Estrogen
LATEST RESEARCH HIGHLIGHTS

Regulation of ERBB2 by oestrogen receptor–PAX2 determines response to tamoxifen

05/12/2008
Crosstalk between the oestrogen receptor (ER) and ERBB2/HER-2 pathways has long been implicated in breast cancer aetiology and drug response1, yet no direct connection at a transcriptional level has been shown. Here we show that oestrogen–ER and tamoxifen–ER complexes directly repress ERBB2 transcription by means of a cis-regulatory element within the ERBB2 gene in human cell lines. We implicate the paired box 2 gene product (PAX2), in a previously unrecognized role, as a crucial mediator of ER repression of ERBB2 by the anti-cancer drug tamoxifen. We show that PAX2 and the ER co-activator AIB-1/SRC-3 compete for binding and regulation of ERBB2 transcription, the outcome of which determines tamoxifen response in breast cancer cells. The repression of ERBB2 by ER-PAX2 links these two breast cancer subtypes and suggests that aggressive ERBB2-positive tumours can originate from ER-positive luminal tumours by circumventing this repressive mechanism. These data provide mechanistic insight into the molecular basis of endocrine resistance in breast cancer.

Nature 456, 663-666 (4 December 2008) | doi:10.1038/nature07483; Received 30 July 2008; Accepted 2 October 2008; Published online 12 November 2008

|

Pancreatic Insulin Content Regulation by the Estrogen Receptor ERα

15/09/2008
The function of pancreatic β-cells is the synthesis and release of insulin, the main hormone involved in blood glucose homeostasis. Estrogen receptors, ERα and ERβ, are important molecules involved in glucose metabolism, yet their role in pancreatic β-cell physiology is still greatly unknown. In this report we show that both ERα and ERβ are present in pancreatic β-cells. Long term exposure to physiological concentrations of 17β-estradiol (E2) increased β-cell insulin content, insulin gene expression and insulin release, yet pancreatic β-cell mass was unaltered. The up-regulation of pancreatic β-cell insulin content was imitated by environmentally relevant doses of the widespread endocrine disruptor Bisphenol-A (BPA). The use of ERα and ERβ agonists as well as ERαKO and ERβKO mice suggests that the estrogen receptor involved is ERα. The up-regulation of pancreatic insulin content by ERα activation involves ERK1/2. These data may be important to explain the actions of E2 and environmental estrogens in endocrine pancreatic function and blood glucose homeostasis.

PLoS ONE 3(4): e2069. doi:10.1371/journal.pone.0002069
|