凋亡抑制蛋白IAP及其调控

调亡过程中关键参与者是caspase家族的多种成员,它们在凋亡过程中要受到严格调控。凋亡抑制蛋白IAP通过抑制caspase的活性从而参与对凋亡的调控,所以IAP的结构特征及其调控机制具有重要意义。     

靶向Survivin基因与肿瘤

Survivin基因不仅表达于绝大多数的肿瘤细胞中,也存在于人体正常的细胞中,它具有抑制凋亡和调节有丝分裂的双重作用．临床研究表明：下调Survivin基因的表达或者抑制Survivin蛋白的功能,可以降低肿瘤细胞的生长潜力、增加凋亡的比例,而且可以增强肿瘤细胞对抗肿瘤药物和放射线的敏感性．许多抗肿瘤药物通过诱导细胞凋亡而发挥功能．但某些肿瘤表现出对它们的耐药性。导致肿瘤耐药性的一个最重要的因素就是Survivin的表达．有关细胞凋亡途径和Survivin基因表达等方面的研究可为发现和发展新型抗肿瘤药物提供新的途径．     

GRF78：预测化疗药物疗效及制导肿瘤靶向治疗的分子

葡萄糖调节蛋白78（glucose—regulated protein 78,GRP78）作为分子伴侣的生物学功能已为人们所熟知。但近年来研究人员发现,它与肿瘤的增殖、迁移,以及肿瘤耐药性有密切的关系,因此人们对GRP78的功能有了新的认识。     

肿瘤新生血管及分子靶向治疗新策略

肿瘤血管靶向治疗是基于肿瘤新生血管与正常血管的不同,药物专一识别并阻断肿瘤新生血管,使肿瘤细胞“饿死”,而不影响正常细胞。从1971年Folkman提出“饿死肿瘤”的假说到2004年第一个血管靶向药物上市,记载着30多年领域发展的传奇经历。当今,肿瘤血管已成为生物医学和临床研究的热点,新的发现层出不穷。该文重点介绍肿瘤血管新靶点、新机制、新药物与未来发展。     

组织因子与肿瘤靶向治疗

组织因子(tissue factor,TF)是一种分子量为47kD的跨膜糖蛋白,作为凝血因子Ⅶ的受体启动外源性凝血过程。近年来,人们发现组织因子在肿瘤血管生成和肿瘤细胞转移过程中也发挥重要作用,并且在针对组织因子的肿瘤靶向的治疗方面取得了一些重要进展。     

肿瘤坏死因子家族新成员——TRAIL

肿瘤坏死因子相关的凋亡诱导配体(TRAIL)或称凋亡素2配体(Apo2 ligand, Apo-2L), 是TNF家族的新成员.它是从表达序列标签库(expressed sequenced tag, EST)中寻找TNF的同源分子时发现的.TRAIL是一种分子质量为32.5 ku的Ⅱ型跨膜糖蛋白, 活性形式呈同源三聚体.TRAIL和可溶性的TRAIL强烈诱导肿瘤细胞株凋亡.新近发现的TRAIL受体DR4和DR5及TRID说明了TRAIL与TNF和Fas/Apo-1配体的作用途径是不同的.随着对TRAIL的受体及作用机理研究的深入, TRAIL很可能成为新一代抗肿瘤制剂.     

肿瘤坏死因子相关的凋亡诱导配体及其与肿瘤治疗前景

肿瘤坏因子相关的凋亡诱导配体（ＴＮＦ－related apoptosis inducing ligand,TRALL)属于肿瘤坏死因子家族,可激活肿瘤细胞的凋亡。本文介绍了ＴＲＡＩＬ的结构与功能,凋亡诱导途径及其肿瘤治疗应用前景。     

选择性剪接与肿瘤靶向治疗

RNA剪接过程受到多种调节因子作用,以保证前体mRNA剪接的准确性。但是大量研究发现,在人类肿瘤中经常发生选择性剪接的异常或者来自特定癌症基因的剪接调控元件的突变。因此,RNA剪接调节剂作为一类新的癌蛋白和肿瘤抑制因子而逐渐受到关注,并有望通过调节参与致癌基因的RNA而达到治疗肿瘤的效果。改变RNA的异常剪接是治疗相关癌症的基础,这也为靶向治疗提供了更加丰富的靶点。本文综述了新发现的和预测的不同的剪接事件导致癌症的相关基因,并且对它们如何促成疾病的发病机制进行讨论。最后,我们总结了最新的针对可变剪接而发展的癌症诊断和治疗方法,包括使用小分子的剪接抑制剂来阻断剪接体或转录因子修饰酶,以调节特异性剪接导致的癌症。     

