title: Bombesin antagonists inhibit growth of MDA-MB-435 estrogen-independent breast cancers and decrease the expression of the ErbB-2/HER-2 oncoprotein and c-jun and c-fos oncogenes.
abstract: Previous studies showed that antagonists of bombesin (BN)/gastrin-releasing peptide (GRP) inhibit the growth of various cancers by interfering with the growth-stimulatory effects of BN-like peptides and down-regulating epidermal growth factor receptors on tumors. Because the overexpression of the human epidermal growth factor receptor-2 (ErbB-2/HER-2/neu) oncogene plays a role in the progression of many breast cancers, we investigated whether BN/GRP antagonists can affect HER-2 in mammary tumors. Female nude mice bearing orthotopic xenografts of MDA-MB-435 human estrogen-independent breast cancers were treated daily with BN/GRP antagonists RC-3095 (20 microg) or RC-3940-II (10 microg) for 6 weeks. The expression of BN/GRP receptors on tumors was analyzed by reverse transcription-PCR and immunoblotting. We also evaluated whether the mRNA expression for the c-jun and c-fos oncogenes is affected by the therapy. Both BN/GRP antagonists significantly inhibited growth of MDA-MB-435 cancers; RC-3095 reduced tumor volume by 40% and RC-3940-II by 65%. The GRP receptors (subtype 1) were detected in MDA-MB-435 tumors, showing that they mediate the inhibitory effect of the antagonists. Tumor inhibition was associated with a substantial reduction in the expression of mRNA and protein levels of the ErbB/HER receptor family as well as with a decrease in the expression of c-jun and c-fos oncogenes. BN/GRP antagonists RC-3940-II and RC-3095 could be considered for endocrine therapy of estrogen-independent breast cancers that express members of the ErbB/HER receptor family and the c-jun and c-fos oncogenes.
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center and Section of Experimental Medicine, Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112, USA.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Bajo
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Schally
authors.forename: Magdalena
authors.initials: M
authors.lastname: Krupa
authors.forename: Francine
authors.initials: F
authors.lastname: Hebert
authors.forename: Kate
authors.initials: K
authors.lastname: Groot
authors.forename: Karoly
authors.initials: K
authors.lastname: Szepeshazi
mesh_terms: D000328:Adult; D000818:Animals; D001839:Bombesin / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000097:blood; D004967:Estrogens / Q000502:physiology; D005260:Female; D005755:Gastrins / Q000097:blood; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D016762:Genes, fos / Q000235:genetics; D016758:Genes, jun / Q000235:genetics; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010446:Peptide Fragments / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics*; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D001839:Bombesin; D004815:Epidermal Growth Factor; D004967:Estrogens; D005755:Gastrins; D010446:Peptide Fragments; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D018719:Erb-b2 Receptor Tyrosine Kinases; C096400:bombesin(6-14), Hca(6)-Leu(13)-psi(CH2N)-Tac(14)-; C071363:bombesin (6-14), Tpi(6)-Leu(13)-psi(CH2NH)-Leu(14)-