Tamoxifen-mediated growth inhibition of human cholangiocarcinoma.
Cholangiocarcinoma represents a challenging primary malignancy of the liver with no effective medical therapy and a poor prognosis. We have investigated the role of tamoxifen and estrogen receptors (ERs) in the regulation of growth of human cholangiocarcinoma. Two human cholangiocarcinoma cell lines, OZ and SK-ChA-1, were grown in the presence of graded concentrations of tamoxifen; the effects on cell growth were determined by cell counting or 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium proliferation assay. The presence of ER protein was tested by indirect immunofluorescence and immunoprecipitation. In addition, cells were grown in estrogen-depleted media supplemented with exogenous 17beta-estradiol. ER mRNA was evaluated by reverse transcription-PCR and Northern blotting. Finally, one cholangiocarcinoma cell line was grown as a xenograft in athymic nude mice; tamoxifen effects on in vivo tumor growth were determined with biweekly caliper measurements. Tamoxifen (5-10 microM) caused dose-dependent in vitro growth inhibition of two human cholangiocarcinoma cell lines. In addition, growth inhibition of one cell line (SK-ChA-1) grown as a xenograft in nude mice by tamoxifen was observed. The presence of ER protein was suggested by 17beta-estradiol stimulation of tumor cell growth in vitro and confirmed by immunoprecipitation. Immunofluorescence microscopy was ineffective at detection of ER protein. Reverse transcription-PCR demonstrated the presence of ER mRNA in both cell lines. Northern blot analysis confirmed the presence of full-length 6.5-kb ER mRNA. No ER deletion mutants were detected. Tamoxifen inhibited the growth of human cholangiocarcinoma in vitro and in vivo. ER protein and mRNA were detected in both cell lines. The mechanism(s) of tamoxifen-mediated growth inhibition is unclear but may occur via ER protein or additional pathways. The ability of tamoxifen to inhibit tumor growth may offer an alternative adjunctive treatment for cholangiocarcinoma.
Sampson
L K
LK
Department of Surgery, The University of Alabama at Birmingham, 35294-0007, USA.
Vickers
S M
SM
Ying
W
W
Phillips
J O
JO
D000818:Animals; D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D018281:Cholangiocarcinoma / Q000188:drug therapy / Q000473:pathology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D011233:Precipitin Tests; D011960:Receptors, Estrogen / Q000235:genetics; D013629:Tamoxifen / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D006131:Growth Inhibitors; D011960:Receptors, Estrogen; D013629:Tamoxifen