Genetic approaches for the identification of apoptotic components

Jun amino-terminal kinase (JNK) mediates a physiological stress signal that leads to cell death. However, the role of the JNK pathway in intrinsic cell death execution mechanisms is largely unknown. In a genetic screen for dominant suppressors of Reaper (Rpr)-induced cell death, we identified Drosophila chromosomal regions that contain genes which are homologous to apoptosis signal-regulating kinase (ASK1) and Drosophila tumor necrosis factor receptor-associated factor 1 (DTRAF1). We present evidence that the killer signal initiates the JNK pathway via proteasome-mediated degradation of Drosophila inhibitor of apoptosis protein 1 (DIAP1) to promote cell death.     

The Effect of HBx Gene on the Apoptosis of Hepatic Cells

To study the effect of HBx gene on the apoptosis of the cell lines (L02, HepG2) and the interaction between HBx and X-linked inhibitor of apoptosis protein (XIAP), the apoptosis of pcDNA3.1-HBx transiently transfected cell lines (L02, HepG2) was detected by flow cytometry and the mRNA expression of XIAP was assayed by real-time RT-PCR. Our study showed (1) the mor- phology of L02/pcDNA3.1-HBx was changed and the appearance of the cells mimicked that of HepG2 cells; (2) HBx gene could be detected in L02/pcDNA3.1-HBx and HepG2/ pcDNA3.1-HBx; (3) the apoptosis rate of L02/pcDNA 3.1-HBx was higher than that of L02 cells (P<0.01) and the apoptosis rate of HepG2/pcDNA3.1-HBx was lower than that of HepG2 cells (P<0.05); (4) the XIAP expression in L02 was about 3 times that in L02/pcDNA3.1-HBx cells (P<0.01), and the expression of XIAP in HepG2/pcDNA3.1-HBx was about 4 times that in HepG2 (P<0.01). It is concluded that HBx gene may promote the apoptosis of normal hepatocytes and inhibit the apoptosis of cells of he- patic carcinoma by regulating the expression of XIAP.     

Caspases on the brain

The basic mechanisms that underlie neurodegenerative diseases are unknown. Loss of function of specific regions of the brain is due to incapacitation of cells that constitute those regions. Cells can simply stop functioning normally (neurons may cease to transmit signals), or they may die. There is now evidence that the pathology of several neurodegenerative diseases is due to inappropriate apoptosis. This being the case, an understanding of the mediators of apoptosis, their identities, and their role in orchestrating death would be a vital step toward remedying the diseases. The central components of apoptotic pathways, proteases of the caspase family, are present in latent forms in all nucleated cells. Their activity is balanced by specific activation and inactivation events, and the molecular and biochemical controls have been well established in vitro and in model transformed cell lines. In this Mini-Review, we consider the current status of the basic control mechanisms and how these may be subverted during neurodegeneration.     

A role of inhibitor of apoptosis (IAP) proteins in increased lymphocyte apoptosis in aged humans

Lymphocytes from aged humans show increased death-receptor-mediated apoptosis, which is associated with an increased and early activation of caspases. Inhibitor of apoptosis (IAP) proteins inhibit apoptosis by inhibiting activation and activity of caspases. Therefore, we examine the expression of two of the IAPs, the cIAP-2 and XIAP in lymphocytes from young and aged subjects by Western blotting. Lymphocytes from aged expressed significantly less cIAP2 whereas no difference was observed in XIAP expression between young and aged subjects. These data may suggest that decreased cIAP2 may play a role in increased apoptosis in aged humans. Possible mechanisms for the regulation of IAPs in aging are discussed.     

Prognostic importance of survivin in breast cancer

Survivin is a member of the inhibitor of apoptosis (IAP) family, and is also involved in the regulation of cell division. Survivin is widely expressed in foetal tissues and in human cancers, but generally not in normal adult tissue. This study examined the expression of surviving protein in a series of 293 cases of invasive primary breast carcinoma. Survivin immunoreactivity was assessed using two different polyclonal antibodies, and evaluated semiquantitatively according to the percentage of cells demonstrating distinct nuclear and/or diffuse cytoplasmic staining. Overall, 60% of tumours were positive for survivin: 31% demonstrated nuclear staining only, 13% cytoplasmic only, and 16% of tumour cells demonstrated both nuclear and cytoplasmic staining. Statistical analysis revealed that survivin expression was independent of patient's age, tumour size, histological grade, nodal status, and oestrogen receptor status. In multivariate analysis, nuclear survivin expression was a significant independent prognostic indicator of favourable outcome both in relapse-free and overall survival (P<0.001 and P=0.01, respectively). In conclusion, our results show that survivin is frequently overexpressed in primary breast cancer. Nuclear expression is most common and is an independent prognostic indicator of good prognosis.     

