中心体扩增与肿瘤

中心体是动物细胞中非常重要的非膜结构细胞器,它除了作为微管组织中心在有丝分裂过程中具有指导两极纺锤体组装的功能外,还参与了细胞内的许多生命活动过程。中心体扩增通常导致异倍体的形成、以及染色体和细胞骨架的不稳定性。因而与肿瘤的发生、发展有着直接的关系。中心体扩增在肿瘤的诊、治中具有广阔的研究与应用前景。中心体扩增的参数可以作为肿瘤诊断以及预后的指标;中心体可望成为肿瘤治疗的靶位点。     

中心体:洞悉肿瘤的发生(英文)

动物细胞中主要作为微管组织中心的中心体在细胞分裂时确保了染色体平均分配到两个子细胞的过程,从而保证了基因组的稳定性。中心体的结构或功能异常都将不可避免的引起基因组不稳定,从而导致肿瘤的发生。鉴于主要由中心体异常引起的染色体不稳定是肿瘤细胞的一个典型特征,而染色体不稳定又与肿瘤细胞的耐药性有着密切联系,因而不难想象以中心体为靶点的肿瘤治疗的合理性。因此,本文将着重阐述中心体在细胞调控,特别是与肿瘤发生密切相关的细胞活动及药物耐受中的重要作用,以期为更好阐明药物耐受机制,并为与中心体相关的抗肿瘤药物研发提供新思路。     

直结肠癌BUBR1的过度表达与TP53突变及微卫星状态关系提示其过度表达与染色体不稳定表型有关

在有丝分裂过程中BUBR1监视微管与着丝点的结合,是保证染色体均等分离的重要分子机制之一.BUBIB变异家谱研究及其敲除模型的研究表明,BUBR1缺陷与染色体不稳定性及肿瘤的发生直接相关.近来在数种人类肿瘤,对BUBR1蛋白过度表达有所报道.但在直结肠癌,BUBR1的过度表达是否与染色体不稳定性的发生有关目前仍无定论.在人类结直肠癌的遗传不稳定性主要表现为两种类型,染色体不稳定性及微卫星不稳定性,它们提示了两条独立的肿瘤发生路径.一般认为不存在高频度微卫星不稳定性表型的肿瘤通过染色体不稳定途径癌变.P53蛋白通过多种机制对维护遗传稳定性起到重要的作用,TP53基因突变经常与染色体不稳定现象并存.DNA倍体情况也是染色体不稳定研究不可缺少的指标.本研究采用免疫组织化学法检测了一组93例进展期散发结直肠癌BUBR1蛋白的表达情况,直接测序法检测TP53变异.高分辨率荧光标记微卫星不稳定检测技术检测微卫星状态,固相激光扫描细胞仪技术检测DNA倍体情况.我们分析了BUBR1表达与三种反映遗传背景的因子的关系.BUBR1蛋白过度表达在人结直肠癌较为常见.在非高频度微卫星不稳定的结直肠癌,BUBR1蛋白过度表达率明显为高(P＜0.01),在TP53基因突变的病例其过度表达率亦较高(P＜0.05).BUBR1蛋白的过度表达与DNA异倍体无统计学相关,但DNA异倍体病例的BuBRl过度表达有偏高倾向.BuBRl表达情况与常用的临床病理学指标无统计学相关.BuBRl过度表达同微卫星状态及TP53突变的关系明确的提示,在人类散发结直肠癌,BUBR1蛋白过度表达与染色体不稳定状态有关.BUBR1过度表达作为一种常见的分子异常,对于肿瘤的早诊预防提供新的标志物.并可能成为治疗的新靶点.     

