Upregulation of estrogen receptor alpha (ERα) expression in transgenic mice expressing human CYP4Z1

CYP4Z1 is a human cytochrome P450 enzyme involved in breast cancer progression and prognosis, but its functional role in these processes is not understood. In order to gain more insight into CYP4Z1’s properties it was recombinantly expressed in a host animal that does not have an endogenous homologue. We generated a transgenic mouse model that specifically expresses human CYP4Z1 in breast tissue under the control of the whey acidic protein promoter. Complementary experiments were done using cell lines derived from human breast cell. Induction of CYP4Z1 expression led to reduction of body weight, activity, and birth rates. Histological analysis revealed no evidence for tumor formation. However, a strong increase in estrogen receptor alpha was observed by immunohistochemistry; weaker but significantly increased immunoreactivity was also detected for collagen I and fibronectin. Overexpression of CYP4Z1 in the human breast cancer cell line MCF7 also led to increased ERα expression. Moreover, increased expression of both CYP4Z1 and ERα was observed in MCF-10A normal breast cells upon cocultivation with MCF-7 cells (with or without overexpression of CYP4Z1). These data suggest that CYP4Z1 facilitates breast cancer development by induction of ERα expression via an as yet undefined mechanism.