An endocrine-disrupting chemical commonly found in polycarbonate hard plastics, currency bills and thermal paper receipts may potentially interfere with the body's hormones to increase the aggressiveness of breast cancer, a new study has showed.

Bisphenol S (BPS), a substitute for the chemical bisphenol A (BPA) in the plastic industry, acts like estrogen in multiplying breast cancer cells. Most breast cancers are estrogen receptor positive, and, according to the National Cancer Institute, 55 to 65 per cent of women who inherit a harmful mutation in the BRCA1 gene -- will develop breast cancer.

"If a woman has a mutated BRAC1 gene and uses products containing BPS, her risk for developing breast cancer may increase further," said principal investigator, Sumi Dinda, Associate Professor at Oakland University in Michigan.
"Despite hopes for a safer alternative to BPA, studies have shown BPS to exhibit similar estrogen-mimicking behaviour to BPA," Dinda added. The results were presented at ENDO 2017, the Endocrine Society's 99th annual meeting in Orlando.

For the study, the team used two commercially available breast cancer cell lines obtained from women with estrogen-receptor-positive breast cancer, to expose the cancer cells to varying strengths of BPS or to an inactive substance as a control.

Compared with the control, BPS heightened the protein expression in oestrogen receptor and BRCA1 after 24 hours, as did oestrogen. After a six-day treatment with BPS, the breast cancer cells in both cell lines reportedly increased in number by 12 per cent at the lowest dose (4 micromolars) and by 60 per cent at eight micromolars.