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Regulation of estrogen receptor‐α gene expression by 1,25‐dihydroxyvitamin D in MCF‐7 cells
Author(s) -
Stoica Adriana,
Saceda Miguel,
Fakhro Amina,
Solomon Harrison B.,
Fenster Bradley D.,
Martin Mary Beth
Publication year - 1999
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(19991215)75:4<640::aid-jcb10>3.0.co;2-8
Subject(s) - estrogen receptor , calcitriol receptor , microbiology and biotechnology , transfection , transcription (linguistics) , mcf 7 , estrogen , hormone response element , promoter , biology , cell culture , gene expression , heterologous , medicine , endocrinology , vitamin d and neurology , gene , cancer cell , biochemistry , cancer , human breast , linguistics , philosophy , genetics , breast cancer
This report describes an investigation of the role of 1,25‐dihydroxyvitamin D (VD 3 ) in the regulation of estrogen receptor‐α (ER) in the ER‐positive breast cancer cell line, MCF‐7. Treatment of cells with 10 nM VD 3 resulted in a 50% decline in the concentration of ER protein at 24 h. Scatchard analysis showed a corresponding decrease in the number of estradiol binding sites and no alteration in the binding affinity of estradiol for the ER (K d = 0.08 nM in VD 3 ‐treated cells compared with K d = 0.07 nM in control cells). Vitamin D treatment also caused a 50% decrease in the steady state amount of ER mRNA, which was maximal by 18 h. In vitro transcription run‐on experiments demonstrated a decrease of approximately 60% in transcription of the estrogen receptor gene. Transient transfections using an ER promoter‐CAT construct also demonstrated a 40% decrease in CAT activity after VD 3 treatment. Sequence analysis identified a potential vitamin D response element (nVDRE) within the ER promoter. When this element was mutated, the ability of VD 3 to block transcription from the ER promoter was lost. When the nVDRE was placed upstream of a heterologous promoter, nVDRE‐SV40‐CAT, treatment with VD 3 resulted in a 50% decrease in CAT activity. Interestingly, co‐transfection of either the ER promoter‐CAT or the nVDRE‐SV40‐CAT construct and a vitamin D receptor expression vector into COS‐1 or CV‐1 cells showed an approximately 4‐fold increase in CAT activity after VD 3 treatment. Taken together these data suggest that VD 3 inhibition of ER gene transcription is mediated through a nVDRE in the ER promoter. Inhibition appears to be cell specific. J. Cell. Biochem. 75:640–651, 1999. © 1999 Wiley‐Liss, Inc.