Mj. Pilat et al., CHARACTERIZATION OF THE ESTROGEN-RECEPTOR TRANSFECTED MCF10A BREAST CELL-LINE 139B6, Breast cancer research and treatment, 37(3), 1996, pp. 253-266
There has been increasing evidence which suggests that abnormal expres
sion of the estrogen receptor (ER) protein in nonmalignant breast tiss
ue may be important in the carcinogenic process. To examine the effect
s of ER expression in immortalized nonmalignant mammary epithelial cel
ls, an expression vector containing human ER cDNA was transfected into
the ER negative human breast cells, MCF10A. Characterization of a clo
ne stably expressing ER, 139B6, provided evidence for the regulated sy
nthesis of a functional ER capable of binding estradiol-17 beta (E(2))
and undergoing processing. Expression of the ER gene did not enable E
(2) to stimulate endogenous genes [progesterone receptor (PgR), pS2, c
athepsin D and TGF alpha] which normally respond to estrogens in breas
t cancer cells. The ER in 139B6 cells was, however, capable of inducin
g expression of an ERE-regulated reporter gene, indicating its ability
to interact with transcriptional machinery. Furthermore, cultures in
log growth displayed a slight increase in doubling time in the presenc
e of E(2). These results indicate that ER expression alone is not suff
icient to induce a transformed phenotype. Thus, the 139B6 cell line sh
ould provide a new model for determining what additional changes lead
to increased growth potential in response to E(2) and for exploring ho
w E(2) itself may help bring about changes leading to progression of p
reneoplastic breast epithelial cells.