以TRAIL为靶点的肿瘤治疗研究进展

肿瘤坏死因子相关凋亡配体（tumor necrosis factor-related apoptosis-inducing ligand,TRAIL）是肿瘤坏死因子（tumor necrosis factor,TNF）超家族成员。TRAIL与其受体结合后启动凋亡信号转导,选择性地诱导肿瘤细胞凋亡,而对正常组织细胞没有明显的伤害,而且一些药物和细胞因子可协同TRAIL诱导肿瘤细胞凋亡。本文就TRAIL及其受体、TRAIL诱导凋亡的机制以及影响凋亡的因素和途径,以TRAIL为靶点的肿瘤治疗的研究现状作一综述。     

肿瘤坏死因子相关凋亡诱导配体（TRAIL）及抗肿瘤作用

肿瘤坏死因子相关凋亡诱导配体（TRAIL）是肿瘤坏死因子（TNF）超家族成员之一,能选择性的诱导肿瘤细胞、转化细胞凋亡,而对正常组织无毒性,有望成为肿瘤治疗的新方法,备受人们的关注。本文从TRAIL的结构、受体、诱导肿瘤细胞凋亡机制及在肿瘤治疗中的应用等方面作了介绍,以期为TRAIL临床应用提供参考。     

Procaspase-8失调与肿瘤细胞对TRAIL的耐受

肿瘤坏死因子相关凋亡诱导配体(TRAIL)可激活胱天蛋白酶（caspase）家族蛋白系列级联反应,最终诱导细胞凋亡. TRAIL选择性地诱导肿瘤细胞凋亡而不损伤正常细胞,使其成为治疗癌症的潜在药物靶点. 目前已知,细胞型FADD样白介素-1-β转换酶抑制蛋白(c FLIP)和凋亡抑制蛋白(IAPs)是肿瘤细胞对TRAIL耐受的主要原因.胱天蛋白酶原-8（procaspase-8）是TRAIL凋亡信号途径中的凋亡起始蛋白. 然而近年发现,在某些肿瘤细胞中procaspase-8功能失调常会阻碍凋亡信号传导,使肿瘤细胞对TRAIL诱导的凋亡产生耐受. 本文就其机制进行概述.     

基于TRAIL的肿瘤治疗策略进展

肿瘤坏死因子相关凋亡诱导配体(TRAIL)能选择性诱导肿瘤细胞凋亡,且对机体正常组织细胞无毒副作用,被认为是一种非常有潜力的抗癌药物。我们简要介绍TRAIL及其配体诱导细胞凋亡的机制、肿瘤细胞对TRAIL的耐受机制及其克服策略。     

TRAIL耐药的研究进展

肿瘤坏死因子相关凋亡诱导配体(tumor necrosis factor-related apoptosis-inducing ligand,TRAIL)能选择性地诱导肿瘤细胞凋亡,因此作为抗肿瘤药物备受瞩目,现已进入II期临床试验,尽管有报道称部分肿瘤细胞对TRAIL耐药,导致治疗效果不如预期,但TRAIL用于肿瘤治疗的前景依旧被人们看好。通过对TRAIL耐药机理的研究将有助于寻找逆转肿瘤细胞耐药的靶点,并通过联合用药来调节相关的信号分子以获得更好的抗肿瘤效应。该文将介绍TRAIL及其介导的细胞凋亡通路并总结近年来TRAIL耐药机理及逆转其耐药方面的研究进展。     

肿瘤细胞抗TRAIL凋亡诱导的分子机制

肿瘤坏死因子相关的凋亡诱导配体(tumornecrosisfactor-relatedapoptosis-inducingligand,TRAIL)是肿瘤坏死因子(tumornecrosisfactor,TNF)超家族的成员之一,它能选择性诱导肿瘤细胞凋亡,对大多数正常细胞无杀伤作用。研究表明,某些恶性肿瘤抵抗TRAIL诱导的凋亡,且TRAIL重复作用使一些TRAIL敏感的细胞产生获得性抗性,这是TRAIL应用于肿瘤治疗的重大障碍。现对与TRAIL凋亡诱导通路直接相关的抗TRAIL机制及由Akt等途径介导的抗性分子机制进行综述。     

肿瘤坏死因子家族及其相关药物的研究进展

细胞凋亡是进化保守的重要生物学过程,具有重要的生理和病理作用,如在免疫系统的发育与稳态以及多种疾病（包括肿瘤）的发 生、发展、预后及治疗等过程中起重要作用。因此,近年来参与细胞凋亡信号转导的肿瘤坏死因子（TNF）/TNF 受体（TNFR）家族的重要 成员TNFα/TNFR、Fas/FasL和TRAIL/TRAILR成为重要的药物靶点,并开发出多个相关靶向药物,尤其是生物药物,其中有些在临床疗 效和商业上获得巨大成功。简介参与细胞凋亡信号转导的TNF/TNFR家族重要成员,着重对其通过介导细胞凋亡而发挥的生物学作用及其 相关药物研发作一综述,希望对我国的药物研发有所裨益。     

