title: HER4 tumor expression in breast cancer patients randomized to treatment with or without tamoxifen.
abstract: The human epidermal growth factor receptor (HER) 4 is a relative of HER2 and has been associated to endocrine breast cancer and prediction of tamoxifen response. In addition to PI3K/Akt and MAPK pathway activation, ligand binding to HER4 triggers proteolytic cleavage and release of an intracellular receptor domain (4ICD) with signaling properties. The aim of the present study was to analyze HER4 protein expression and intracellular localization in breast cancer tissue from patients randomized to treatment with or without adjuvant tamoxifen. To investigate HER4 expression and localization in response to estradiol (E2) and 4-hydroxytamoxifen (4-OHT) exposure, we also performed in vitro studies. Cytoplasmic, nuclear and membrane expression of HER4 protein was evaluated by immunohistochemical staining in tumor tissue from 912 breast cancer patients. Three different breast epithelia cancer cell lines were exposed to E2 and 4-OHT and mRNA expression was analyzed using qPCR. Further, nuclear and cytoplasmic proteins were separated and analyzed with western blotting. We found an association between nuclear HER4 protein expression and ER-positivity (P=0.004). Furthermore, significant association was found between cytoplasmic HER4 and ER-negativity (P<0.0005), PgR-negativity (P<0.0005), tumor size >20 mm (P=0.001) and HER2-negativity (P=0.008). However, no overall significance of HER4 on recurrence-free survival was found. After E2 exposure, HER4 mRNA and protein expression had decreased in two cell lines in vitro yet no changes in nuclear or cytoplasmic protein fractions were seen. In conclusion, nuclear HER4 seem to be co-located with ER, however, we did not find support for overall HER4 expression in independently predicting response of tamoxifen treatment. The possible influence of separate isoforms was not tested and future studies may further evaluate HER4 significance.
authors.affiliation: Faculty of Medicine and Health, School of Health and Medical Sciences, Örebro University, SE-701 82 Örebro, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Göthlin Eremo
authors.affiliation: Clinical Research Centre, Örebro University Hospital, SE-701 85 Örebro, Sweden.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Tina
authors.affiliation: Department of Clinical Genetics, University Hospital, SE-581 85 Linköping, Sweden.
authors.forename: Pia
authors.initials: P
authors.lastname: Wegman
authors.affiliation: Department of Clinical and Experimental Medicine and Department of Oncology, Linköping University, SE-581 85 Linköping, Sweden.
authors.forename: Olle
authors.initials: O
authors.lastname: Stål
authors.affiliation: Faculty of Medicine and Health, School of Health and Medical Sciences, Örebro University, SE-701 82 Örebro, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Fransén
authors.affiliation: Department of Oncology, Karolinska University Hospital, Karolinska Institute, SE-171 76 Stockholm, Sweden.
authors.forename: Tommy
authors.initials: T
authors.lastname: Fornander
authors.affiliation: Faculty of Medicine and Health, School of Health and Medical Sciences, Örebro University, SE-701 82 Örebro, Sweden.
authors.forename: Sten
authors.initials: S
authors.lastname: Wingren
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D016016:Proportional Hazards Models; D060888:Real-Time Polymerase Chain Reaction; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis; D066247:Receptor, ErbB-4 / Q000096:biosynthesis*; D011960:Receptors, Estrogen / Q000096:biosynthesis; D020845:Selective Estrogen Receptor Modulators / Q000627:therapeutic use*; D013629:Tamoxifen / Q000627:therapeutic use*; D046888:Tissue Array Analysis
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; D066247:Receptor, ErbB-4; D011960:Receptors, Estrogen; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen; C508053:ERBB2 protein, human; C587689:ERBB4 protein, human