title: Paradoxical regulation of Bcl-2 family proteins by 17beta-oestradiol in human breast cancer cells MCF-7.
abstract: Tumorigenesis is related to the dysregulation of cell growth or cell death pathways. Hence, elucidation of the mechanisms involved in the modulation of pro- or anti-apoptotic proteins is important in furthering understanding of breast cancer aetiology and may aid in designing prevention and treatment strategies. In the present study, we examined the role of 17beta-oestradiol on the regulation of apoptosis in the breast cancer cell line MCF-7. Using multi-probe RNAase protection assays, we found changes in the mRNA levels of several Bcl-2 family proteins upon treatment of MCF-7 cells with 17beta-oestradiol. Unexpectedly, we found a paradoxical effects of 17beta-oestradiol on two anti-apoptotic proteins Bcl-2 and Bcl-x. Treatment with 17beta-oestradiol resulted in up-regulation of Bcl-2 mRNA and protein, but down-regulated Bcl-x(L) mRNA and protein. The effect of 17beta-oestradiol on Bcl-x(L) occurred at concentration-dependent fashion. The effect was specific to 17beta-oestradiol since other steroid hormones exert no effect on Bcl-x(L). Tamoxifen, an anti-oestrogen, blocked the down-regulation of Bcl-x(L) by 17beta-oestradiol demonstrating this effect is oestrogen receptor-dependent. We speculate that different members of the Bcl-2 family proteins may be regulated through different pathway and these pathways may be modulated by 17beta-oestradiol.
authors.affiliation: Basic Research Laboratory, Division of Basic Sciences, National Cancer Institute, Frederick, MD 21702-1201, USA.
authors.forename: L K
authors.initials: LK
authors.lastname: Leung
authors.forename: T T
authors.initials: TT
authors.lastname: Wang
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology*; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000473:pathology*; D002452:Cell Count / Q000187:drug effects; D013196:Dihydrotestosterone / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D019254:Genes, bcl-2; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009376:Neoplasms, Hormone-Dependent / Q000473:pathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000494:pharmacology; D013629:Tamoxifen / Q000494:pharmacology; D051020:bcl-X Protein
chemical_list: C494811:BCL2L1 protein, human; D004965:Estrogen Antagonists; D004967:Estrogens; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011994:Recombinant Proteins; D051020:bcl-X Protein; D013196:Dihydrotestosterone; D013629:Tamoxifen; D004958:Estradiol; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I