Aurora-A在细胞中的功能以及与肿瘤的关系

Aurora蛋白激酶家族,在细胞的有丝分裂期发挥着重要作用。目前分为3种即Aurora-A、Au-rora-B、Aurora-C。其中Aurora-A定位于中心体和纺锤体,主要参与中心体的成熟、分离和纺锤体形成。此外Aurora-A可以参与p53通路的调节,细胞凋亡和分裂之间平衡的调节等。Aurora-A高表达可引起中心体异常扩增,异倍体产生。在肿瘤组织中的研究显示它在多种肿瘤乳腺癌、卵巢癌、结肠癌、胃癌等组织中存在着高表达,并且与某些肿瘤的预后相关。Aurora-A可能通过多种机制参与了肿瘤的发生和发展。     

Aurora-A在细胞中的功能以及与肿瘤的关系

Aurora蛋白激酶家族，在细胞的有丝分裂期发挥着重要作用。目前分为3种即Aurora-A、Aurom-B、Aurora-C。其中Aurora-A定位于中心体和纺锤体，主要参与中心体的成熟、分离和纺锤体形成。此外Aurora-A可以参与p53通路的调节，细胞凋亡和分裂之间平衡的调节等。Aurom-A高表达可引起中心体异常扩增，异倍体产生。在肿瘤组织中的研究显示它在多种肿瘤乳腺癌、卵巢癌、结肠癌、胃癌等组织中存在着高表达，并且与某些肿瘤的预后相关。Aurom-A可能通过多种机制参与了肿瘤的发生和发展。     

有丝分裂激酶Aurora-A活性调节的分子机制

Aurora-A是一种参与有丝分裂的丝氨酸/苏氨酸激酶,其过表达与肿瘤形成有关。Aurora-A激酶活性可以通过磷酸化、去磷酸化以及依赖蛋白酶体的降解等方式进行调节。TPX2(target protein for Xenopus kinesin-like protein 2)、1-2(Inhibitor 2)、Ajuba通过磷酸化Aurora-A将其活化,PP1(type-1 proteinphosphatase)等通过去磷酸化Aurora-A而抑制其活性,而且APC／C-Cdh1依赖的蛋白酶体等可以将其降解。了解和认识Aumra-A激酶活性调节的分子机制将有助于理解它在有丝分裂及肿瘤形成中的作用。     

Gadd45a的表达调控与功能

哺乳动物细胞对于遗传毒性的刺激会产生一系列应答,如细胞周期阻滞,DNA修复和细胞凋亡等。Gadd45a在DNA损伤诱导的细胞应答中发挥重要作用。细胞内外环境的多种因素在转录水平、转录后水平、翻译后水平等多个层次对Gadd45a进行精确调节。Gadd45a通过与Cdc2相互作用调控细胞周期G2-M检测点,直接抑制Aurora-A激酶参与中心体稳定性的调节,通过G1-S期调控参与维持基因组的稳定性。Gadd45a参与p38/JNK、MAPK、线粒体介导的凋亡途径和NF-κB介导的生存通路调控。     

