Effects of neonicotinoids on promoter-specific expression and activity of aromatase: implications for the development of hormone-dependent breast cancer

Aromatase (CYP19) is the key enzyme in the biosynthesis of estrogens. In humans, it is expressed in a tissue- and promoter-specific manner. In hormone-dependent breast cancer, CYP19 is overexpressed through the activation of several additional promoters (PII, I.3 and I.7) that are normally inactive in the healthy mammary gland. In the normal mammary gland, low basal CYP19 expression is regulated by the I.4 promoter, which is also active in adipose tissue. Here, we highlight our recent study of the effects of neonicotinoid pesticides on the promoter-specific expression of CYP19 in various human in vitro models. We also discuss the implications of endocrine disruption by environmental chemicals for the development of hormone-dependent diseases, such as breast cancer.