Regulation of estrogen target genes and growth by selective estrogen-receptor modulators in endometrial cancer cells.
OBJECTIVE
Tamoxifen has mixed agonist/antagonist activities, leading to tissue-specific estrogen-like actions and endometrial cancer. The purpose of this study was to evaluate the effects of antiestrogens on the growth of estrogen receptor (ER)-positive ECC-1 endometrial cancer cells in vitro and in vivo.


METHODS
We performed growth studies and luciferase assays using ERE-tK and AP-1 reporters. ERalpha protein expression was measured by Western blot after antiestrogen treatments. We investigated the actions of antiestrogens on the transcription of the pS2 gene in situ measured by Northern blot and the actions of antiestrogens on the VEGF protein secreted by ELISA. ERalpha, ERbeta, EGFR, and HER2/neu mRNAs were determined by RT-PCR. Last, ECC-1 tumors were developed by inoculation of cells into ovariectomized athymic mice and treated with estradiol (E2), tamoxifen, raloxifene, and a combination.


RESULTS
E2 induced cell proliferation while antiestrogens did not. E2 and raloxifene down regulated ERalpha protein; in contrast, 4OHT did not. ICI182,780 completely degraded the receptor. ECC-1 cells express ERbeta at insignificant levels. Luciferase assays did not show any induction in ERE- nor AP-1-mediated transcription by antiestrogens. E2 caused a concentration-dependent increase in pS2 mRNA but antiestrogens did not. E2 increased VEGF expression in a dose-dependent manner and antiestrogens blocked E2 action. E2 down regulated HER2/neu while 4OHT and raloxifene did not change HER2/neu levels compared to control. In addition, EGFR mRNA was down regulated by E2 but raloxifene did not change it. Tamoxifen and raloxifene did not promote tumor growth in vivo. However, raloxifene (1.5 mg daily) only partially blocked E2-stimulated growth.


CONCLUSIONS
Tamoxifen and raloxifene are antiproliferative agents and antiestrogens in ECC-1 endometrial cells in vitro and in vivo. The observation that selective estrogen-receptor modulators do not down regulate EGFR and HER2/neu mRNA may provide a potential role for these oncogenes in the development of raloxifene- or tamoxifen-stimulated endometrial cancer. The ECC-1 cell line could provide important new clues about the evolution of drug resistance to tamoxifen and raloxifene.
Dardes
R C
RC
Department of Gynecology, Federal University of São Paulo, São Paulo, Brazil.
Schafer
J MacGregor
JM
Pearce
S Timm
ST
Osipo
C
C
Chen
B
B
Jordan
V C
VC
D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D000818:Animals; D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D016889:Endometrial Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D016228:Endothelial Growth Factors / Q000378:metabolism; D066246:ErbB Receptors / Q000096:biosynthesis / Q000235:genetics; D004958:Estradiol / Q000494:pharmacology; D020847:Estrogen Receptor Modulators / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D005260:Female; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008222:Lymphokines / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011506:Proteins; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020849:Raloxifene Hydrochloride / Q000494:pharmacology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics; D011960:Receptors, Estrogen / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D013629:Tamoxifen / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D066246:ErbB Receptors; D004958:Estradiol; D020847:Estrogen Receptor Modulators; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D008156:Luciferases; D008222:Lymphokines; D011506:Proteins; D012333:RNA, Messenger; D020849:Raloxifene Hydrochloride; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C051838:TFF1 protein, human