Several clinical observations and experimental studies indicate that pituit
ary hormones, including growth hormone, play a role in the development of h
uman breast cancer, We analyzed 48 human breast carcinomas using reverse tr
anscription polymerase chain reaction, irnmunohistochemistry, and Western b
lotting techniques to assess growth hormone receptor expression. In 17 of t
hese cases, adjacent normal breast tissue was similarly analyzed. These ana
lyses revealed that growth hormone receptor (GHR) is expressed in human bre
ast cancer and appeals to be up-regulated compared to adjacent normal breas
t tissue. GHR expression correlated inversely with tumor grade and MIB-1 in
dex. Progesterone receptor expression correlated positively with GHR expres
sion. These findings, along with our observation of GHR expression in breas
t cancer stromal cells and previous reports of local production of growth h
ormone in breast carcinoma, suggest that GHR-mediated signaling pathways ar
e involved in the development of human breast cancer, possibly via autocrin
e or paracrine mechanisms.