酵母纺锤体极体复制缺陷与染色体不稳定性的发生

纺锤体极体作为酵母细胞的微管组织中心,在功能上等同于高等真核细胞的中心体,它在细胞周期中的准确复制是两极纺锤体组装和染色体正确分离的前提。纺锤体极体复制缺陷会导致异倍体和多倍体的形成,造成染色体不稳定性的发生。以酿酒酵母细胞为模型,研究纺锤体极体复制过程相关蛋白质的突变,有助于揭示酵母细胞中染色体不稳定性发生的分子机制,并为动物细胞中心体复制的研究提供良好的借鉴。     

DNA甲基化与癌症

DNA甲基化是重要的表观遗传修饰,主要发生在DNA的CpG岛. DNA的甲基化通过DNA甲基转移酶（DNA methyltransferases, DNMTs）完成. DNA甲基化参与了细胞分化、基因组稳定性、X染色体失活、基因印记等多种细胞生物学过程.单基因水平及基因组范围内的DNA甲基化改变在肿瘤发生发展中亦发挥重要作用. 抑癌基因的异常甲基化引起的表达抑制,可导致肿瘤细胞的增殖失控和侵袭转移,并参与肿瘤组织的血管生成过程.在许多肿瘤的研究中都发现了基因组整体DNA低甲基化所导致的染色体不稳定性. 本文从DNA的异常高甲基化和低甲基化两方面论述了DNA甲基化在细胞恶变发生发展过程中的改变及其影响,并阐述了DNA甲基化改变在肿瘤诊断和治疗中的作用.     

中心体异常扩增的研究进展及其与肿瘤发生之间的关系

中心体是肿瘤细胞中重要的研究对象。起初研究人员就假设中心体的异常及随之而来的有丝分裂紊乱,是导致肿瘤发生的重要原因之一。中心体既有基本的复制机器,也有完善的扩增制动机制。在多数肿瘤细胞中都可以观察到中心体异常扩增的现象。因此,中心体异常扩增也成为肿瘤细胞的"标志"之一。总结了中心体相关研究的最新进展,并重点讨论了中心体与肿瘤发生之间的关系,为进一步了解中心体发挥功能的机制提供参考。     

喉癌STK15基因表达和染色体不稳定的研究

为研究喉鳞状细胞癌中STK15基因表达及其与染色体不稳定的相关性,提取50例喉鳞状细胞癌及配对癌旁正常组织和喉鳞状细胞癌Hep-2细胞系的RNA,反转录合成cDNA,以β-actin为内对照进行PCR扩增,用软件分析电泳结果,研究喉癌中STK15基因表达的水平;以Hep-2细胞系为代表应用常规和高分辨G显带方法进行核型分析。在50例喉癌中,癌组织STK15表达高于配对癌旁正常组织的有34例,占68％,经统计学分析,肿瘤组与对照组差异显著,Hep-2细胞系中STK15基因表达高于内对照β-actin;Hep-2细胞系中存在显著的染色体不稳定,染色体数目变化于43－84条之间,众数为69－74条,结构畸变主要表现为13条标记染色体,本研究首次发现STK15基因在喉癌中表达增高,它可能通过中心体异常而引起染色体不稳定,在喉癌的发生,发展中发挥一定作用。     

极光(aurora)激酶在细胞有丝分裂和肿瘤形成中的重要功能

极光激酶（aurora kinases）是负责调控细胞有丝分裂的一类重要的丝氨酸／苏氨酸激酶。在不同的模式生物中,极光激酶各家族成员的结构和功能都高度保守。近年来,随着极光激酶相关研究的不断深入,人们逐渐认识到极光激酶在细胞有丝分裂以及肿瘤形成中的重要功能。在细胞有丝分裂中,极光激酶参与了诸如中心体成熟分离、纺锤体组装和维持、染色体分离以及胞质分裂等多个事件。异常表达的极光激酶往往会导致细胞在有丝分裂的过程中出现大量的异常现象。此外,极光激酶还参与了肿瘤形成的过程,已经发现一些靶向作用于极光的小分子具有显著的抑癌作用。本文围绕哺乳动物的三种极光激酶,重点讨论了它们在细胞有丝分裂中的动态定位、生物学功能以及时空上的调节方式,并分析了异常表达的极光激酶参与肿瘤形成的可能途径,提出了肿瘤治疗的新思路。     