小鼠卵母细胞减数分裂过程中LIMK1参与调控Aurora-A在纺锤体的定位

目的研究小鼠卵母细胞减数分裂进程中活化的LIMK1(pLIMK1^Thr508)与Aurora-A亚细胞分布的相关性,LIMK1活性变化对Aurora-A和纺锤体组装的影响。方法收集21日龄CB6F1小鼠卵母细胞,分别体外培养至生发泡期(GV)、生发泡破裂期(GVBD)、第1次减数分裂中期(MI)、第1次减数分裂后期(AI)和末期(Tel I)以及第2次减数分裂中期(MII),固定并利用免疫荧光染色法分析减数分裂进程中pLIMK1^Thr508的亚细胞定位模式及其与纺锤体组装调控因子Aurora-A的时空相关性;利用抑制剂BMS-3处理MI期细胞,结合免疫荧光染色分析LIMK1活性缺失对于Aurora-A空间分布和纺锤体形成的影响。结果在小鼠卵母细胞减数分裂前期(prophase)(即GV期),pLIMK1^Thr508信号微弱并主要聚集于生发泡,此时Aurora-A在胞内没有特殊聚集;在临近减数分裂重启时,pLIMK1^Thr508离开生发泡,Aurora-A信号出现,两者呈高度致密的点状聚集并紧密重合;在生发泡完全破裂后,pLIMK1^Thr508和Aurora-A又呈多个点片状聚集在凝集的染色体周围;在MI期和MII期,pLIMK1^Thr508与Aurora-A共同定位于纺锤体两极;在从AI期到Tel I期进程中pLIMK1^Thr508离开纺锤体两极,聚集在收缩环部位,Aurora-A在纺锤体两极有微弱聚集。LIMK1抑制剂BMS-3能够破坏Aurora-A在纺锤体两极的聚集,并影响纺锤体结构。结论pLIMK1^Thr508在卵母细胞减数分裂中是一种微管组织中心(MTOC)相关蛋白,可能通过调控Aurora-A而参与纺锤体结构的形成和维持。     

敲低 Aurora-A 抑制 HepG2人肝癌细胞增殖并促进其凋亡

目的探讨敲低Aurora-A对HepG2人肝癌细胞增殖和凋亡的影响。方法设计Aurora-A短发夹RNA(shRNA)片段,构建和包装Aurora-A shRNA慢病毒载体,转染HepG2细胞,实时定量PCR检测Aurora-A mRNA表达,Westernblot法检测Aurora-A蛋白及磷酸化水平,噻唑蓝(MTT)法检测细胞增殖,流式细胞术检测细胞凋亡。结果成功构建Aurora-A shRNA慢病毒载体,转染后的HepG2细胞Aurora-A蛋白磷酸化水平明显降低。敲低Aurora-A后,HepG2细胞增殖显著降低,细胞凋亡率显著增加。结论敲低Aurora-A的表达抑制HepG2细胞增殖并促进其凋亡。     

核移植供体细胞中心体遗传的研究进展

中心体作为动物细胞主要的微管组织中心，在微管成核过程以及纺锤体两极的建立起重要作用。来源于供体细胞的中心体成分参与了核移植重组胚瞬间纺锤体和第一次有丝分裂纺锤体组装，为维持正常纺锤体功能所必需。核移植后中心体功能是否正常是影响染色体组和胚胎后期发育的重要因素。中心体蛋白包括γ-tubulin、NuMA(Nuclear-Mitotic Apparatus protein，核有丝分裂器蛋白)在核移植后纺锤体组装中发挥重要作用。     

p53突变和STKl5过表达与肿瘤中心体不稳定的相关性

中心体异常与肿瘤发生的相关性已越来越受到人们的重视。本文综述了中心体异常与肿瘤发生的关系，论述了与中心体异常和肿瘤发生相关的基因p53和STKl5以及二者相关性，对研究中心体在肿瘤的发生机制、诊断、治疗中的应用前景作以展望，并提出了一些尚需探讨的问题。     

miRNA调控中心体与肿瘤发生的相关性

microRNA(miRNA)是长度为21-25个核苷酸的非编码小RNA,miRNA与靶RNA的3′UTR碱基配对,通过转录后水平对基因表达的负调控,抑制mRNA翻译或直接使其降解。某些miRNA可以通过靶向E2F、cycling、Cdk、CKI等调节因子,调节细胞周期以及中心体的复制,进而影响基因组的稳定性,最终促进或抑制肿瘤的发生。     

中心体异常与肿瘤发生的相关性

中心体这一微小的细胞器已越来越受到人们的重视。本文综述了中心体的结构、功能、复制过程及中心体蛋白，论述了中心体的异常与肿瘤发生的关系及与二者相关的基因，对研究中心体在肿瘤的发生机制、诊断和治疗中的应用前景作一展望，并提出了一些尚需探讨的问题。     

