High-content analysis shows synergistic effects of low perfluorooctanoic acid (PFOS) and perfluorooctane sulfonic acid (PFOA) mixture concentrations on human breast epithelial cell carcinogenesis

Perfluoroalkyl substances (PFAS) have been associated with cancer, but the potential underlying mechanisms need to be further elucidated and include studies of PFAS mixtures. This mechanistic study revealed that very low concentrations (500 pM) of the binary PFOS and PFOA mixture induced synergistic effects on human epithelial breast cell (MCF-10A) proliferation. The cell proliferation was mediated by pregnane X receptor (PXR) activation, an increase in cyclin D1 and CDK6/4 levels, decrease in p21 and p53 levels, and by regulation of phosphor-Akt and beta-catenin. The PFAS mixture also altered histone modifications, epigenetic mechanisms implicated in tumorigenesis, and promoted cell migration and invasion by reducing the levels of occludin. High -content screening using the cell painting assay, revealed that hundreds of cell features were affected by the PFAS mixture even at the lowest concentration tested (100 pM). The detailed phenotype profiling further demon-strated that the PFAS mixture altered cell morphology, mostly in parameters related to intensity and texture associated with mitochondria, endoplasmic reticulum, and nucleoli. Exposure to higher concentrations (>= 50 mu M) of the PFOS and PFOA mixture caused cell death through synergistic interactions that induced oxidative stress, DNA/RNA damage, and lipid peroxidation, illustrating the complexity of mixture toxicology. Increased knowl-edge about mixture-induced effects is important for better understanding of PFAS' possible role in cancer eti-ology, and may impact the risk assessment of these and other compounds. This study shows the potential of image-based multiplexed fluorescence assays and high-content screening for development of new approach methodologies in toxicology.

Automated summary

This study revealed that the binary PFOS and PFOA mixture at very low concentrations induced synergistic effects on breast cell proliferation. The mechanisms involved activation of PXR, regulation of cell cycle proteins, alteration of histone modifications, and promotion of cell migration and invasion. At higher concentrations, the mixture caused cell death through oxidative stress and DNA/RNA damage. Understanding the effects of mixtures is important for cancer etiology and risk assessment.