Sustained phosphorylation of Bid is a marker for resistance to Fas-induced apoptosis during chronic liver diseases

BACKGROUND & AIMS: Increased rates of apoptosis have been reported to play a role in the pathophysiology of many disorders, including liver diseases. Conversely, genetic mutations that result in impairment of programmed cell death have been associated with cancer development. However, apoptosis resistance can also be the result of nongenetic stress adaptation, as seen in the cancer-prone metabolic liver disease hereditary tyrosinemia. To clarify whether stress-induced apoptosis resistance is a general feature of chronic liver diseases, an animal model of chronic cholestasis was examined. METHODS: Studies were performed with mice before and 2 weeks following bile duct ligation and with Fah-/- and Fah/p21-/- mice before and after NTBC withdrawal. RESULTS: Here we show that bile duct ligation induced profound resistance against Fas monoclonal antibody-mediated hepatocyte death. The apoptosis signaling pathway was blocked downstream of caspase-8 activation and proximal to mitochondrial cytochrome c release. In controls, activation of the Fas receptor resulted in rapid dephosphorylation of Bid and its subsequent cleavage, whereas Bid remained phosphorylated and uncleaved in chronic cholestasis and other models of hepatic apoptosis resistance. CONCLUSIONS: We propose a model in which the phosphorylation status of Bid determines the apoptotic threshold of hepatocytes in vivo. Furthermore, resistance to apoptosis in chronic cholestasis may contribute to the long-term risk of cancer in this setting.     

凋亡抑制蛋白抑制剂的设计合成与抗肿瘤活性评价

目的设计并合成具有抗肿瘤活性的小分子凋亡抑制蛋白广泛性抑制剂。方法运用基于靶点结构的药物设计策略改造前期得到的苗头化合物,设计合成新结构化合物,并进行多靶点的凋亡抑制蛋白家族（IAPs）结合实验和多个细胞系的肿瘤细胞增殖抑制活性评价。结果合成了25个新结构化合物,部分表现出较强的IAPs抑制活性和多种肿瘤细胞增殖抑制能力（微摩尔级别）,Ⅱc系列化合物显示出较强的ciAP1选择性（〉1000）。结论五元杂环烷当中的4s-甲基是化合物对两类IAPs产生选择性差异的结构基础。     

Targeting cell death signalling in cancer: minimising ‘Collateral damage'

Targeting apoptosis for the treatment of cancer has become an increasingly attractive strategy, with agents in development to trigger extrinsic apoptosis via TRAIL signalling, or to prevent the anti-apoptotic activity of BCL-2 proteins or inhibitor of apoptosis (IAP) proteins. Although the evasion of apoptosis is one of the hallmarks of cancer, many cancers have intact apoptotic signalling pathways, which if unblocked could efficiently kill cancerous cells. However, it is becoming increasing clear that without a detailed understanding of both apoptotic and non-apoptotic signalling, and the key proteins that regulate these pathways, there can be dose-limiting toxicity and adverse effects associated with their modulation. Here we review the main apoptotic pathways directly targeted for anti-cancer therapy and the unforeseen consequences of their modulation. Furthermore, we highlight the importance of an in-depth mechanistic understanding of both the apoptotic and non-apoptotic functions of those proteins under investigation as anti-cancer drug targets and outline some novel approaches to sensitise cancer cells to apoptosis, thereby improving the efficacy of existing therapies when used in combination with novel targeted agents.     

Denbinobin induces apoptosis in human lung adenocarcinoma cells via Akt inactivation, Bad activation, and mitochondrial dysfunction

Increasing evidence demonstrated that denbinobin, isolated from Ephemerantha lonchophylla, exert cytotoxic effects in cancer cells. The purpose of this study was to investigate whether denbinobin induces apoptosis and the apoptotic mechanism of denbinobin in human lung adenocarcinoma cells (A549). Denbinobin (1-20microM) caused cell death in a concentration-dependent manner. Flow cytometric analysis and annexin V labeling demonstrated that denbinobin increased the percentage of apoptotic cells. A549 cells treated with denbinobin showed typical characteristics of apoptosis including morphological changes and DNA fragmentation. Denbinobin induced caspase 3 activation, and N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD-fmk), a broad-spectrum caspase inhibitor, prevented denbinobin-induced cell death. Denbinobin induced the loss of the mitochondrial membrane potential and the release of mitochondrial apoptotic proteins including cytochrome c, second mitochondria derived activator of caspase (Smac), and apoptosis-inducing factor (AIF). In addition, denbinobin-induced Bad activation was accompanied by the dissociation of Bad with 14-3-3 and the association of Bad with Bcl-xL. Furthermore, denbinobin induced Akt inactivation in a time-dependent manner. Transfection of A549 cells with both wild-type and constitutively active Akt significantly suppressed denbinobin-induced Bad activation and cell apoptosis. These results suggest that Akt inactivation, followed by Bad activation, mitochondrial dysfunction, caspase 3 activation, and AIF release, contributes to denbinobin-induced cell apoptosis.     

凋亡抑制蛋白与卵巢癌化疗耐药

卵巢癌是严重威胁妇女健康的恶性肿瘤之一,其病死率在妇科肿瘤中占第一位.化疗耐药是导致其治疗失败、病死率居高不下的重要原因.已有的研究表明,抗凋亡机制在肿瘤细胞发生、发展及化疗耐药中起重要作用.凋亡抑制蛋白(IAPs)是重要的细胞凋亡调节因子,在细胞凋亡中起关键作用.本文主要综述IAPs与卵巢癌化疗耐药的相关进展.