The N-terminal domain of the Aurora-A Phe-31 variant encodes an E3 ubiquitin ligase and mediates ubiquitination of IkappaBalpha

Aurora-A is an important regulator of mitosis and is frequently amplified in human cancer. Ectopic expression of Aurora-A in mammalian cells induces centrosome amplification, genomic instability and transformation. A common genetic variant in Aurora-A (F31I) is preferentially amplified and is associated with the occurrence and the status of colon, oesophageal and breast cancers. Here we demonstrate that the N-terminal domain of Aurora-A Phe-31 variant exhibits an intrinsic ubiquitin ligase activity. Mutation of cysteines 8, 33 and 49 of Aurora-A abolishes the ubiquitin ligase activity of the protein. Aurora-A in a complex with UBE2N/MMS2 catalyses polyubiquitination of IkappaBalpha in vitro and in vivo.     

Aurora-A/STK-15 is a predictive factor for <Emphasis Type="Italic">recurrent</Emphasis> behaviour in non-invasive bladder carcinoma: a study of 128 cases of non-invasive neoplasms

Aurora-A, a member of serine/threonine kinase, is implied in mitosis and centrosome maturation. Increasing levels of Aurora-A have been shown to be present in several malignancies and especially in bladder cancer. No immunohistochemical marker has shown to be able to predict the clinical outcome of patients with superficial bladder cancer, except MIB-1, as a predictive marker of relapse and progression. The aim was to investigate the expression of Aurora-A and MIB-1 in tissue micro arrays of superficial bladder cancer representative of pTa papillary urothelial neoplasm with different degrees of aggressiveness (low malignant potential [PUNLMP], non-invasive papillary urothelial carcinoma low grade [NILGC], non-invasive papillary urothelial carcinoma high grade [NIHGC] and carcinoma in situ). We analysed predictive values of both markers, their specificity and sensitivity in tumor recurrence. Aurora-A was a sensitive marker to predict tumor recurrence especially for pTa (PUNLMP, NILGC; PUNLMP p < 0.001, NILGC p < 0.001) with statistical significant correlation between immunohistochemical staining and clinical outcome. MIB-1 expression displayed statistical difference p = 0.002 in the PUNLMP group and p = 0.03 in the NILGC group. Aurora-A is a more sensitive marker than MIB-1 to predict relapse in pTa bladder neoplasias. The combination of both markers seems to have a very powerful predictive value of recurrence (p < 0.001).     

Centrosome-, chromosomal-passenger- and cell-cycle-associated mRNAs are differentially regulated in the development of sporadic colorectal cancer

Dysregulation of the centrosome complex and chromosomal segregation has been associated with aneuploid cells and aggressive solid tumours, but the relevance of this mechanism to the adenoma-carcinoma sequence of sporadic colorectal cancer (sCRC), especially tumours showing chromosomal instability (CIN), is still unknown. In a series of matching normal epithelial cells (n = 41), dysplastic cells (n = 18), and invasive carcinoma cells (n = 41) from cases with sCRC, mRNA levels of the centrosomal kinase Aurora-A/STK15 and the chromosomal passenger- and cell cycle-associated molecules Incenp, Survivin, Mad-2, and Cyclin-D1 were therefore measured with specific reference to the type of genetic instability. Compared with normal epithelium, significant up-regulation of mRNAs was already present for Aurora-A/STK15 (p = 0.0313) in dysplastic cells and for all investigated markers in invasive carcinoma. Whereas Aurora-A/STK15 mRNA levels were similarly up-regulated in dysplastic and invasive carcinoma cells (p = 0.0797), Survivin (p = 0.0046) and Cyclin-D1 (p = 0.0017) mRNA levels increased from dysplastic to invasive carcinoma cells. In carcinomas, Incenp mRNA correlated with T category (p = 0.0149), and Survivin (p = 0.0382) and Cyclin-D1 (p = 0.0185) were associated with tumour differentiation. Importantly, a significantly higher (p = 0.0419) fold-change of Aurora-A/STK15 mRNA (p = 0.0419), but not Incenp, Survivin, Mad-2 or Cyclin-D1, was observed in sCRC cases with CIN (n = 29) when compared with tumours showing microsatellite instability (MIN, n = 10). The present data are the first to show an early increase of the centrosomal kinase Aurora-A/STK15 in the adenoma-carcinoma sequence of sCRC. The regulation of this kinase differs in CIN- and MIN-type sCRCs and the pattern of changes is different from those of the cell-cycle-associated markers Survivin, Mad-2, and Cyclin-D1. This reinforces the concept of preferential dysregulation of the centrosome complex in CIN-type (aneuploid), compared with MIN-type, sporadic colorectal cancers and may influence the response to and efficiency of novel therapeutics targeting Aurora kinases.     

