title: Beta1-integrin circumvents the antiproliferative effects of trastuzumab in human epidermal growth factor receptor-2-positive breast cancer.
abstract: Resistance to trastuzumab, the monoclonal antibody targeting human epidermal growth factor receptor 2 (HER-2), is a major concern for HER-2-positive metastatic breast cancer (MBC) patients. To date, HER-2 status is the only available biomarker for selecting patients for trastuzumab-based therapy. Beta(1)-integrin, an adhesion molecule involved in cell survival and drug resistance, shares common downstream signaling elements with HER-2, such as the phosphatidylinositol 3-kinase/Akt and extracellular signal-regulated kinase-1/2 (ERK1/2) pathways. The significance of beta(1)-integrin expression in HER-2-positive breast cancer and its involvement in a patient's response to trastuzumab-based therapy are unknown. We show here that overexpression of beta(1)-integrin is an independent negative prognostic factor for tumor progression of HER-2-positive MBC patients treated with trastuzumab-based chemotherapy. Enforced overexpression of beta(1)-integrin, its small interfering RNA-induced knockdown or treatment with a beta(1)-integrin-blocking antibody in HER-2-positive breast cancer cells, identified a strong inverse relationship between expression level of beta(1)-integrin and in vitro sensitivity to trastuzumab. Notably, beta(1)-integrin overexpression increased the phosphorylation of Akt-Ser473 and ERK1/2, thereby promoting survival and mitogenic signals to bypass the antiproliferative effects of trastuzumab. Our findings show that beta(1)-integrin provides a novel independent prognostic biomarker of trastuzumab response in HER-2-positive MBC patients and suggest a new target to augment the antiproliferative effects of trastuzumab.
authors.affiliation: Department of Experimental Oncology, Cross Cancer Institute and University of Alberta, Edmonton, Alberta, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Lesniak
authors.forename: Yaoxian
authors.initials: Y
authors.lastname: Xu
authors.forename: Jean
authors.initials: J
authors.lastname: Deschenes
authors.forename: Raymond
authors.initials: R
authors.lastname: Lai
authors.forename: John
authors.initials: J
authors.lastname: Thoms
authors.forename: David
authors.initials: D
authors.lastname: Murray
authors.forename: Sunita
authors.initials: S
authors.lastname: Gosh
authors.forename: John R
authors.initials: JR
authors.lastname: Mackey
authors.forename: Siham
authors.initials: S
authors.lastname: Sabri
authors.forename: Bassam
authors.initials: B
authors.lastname: Abdulkarim
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology*; D014408:Biomarkers, Tumor / Q000032:analysis*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D018450:Disease Progression; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D019012:Integrin beta1 / Q000235:genetics* / Q000378:metabolism; D011379:Prognosis; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D019012:Integrin beta1; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab