The Forkhead box M1 protein regulates the transcription of the estrogen receptor alpha in breast cancer cells.
In this study, we have identified the Forkhead transcription factor FoxM1 as a physiological regulator of estrogen receptor alpha (ERalpha) expression in breast carcinoma cells. Our survey of a panel of 16 different breast cell lines showed a good correlation (13/16) between FoxM1 expression and expression of ERalpha at both protein and mRNA levels. We have also demonstrated that ectopic expression of FoxM1 in two different estrogen receptor-positive breast cancer cell lines, MCF-7 and ZR-75-30, led to up-regulation of ERalpha expression at protein and transcript levels. Furthermore, treatment of MCF-7 cells with the MEK inhibitor U0126, which blocks ERK1/2-dependent activation of FoxM1, also repressed ERalpha expression. Consistent with this, silencing of FoxM1 expression in MCF-7 cells using small interfering RNA resulted in the almost complete abrogation of ERalpha expression. We also went on to show that FoxM1 can activate the transcriptional activity of human ERalpha promoter primarily through two closely located Forkhead response elements located at the proximal region of the ERalpha promoter. Chromatin immunoprecipitation and biotinylated oligonucleotide pulldown assays have allowed us to confirm these Forkhead response elements as important for FoxM1 binding. Further co-immunoprecipitation experiments showed that FoxO3a and FoxM1 interact in vivo. Together with the chromatin immunoprecipitation and biotinylated oligonucleotide pulldown data, the co-immunoprecipitation results also suggest the possibility that FoxM1 and FoxO3a cooperate to regulate ERalpha gene transcription.
Madureira
Patricia A
PA
Cancer Research-United Kingdom Laboratories, Department of Oncology, MRC Cyclotron Building, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, United Kingdom.
Varshochi
Rana
R
Constantinidou
Demetra
D
Francis
Richard E
RE
Coombes
R Charles
RC
Yao
Kwok-Ming
KM
Lam
Eric W-F
EW
D019921:Biotinylation; D001943:Breast Neoplasms / Q000378:metabolism*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D047628:Estrogen Receptor alpha / Q000096:biosynthesis* / Q000235:genetics; D000072278:Forkhead Box Protein M1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000737:chemistry / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008957:Models, Genetic; D009841:Oligonucleotides / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic; D015854:Up-Regulation
D047628:Estrogen Receptor alpha; C107585:FOXM1 protein, human; C499517:FOXO3 protein, human; D000072278:Forkhead Box Protein M1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D009841:Oligonucleotides; D012333:RNA, Messenger