光温敏核雄性不育小麦BS366花粉母细胞减数分裂的细胞学研究

要以小麦光温敏核雄性不育系BS366为材料,采用卡宝品红压片法研究花粉母细胞减数分裂的细胞学变化。结果表明:不育环境下的BS366花粉母细胞减数分裂过程中染色体和细胞形态异常现象较多。染色体异常主要表现为:染色体落后,染色体桥、染色体散乱排列,微核、染色体分离不同步。细胞形态异常表现为:二分体时期细胞质不完全分裂,细胞板不平整;四分体时期子细胞大小不一。花粉母细胞减数分裂后,异常四分体的比例为62.88%;成熟花粉粒中败育率为89.5%。推测减数分裂期间异常的染色体行为以及细胞形态可能是影响花粉育性降低的重要原因。     

DNA错配修复、染色体不稳定和肿瘤的关系

DNA错配修复系统可以识别并纠正DNA复制过程中出现的错误.保证基因组的稳定性和完整性.错配修复系统缺陷可能导致遗传物质发生突变,引发恶性肿瘤.肿瘤患者经常表现出染色体不稳定,具体表现为微卫星不稳定性和杂合性缺失.本文就DNA错配修复、染色体不稳定和肿瘤之间的联系予以综述.     

ECRG2 disruption leads to centrosome amplification and spindle checkpoint defects contributing chromosome instability

Cancer cells contain an abnormal number of chromosomes (aneuploidy), which is a prevalent form of genetic instability in human cancers. Abnormal amplification of centrosomes and defects of spindle assembly checkpoint are the major causes of chromosome instability in cancer cells. Here we present biochemical evidence to suggest a role of ECRG2, a novel tumor suppressor gene, in maintaining chromosome stability. ECRG2 localized to centrosomes during interphase and kinetochores during mitosis. Further analysis revealed that ECRG2 participates in centrosome amplification in a p53-dependent manner. Depletion of ECRG2 not only destabilized p53, down-regulated p21, and increased the cyclin E/CDK2 activity, thus initiating centrosome amplification, but also abolished the ability of p53 localize to centrosomes. Overexpression of ECRG2 restored the p53-dependent suppression of centrosome duplication. Furthermore, ECRG2-depleted cells show severely disrupted spindle phenotype but fail to maintain the mitotic arrest due to minimal BUBR1 protein levels. Taken together, our results indicate that ECRG2 is important for ensuring centrosome duplication, spindle assembly checkpoint, and accurate chromosome segregation, and its depletion may contribute to chromosome instability and aneuploidy in human cancers.     

Effect of p53 on centrosome amplification in prostate cancer cells.

Chromosomal instability (CIN) is one of the common features in prostate cancer, especially in advanced stages. Recently, the involvement of p53 in CIN through the regulation of centrosome amplification has been proposed in certain tumor types. In this study, we investigated the relationship between p53 and centrosome amplification in prostate cancer cells. Increased centrosome number and size were observed in DU145 and PC3 containing nonfunctional p53 compared to LNCap which expressed wild-type p53. Transfection of p53 into PC3 cells resulted in a decreased cell growth rate, G2/M arrest and decreased centrosome abnormalities. We provide the first evidence on a correlation between loss of p53 function and centrosome amplification in prostate cancer cells. Our results indicate that p53 may play a role in the regulation of centrosome amplification and loss of p53 may be one of the mechanisms involving CIN in prostate cancer cells.     

Centrosome overduplication and mitotic instability in PKD2 transgenic lines

Polycystin-2 (PC-2), a protein encoded by PKD2 and involved in autosomal dominant polycystic kidney disease (ADPKD), is a non-selective cationic channel recently implicated in the function of primary cilia. We recently constructed a new animal model in the form of a transgenic mouse with a BAC-containing human PKD2 inserted in its genome. Two transgenic mouse lines overexpressing human PKD2 showed mitotic instability. Fibroblasts from these transgenic mouse lines have abnormal chromosomal numbers. These lines also have supernumerary centrosomes. PC-2 overexpression is associated with mitotic instability and centrosome overduplication. PC-2 therefore seems to play a role in centrosome duplication, and this hypothesis is being evaluated in other models.     

