title: Ron receptor tyrosine kinase activation confers resistance to tamoxifen in breast cancer cell lines.
abstract: Although tamoxifen treatment is associated with improved survival in patients with estrogen receptor (ER)-positive breast tumors, resistance remains an important clinical obstacle. Signaling through growth factor signaling pathways, in particular through receptor tyrosine kinases, has been demonstrated to confer tamoxifen resistance in an estradiol-independent manner. The Ron receptor tyrosine kinase, a member of the c-Met family of receptors, is expressed in a number of human epithelial tumors, and elevated expression of Ron is associated with poor prognosis in women with breast cancer. In this report, we evaluated the role of Ron receptor activation in conferring resistance to tamoxifen in human and murine breast cancer cell lines. Activation of Ron by its ligand, hepatocyte growth factor-like protein (HGFL) was associated with partial rescue from tamoxifen-induced growth inhibition in Ron-expressing cell lines. Western analysis revealed that treatment of the T47D human breast cancer cell line with tamoxifen and HGFL was associated with increased phosphorylation of mitogen-activated protein kinase (MAPK) 1/2 and phosphorylation of serine residue 118 of ER. Expression of ER-dependent genes was increased in cells treated with tamoxifen and HGFL by quantitative reverse transcription-polymerase chain reaction. All of these effects were inhibited by treatment with either a Ron-neutralizing antibody or a MEK1 inhibitor, suggesting the specificity of the effect to Ron, and the involvement of the MAPK 1/2 signaling pathway. In summary, these results illustrate a novel connection between the Ron receptor tyrosine kinase and an important mechanism of tamoxifen resistance in breast cancer.
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: McClaine
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Marshall
authors.forename: Purnima K
authors.initials: PK
authors.lastname: Wagh
authors.forename: Susan E
authors.initials: SE
authors.lastname: Waltz
mesh_terms: D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002277:Carcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000494:pharmacology; D020794:Receptor Protein-Tyrosine Kinases / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D013629:Tamoxifen / Q000627:therapeutic use*; D014162:Transfection
chemical_list: D018931:Antineoplastic Agents, Hormonal; D005419:Flavonoids; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011960:Receptors, Estrogen; C082332:macrophage stimulating protein; D013629:Tamoxifen; D017228:Hepatocyte Growth Factor; C080835:RON protein; D020794:Receptor Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one