J Steroid Biochem Mol Biol. 1994 Jun;49(4-6):319-26.  

Aromatase gene expression in adipose tissue: relationship to breast cancer.

Bulun SE, Mahendroo MS, Simpson ER.

Cecil H. and Ida Green Center for Reproductive Biology Sciences, University of
Texas Southwestern Medical Center at Dallas 75235.

Recent studies have established that concentration gradients of aromatase
expression occur within the breast, with the highest levels of expression
occurring in sites proximal to a tumor. These variations in aromatase expression
correlate with regional differences in the relative proportions of the
histologic components of breast adipose tissue, in particular adipocytes and
stromal cells, since regions containing the highest numbers of stromal cells are
the sites of elevated aromatase transcript levels. Although the initiating
events are unknown, it is proposed that, once neoplastic cells start to
replicate, tumor growth will be promoted by locally increased estrogen levels.
In turn, growth factors produced by the tumor in response to locally increased
estrogen levels may further increase aromatase expression in the surrounding
adipose tissue. Thus a positive feed-back loop is established in which
locally-produced estrogens and tumor-derived growth factors act by paracrine and
autocrine mechanisms to sustain the growth and development of the tumor. Further
support for this concept is obtained from the observation that aromatase
expression in breast adipose is regulated by enhancer elements that appear to
respond positively to growth factors, in contrast to expression in granulosa
cells, which is inhibited by growth factors.

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PMID: 8043495 [PubMed - indexed for MEDLINE]