肿瘤细胞死亡受体的调控

肿瘤坏死因子相关凋亡诱导配体(tumor necrosis factor related apoptosis inducing ligand,TRAIL)只有与细胞膜上死亡受体结合才能促使癌细胞凋亡,一旦细胞膜上的死亡受体发生缺失或失去活性,将使癌细胞对TRAIL极为耐受。近年来,对死亡受体的研究发现,死亡受体异常表达可能是死亡受体在细胞膜上发生功能性缺失的最主要原因。该文主要探究肿瘤细胞中死亡受体在转录调控、翻译后修饰、转运和内化过程中的异常情况,期望为今后研发克服TRAIL耐受的联合药物及癌症治疗提供参考。     

CCN1对食管癌细胞凋亡的作用及其机制研究

为了研究TRAIL的诸多受体能否触发细胞凋亡以及其通过诱导凋亡治疗食管癌的原因治疗食管癌的原因,本研究利用单分类单因素方差分析对采用pCMV6:CCN1、TRAIL、TRAILR2、TRAILR3、TRAILR4和OPG,以及其中每一种shRNA的pRS转染的细胞进行细胞凋亡分析、实时RT-PCR和阵列分析、Western印迹分析采集的数据进行分析。同时观察其免疫荧光和免疫组织化学。研究结果表明CCN1在患有胃食管反流病的患者的食管上皮中高度表达,但随着情况恶化为腺癌而消失。用CCN1处理肿瘤细胞导致细胞凋亡,而对正常细胞的相同处理则会滋养细胞生长。CCN1改变了TRAIL及其受体在肿瘤细胞中的表达谱,即激活TRAIL及其死亡受体并关闭其诱饵受体,而TRAIL是该过程的介导。本研究结论初步表明,CCN1和TRAIL都不能单独使癌细胞凋亡,但它们联合可以将癌细胞致死。     

TRAIL耐药产生的机制及逆转耐药的最新策略

肿瘤坏死因子相关凋亡诱导配体（tumor necrosis factor-related apoptosis inducing li-gand,TRAIL）是唯一能诱导癌细胞凋亡而对机体正常组织无明显损伤的内源性细胞因子,因而被认为是一种极具前景的抗癌药物。然而目前研究发现,许多恶性肿瘤细胞对TRAIL具有耐药性,使TRAIL在临床应用中遭遇瓶颈。越来越多的证据表明,一些关键信号通路可能与TRAIL耐药有关,且利用靶向基因治疗策略以及借助某些天然药物或小分子抑制剂能够部分恢复癌细胞对TRAIL的敏感性。该文主要描述了肿瘤细胞对TRAIL的耐药机制,并对如何有效克服和逆转TRAIL耐药的策略作了简要概括。     

Reovirus-induced apoptosis is mediated by TRAIL

Members of the tumor necrosis factor (TNF) receptor superfamily and their activating ligands transmit apoptotic signals in a variety of systems. We now show that the binding of TNF-related, apoptosis-inducing ligand (TRAIL) to its cellular receptors DR5 (TRAILR2) and DR4 (TRAILR1) mediates reovirus-induced apoptosis. Anti-TRAIL antibody and soluble TRAIL receptors block reovirus-induced apoptosis by preventing TRAIL-receptor binding. In addition, reovirus induces both TRAIL release and an increase in the expression of DR5 and DR4 in infected cells. Reovirus-induced apoptosis is also blocked following inhibition of the death receptor-associated, apoptosis-inducing molecules FADD (for FAS-associated death domain) and caspase 8. We propose that reovirus infection promotes apoptosis via the expression of DR5 and the release of TRAIL from infected cells. Virus-induced regulation of the TRAIL apoptotic pathway defines a novel mechanism for virus-induced apoptosis.     

TRAIL,a mighty apoptosis inducer

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a membrane-bound cytokine molecule that belongs to the family of tumor necrosis factor (TNF). TRAIL has been shown to be a potent apoptosis inducer in a wide variety of cancer cells in vitro and to limit tumor growth efficiently in vivo without damaging normal tissues. These features have focused considerable attention on TRAIL as a potential therapeutic agent to treat human cancers. Recent data also suggest the implication of TRAIL in a natural defense mechanism since its abrogation results in certain autoimmune disorders. This review will summarize recent progress in TRAIL research, including understanding of apoptotic signaling, regulation of TRAIL action, and possible therapeutic applications.     

