Immunohistochemical analysis of Smac/DIABLO expression in human carcinomas and sarcomas

Second mitochondria-derived activator of caspases (Smac/DIABLO) is released from mitochondria into the cytosol during apoptosis, promoting caspase activation by neutralizing the inhibition of inhibitor of apoptosis proteins (IAPs) on caspases. Alteration of apoptosis is essential for cancer development, and cancer cell death by radiation and chemotherapy is largely dependent upon apoptosis. In this study, archival tissues of 100 carcinomas and 50 sarcomas from various origins were analyzed by immunohistochemistry for the expression of Smac/DIABLO. Smac/DIABLO immunoreactivity was seen in 62 of 100 (62%) carcinomas, including 42 of 60 stomach carcinomas, 7 of 10 colorectal carcinomas, 4 of 10 lung carcinomas, 7 of 10 ovarian carcinomas, and 2 of 10 prostate carcinomas. Smac/DIABLO is expressed in 11 of 50 (22%) sarcomas, including 2 of 8 malignant schwannomas, 5 of 11 rhabdomyosarcomas, 2 of 7 malignant fibrous histiocytomas, 1 of 6 leiomyosarcomas, 0 of 8 angiosarcomas, 0 of 8 liposarcomas, and 1 of 2 Ewing's sarcomas. These data demonstrated that Smac/DIABLO expression levels vary depending on the individual cancer types. Furthermore, the present study showed that many human cancers do not express Smac/DIABLO, and suggest that lack of Smac/DIABLO expression in the cancer cells may inhibit apoptosis, thereby promoting their survival.     

Smac合成肽靶向下调凋亡抑制蛋白XIAP提高胰腺癌细胞化疗敏感性

目的:探讨包含目的蛋白功能结构域的Smac合成肽能否增强胰腺癌细胞的化疗药物敏感性及其作用机制.方法:化学合成SmacN7细胞可穿透融合多肽,共沉淀实验观察SmacN7细胞穿透肽与胰腺癌Panc-1细胞内的XIAP的相互作用,应用流式细胞术检测SmacN7细胞穿透肽与顺铂、5-FU联用对Panc-1细胞凋亡的影响,MTT法检测SmacN7细胞穿透肽应用前后Panc-1细胞的化疗药物敏感性.结果:SmacN7融合多肽能与内源性XIAP结合,明显下调Panc-1细胞XIAP表达水平,显著增强顺铂或5-FU诱导的Panc-1细胞凋亡,使其对顺铂、5-FU的药物半数抑制浓度(IC50)分别降低1.98倍、2.62倍.结论:应用包含目的蛋白功能结构域的Smac合成肽能靶向下调胰腺癌Panc-1细胞XIAP表达,显著提高其化疗敏感性,为胰腺癌的生物治疗协同化疗提供了新思路.     

携带mda-7基因的复制缺陷型腺病毒通过促进线粒体释放促凋亡蛋白杀伤肝癌细胞

目的 探讨黑色素瘤分化相关基因7/白介素24(mda-7/IL-24)基因选择性杀伤肝癌细胞的机制.方法 应用携带mda-7基因的复制缺陷型腺病毒Ad.mda-7感染正常肝细胞L02和肝癌细胞HepG2.通过逆转录聚合酶链反应(RT-PCR)、酶联免疫吸附实验(ELISA)及Western blot方法,观察mda-7/IL-24基因的表达;应用Hoeehst染色和流式细胞仪观察mda-7/IL-24对肝癌细胞的杀伤作用;采用RT-PCR和Western blot方法,观察Bcl-2家族和caspase-9基因表达的变化,分离不同感染时点细胞内线粒体和胞浆蛋白,并检测线粒体释放促凋亡蛋白细胞色素C(Cyt-C)和Smac/DIABLO的变化过程.结果 Ad.mda-7能介导mda-7/IL-24在两种细胞株中的高效表达.能选择性杀伤肝癌细胞,感染24 h后,HepG2细胞凋亡率为24.0%±4.6%,而对正常的肝细胞没有影响.RT-PCR和亚细胞蛋白的分析结果显示,胞浆内Bel-2和Bcl-xL的表达在HepG2细胞中明显下降,而在L02细胞中的表达无变化,Bax在肝癌细胞中的表达明显增强,Bak的表达无变化;Ad.mda-7能促进细胞线粒体释放cyt-C和Smac/DIABLO蛋白,并促进caspase-9的表达.结论 Ad.mda-7能选择性杀伤肝癌细胞HepG2,通过促进线粒体促凋亡蛋白的释放而诱导肝癌细胞凋亡.     

