title: Inhibitor of Apoptosis (IAP) survivin is indispensable for survival of HER2 gene-amplified breast cancer cells with primary resistance to HER1/2-targeted therapies.
abstract: Primary resistance of HER2 gene-amplified breast carcinomas (BC) to HER-targeted therapies can be explained in terms of overactive HER2-independent downstream pro-survival pathways. We here confirm that constitutive overexpression of Inhibitor of Apoptosis (IAP) survivin is indispensable for survival of HER2-positive BC cells with intrinsic cross-resistance to multiple HER1/2 inhibitors. The IC₅₀ values for the HER1/2 Tyrosine Kinase Inhibitors (TKIs) gefitinib, erlotinib and lapatinib were up to 40-fold higher in trastuzumab-unresponsive JIMT-1 cells than in trastuzumab-naïve SKBR3 cells. ELISA-based and immunoblotting assays demonstrated that trastuzumab-refractory JIMT-1 cells constitutively expressed ~ 4 times more survivin protein than trastuzumab-responsive SKBR3 cells. In response to trastuzumab, JIMT-1 cells accumulated ~10 times more survivin than SKBR3 cells. HER1/2 TKIs failed to down-regulate survivin expression in JIMT-1 cells whereas equimolar doses of HER1/HER2 TKIs drastically depleted survivin protein in SKBR3 cells. ELISA-based detection of histone-associated DNA fragments confirmed that trastuzumab-refractory JIMT-1 cells were intrinsically protected against the apoptotic effects of HER1/2 TKIs. Of note, when we knocked-down survivin expression using siRNA and then added trastuzumab, cell proliferation and colony formation were completely suppressed in JIMT-1 cells. Our current findings may be extremely helpful to design successful combinatorial strategies aimed to circumvent the occurrence of de novo resistance to HER2-directed drugs using survivin antagonists.
authors.affiliation: Unit of Translational Research, Catalan Institute of Oncology-Girona, Avenida de Francia S/N, E-17007 Girona, Catalonia, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Oliveras-Ferraros
authors.forename: Alejandro
authors.initials: A
authors.lastname: Vazquez-Martin
authors.forename: Sílvia
authors.initials: S
authors.lastname: Cufí
authors.forename: Violeta Zenobia
authors.initials: VZ
authors.lastname: Torres-Garcia
authors.forename: Tamara
authors.initials: T
authors.lastname: Sauri-Nadal
authors.forename: Sonia Del
authors.initials: SD
authors.lastname: Barco
authors.forename: Eugeni
authors.initials: E
authors.lastname: Lopez-Bonet
authors.forename: Joan
authors.initials: J
authors.lastname: Brunet
authors.forename: Begoña
authors.initials: B
authors.lastname: Martin-Castillo
authors.forename: Javier A
authors.initials: JA
authors.lastname: Menendez
mesh_terms: D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology*; D002470:Cell Survival; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D005260:Female; D005784:Gene Amplification; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D000077341:Lapatinib; D011799:Quinazolines / Q000627:therapeutic use; D034622:RNA Interference; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics*; D000077022:Survivin; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D066246:ErbB Receptors; D051034:Inhibitor of Apoptosis Proteins; D000077341:Lapatinib; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; D000077022:Survivin; D000068878:Trastuzumab; C107489:BIRC5 protein, human; C512478:EGFR protein, human; C508053:ERBB2 protein, human