Enhanced sensitivity of G1 arrested human cancer cells suggests a novel therapeutic strategy using a combination of simvastatin and TRAIL

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) preferentially induces apoptosis in tumor cells over normal cells. To study the relationship between cell cycle progression and TRAIL-induced apoptosis, SW480 colon cancer and H460 lung cancer cell lines were examined for their sensitivity to TRAIL after arrest in different cell cycle phases. Cells were synchronized in G0/G1, S, and G2/M phase by serum starvation, aphidicolin, or nocodazole treatment, respectively. We found that arrest of cells in G0/G1 phase confers significantly higher susceptibility to TRAIL-induced apoptosis as compared to cells in late G1, S, or G2/M phase. To determine if cell cycle phase could be harnessed for therapeutic gain in the presence of TRAIL, we used the HMG-CoA reductase inhibitor, Simvastatin and lovastatin, to enrich a cancer cell population in G0/G1. Both simvastatin and lovastatin significantly augmented TRAIL-induced apoptosis in tumor cells, but not in normal keratinocytes. The results indicate that TRAIL, in combination with a HMG-CoA reductase inhibitor, may have therapeutic potential in the treatment of human cancer.     

The Transmembrane Domains of TNF-Related Apoptosis-Inducing Ligand (TRAIL) Receptors 1 and 2 Co-Regulate Apoptotic Signaling Capacity

TNF-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor (TNF) ligand family that exerts its apoptotic activity in human cells by binding to two transmembrane receptors, TRAILR1 and TRAILR2. In cells co-expressing both receptors the particular contribution of either protein to the overall cellular response is not well defined. Here we have investigated whether differences in the signaling capacities of TRAILR1 and TRAILR2 can be attributed to certain functional molecular subdomains. We generated and characterized various chimeric receptors comprising TRAIL receptor domains fused with parts from other members of the TNF death receptor family. This allowed us to compare the contribution of particular domains of the two TRAIL receptors to the overall apoptotic response and to identify elements that regulate apoptotic signaling. Our results show that the TRAIL receptor death domains are weak apoptosis inducers compared to those of CD95/Fas, because TRAILR-derived constructs containing the CD95/Fas death domain possessed strongly enhanced apoptotic capabilities. Importantly, major differences in the signaling strengths of the two TRAIL receptors were linked to their transmembrane domains in combination with the adjacent extracellular stalk regions. This was evident from receptor chimeras comprising the extracellular part of TNFR1 and the intracellular signaling part of CD95/Fas. Both receptor chimeras showed comparable ligand binding affinities and internalization kinetics. However, the respective TRAILR2-derived molecule more efficiently induced apoptosis. It also activated caspase-8 and caspase-3 more strongly and more quickly, albeit being expressed at lower levels. These results suggest that the transmembrane domains together with their adjacent stalk regions can play a major role in control of death receptor activation thereby contributing to cell type specific differences in TRAILR1 and TRAILR2 signaling.     

Enhanced Sensitivity of G1 Arrested Human Cancer Cells Suggests a Novel Therapeutic Strategy Using a Combination of Simvastatin and TRAIL

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) preferentially induces apoptosis in tumor cells over normal cells. To study the relationship between cell cycle progression and TRAIL-induced apoptosis, SW480 colon cancer and H460 lung cancer cell lines were examined for their sensitivity to TRAIL after arrest in different cell cycle phases. Cells were synchronized in G0/G1, S, and G2/M phase by serum starvation, aphidicolin, or nocodazole treatment, respectively. We found that arrest of cells in G0/G1 phase confers significantly higher susceptibility to TRAIL-induced apoptosis as compared to cells in late G1, S, or G2/M phase. To determine if cell cycle phase could be harnessed for therapeutic gain in the presence of TRAIL, we used the HMG-CoA reductase inhibitor, Simvastatin and lovastatin, to enrich a cancer cell population in G0/G1. Both simvastatin and lovastatin significantly augmented TRAIL-induced apoptosis in tumor cells, but not in normal keratinocytes. The results indicate that TRAIL, in combination with a HMG-CoA reductase inhibitor, may have therapeutic potential in the treatment of human cancer.

Key Words

TRAIL, Synchronization, Simvastatin, Cancer Therapy, Lovastatin, Cell Cycle, Apoptosis     

The secretable form of trimeric TRAIL, a potent inducer of apoptosis

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a type II transmembrane cytokine molecule of the TNF family. Soluble recombinant TRAIL has been shown to induce apoptosis in a wide variety of cancer cells in vitro and to specifically limit tumor growth without damaging normal cells and tissues in vivo. These results suggest a strong potential of TRAIL as an anticancer therapy. Here we report an artificial TRAIL gene that expresses and secretes trimeric TRAIL into the culture supernatant. This novel TRAIL gene is composed of three functional elements, including a secretion signal, a trimerization domain, and an apoptosis-inducing moiety of TRAIL gene sequence. The expression vectors delivering this TRAIL gene produced secretable forms of trimeric TRAIL proteins. These TRAIL proteins showed greater apoptotic activity than the known TRAIL protein that does not contain an additional trimerization domain. Our data suggest that the gene therapy using our artificial TRAIL gene may be used as an anticancer therapy.