A novel role for the deubiquitinase USP1 in the control of centrosome duplication

Defects in the regulation of centrosome duplication lead to tumorigenesis through abnormal cell division and resulting chromosome missegregation. Therefore, maintenance of accurate centrosome number is critical for cell fate. The deubiquitinating enzyme USP1 plays important roles in DNA repair and cell differentiation. Importantly, increased levels of USP1 are detected in certain types of human cancer, but little is known about the significance of USP1 overexpression in cancer development. Here we show that Usp1 plays a novel role in regulating centrosome duplication. The ectopic expression of wild-type Usp1, but not C90S Usp1 (catalytically inactive mutant form), induced centrosome amplification. Conversely, ablation of Usp1 in mouse embryonic fibroblasts (MEFs) showed a significant delay in centrosome duplication. Moreover, Usp1-induced centrosome amplification caused abnormal mitotic spindles, chromosome missegregation and aneuploidy. Interestingly, loss of inhibitor of DNA binding protein 1 (ID1) suppressed Usp1-induced centrosome amplification. Taken together, our results strongly suggest that Usp1 is involved in the regulation of centrosome duplication, at least in part via ID1, and Usp1 may exert its oncogenic activity, partially through inducing centrosome abnormality.     

Centrosome-centriole abnormalities are markers for abnormal cell divisions and cancer in the transgenic adenocarcinoma mouse prostate (TRAMP) model

We utilized the transgenic adenocarcinoma mouse prostate (TRAMP) model to study the formation of abnormal mitosis in malignant tumors of the prostate. The results presented here are focused on centrosome and centriole abnormalities and the implications for abnormal cell divisions, genomic instability, and apoptosis. Centrosomes are microtubule organizing organelles which assemble bipolar spindles in normal cells but can organize mono-, tri-, and multipolar mitoses in tumor cells, as shown here with histology and electron microscopy in TRAMP neoplastic tissue. These abnormalities will cause unequal distribution of chromosomes and can initiate imbalanced cell cycles in which checkpoints for cell cycle control are lost. Neoplastic tissue of the TRAMP model is also characterized by numerous apoptotic cells. This may be the result of multipolar mitoses related to aberrant centrosome formations. Our results also reveal that centrosomes at the poles in mitotic cancer cells contain more than the regular perpendicular pair of centrioles which indicates abnormal distribution of centrioles during separation to the mitotic poles. Abnormalities in the centriole-centrosome complex are also seen during interphase where the complex is either closely associated with the nucleus or loosely dispersed in the cytoplasm. An increase in centriole numbers is observed during interphase, which may be the result of increased centriole duplication. Alternatively, these centrioles may be derived from basal bodies that have accumulated in the cell's cytoplasm, after the loss of cell borders. The supernumerary centrioles may participate in the formation of abnormal mitoses during cell division. These results demonstrate multiple abnormalities in the centrosome-centriole complex during prostate cancer that result in abnormal mitoses and may lead to increases in genomic instability and/or apoptosis.     

Remodeling of Centrosomes in Intraspecies and Interspecies Nuclear Transfer Porcine Embryos

