Methylmercury promotes the growth and progression of breast cancer in danio rerio embryos.

Abstract

Estrogen is a female sex hormone that is important in the development of secondary sex characteristics in females and promotes breast cancer growth and metastasis of estrogen receptor (ER)-positive breast cancer cells. Environmental estrogens, such as metalloestrogens, have also been shown to promote breast cancer growth. Methylmercury (MeHg) is a metalloestrogen whose role in breast cancer growth and progression has not been elucidated. MeHg is of interest because it is the main form of mercury in humans and aquatic life, as it accumulates through the aquatic food chain. To test whether MeHg promotes the growth of breast cancer cells in vivo, a Danio rerio embryo model was used. MCF-7 ER positive breast cancer cells were transplanted into a 2-day post fertilization embryos (dpf). Tumor growth and metastasis were observed on 7 dpf using fluorescent imagery. We hypothesized that ER-postivie breast cancer cells treated with MeHg would have increased tumor growth and more metastases compared to untreated embryos. MeHg treated embryos showed higher percentages of embryos with cancer, tumor count, and tumor area compared to untreated embryos. From these results, we conclude that MeHg may be acting as a metalloestrogen to promote the growth and progression of ER-positive breast cancer in xenografted Danio rerio embryos.