Inhibiting estrogen responses in breast cancer cells using a fusion protein encoding estrogen receptor-alpha and the transcriptional repressor PLZF.
Estrogen receptor alpha (ERalpha) is a ligand-inducible transcription factor that acts to regulate gene expression by binding to palindromic DNA sequence, known as the estrogen response element, in promoters of estrogen-regulated genes. In breast cancer ERalpha plays a central role, where estrogen-regulated gene expression leads to tumor initiation, growth and survival. As an approach to silencing estrogen-regulated genes, we have studied the activities of a fusion protein between ERalpha and the promyelocytic leukemia zinc-finger (PLZF) protein, a transcriptional repressor that acts through chromatin remodeling. To do this, we have developed lines from the estrogen-responsive MCF-7 breast cancer cell line in which the expression of the fusion protein PLZF-ERalpha is conditionally regulated by tetracycline and shows that these feature long-term silencing of the expression of several well-characterized estrogen-regulated genes, namely pS2, cathepsin-D and the progesterone receptor. However, the estrogen-regulated growth of these cells is not inhibited unless PLZF-ERalpha expression is induced, an observation that we have confirmed both in vitro and in vivo. Taken together, these results show that PLZF-ERalpha is a potent repressor of estrogen-regulated gene expression and could be useful in distinguishing estrogen-regulated genes required for the growth of breast cancer cells.
Buluwela
L
L
Department of Cancer Medicine, Imperial College London, London, UK.
Pike
J
J
Mazhar
D
D
Kamalati
T
T
Hart
S M
SM
Al-Jehani
R
R
Yahaya
H
H
Patel
N
N
Sarwar
N
N
Sarwarl
N
N
Heathcote
D A
DA
Schwickerath
O
O
Phoenix
F
F
Hill
R
R
Aboagye
E
E
Shousha
S
S
Waxman
J
J
Lemoine
N R
NR
Zelent
A
A
Coombes
R C
RC
Ali
S
S
D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism* / Q000628:therapy*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000235:genetics* / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D051741:Kruppel-Like Transcription Factors; D008156:Luciferases / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D000075722:Promyelocytic Leukemia Zinc Finger Protein; D011993:Recombinant Fusion Proteins / Q000627:therapeutic use*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014162:Transfection / Q000379:methods; D001616:beta-Galactosidase / Q000235:genetics
D004268:DNA-Binding Proteins; D047628:Estrogen Receptor alpha; D004967:Estrogens; D051741:Kruppel-Like Transcription Factors; D000075722:Promyelocytic Leukemia Zinc Finger Protein; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C513267:Zbtb16 protein, mouse; C092037:ZBTB16 protein, human; D008156:Luciferases; D001616:beta-Galactosidase