Evaluation of transcriptional activity of the oestrogen receptor with sodium iodide symporter as an imaging reporter gene.
BACKGROUND
Oestrogen receptors are ligand-dependent transcription factors whose activity is modulated either by oestrogens or by an alternative signalling pathway. Oestrogen receptors interact via a specific DNA-binding domain, the oestrogen responsive element (ERE), in the promoter region of sensitive genes. This binding leads to an initiation of gene expression and hormonal effects.


OBJECTIVE
To determine the transcriptional activity of the oestrogen receptor, we developed a molecular imaging system using sodium iodide symporter (NIS) as a reporter gene.


METHODS
The NIS reporter gene was placed under the control of an artificial ERE derived from pERE-TA-SEAP and named as pERE-NIS. pERE-NIS was transferred to MCF-7, human breast cancer cells, which highly expressed oestrogen receptor-alpha with lipofectamine. Stably expressing cells were generated by selection with G418 for 14 days. After treatment of 17beta-oestradiol and tamoxifen with serial doses, the (125)I uptake was measured for the determination of NIS expression. The inhibition of NIS activity was performed with 50 micromol x l(-1) potassium perchlorate.


RESULTS
The MCF7/pERE-NIS treated with 17beta-oestradiol accumulated (125)I up to 70-80% higher than did non-treated cells. NIS expression was increased according to increasing doses of 17beta-oestradiol. MCF7/pERE-NIS treated with tamoxifen also accumulated (125)I up to 50% higher than did non-treated cells. Potassium perchlorate completely inhibited (125)I uptake. When MDA-MB231 cells, the oestrogen receptor-negative breast cancer cells, were transfected with pERE-NIS, (125)I uptake of MDA-MB-231/pERE-NIS did not increase.


CONCLUSIONS
This pERE-NIS reporter system is sufficiently sensitive for monitoring transcriptional activity of the oestrogen receptor. Therefore, cis-enhancer reporter systems with ERE will be applicable to the development of a novel selective oestrogen receptor modulator with low toxicity and high efficacy.
Kang
Joo Hyun
JH
Laboratory of Nuclear Medicine, Korea Institute of Radiological and Medical Science, Korea.
Chung
June-Key
JK
Lee
Yong Jin
YJ
Kim
Kwang Il
KI
Jeong
Jae Min
JM
Lee
Dong Soo
DS
Lee
Myung Chul
MC
D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D004247:DNA / Q000737:chemistry; D004958:Estradiol / Q000494:pharmacology; D017930:Genes, Reporter; D006801:Humans; D007457:Iodine Radioisotopes / Q000494:pharmacology; D011485:Protein Binding; D011877:Radionuclide Imaging / Q000295:instrumentation* / Q000379:methods*; D011960:Receptors, Estrogen / Q000096:biosynthesis* / Q000235:genetics*; D020218:Response Elements; D027981:Symporters / Q000737:chemistry* / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology; D014158:Transcription, Genetic; D000099209:Sodium-Iodide Symporters
D004247:DNA; D004958:Estradiol; D007457:Iodine Radioisotopes; D011960:Receptors, Estrogen; D027981:Symporters; D013629:Tamoxifen; D000099209:Sodium-Iodide Symporters