Regulators of apoptosis are thought to work in concert, but the molecular interactions of this process are not understood. Here, we show that in response to cell death stimulation, survivin, a member of the inhibitor of apoptosis (IAP) gene family, associates with another IAP protein, XIAP, via conserved baculovirus IAP repeats. Formation of a survivin-XIAP complex promotes increased XIAP stability against ubiquitination/proteasomal destruction and synergistic inhibition of apoptosis, which is abolished in XIAP ؊/؊ cells. Therefore, orchestration of an IAP-IAP complex regulates apoptosis.Among the regulators of programmed cell death, or apoptosis (1), Bcl-2 proteins (2) control the release of apoptogenic proteins from mitochondria, notably cytochrome c (3), whereas members of the inhibitor of apoptosis (IAP) 1 gene family act as endogenous inhibitors of caspases (4), the enzymatic effectors of apoptosis (1). The structural requirements of IAP-caspase(s) complexes have been defined in considerable detail (5).Survivin is a structurally unique IAP protein that has been implicated in protection from apoptosis and regulation of mitosis (6). A role of survivin in cell division has been linked to assembly/stability of metaphase and anaphase microtubules (7) and spindle checkpoint function (8). In contrast, despite its ability to counteract apoptosis in vitro, and in transgenic animals (6), the mechanism(s) by which survivin inhibits apoptosis has remained elusive. This is important because IAPs, especially XIAP (9) and survivin (6), have emerged as critical regulators of cell survival in tumors and promising targets for rational anti-cancer therapy (10,11).In this study, we investigated the mechanism(s) of survivin cytoprotection. We found that in response to cell death stimulation, survivin physically associates with XIAP, and this complex promotes enhanced XIAP stability and synergistic inhibition of caspase-9 activation. MATERIALS AND METHODSCell Culture-Breast carcinoma MCF-7, lymphoblastoid Raji, and kidney embryonic HEK293T cells were from the American Type Culture Collection (ATCC, Manassas, VA). Wild type (WT) or XIAP Ϫ/Ϫ mouse embryonic fibroblasts (MEF) (12) were the gift of Dr. C. Duckett (University of Michigan).Protein-Protein Interactions-Affinity fractionation and immunoprecipitation experiments were carried out as described (10, 13). Fulllength survivin, truncated survivin BIR-(1-87), full-length XIAP, cIAP1, cIAP2, or the three isolated XIAP, BIR1-(1-123), BIR2-(123-259) and BIR3-(260 -336) were expressed as GST fusion proteins (14). Replication-deficient adenoviruses encoding GFP (pAd-GFP) or survivin (pAd-survivin) were described (15). Pull-down experiments with recombinant survivin (0.1-0.4 g) and GST, GST-XIAP, GST-cIAP1, GST-cIAP2 (8 g), or the individual GST-BIR1, -BIR2, or -BIR3 of XIAP (10 g) bound to glutathione beads (100 l) were as described (13). Alternatively, XIAP was translated in vitro in the presence of [ 35 S]methionine (Amersham Sciences), mixed with 5 g of GST or GST-survivin, and u...

We identified 2 useful predictive factors for malignancy in branch duct type IPMN; a mural nodule size >5 mm and a CEA level in the pancreatic juice obtained by preoperative ERP >30 ng/mL.

This is the first report showing that co-expression of mesothelin and CA125 were in pancreatic ductal adenocarcinoma, and such co-expression is associated with a poor prognosis. Our finding suggests that co-expression of these two factors plays a significant role in the acquisition of aggressive clinical behavior.

Caspase-associated recruitment domains (CARDs) are protein interaction domains that participate in activation or suppression of CARD-carrying members of the caspase family of apoptosis-inducing proteases. A novel CARDcontaining protein was identified that is overexpressed in some types of cancer and that binds and suppresses activation of procaspase-9, which we term TUCAN (tumor-upregulated CARD-containing antagonist of caspase nine). The CARD domain of TUCAN selectively binds itself and procaspase-9. TUCAN interferes with binding of Apaf1 to procaspase-9 and suppresses caspase activation induced by the Apaf1 activator, cytochrome c. Overexpression of TUCAN in cells by stable or transient transfection inhibits apoptosis and caspase activation induced by Apaf1/ caspase-9-dependent stimuli, including Bax, VP16, and staurosporine, but not by Apaf1/caspase-9-independent stimuli, Fas and granzyme B. High levels of endogenous TUCAN protein were detected in several tumor cell lines and in colon cancer specimens, correlating with shorter patient survival. Thus, TUCAN represents a new member of the CARD family that selectively suppresses apoptosis induced via the mitochondrial pathway for caspase activation.

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