title: Insulin-like growth factor binding protein 2 is a marker for antiestrogen resistant human breast cancer cell lines but is not a major growth regulator.
abstract: Antiestrogens target the estrogen receptor and counteract the growth stimulatory action of estrogen on human breast cancer. However, acquired resistance to antiestrogens is a major clinical problem in endocrine treatment of breast cancer patients. To mimic acquired resistance, we have used a model system with the antiestrogen sensitive human breast cancer cell line MCF-7 and several antiestrogen resistant cell lines derived from the parental MCF-7 cell line. This model system was used to study the expression and possible involvement in resistant cell growth of insulin-like growth factor binding protein 2 (IGFBP-2). By an oligonucleotide based microarray, we compared the expression of mRNAs encoding insulin-like growth factor binding protein 1,2,3,4,5 and 6 (IGFBP-1 to -6) in the parental MCF-7 cell line to three human breast cancer cell lines, resistant to the antiestrogen ICI 182,780 (Faslodex/Fulvestrant). Only IGFBP-2 mRNA was overexpressed in all three resistant cell lines. Thus, we compared the IGFBP-2 protein expression in MCF-7 cells to nine antiestrogen resistant breast cancer cell lines, resistant to either ICI 182,780 or tamoxifen or RU 58,668 and found that IGFBP-2 was overexpressed in all nine resistant cell lines. Three of the resistant cell lines, resistant to different antiestrogens, were selected for further studies and IGFBP-2 overexpression was demonstrated at the mRNA level as well as the intra- and extracellular protein level. The objective of this study was to examine if IGFBP-2 is involved in growth of antiestrogen resistant human breast cancer cells. Therefore, IGFBP-2 expression was inhibited by antisense oligonucletides and siRNA. Specific inhibition of IGFBP-2 protein expression was achieved in MCF-7 and the three selected antiestrogen resistant cell lines, but no effect on resistant cell growth was observed. Thus, we were able to establish IGFBP-2 as a marker for antiestrogen resistant breast cancer cell lines, although IGFBP-2 was not a major contributor to the resistant cell growth.
authors.affiliation: Department of Tumor Endocrinology, Institute of Cancer Biology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
authors.forename: A
authors.initials: A
authors.lastname: Juncker-Jensen
authors.forename: A E
authors.initials: AE
authors.lastname: Lykkesfeldt
authors.forename: J
authors.initials: J
authors.lastname: Worm
authors.forename: U
authors.initials: U
authors.lastname: Ralfkiaer
authors.forename: U
authors.initials: U
authors.lastname: Espelund
authors.forename: J S
authors.initials: JS
authors.lastname: Jepsen
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism*; D001943:Breast Neoplasms / Q000188:drug therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology* / Q000627:therapeutic use; D004967:Estrogens / Q000494:pharmacology; D000077267:Fulvestrant; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism* / Q000494:pharmacology; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology; D005466:Fluorocarbons
chemical_list: D014408:Biomarkers, Tumor; D004958:Estradiol; D004965:Estrogen Antagonists; D004967:Estrogens; D000077267:Fulvestrant; D018971:Insulin-Like Growth Factor Binding Protein 2; D018969:Insulin-Like Growth Factor Binding Proteins; D016376:Oligonucleotides, Antisense; D053284:Polyunsaturated Alkamides; D017526:Receptor, IGF Type 1; D013629:Tamoxifen; C086511:RU 58668; D005466:Fluorocarbons; C051781:ICI 164384