Livin 蛋白在非小细胞肺癌中的表达及其临床意义

目的：研究livin 蛋白在非小细胞肺癌中的表达及其与非小细胞肺癌的生物学特性及临床预后的关系。方法：通过免疫组化 的方法检测和比较88 例非小细胞肺癌组织和20例癌旁正常肺组织中livin 蛋白的表达,并分析其与非小细胞肺癌的临床病理特 征和预后的相关性。结果：非小细胞肺癌组织及癌旁正常肺组织中livin 蛋白的阳性表达率分别为54.55%和5%,差异有显著统计 学差异(P<0.05)。非小细胞肺癌组织中livin 蛋白的表达水平与淋巴结转移、TNM分期显著相关(P<0.05),但与患者的性别、年龄、 分化程度及病理学类型无关(P>0.05)。Livin 高表达的非小细胞肺癌患者生存时间显著短于livin 低表达的患者(P<0.05)。结论： Livin 蛋白在非小细胞肺癌的发生及发展中起重要作用并与患者的预后相关,可能作为非小细胞肺癌新的防治靶点。     

Poriferan survivin exhibits a conserved regulatory role in the interconnected pathways of cell cycle and apoptosis

Survivin orchestrates intracellular pathways during cell division and apoptosis. Its central function as mitotic regulator and inhibitor of cell death has major implications for tumor cell proliferation. Analyses in early-branching Metazoa so far propose an exclusive role of survivin as a chromosomal passenger protein, whereas only later during evolution a complementary antiapoptotic function might have arisen, concurrent with increased organismal complexity. To lift the veil on the ancestral function(s) of this key regulator, a survivin-like protein (SURVL) of one of the earliest-branching metazoan taxa was identified and functionally characterized. SURVL of the sponge Suberites domuncula shares considerable similarities with its metazoan homologs, ranging from conserved exon/intron structure to presence of protein-interaction domains. Whereas sponge tissue shows a low steady-state level, SURVL expression was significantly upregulated in rapidly proliferating primmorph cells. In addition, challenge of tissue and primmorphs with heavy metal or lipopeptide stimulated SURVL expression, concurrent with the expression of a newly discovered caspase. Complementary functional analyses in transfected HEK-293 cells revealed that heterologous expression of a SURVL–EFGP fusion not only promotes proliferation but also enhances resistance to cadmium-induced cell death. Taken together, these results suggest both a deep evolutionary conserved dual role of survivin and an equally conserved central position in the interconnected pathways of cell cycle and apoptosis.     

OTUB1 modulates c‐IAP1 stability to regulate signalling pathways

The cellular inhibitor of apoptosis (c‐IAP) proteins are E3 ubiquitin ligases that are critical regulators of tumour necrosis factor (TNF) receptor (TNFR)‐mediated signalling. Through their E3 ligase activity c‐IAP proteins promote ubiquitination of receptor‐interaction protein 1 (RIP1), NF‐κB‐inducing kinase (NIK) and themselves, and regulate the assembly of TNFR signalling complexes. Consequently, in the absence of c‐IAP proteins, TNFR‐mediated activation of NF‐κB and MAPK pathways and the induction of gene expression are severely reduced. Here, we describe the identification of OTUB1 as a c‐IAP‐associated deubiquitinating enzyme that regulates c‐IAP1 stability. OTUB1 disassembles K48‐linked polyubiquitin chains from c‐IAP1 in vitro and in vivo within the TWEAK receptor‐signalling complex. Downregulation of OTUB1 promotes TWEAK‐ and IAP antagonist‐stimulated caspase activation and cell death, and enhances c‐IAP1 degradation. Furthermore, knockdown of OTUB1 reduces TWEAK‐induced activation of canonical NF‐κB and MAPK signalling pathways and modulates TWEAK‐induced gene expression. Finally, suppression of OTUB1 expression in zebrafish destabilizes c‐IAP (Birc2) protein levels and disrupts fish vasculature. These results suggest that OTUB1 regulates NF‐κB and MAPK signalling pathways and TNF‐dependent cell death by modulating c‐IAP1 stability.     

Identification of DR5 as a critical,NF-κB-regulated mediator of Smac-induced apoptosis