艾灸血浆对离体人胃黏膜上皮细胞损伤的保护作用及其线粒体细胞凋亡通路机制

目的:探讨艾灸血浆对胃黏膜细胞凋亡的影响,揭示艾灸对胃黏膜细胞的保护作用及其信号转导机制。方法:24名健康人随机等分为艾灸穴位组和艾灸非穴位组,分别艾灸中脘、关元和足三里穴及非穴位对照点各10 d。将人体胃黏膜上皮(GES-1)细胞分为空白组、模型组、艾灸穴位血浆组、艾灸非穴位血浆组,采用含8%乙醇的培养液造成GES-1细胞损伤模型,分别加以预先提取的灸前人体血浆、艾灸穴位和非穴位血浆。流式细胞技术检测细胞凋亡率;Western-blot法检测细胞内热休克蛋白70(HSP70)、第二个线粒体来源的胱氨酸酶激活物(Smac)、凋亡诱导因子(AIF)的表达;细胞免疫化学法检测半胱氨酸天冬酸蛋白酶-3、9(Caspase-3、9)的表达。结果:模型组与空白组比较,细胞凋亡率明显增加,HSP70、Smac、AIF、Caspase-3、Caspase-9表达均上调(均P<0.01);艾灸穴位血浆组与模型组比较,凋亡率明显下降(P<0.01),HSP70表达进一步提高(P<0.01),Smac、AIF、Caspase-3、Caspase-9表达下调(均P<0.01);艾灸非穴位血浆组与模型组比较,凋亡率、Smac表达下降,Caspase-3、Caspase-9表达也下调(均P<0.01),但高于艾灸穴位血浆组(P<0.05,P<0.01)。结论:艾灸中脘、关元和足三里穴位后提取的人体血浆能抑制GES-1细胞凋亡,其信号转导通路可能是:促进细胞内HSP70合成,通过线粒体凋亡通路,抑制Smac、AIF表达,同时阻断其与Caspase-9的结合,减少Caspase-3含量,抑制细胞凋亡。     

第二线粒体源性胱氨酸酶激活因子及其类似物与肿瘤的相关性研究进展

第二线粒体源性胱氨酸酶激活因子(Smac)是一种存在线粒体中并具有促凋亡作用的蛋白,Smac主要通过参与细胞凋亡的线粒体途径和死亡受体途径的下游反应,特异性地与凋亡抑制因子(IAPs)结合,解除IAPs对Caspase的抑制效应从而促进细胞凋亡。在肿瘤细胞中,Smac的过表达可以抑制或延缓肿瘤的发生发展过程,提高细胞浆Smac含量可增强细胞对放化疗的敏感性。人工合成的Smac类似物可通过级联放大效应提高肿瘤细胞对放化疗的敏感性,具有高效、低毒、高通透性等优点,为肿瘤的治疗提供了新的方法和思路,具有重要的临床意义。该研究就Smac、Smac类似物与肿瘤的相关性研究进展做一综述。     

全反式维甲酸对环孢素诱导的肾小球系膜细胞增殖与凋亡的影响及其机制

目的  探讨全反式维甲酸（ATRA）对环孢素（CsA）诱导的大鼠肾小球系膜细胞增殖及凋亡的影响及机制。方法  采用不同剂量ATRA作用于不同剂量CsA诱导下的肾小球系膜细胞。采用MTT比色法检测细胞增殖,Hoechst 33258荧光染色观察细胞凋亡形态,后用流式细胞仪检测细胞凋亡率,免疫荧光法检测线粒体促凋亡的Smac蛋白的表达。结果  与对照组比较,CsA剂量为0.5 μg/mL及以上可抑制细胞増殖,CsA剂量为1.0 μg/mL及以上可诱导细胞凋亡,且Smac蛋白的表达随CsA剂量的增加而增加,具有剂量和时间依赖的特征（均为P＜0.05）。而与CsA组比较,CsA+ATRA处理组对细胞增殖的抑制作用更为明显,而加入ATRA可呈剂量依赖性抑制CsA诱导的肾小球系膜细胞凋亡及Smac蛋白的表达（均为P＜0.05）。结论  CsA可抑制肾小球系膜细胞增殖,诱导其凋亡并刺激Smac蛋白的表达。ATRA可以抑制CsA诱导的肾小球系膜细胞凋亡,且可能是通过Smac信号通路介导的。     

