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Effects of exposure to six chemical ultraviolet filters commonly used in personal care products on motility of MCF‐7 and MDA‐MB‐231 human breast cancer cells in vitro

Benzophenone (BP)‐1, BP‐2, BP‐3, octylmethoxycinnamate (OMC), 4‐methylbenzilidenecamphor and homosalate are added to personal care products to absorb ultraviolet light. Their presence in human milk and their oestrogenic activity suggests a potential to influence breast cancer development. As metastatic tumour spread is the main cause of breast cancer mortality, we have investigated the effects of these compounds on migration and invasion of human breast cancer cell lines. Increased motility of oestrogen‐responsive MCF‐7 human breast cancer cells was observed after long‐term exposure (>20 weeks) to each of the six compounds at ≥10−7 m concentrations using three independent assay systems (scratch assay, live cell imaging, xCELLigence technology) and increased invasive activity was observed through matrigel using the xCELLigence system. Increased motility of oestrogen‐unresponsive MDA‐MB‐231 human breast cancer cells was observed after 15 weeks of exposure to each of the six compounds by live cell imaging and xCELLigence technology, implying the increased migratory activity was not confined to oestrogen‐responsive cells. Molecular mechanisms varied between compounds and cell lines. Using MCF‐7 cells, reduction in E‐cadherin was observed following 24 weeks' exposure to 10−5 m BP‐1 and 10−5 m homosalate, and reduction in β‐catenin was noted following 24 weeks' exposure to 10−5 m OMC. Using MDA‐MB‐231 cells, increased levels of matrix metalloproteinase 2 were observed after 15 weeks exposure to 10−7 m OMC and 10−7 m 4‐methylbenzilidenecamphor. Although molecular mechanisms differ, these results demonstrate that exposure to any of these six compounds can increase migration and invasion of human breast cancer cells.