Remodeling of donor cell centrosomes and the centrosome-associated cytoskeleton is crucially important for nuclear cloning as centrosomes are the main microtubule organizing centers that play a significant role in cell division and embryo development. Centrosome dysfunctions have been implicated in various diseases including cancer and metabolic disorders and may also play a role in developmental abnormalities that are frequently seen in cloned animals. In the present studies we investigated microtubule organization and the reorganization and fate of the integral centrosome protein γ-tubulin and the centrosome-associated protein centrin in intraspecies (pig oocytes; pig fetal fibroblast cells) and interspecies (pig oocytes; mouse fibroblast cells) reconstructed embryos by using antibodies to γ-tubulin or GFP-centrin transfected mouse fibroblasts as donor cells. Microtubules were stained with antibodies to α-tubulin. In-vitro-fertilized oocytes and nuclear transfer (NT) reconstructed oocytes were sequentially analyzed at different developmental stages. Epi-fluorescence results revealed mitotic spindle abnormalities in NT embryos during the first cell cycle (39.4%, 13/33) which were significantly higher than those in IVF embryos (17.0%, 7/41). The abnormalities in IVF embryos are due to polyspermy while the abnormalities in NT embryos are due to donor cell centrosome dysfunctions. In the NT embryos with abnormal microtubule and centrosome organization, γ-tubulin staining revealed multipolar centrosome foci while DAPI staining showed misalignment of chromosomes. In intraspecies and interspecies embryos the GFP-centrin signal was detected until 3 hrs after fusion. GFP-centrin was not detected at 8 hrs after NT which is consistent with previous results using anti-centrin antibody staining in intraspecies NT porcine embryos. These data indicate that 1) abnormalities in microtubule and centrosome organization are associated with nuclear cloning at a higher rate than observed in IVF embryos; 2) centrosome and cytoskeletal abnormalities in IVF embryos are due to polyspermy while centrosome and cytoskeletal abnormalities in NT embryos are due to donor cell centrosome dysfunctions; and 3) GFP-centrin of the donor cell centrosome provides a reliable marker to follow its fate in intraspecies reconstructed embryos.     

p53-Driven apoptosis limits centrosome amplification and genomic instability downstream of NPM1 phosphorylation

Chromosome loss or gain is associated with a large number of solid cancers, providing genomic plasticity and thus adaptability to cancer cells. Numerical centrosome abnormalities arising from centrosome over-duplication or failed cytokinesis are a recognized cause of aneuploidy. In higher eukaryotic cells, the centrosome duplicates only once per cell cycle to ensure the formation of a bipolar mitotic spindle that orchestrates the balanced distribution of the sister chromatids to the respective daughter cells. Here we delineate the events that allow abnormal centrosome duplication, resulting in mitotic errors and incorrect chromosome segregation in cells with sustained cyclin-dependent kinase (CDK) activity. We have identified NPM1 as a substrate for CDK6 activated by the Kaposi's sarcoma herpesvirus (KSHV) D-type cyclin and shown that p53-driven apoptosis occurs downstream of NPM1 phosphorylation as a checkpoint mechanism that prevents accumulation of cells with supernumerary centrosomes. Our findings provide evidence that abnormal chromosome segregation in KSHV-infected cells is a direct consequence of NPM1 phosphorylation and predict that genomic instability is an inevitable consequence of latent KSHV infection.     

HOPS is an essential constituent of centrosome assembly

Centrosomes direct microtubule organization during cell division. Aberrant number of centrosomes results from alteration of its components and leads to abnormal mitoses and chromosome instability. HOPS is a newly discovered protein isolated during liver regeneration, implicated in cell proliferation. Here, we provide evidence that HOPS is an integral constituent of centrosomes. HOPS is associated with classical markers of centrosomes and found in cytosolic complexes containing CRM-1, γ-tubulin, eEF-1A and HSP70. These features suggest that HOPS is involved in centrosome assembly and maintenance. HOPS depletion generates supernumerary centrosomes, multinucleated cells and multipolar spindle formation leading to activation of p53 checkpoint and cell cycle arrest. The presence of HOPS in cytosolic complexes supports that centrosome proteins might be preassembled in the cytoplasm to then be rapidly recruited for centrosome duplication. Altogether these data show HOPS implication in the control of cell division. HOPS contribution appears relevant to understand genomic instability and centrosome amplification in cancer.     

中心体异常和肿瘤

中心体是紧靠细胞核的小体积细胞器,由中心粒和中心粒外周基质(PCM)组成.中心体的蛋白质组成、形态、大小和位置随细胞周期不断发生变化.中心体复制过程与细胞核内其他事件相耦合,并与DNA复制一样,以半保留方式复制.现已发现了许多中心体蛋白及与中心体复制相关的蛋白激酶,调控着中心体复制的各个步骤.中心体复制还受p53,Rb,p21,Gadd45和Brca1/2等多个负性基因调节,中心体异常与基因组不稳定性存在相关性,并有可能与肿瘤发生过程相关.