Inhibitor of apoptosis proteins as targets for anticancer therapy

Cell death by apoptosis plays a critical role in regulating the subtle balance between cell death and proliferation to maintain tissue homeostasis. Accordingly, tipping the balance in either direction may cause human disease. Too little cell death may promote tumor formation and progression. In addition, killing of cancer cells by current therapies is largely due to induction of apoptosis in tumor cells. Since a hallmark of human cancers is their resistance to apoptosis, there is a demand to develop novel strategies that restore the apoptotic machinery in order to overcome cancer resistance. Inhibitor of apoptosis proteins (IAPs) block apoptosis at the core of the apoptotic machinery by inhibiting caspases. Elevated levels of IAPs are found in many human cancers and have been associated with poor prognosis. Recent insights into the role of IAPs have provided the basis for various exciting developments that aim to modulate the expression or function of IAPs in human cancers. Targeting IAPs (e.g., by antisense approaches or small-molecule inhibitors) presents a promising novel approach to either directly trigger apoptosis or to potentiate the efficacy of cytotoxic therapies in cancer cells. Thus, inhibition of IAPs such as X chromosome-linked IAP may prove to be a successful strategy to overcome apoptosis resistance of human cancers that deserves further exploitation.     

Differential role of RIP1 in Smac mimetic-mediated chemosensitization of neuroblastoma cells

We explored the potential of Smac mimetics, which antagonize Inhibitor of Apoptosis (IAP) proteins, for chemosensitization of neuroblastoma (NB). Here, we report that Smac mimetics, e.g. BV6, prime NB cells for chemotherapeutics including the topoisomerase II inhibitor doxorubicin (DOX) and vinca alkaloids such as Vincristine (VCR), Vinblastine (VBL) and Vinorelbine (VNR). Additionally, BV6 acts in concert with DOX or VCR to suppress long-term clonogenic growth. While BV6 causes rapid downregulation of cellular IAP (cIAP)1 protein and nuclear factor-kappaB (NF-κB) activation, DOX/BV6- or VCR/BV6-induced apoptosis occurs independently of NF-κB or TNFα signaling, since overexpression of dominant-negative IκBα superrepressor or the Tumor Necrosis Factor (TNF)α-blocking antibody Enbrel fail to block cell death. Mechanistic studies reveal that Receptor-interacting protein (RIP)1 is required for DOX/BV6-, but not for VCR/BV6-induced apoptosis, since transient or stable knockdown of RIP1 or the pharmacological RIP1 inhibitor necrostatin-1 significantly reduce apoptosis. By comparison, VCR/BV6-mediated apoptosis critically depends on the mitochondrial pathway. VCR/BV6 cotreatment causes phosphorylation of BCL-2 during mitotic arrest, enhanced activation of BAX and BAK and loss of mitochondrial membrane potential (MMP). Additionally, overexpression of BCL-2 profoundly suppresses VCR/BV6-induced apoptosis. Thus, BV6 sensitizes NB cells to chemotherapy-induced apoptosis via distinct initial signaling mechanisms depending on the chemotherapeutic drug. These findings provide novel mechanistic insights into Smac mimetic-mediated chemosensitization of NB.     

The role of NF-κB and Smac/DIABLO proteins in the treatment response and survival of acute myeloid leukemia patients

IntroductionThe misbalance between a family of inhibitor of apoptosis proteins (IAP), regulated by the nuclear factor kappa B (NF-κB) and their natural antagonist second mitochondrial-derived activator of caspases/direct IAP binding protein with low pI (Smac/DIABLO) are important to biology of acute myeloid leukemia (AML).Material and methodsThe aim of the study was to assess NF-κB and Smac/DIABLO proteins expression in blasts of 109 newly diagnosed AML patients using the multicolor flow cytometry and evaluate their influence on AML patients outcome.ResultsExpression of NF-κB and of Smac/DIABLO proteins were found in 95% and 98% of the patients, respectively. A negative correlation between Smac/DIABLO and NF-κB was observed. Age < 60 years old as well as higher Smac/DIABLO expression were associated with a higher probability of complete response achievement in the multivariate analysis. Longer overall survival (OS) in the univariate and multivariate analyses was influenced by age < 60 years old, a favorable or intermediate-risk karyotype and high Smac/DIABLO expression. Additionally, in the survival analysis of the subgroups, the patients aged < 60 years old, with high Smac/DIABLO expression, lower NF-κB expression and < 50% of bone marrow blasts who were treated with standard treatment had better OS.ConclusionsLower NF-κB and higher Smac/DIABLO expression may influence AML patients outcome.