxicology and contribute to the weight of evidence for the regulatory classification of PFAS, we used the BALB/c 3T3 cell transformation assay (CTA), an in vitro model under consideration to be included in an integrated approach to testing and assessment for non-genotoxic carcinogens (NGTxCs). PFOS and PFOA were tested at several concentrations using a validated experimental protocol. Our results demonstrate that PFOA does not induce cell transformation, whereas PFOS exposure induced a concentration-related increase of type III foci. Malignant foci formation was triggered at PFOS concentrations equal to or higher than 50 ppm and was not directly associated with cytotoxicity or proliferation induction. The divergent CTA outcomes suggest that different molecular events could be responsible for the toxicological profiles of PFOS and PFOA, which were not fully captured in our study.
Plain language summary
PFAS chemicals are known for their durability and resistance to heat, water, and oil. They are persistent in the environment and may pose health risks despite decreased use. This study explored PFOS and PFOA, two common PFAS chemicals, to understand their potential harm and cancer risk. To better understand how they might be harmful, we conducted a cell-based test that can resemble the carcinogenesis process in experimental animals. The test revealed PFOS, but not PFOA, can cause cancer-like changes, at levels of 50 parts per million or higher. This result suggests different PFAS chemicals affect cells differently, but we need more research to understand exactly how they work and how they might cause cancer. Understanding this could help regulate and reduce PFAS harmful effects. This research aligns with 3R principles by using cell-based tests as an alternative to animal testing, thereby promoting ethical research practices.
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