Down-regulation of transforming growth factor-alpha by tamoxifen in human breast cancer.
BACKGROUND
The influence of tamoxifen treatment on transforming growth factor-alpha (TGF-alpha) levels in human breast cancer rarely has been studied in vivo.


METHODS
Postmenopausal patients with estrogen receptor (ER)-positive and progesterone receptor (PR)-positive primary breast cancer underwent two fine-needle aspiration biopsies (FNA) of the tumors. Between the two FNAs, 10 patients received no treatment (control group), and the other 10 patients received tamoxifen (20 mg/day) for 10 (8-12) days (TAM group). TGF-alpha levels in FNA samples were assayed by enzyme immunoassay.


RESULTS
No significant difference was found in TGF-alpha levels between the first and second FNA samples in the control group. On the other hand, in the TAM group, TGF-alpha levels in the second FNA samples (2.5 +/- 0.5; mean +/- SEM ng/mg.DNA) were significantly (P < 0.01) lower than those in the first (4.5 +/- 0.8). Studies on the influence of tamoxifen treatment on TGF-alpha levels in ER-negative and PR-negative breast cancer showed that TGF-alpha levels were not affected by tamoxifen treatment. Positivity of epidermal growth factor receptor (EGFR) was 60% in ER-negative and PR-negative breast cancer and 30% in ER-positive and PR-positive breast cancer.


CONCLUSIONS
Tamoxifen downregulates TGF-alpha levels in ER-positive and PR-positive breast cancers through ER. The significance of TGF-alpha as an autocrine growth factor appears to be more important in ER-negative and PR-negative breast cancer with high EGFR positivity than in ER-positive and PR-positive breast cancer with low EGFR positivity.
Department of Surgery, Center for Adult Diseases, Osaka, Japan.
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S
Noguchi
K
K
Motomura
H
H
Inaji
S
S
Imaoka
H
H
Koyama
D001707:Biopsy, Needle; D001940:Breast / Q000378:metabolism / Q000473:pathology; D001943:Breast Neoplasms / Q000737:chemistry / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D015536:Down-Regulation; D066246:ErbB Receptors / Q000032:analysis; D005260:Female; D006801:Humans; D011960:Receptors, Estrogen / Q000032:analysis / Q000187:drug effects / Q000378:metabolism; D011980:Receptors, Progesterone / Q000032:analysis / Q000187:drug effects / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology*; D016211:Transforming Growth Factor alpha / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*
D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D016211:Transforming Growth Factor alpha; D013629:Tamoxifen; D066246:ErbB Receptors