Authors’ Affiliations: Cell Death Regulation Laboratory, Departments of Medicine and Cell and Molecular Biology, Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois and Division of Medical Science, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

PURPOSE: Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and agonistic antibodies targeting its receptors are promising cancer therapies because of their tumor selectivity, many tumors are resistant to TRAIL-based therapies. We examined whether the nonsteroidal anti-inflammatory drug aspirin sensitized cancer cells to TRAIL agonists in vitro and in vivo and investigated the underlying mechanism. EXPERIMENTAL DESIGN: The effects of aspirin on sensitivity to TRAIL agonists and expression of apoptosis regulators was determined in human breast cancer cell lines and xenograft tumors. The specific role of survivin depletion in the TRAIL-sensitizing effects of aspirin was determined by silencing survivin. RESULTS: Aspirin sensitized human breast cancer cells, but not untransformed human mammary epithelial cells, to TRAIL-induced caspase activation and apoptosis by a cyclooxygenase-2-independent mechanism. Aspirin also sensitized breast cancer cells to apoptosis induced by a human agonistic TRAIL receptor-2 monoclonal antibody (lexatumumab). Aspirin treatment led to G(1) cell cycle arrest and a robust reduction in the levels of the antiapoptotic protein survivin by inducing its proteasomal degradation, but did not affect the levels of many other apoptosis regulators. Silencing survivin with small interfering RNAs sensitized breast cancer cells to TRAIL-induced apoptosis, underscoring the functional role of survivin depletion in the TRAIL-sensitizing actions of aspirin. Moreover, aspirin acted synergistically with TRAIL to promote apoptosis and reduce tumor burden in an orthotopic breast cancer xenograft model. CONCLUSIONS: Aspirin sensitizes transformed breast epithelial cells to TRAIL-based therapies in vitro and in vivo by a novel mechanism involving survivin depletion. These findings provide the first in vivo evidence for the therapeutic utility of this combination.

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We previously reported a proteome map of lung adenocarcinomas in serine-threonine kinase of the Raf family (c-raf) transgenic mice. We now extend our initial studies to serum proteins at early stage (1 month) and advanced stages of tumorigenesis (12 months). Notably, serum proteins from wild-type and tumor bearing mice were extracted with a lysis buffer containing 5 mol/L urea, 2 mol/L thiourea, 40 mmol/L Tris, 4% CHAPS, 100 mmol/L DTT, 0.5% BioLyte 3-10, separated by 2-DE and studied by image analysis. On average 400 protein spots per gel were excised and analyzed by MALDI-TOF MS. We identified 45 common and 5 uniquely expressed proteins in wild-type and tumor bearing mice. Apart from uniquely identified proteins we observed for n = 9 proteins differential expression when wild-type and tumor bearing mice were compared. This included serpins and other protease inhibitors, lipocalins, transthyretins, globins, and Igs. Notably, we demonstrate significant regulation of alpha-1-antitrypsin, alpha-2-macroglobulin, hemoglobin subunit alpha, vitamin D-binding protein, major urinary proteins, and transthyretin (up to eight-fold) in serum of lung tumor bearing mice. Disease association of these proteins in human malignancies has been reported. Thus, an identification of regulated serum proteins in this lung cancer disease model provides excellent opportunities for the search of novel biomarkers.

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