Over-expression of Aurora-A targets cytoplasmic polyadenylation element binding protein and promotes mRNA polyadenylation of Cdk1 and cyclin B1

Aurora-A is a centrosomal serine-threonine kinase that regulates mitosis. Over-expression of Aurora-A has been found in a wide range of tumors and has been implicated in oncogenic transformation. However, how Aurora-A over-expression contributes to promotion of carcinogenesis remains elusive. Immunohistochemical analysis of breast tumors revealed that over-expressed Aurora-A is not restricted to the centrosomes but is also found in the cytoplasm. This over-expressed Aurora-A appeared to be phosphorylated on Thr288, which is known to be required for its enzymatic activation. In analogy to Aurora-A's role in oocyte maturation and the early embryonic cell cycle, here we investigated whether ectopically over-expressed Aurora-A can similarly stimulate polyadenylation of mRNA in human somatic cultured cells by interacting with a human ortholog of cytoplasmic polyadenylation element binding protein, h-CPEB. In vitro experiments revealed that Aurora-A binds directly to, and phosphorylates, h-CPEB. We found that polyadenylation of mRNA tails of cyclin B1 and Cdk1 was synergistically stimulated when Aurora-A and h-CPEB were over-expressed, and they were further promoted in the presence of an Aurora-A activator Ajuba. Our results suggest a function of ectopically over-expressed Aurora-A that might be relevant for carcinogenesis.     

Inhibitors of histone deacetylases induce tumor-selective cytotoxicity through modulating Aurora-A kinase

The molecular basis of the antitumor selectivity of histone deacetylase inhibitors (HDIs) remains unclear. Centrosomal Aurora-A kinase regulates chromosomal segregation during mitosis. The overexpression or amplification of Aurora-A leads to genetic instability, and its inhibition has shown significant antitumor effects. In this paper, we report that structurally related hydroxamate LAQ824 and SK-7068 induce tumor-selective mitotic defects by depleting Aurora-A. We found that HDI-treated cancer cells, unlike nontransformed cells, exhibit defective mitotic spindles. After HDI, Aurora-A was selectively downregulated in cancer cells, whereas Aurora-B remained unchanged in both cancer and nontransformed cells. LAQ824 or SK-7068 treatment inhibited histone deacetylase (HDAC) 6 present in Aurora-A/heat shock protein (Hsp) 90 complex. Inhibition of HDAC6 acetylated Hsp90 and resulted in dissociation of acetylated Hsp90 from Aurora-A. As a result, Hsp70 binding to Aurora-A was enhanced in cancer cells, leading to proteasomal degradation of Aurora-A. Overall, these provide a novel molecular basis of tumor selectivity of HDI. LAQ824 and SK-7068 might be more effective HDIs in cancer cells with Aurora-A overexpression.     