Smac mimetic promotes apoptosis by neutralizing inhibitor of apoptosis (IAP) proteins and is considered as a promising cancer therapeutic. Although an autocrine/paracrine tumor necrosis factor-α (TNFα) loop has been implicated in Smac mimetic-induced cell death, little is yet known about additional factors that determine sensitivity to Smac mimetic. Using genome-wide gene expression analysis, we identify death receptor 5 (DR5) as a novel key mediator of Smac mimetic-induced apoptosis. Although several cell lines that are sensitive to the Smac mimetic BV6 die in a TNFα-dependent manner, A172 glioblastoma cells undergo BV6-induced apoptosis largely independently of TNFα/TNFR1, as the TNFα-blocking antibody Enbrel or TNFR1 knockdown provide little protection. Yet, BV6-stimulated nuclear factor-κB (NF-κB) activation is critically required for apoptosis, as inhibition of NF-κB by overexpression of dominant-negative IκBα superrepressor (IκBα-SR) blocks BV6-induced apoptosis. Unbiased genome-wide gene expression studies in IκBα-SR-overexpressing cells versus vector control cells reveal that BV6 increases DR5 expression in a NF-κB-dependent manner. Importantly, this BV6-stimulated upregulation of DR5 is critically required for apoptosis, as transient or stable knockdown of DR5 significantly inhibits BV6-triggered apoptosis. In addition, DR5 silencing attenuates formation of a RIP1/FADD/caspase-8 cytosolic cell death complex and activation of caspase-8, -3 and -9. By identifying DR5 as a critical mediator of Smac mimetic-induced apoptosis, our findings provide novel insights into the determinants that control susceptibility of cancer cells to Smac mimetic.     

Induction of the intrinsic apoptosis pathway in insulin-secreting cells is dependent on oxidative damage of mitochondria but independent of caspase-12 activation

Pro-inflammatory cytokine-mediated beta cell apoptosis is activated through multiple signaling pathways involving mitochondria and endoplasmic reticulum. Activation of organelle-specific caspases has been implicated in the progression and execution of cell death. This study was therefore performed to elucidate the effects of pro-inflammatory cytokines on a possible cross-talk between the compartment-specific caspases 9 and 12 and their differential contribution to beta cell apoptosis. Moreover, the occurrence of ROS-mediated mitochondrial damage in response to beta cell toxic cytokines has been quantified. ER-specific caspase-12 was strongly activated in response to pro-inflammatory cytokines; however, its inhibition did not abolish cytokine-induced mitochondrial caspase-9 activation and loss of cell viability. In addition, there was a significant induction of oxidative mitochondrial DNA damage and elevated cardiolipin peroxidation in insulin-producing RINm5F cells and rat islet cells. Overexpression of the H₂O₂ detoxifying enzyme catalase effectively reduced the observed cytokine-induced oxidative damage of mitochondrial structures. Taken together, the results strongly indicate that mitochondrial caspase-9 is not a downstream substrate of ER-specific caspase-12 and that pro-inflammatory cytokines cause apoptotic beta cell death through activation of caspase-9 primarily by hydroxyl radical-mediated mitochondrial damage.     

Novel functions of vimentin in cell adhesion, migration, and signaling

Vimentin is the major intermediate filament (IF) protein of mesenchymal cells. It shows dynamically altered expression patterns during different developmental stages and high sequence homology throughout all vertebrates, suggesting that the protein is physiologically important. Still, until recently, the real tasks of vimentin have been elusive, primarily because the vimentin-deficient mice were originally characterized as having a very mild phenotype. Recent studies have revealed several key functions for vimentin that were not obvious at first sight. Vimentin emerges as an organizer of a number of critical proteins involved in attachment, migration, and cell signaling. The highly dynamic and complex phosphorylation of vimentin seems to be a likely regulator mechanism for these functions. The implicated novel vimentin functions have broad ramifications into many different aspects of cell physiology, cellular interactions, and organ homeostasis.     

Fas death receptor signalling: roles of Bid and XIAP

Fas (also called CD95 or APO-1), a member of a subgroup of the tumour necrosis factor receptor superfamily that contain an intracellular death domain, can initiate apoptosis signalling and has a critical role in the regulation of the immune system. Fas-induced apoptosis requires recruitment and activation of the initiator caspase, caspase-8 (in humans also caspase-10), within the death-inducing signalling complex. In so-called type 1 cells, proteolytic activation of effector caspases (-3 and -7) by caspase-8 suffices for efficient apoptosis induction. In so-called type 2 cells, however, killing requires amplification of the caspase cascade. This can be achieved through caspase-8-mediated proteolytic activation of the pro-apoptotic Bcl-2 homology domain (BH)3-only protein BH3-interacting domain death agonist (Bid), which then causes mitochondrial outer membrane permeabilisation. This in turn leads to mitochondrial release of apoptogenic proteins, such as cytochrome c and, pertinent for Fas death receptor (DR)-induced apoptosis, Smac/DIABLO (second mitochondria-derived activator of caspase/direct IAP binding protein with low Pi), an antagonist of X-linked inhibitor of apoptosis (XIAP), which imposes a brake on effector caspases. In this review, written in honour of Juerg Tschopp who contributed so much to research on cell death and immunology, we discuss the functions of Bid and XIAP in the control of Fas DR-induced apoptosis signalling, and we speculate on how this knowledge could be exploited to develop novel regimes for treatment of cancer.