title: Insulin-like growth factor-binding protein-5 inhibits the growth of human breast cancer cells in vitro and in vivo.
abstract: The role of insulin-like growth factor-binding protein (IGFBP)-5 in human breast cancer cell growth is unclear. We determined the effects of IGFBP-5 expression on the growth of human breast cancer cell lines in vivo and in vitro. Expression of IGFBP-5, both by stable transfection and adenoviral-mediated infection, was inhibitory to the growth of MDA-MB-231 and Hs578T human breast cancer cells over a 13-day period. IGFBP-5 expression resulted in a G2/M cell cycle arrest and the induction of apoptosis in both cell lines, an effect that was abrogated in the presence of the broad-spectrum caspase inhibitor, z-VAD-fmk. IGFBP-5-induced apoptosis was associated with a transcriptional increase in expression of the proapoptotic regulator bax and decrease in the anti-apoptotic bcl-2 compared with vector controls. Secreted IGFBP-5 when added exogenously to breast cancer cells was not internalized and had no effect on cell growth or apoptosis, suggesting that IGFBP-5 may elicit its inhibitory effects via a novel, intracrine mechanism. In athymic nude mice, stable expression of IGFBP-5 significantly inhibited both the formation and growth of tumors derived from MDA-MB-231 cells. IGFBP-5-expressing tumors also had a significantly elevated level of bax mRNA and decreased levels of bcl-2 mRNA compared with vector tumors. These data suggest that IGFBP-5 is a potent growth inhibitor and proapoptotic agent in human breast cancer cells via modulation of cell cycle regulation and apoptotic mediators.
authors.affiliation: Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, St. Leonards, New South Wales 2065, Australia. abutt@med.usyd.edu.au
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Butt
authors.forename: Kristie A
authors.initials: KA
authors.lastname: Dickson
authors.forename: Fiona
authors.initials: F
authors.lastname: McDougall
authors.forename: Robert C
authors.initials: RC
authors.lastname: Baxter
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D015152:Blotting, Northern; D001943:Breast Neoplasms / Q000378:metabolism*; D002453:Cell Cycle; D002455:Cell Division; D017077:Culture Media, Conditioned / Q000494:pharmacology; D053938:DNA Fragmentation; D004307:Dose-Response Relationship, Radiation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D005822:Genetic Vectors; D006801:Humans; D015151:Immunoblotting; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000378:metabolism / Q000502:physiology*; D008024:Ligands; D051379:Mice; D008819:Mice, Nude; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013936:Thymidine / Q000494:pharmacology; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein
chemical_list: D000590:Amino Acid Chloromethyl Ketones; C494826:BAX protein, human; C494827:Bax protein, mouse; D017077:Culture Media, Conditioned; D004791:Enzyme Inhibitors; D018975:Insulin-Like Growth Factor Binding Protein 5; D008024:Ligands; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D013936:Thymidine