Up-regulation of estrogen receptor by tamoxifen in human breast cancer.
BACKGROUND
Influence of tamoxifen treatment on estrogen receptor (ER) and progesterone receptor (PR) levels in human breast cancer has not been fully elucidated in vivo. This problem was studied in 20 postmenopausal patients with ER-positive and PR-positive primary breast cancer.


METHODS
Each patient underwent two fine-needle aspiration (FNA) biopsies. Between two FNA, 10 patients received no treatment (control group) and the other 10 patients were given tamoxifen (20 mg/day) for an average of 8 days (range, 6-10 days) (TAM group). Total ER and PR values (cytosolic plus nuclear fraction) in FNA samples were determined by enzyme immunoassay (EIA) for detecting ER and PR regardless of their occupancy with corresponding ligands.


RESULTS
In the control group, no significant difference was found in ER and PR values between the first and second FNA samples. In the TAM group, ER and PR values (mean +/- standard error of the mean [SEM] fmol/mg DNA) in the second FNA samples were 605 +/- 186 and 1130 +/- 344, respectively, and were significantly higher (P < 0.05) than ER and PR values in the first FNA samples, which were 312 +/- 74 and 639 +/- 159, respectively. ER and PR values increased by 201 +/- 27% and 163 +/- 23%, respectively, on an individual basis after tamoxifen treatment.


CONCLUSIONS
These results demonstrated that tamoxifen up-regulates ER and PR in human breast cancer.
Department of Surgery, Center for Adult Diseases, Osaka, Japan.
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Noguchi
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Motomura
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Inaji
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Imaoka
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Koyama
D001707:Biopsy, Needle; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D002467:Cell Nucleus / Q000737:chemistry; D002499:Centrifugation, Density Gradient; D003600:Cytosol / Q000737:chemistry; D005260:Female; D006801:Humans; D008408:Mastectomy; D008593:Menopause; D011960:Receptors, Estrogen / Q000032:analysis / Q000187:drug effects*; D011980:Receptors, Progesterone / Q000032:analysis / Q000187:drug effects*; D015203:Reproducibility of Results; D013629:Tamoxifen / Q000627:therapeutic use*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects*
D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D013629:Tamoxifen