title: Trastuzumab signaling in ErbB2-overexpressing inflammatory breast cancer correlates with X-linked inhibitor of apoptosis protein expression.
abstract: Inflammatory breast cancer (IBC) patients show poor survival and a significant incidence of epidermal growth factor receptor-2 (ErbB2) overexpression. A distinct mechanism involving increased expression of X-linked inhibitor of apoptosis protein (XIAP) and survivin, key members of the inhibitor of apoptosis protein (IAP) family, was observed post-trastuzumab (an ErbB2 monoclonal antibody) treatment in an ErbB2-overexpressing, estrogen receptor negative, IBC cellular model, SUM190PT, isolated from a primary IBC tumor. In contrast, a decrease in the IAP expression was observed in the non-IBC, ErbB2-overexpressing SKBR3 cells in which trastuzumab treatment also decreased p-AKT and cell viability. Further, in SUM190PT cells, therapeutic sensitivity to GW583340 (a dual epidermal growth factor receptor/ErbB2 kinase inhibitor) corresponded with XIAP down-regulation and abrogation of XIAP inhibition on active caspase-9 release. Specific small interfering RNA-mediated XIAP inhibition in combination with trastuzumab caused decrease in inactive procaspase-9 and inhibition of p-AKT corresponding with 45% to 50% decrease in cell viability in the SUM190PT cells, which have high steady-state p-AKT levels. Further, embelin, a small-molecule inhibitor that abrogates binding of XIAP to procaspase-9, caused significant decrease in SUM190PT viability. However, embelin in combination with trastuzumab failed to affect SUM190PT viability because it has no direct effect on XIAP, which is induced by trastuzumab treatment. These data have identified a novel functional link between ErbB2 signaling and antiapoptotic pathway mediated by XIAP. Blockade of the IAP antiapoptotic pathway alone or in combination would be an attractive strategy in IBC therapy.
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Aird
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Ding
authors.forename: Aris
authors.initials: A
authors.lastname: Baras
authors.forename: Junping
authors.initials: J
authors.lastname: Wei
authors.forename: Michael A
authors.initials: MA
authors.lastname: Morse
authors.forename: Timothy
authors.initials: T
authors.lastname: Clay
authors.forename: Herbert K
authors.initials: HK
authors.lastname: Lyerly
authors.forename: Gayathri R
authors.initials: GR
authors.lastname: Devi
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D001943:Breast Neoplasms / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D051616:Neuronal Apoptosis-Inhibitory Protein / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D019076:Transgenes / Q000235:genetics; D000068878:Trastuzumab; D015854:Up-Regulation / Q000187:drug effects; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D053453:Caspase 9; D051616:Neuronal Apoptosis-Inhibitory Protein; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; D051636:X-Linked Inhibitor of Apoptosis Protein; C508053:ERBB2 protein, human