新生血管靶向肽NGR与肿瘤靶向治疗

NGR(Asn-Gly-Arg)是通过噬菌体展示技术筛选出来的能够和肿瘤新生血管特异结合的三肽模体,可以通过内皮细胞上的氨肽酶N(aminopeptidase N,亦称CD13)与新生血管发生特异性的结合。NGR多肽可以将多种药物分子和病毒载体靶向运输到肿瘤或者进行血管再生的组织中。NGR模体上的天冬酰胺脱酰胺后生成异天冬氨酸-甘氨酸-精氨酸异构体(isoDGR)。isoDGR是整联蛋白αvβ3的配体,可以作为一种新的肿瘤新生血管靶向肽用于肿瘤靶向治疗的研究。本文主要对NGR模体的结构和功能以及其在肿瘤靶向治疗中的应用作一综述。     

The IAP family：endogenous caspase inhibitors with multiple biological activities

IAPs (inhibitors of apoptosis) are a family of proteins containing one or more characteristic BIR domains.These proteins have multiple biological activities that include binding and inhibiting caspases,regulating cell cycle progression,and modulating receptor-mediated signal transduction.Our recent studies found the IAP family members XIAP and c-IAP1 are ubiquitinated and degraded in proteasomes in response to apoptotic stimuli in T cells,and their degradation appears to be important for T cells to commit to death.In addition to three BIR domains,each of these IAPs also contains a RING finger domain. We found this region confers ubiquitin protease ligase(E3) activity to IAPs,and is responsible for the auto-ubiquitination and degradation of IAPs after an apoptotic stimulus.Given the fact that IAPs can bind a variety of proteins,such as caspases and TRAFs,it will be of interest to characterize potential substrates of the E3 activity of IAPs and the effects of ubiquitination by IAPs on signal transduction,cell cycle,and apoptosis.     

The inhibitor of apoptosis protein family and its antagonists in acute leukemias

The Inhibitor of Apoptosis Protein family (IAP) functions as inhibitors of apoptotic pathways, both death receptor- and mitochondrial mediated. We detail the current body of knowledge for the IAP family with regard to their structure and function, their expression in normal and leukemic cells, and their prognostic importance in acute leukemia. Although there is some evidence that IAPs play an important role in the chemoresistance of leukemia cell lines, little is known about their influence on this phenomenon in acute leukemia cells of human origin. IAPs are also explored as a specific target for new antitumor strategies, including antisense oligonucleotides of XIAP (X-chromosome-linked IAP) or survivin and small molecules of polyphenylurea-based XIAP inhibitors. Several proteins negatively regulate the function of the IAP family. One of those antagonists is Smac/DIABLO. Short peptides of Smac were found to enhanced apoptosis, induced by chemo- or immunotherapy, in the leukemic cells in vitro. Moreover, small-molecule agents, resembling Smac/DIABLO in function, were shown to potentiate cytotoxicity of chemotherapy in different malignancies. IAPs, exhibiting downstream influence on both external and intrinsic pathways as well as on some caspase-independent mechanisms of apoptosis, are potentially attractive target for anti-tumor therapy, although their role in the pathology and prognosis of acute leukemia has to be further elucidated.     

Expression of IAP family proteins in colon cancers from patients with different age groups

Members of the inhibitor of apoptosis protein (IAP) family including survivin, are expressed in many tumors. However, age-related changes in their expression in cancer have not been clarified. Thus, we investigated the expression of mRNA-coding for IAP family proteins in colon cancer samples from young (<70 years of age) and elderly (>70 years) patients by real-time quantitative RT-PCR. Samples were collected from cases with well-differentiated adenocarcinoma or moderately differentiated adenocarcinoma and their adjacent normal epithelial tissue. Well-differentiated adenocarcinoma tended to express higher levels of survivin than normal mucosa, and expression in moderately differentiated adenocarcinoma was significantly greater than in normal mucosa in samples from both groups of patients (p<0.05, respectively). When samples were compared between the different age groups, the normal mucosa exhibited similar levels of survivin expression. However, samples from older patients showed a significantly higher level of expression than those from younger patients in well and moderately differentiated adenocarcinomas (p<0.05, respectively). In contrast, the levels of expression of cIAP1, cIAP2, and NAIP in the cancerous tissues were lower than those found in normal mucosa regardless of age. As for age-related changes, the expression of cIAP2 in normal mucosa and moderately differentiated adenocarcinoma was stronger in the elderly group than the young group (p<0.05, respectively), and NAIP expression in well-differentiated adenocarcinoma was higher in the young group than the elderly group (p<0.05). XIAP expression was similar in normal and cancerous tissues in both the young and elderly groups. These results suggest that the expression of IAP family proteins, especially survivin, is associated with the age-related biological characteristics of colon cancer.     

