Herceptin Research Today is a free monthly online journal that collates and summarizes the latest research about Herceptin, including details on side-effects, breast cancer, treatment, therapy. | ||||||||
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Trastuzumab signaling in ErbB2-overexpressing inflammatory breast cancer correlates with X-linked inhibitor of apoptosis protein expression.Aird KM, Ding X, Baras A, Wei J, Morse MA, Clay T, Lyerly HK, Devi GR Duke University Medical Center, 477 Medical Sciences Research Building-I, 2606 DUMC, Duke University Medical Center, Durham, NC 27710. devi0001@mc.duke.edu. 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. [Mol Cancer Ther 2008;7(1):38-47]. Published 18 January 2008 in Mol Cancer Ther, 7(1): 38-47.
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