Prognostic significance of Aurora-A expression in human bladder cancer

Aurora-A is an oncogenic serine/threonine kinase, which plays important roles in tumorigenesis, development and chemoresistance of human cancers. The aim of the study was to detect the expression of Aurora-A gene in bladder cancer tissues and analyze its association with prognosis of bladder cancer patients. RT-PCR was performed to detect the expression of Aurora-A mRNA in 20 cases of bladder cancer and corresponding non-tumor tissue samples. Immunohistochemistry was performed to detect the localization of Aurora-A protein in 96 cases of bladder cancer tissue samples. Associations between Aurora-A protein expression and clinico-pathological factors or survival of bladder cancer patients were statistically analyzed. It was found that the expression levels of Aurora-A mRNA in bladder cancer tissues (1.08 ± 0.24) were significantly higher than those in corresponding non-tumor tissues (0.22 ± 0.07; P < 0.01). Moreover, immunohistochemical staining results showed the localization of Aurora-A protein to be mainly located in the cytoplasm of bladder cancer cells. High levels of Aurora-A protein expression were correlated with pathological stage (P = 0.007), lymph node metastasis (P = 0.014) and venous invasion (P = 0.008), but not with other factors including age, gender, tumor grade and recurrence of superficial cancer. Patients with high expression levels of Aurora-A protein showed lower disease-free and overall survival rates than those with low expression levels (P = 0.0072 and 0.0009, respectively). Univariate and multivariate analysis of prognostic factors in bladder cancer patients indicated that Aurora-A expression was an independent unfavorable prognostic factor (hazard ratio: 0.673; 95% confidence interval: 0.388-0.912; P < 0.001). Our study suggests that overexpression of Aurora-A gene may play an important role in the progression of bladder cancer and that Aurora-A expression is an independent factor for predicting the prognosis of bladder cancer in patients.     

The centrosomal protein Lats2 is a phosphorylation target of Aurora-A kinase

Human Lats2, a novel serine/threonine kinase, is a member of the Lats kinase family that includes the Drosophila tumour suppressor lats/warts. Lats1, a counterpart of Lats2, is phosphorylated in mitosis and localized to the mitotic apparatus. However, the regulation, function and intracellular distribution of Lats2 remain unclear. Here, we show that Lats2 is a novel phosphorylation target of Aurora-A kinase. We first showed that the phosphorylated residue of Lats2 is S83 in vitro. Antibody that recognizes this phosphorylated S83 indicated that the phosphorylation also occurs in vivo. We found that Lats2 transiently interacts with Aurora-A, and that Lats2 and Aurora-A co-localize at the centrosomes during the cell cycle. Furthermore, we showed that the inhibition of Aurora-A-induced phosphorylation of S83 on Lats2 partially perturbed its centrosomal localization. On the basis of these observations, we conclude that S83 of Lats2 is a phosphorylation target of Aurora-A and this phosphorylation plays a role of the centrosomal localization of Lats2.     

Aurora-A遗传变异Phe31Ile与小儿神经母细胞瘤遗传易感性

目的Aurora-A基因过度表达可引起中心粒异常、染色体不稳定和肿瘤形成。本研究探讨Aurora-APhe31Ile多态与神经母细胞瘤（neuroblastoma,NB）遗传易感性的关系。方法以聚合酶链反应（PCR）和限制性片段长度多态性（RFLP）分析方法,检测了19例NB病人和144例正常对照者Aurora-APhe31Ile基因型,比较不同基因型与NB发生和发展的关系。结果Aurora-AIle等位基因频率在NB患者和正常对照中的分布有显著性差异（76.3%vs.49.0%,P=0.04）。Aurora-A三种基因型Phe/Phe、Phe/Ile和Ile/Ile在病例和对照组中的分布有统计学显著性差异（P=0.05,趋势检验）,携带Aurora-AIle/Ile基因型者罹患NB的风险是Phe/Phe或Phe/Ile基因型携带者的2.51倍（95%CI,0.86-7.37）。结论Aurora-A遗传变异Phe31Ile可能是我国神经母细胞瘤的遗传易感因素。