Pvm. Shekhar et al., TRANSCRIPTIONAL ACTIVATION OF FUNCTIONAL ENDOGENOUS ESTROGEN-RECEPTORGENE-EXPRESSION IN MCF10AT CELLS - A MODEL FOR EARLY BREAST-CANCER, International journal of oncology, 13(5), 1998, pp. 907-915
Utilizing the MCF10AT xenograft model for progression of human prolife
rative breast disease, we detected expression of the endogenous estrog
en receptor (ER) gene only in MCF10AneoT and cells of the MCF10AT syst
em, all of which stably express a transfected mutated T24 Ha-ras gene.
ER transcripts were undetectable in the parental MCF10A cells and in
MCF10A cells transfected with normal c-Ha-ras or vector. ER transcript
s expressed in MCF10AT cells contain a normal full-length ER coding re
gion and direct synthesis of a normally sized ER protein. The protein
is functional based on its ability to mediate estradiol (E-2)-induced
increases of transcription from both endogenous and exogenous E-2-regu
lated genes. Transcriptional activation of the endogenous ER gene does
not appear to be related to a change in methylation status of the gen
e since a diagnostic CpG site in exon 1 that is methylated in ER-negat
ive breast tumors and completely unmethylated in ER-positive breast tu
mors is hypomethylated to the same extent in ER-negative MCF10A cells
and ER-positive MCF10AT cells. E-2 increased both the number and size
of soft-agar colonies formed by MCF10AT3c cells, a line from a third g
eneration MCF10AT xenograft lesion. This suggests that xenograft passa
ge has selected for growth regulatory pathways that are E-2-responsive
and that identification of these pathways and their role in progressi
on will aid in determining how E-2 acts to increase risk of breast can
cer.