Abstract/Summary

The incidence of female breast cancer is rising globally at unprecedented rates with a near doubling in many countries. Oestrogen is a main risk factor and many environmental chemicals have been shown to possess oestrogenic activity (xenoestrogens) and to enter the human breast from exposure through diet, the domestic environment or personal care products. The aims of this project were to investigate whether xenoestrogens also possess genotoxic activity. The compounds studied were three cyclosiloxanes (D3, D4, and D5), butylphenylmethylpropional (Lilial), triclosan and aluminium salts which are used extensively in personal care products, and bisphenol-A which is used widely in the manufacture of plastics. Genotoxicity was assessed from their ability to enable growth in suspension culture, to damage DNA in a comet assay and to interfere with cellular DNA repair systems in two immortalised non-transformed human breast epithelial cell lines (MCF10A and MCF10F). The ability of non-transformed epithelial cells to grow in suspension culture is an established marker of transformation. All these compounds enabled growth of MCF10A and MCF10F cells in suspension with maximal effects observed at 10-10M D3, 10-5M D4, 10-5M D5, 10-5M bisphenol A, 10-7M triclosan and 10-5M butylphenylmethylpropional (Lilial). The comet assay showed DNA damage after 1 hour exposure to 17β-oestradiol in both cell lines as well as to 10-5M D3, 10-5M D4 or 10-5M butylphenylmethylpropional (Lilial). Reverse-transcriptase polymerase chain reaction (RTPCR) was used to detect effects of these chemicals on mRNA levels in MCF-10A and MCF-10F cells for 14 key DNA repair proteins (BRCA1, BRCA2, ATM, ATR, BRIP1, CHK1, CHK2, p53, PALB2, PARP1, PTEN, Rad50, Rad51 and STK111). Increases in mRNA for BRCA1 were detected after both short-term (1 week) and long-term (30 weeks) exposure to 10-5M D3 and 10-5M D4, 10-5M D5 gave an increase only after shortterm exposure (1 week). Decreases in BRCA2 mRNA were found after both short-term (1 week) and long-term (30 weeks) exposure to 10-5M D3 and 10-7M triclosan: long-term exposure (30 weeks) resulted in increases after exposure to 10-5M D5, 10-5M bisphenol A and 10-5M butylphenylmethylpropional (Lilial). Western immunoblotting showed that BRCA1 protein was reduced in line with the mRNA results, demonstrating that in this case transcription and translation followed the same pattern. A shorter study using long–term exposure (20 weeks) to aluminium based antiperspirant salts at 10-4M concentrations showed reduced expression also of BRCA1 mRNA and BRCA1 protein together with reduced expression of other mRNAs. In summary, all these compounds showed genotoxic activity in MCF10A and MCF10F cells and points to the potential for reduction in exposure as a strategy for breast cancer prevention