Differential Effects of Organic and Inorganic Mercury on Phenotypically Variant Breast Cancer Cell Lines

Heavy metals such as cadmium, cobalt and lead among others are considered to be “metalloestrogens”, which interfere with, or disrupt, the estrogen system and its subsequent cellular pathways. Metalloestrogens can be found in cosmetics, pesticides, food additives, tobacco smoke, industrial operations and other environmental contaminates. There has been a growing interest in these metalloestrogens and their role in estrogen-dependent breast cancers. Evidence has suggested that each of the estrogen receptors (ERα, ERβ and GPR30) can be involved in the development of various breast cancers. There has been little research exploring the potential of mercury as a metalloestrogen and its effect on estrogen receptor mediated pathways. To be a metalloestrogen, the compound does not have to directly influence the functioning of estrogen receptors; instead, it may affect one or more steps in the estrogen-response cascade. For those reasons we have chosen to examine inorganic and organic mercury effects on breast cancer cell line growth. The lines consist of a control epithelial line, an ER+ line and an ER- line.

Phenotypically Variant Breast Cancer Cell Lines

The amount of mercury that is still used in commercial products would surprise some consumers. Although exposure risk has been reduced over the last few decades, there are still multiple exposure routes. Environmental exposure to mercury compounds is varied. Besides industrial exposure, the major means by which a person can be exposed is by consuming contaminated fish. Major chemical forms of mercury are elemental, organic (methylmercury; CH3Hg+), or inorganic (mercuric chloride; HgCl2). Of these, methylmercury appears to be the most pervasive with regard to ingestion, and inhalation exposures. Once exposed, the most sensitive population appears to be the very young and the very old. Exposure via the ingestion of contaminated seafood is the best understood pathway. Since the fetus or newborn represents a highly sensitive population to the actions of mercury, there is considerable concern that mercury can be passed to the newborn via the breast milk. Contamination of consumer products can also be an area of concern and some imported ‘natural’ remedies have been shown to be contaminated with mercury. Of particular interest is the ability of mercury to remain in the body for extended periods, bioaccumulating and posing a risk later in life.

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