Design,stereoselective synthesis,and biological evaluation of novel tri-cyclic compounds as inhibitor of apoptosis proteins (IAP) antagonists

We recently reported the discovery of octahydropyrrolo[1,2-a]pyrazine A as a lead compound for an inhibitor of apoptosis proteins (IAP) antagonist. To develop IAP antagonists with favorable PK profiles, we designed novel tri-cyclic compounds, octahydro-1H-cyclopropa[4,5]pyrrolo[1,2-a]pyrazines 1 and 2 based on co-crystal structural analysis of A with cellular IAP-1 (cIAP-1). The additional cyclopropane moiety was used to block the predicted metabolic site of compound A without detriment to the binding affinity for cIAP. Compounds 1 and 2 were stereoselectively synthesized via intermediates 4a and 5b′, which were obtained by Simmons?Smith cyclopropanation of ethylester 3a and silyl ether 3b′. Compounds 1 and 2 showed strong growth inhibition in MDA-MB-231 breast cancer cells and improved metabolic stability in comparison to A. Compound 2 exhibited significant in vivo PD effects to increase tumor necrosis factor-alpha mRNA in a dose dependent manner.     

Apoptosis and lung cancer: a review

It is important to understand the molecular events that contribute to drug-induced apoptosis, and how tumors evade apoptotic death. Defects in apoptosis are implicated in both tumorigenesis and drug resistance, and these defects are cause of chemotherapy failures. These studies should explain the relationship between cancer genetics and treatment sensitivity, and should enable a more rational approach to anticancer drug design and therapy. Lung cancer is a major cause of cancer deaths throughout the world. Small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC) represent the two major categories of lung cancer that differ in their sensitivity to undergo apoptosis. The role of apoptosis regulation in lung cancer with major focus on the differential sensitivities of the major subtypes is reviewed.     

Structural Basis for Bivalent Smac-Mimetics Recognition in the IAP Protein Family

XIAP is an apoptotic regulator protein that binds to the effector caspases -3 and -7 through its BIR2 domain, and to initiator caspase-9 through its BIR3 domain. Molecular docking studies suggested that Smac-DIABLO may antagonize XIAP by concurrently targeting both BIR2 and BIR3 domains; on this basis bivalent Smac-mimetic compounds have been proposed and characterized. Here, we report the X-ray crystal structure of XIAP-BIR3 domain in complex with a two-headed compound (compound 3) with improved efficacy relative to its monomeric form. A small-angle X-ray scattering study of XIAP-BIR2BIR3, together with fluorescence polarization binding assays and compound 3 cytotoxicity tests on HL60 leukemia cell line are also reported. The crystal structure analysis reveals a network of interactions supporting XIAP-BIR3/compound 3 recognition; moreover, analytical gel-filtration chromatography shows that compound 3 forms a 1:1 stoichiometric complex with a XIAP protein construct containing both BIR2 and BIR3 domains. On the basis of the crystal structure and small-angle X-ray scattering, a model of the same BIR2-BIR3 construct bound to compound 3 is proposed, shedding light on the ability of compound 3 to relieve XIAP inhibitory effects on caspase-9 as well as caspases -3 and -7. A molecular modeling/docking analysis of compound 3 bound to cIAP1-BIR3 domain is presented, considering that Smac-mimetics have been shown to kill tumor cells by inducing cIAP1 and cIAP2 ubiquitination and degradation. Taken together, the results reported here provide a rationale for further development of compound 3 as a lead in the design of dimeric Smac mimetics for cancer treatment.     

Discovery of tetrahydroisoquinoline-based bivalent heterodimeric IAP antagonists

Bivalent heterodimeric IAP antagonists that incorporate (R)-tetrahydroisoquinoline in the P3′ subunit show high affinity for the BIR2 domain and demonstrated potent IAP inhibitory activities in biochemical and cellular assays. Potent in vivo efficacy was observed in a variety of human tumor xenograft models. The bivalent heterodimeric molecule 3 with a P3–P3′ benzamide linker induced pharmacodynamic markers of apoptosis and was efficacious when administered intravenously at a dose of 1 mg/kg to mice harboring A875 human melanoma tumors. Analog 5, with a polyamine group incorporated at the P2′ thiovaline side chain exhibited antiproliferative activity against the P-gp expressing HCT116/VM46 cell line.     

新的凋亡抑制因子Survivin的研究进展

Survivin是近年来发现的一种凋亡抑制因子,属于凋亡抑制蛋白（inhibitor of apoptosis proteins,IAP）家族的新成员;主要通过抑制caspase-3和caspase-7的活性而阻断细胞凋亡过程. Survivin选择性地表达于胚胎发育组织和大多数肿瘤组织,而正常成人终末分化组织中不表达. Survivin参与了细胞周期调控,与肿瘤的发生、发展和预后密切相关,可作为肿瘤治疗的新靶点.