title: Increased expression of estrogen receptor beta mRNA in tamoxifen-resistant breast cancer patients.
abstract: Tamoxifen is currently the first-line therapy for treatment of hormone-dependent breast cancer. However, despite initial benefits, most patients eventually relapse. Two groups of patients were identified: (a) a tamoxifen-sensitive group (n = 8); and (b) a tamoxifen-resistant group (n = 9). Using reverse transcription-PCR, the relative expression of mRNA for both estrogen receptor (ER) beta and transforming growth factor beta1 was determined in each patient group and quantified against a known reference standard. ER-beta mRNA was significantly up-regulated in the tamoxifen-resistant group as compared with the tamoxifen-sensitive group (P = 0.001 by Fisher's exact test), and, consistent with previous findings, transforming growth factor beta1 was also up-regulated in the tamoxifen-resistant cohort (P = 0.02). The importance of ER-beta in tamoxifen resistance was validated using tamoxifen-sensitive and -resistant cell lines, in which it was demonstrated that ER-beta mRNA was significantly up-regulated in the resistant cells. These results lend further support to a role for ER-beta as a poor prognostic factor in breast cancer.
authors.affiliation: Department of Medicine, University of Hull, England, United Kingdom. v.speirs@leeds.ac.uk
authors.forename: V
authors.initials: V
authors.lastname: Speirs
authors.forename: C
authors.initials: C
authors.lastname: Malone
authors.forename: D S
authors.initials: DS
authors.lastname: Walton
authors.forename: M J
authors.initials: MJ
authors.lastname: Kerin
authors.forename: S L
authors.initials: SL
authors.lastname: Atkin
mesh_terms: D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism*; D016022:Case-Control Studies; D018076:DNA, Complementary / Q000032:analysis; D019008:Drug Resistance, Neoplasm; D047629:Estrogen Receptor beta; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013629:Tamoxifen / Q000494:pharmacology*; D013737:Testis / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D018931:Antineoplastic Agents, Hormonal; D018076:DNA, Complementary; D047629:Estrogen Receptor beta; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D016212:Transforming Growth Factor beta; D013629:Tamoxifen