Metals
CATEGORY: IARC known, NTP known
USED IN: Some cosmetics, dental fillings, paints, electronics batteries, manufacturing
Higher accumulations of iron, nickel, chromium, zinc, cadmium, mercury and lead have been found in cancerous breast biopsies as opposed to biopsies taken from women without breast cancer. These metals also have been found in serum samples of women diagnosed with cancer as compared with healthy women (Ionescu, 2006; Wu, 2006).
Laboratory studies have shown that a number of metals including copper, cobalt, nickel, lead, mercury, methylmercury, tin, cadmium and chromium have estrogenic effects on breast cancer cells (MCF-7) cultured in vitro (Brama, 2007; Martin, 2003; Sukocheva, 2005).
In a study exploring dietary intake of cadmium in women who have been diagnosed with breast cancer and appropriate age-matched controls, higher exposure to cadmium was associated with a significant increase in risk for breast cancer, independent of age at diagnosis (McElroy, 2006).
In young rats, treatment with low doses of cadmium led to an increase in branching and bud formation in mammary tissue, and the induction of several estrogen-associated proteins. Prenatal exposure of rats to cadmium led to early onset of puberty and greater numbers of mammary terminal end buds, both known risk factors for breast cancer (Johnson, 2003).
Estrogenic effects of cadmium have been studied in some detail. It has been shown to interfere with a number of normal estrogen-sensitive pathways and to affect the rates of both endometrial and breast cancers. (Byrne, 2009). In addition to its endocrine effects on mammary tumor cells, cadmium transforms healthy breast epithelial cells into cells with a cancer-like profile through non-hormone-related pathways. Thus, in the presence of cadmium, the cells have altered gene expression and changes in DNA methylation (an epigenetic change) that are typical of cells undergoing transformation from healthy to cancerous cells (Benbrahim-Tallaa, 2009).
