人肝细胞癌中抑癌基因PTEN/MMAC1/TEP1的突变分析

PTEN／MMAC1／TEP1(PTEN)是新近分离到的抑癌基因,在多种肿瘤中存在突变。我们检测了34例人肝细胞癌中PTEN基因第5外显子和第8外显子的突变。采用聚合酶链方法以内含子引物扩增第5和第8外显子,继之以单链构象多态性和测序技术分析PTEN基因突变。有4例肝细胞癌SSCP显示异常条带并经测序证实存在突变。2例发生于第4内含子,突变位点相同;另两例发生于第8外显子,其中1例碱基颠换导致PTEN蛋白产物304位半胱氨酸突变为甘氨酸。     

抑癌基因PTEN／MMAC1的cDNA克隆及其表达质粒的构建

为了获得了PTEN/MMAC1的cDNA并构建其酵母双杂交系统中的诱饵质粒和逆转录病毒表达质粒。利用RTPCR方法,从293细胞中扩增出一约12.kb的DNA片段,与pGEMT Easy连接,作全自动测序确证,重组入pLexA载体,构建成pLexA-PTEN/MMAC1,并用醋酸锂法转化酶母菌EGY48（p8op-LacZ）,在选择性培养基上观察pLexA-PTEN/MMAC1在EGY48(p8op-LacZ）中的表达情况;同时,PTEN/MMAC1的cDNA也重组入pLXSN构建pLXSN-PTEN/MMAC1。结果PCR获得1.2kb的DNA序列与献报道的PTEN/MMAC1的cDNA一致,转化的酵母菌在选择性培养上培养3d后,长出约1mm大小的白色菌落;pLXSN-PTEN/MMAC1可酶切出1.2kb的PTEN/MMAC1片段。结果表明获得了PTEN/MMAC1的cDNA,pLexA-PTEN/MMAC1可作为酵母双杂交系统中的诱饵质粒,而pLXSN-PTEN/MMAC1的构建为进一步研究其抑癌作用打下了基础。     

抑癌基因PTEN及其在肿瘤中的突变失活

正常细胞和肿瘤细胞的蛋白质磷酸化及去磷酸化研究一直引人注目。研究表明,细胞内蛋白质酪氨酸磷酸化水平受蛋白质酪氨酸激酶和蛋白质酪氨酸磷酸酶动态调控。多种癌基因的表达产物具有蛋白质酪氨酸激酶活性并参与肿瘤形成进程,提示蛋白质磷酸酪氨酸磷酸酶可能抑制肿瘤形...     

肝细胞癌中抑癌基因的发现与研究进展

肝细胞癌（HCC）的发病率高、治疗效果差。HCC的发病机制复杂,主要有2类：肝炎、酒精、黄曲霉素、代谢紊乱引起的肝损伤,进而导致的肝硬化;致癌基因和抑癌基因的突变或对应染色体区域的扩增或缺失。细胞内一些信号通路参与了HCC的发生发展,包括RAF／MEK／ERK、P13K／AKT／mTOR、WNT/β-catenin、胰岛素样生长因子、肝细胞生长因子／c-MET、生长因子调节的血管新生等6类信号通路。抑癌基因通过调节信号通路而调节细胞增殖、细胞周期、细胞凋亡等对肿瘤的发生、发展起重要作用的过程。我们简要概述HCC相关的肿瘤抑制分子及其所在的信号通路及作用的分子机制。     

鼻咽癌、胃癌中抑癌基因ING1的突变检测

为探讨抑癌基因ING1是否在鼻咽癌和胃癌中存在基因突变,以确定该基因在鼻咽癌、胃癌发病过程中所起的作用,本研究运用PCR－SSCP法分别对鼻咽癌和胃癌组织ING1点突变情况进行检测;对30例鼻咽癌组织和26例胃癌组织的ING1外显子1b扩增的PCR产物进行SSCP分析,结果未发现所扩增的片段有泳运速率的改变,以上结果可以初步排除ING1在鼻咽癌和胃癌中以基因突变方式失活的可能。     

抑癌基因PTEN在胃癌中的研究进展

近年来国内外的学者在多种肿瘤中发现抑癌基因PTEN的等位基因缺失、基因突变、甲基化,PTEN基因杂合性丢失(LOH)频繁的发生于胃癌,而该基因发生突变的频率较低,蛋白表达普遍下降.抑癌基因PTEN异常与胃癌的发生和发展相关,对PTEN功能的进一步研究将为胃癌的诊断和治疗提供新的思路.     

PTEN—第一个具磷酸酯酶活性的抑癌蛋白

本文综述了ＰＴＥＮ／ＭＭＡＣ１／ＴＥＰ１,第一个具磷酸酯酶活性的抑癌基因的最新研究进展。阐述了其ＤＮＡ和蛋白结构特征,ＰＴＥＮ生理性底物的发现过程,ＰＴＥＮ的抑癌机理及在肿瘤中的异常表达情况。     

乳腺癌组织抑癌基因PTEN的表达及其意义

目的探讨PTEN基因在人乳腺癌组织的表达及其与临床病理参数的关系.方法采用免疫组织化学法和原位杂交法,对70例乳腺癌组织PTEN基因mRNA和蛋白表达进行分析.结果 15例乳腺良性肿瘤均见PTENmRNA和蛋白表达,其阳性率为(100.0% 15/15);70例乳腺癌组织中PTENmRNA和蛋白表达明显降低,阳性率分别为51.4%(36/70)和47.1%(33/70),与对照组比较差异有显著性(P<0.01);PTEN基因表达下调与乳腺癌的组织学分级,TNM分期和腋淋巴结转移有关,而与肿瘤的大小和ER、PR状况无关.乳腺癌PTEN mRNA表达检测结果与PTEN蛋白相似.结论乳腺癌中存在PTEN基因表达异常,PTEN表达下调与乳腺癌的进展、转移关系密切.     

抑癌基因PTEN在鼻咽癌细胞株中表达的研究

目的:检测人鼻咽癌细胞株中PTEN表达情况,探讨鼻咽癌细胞中PTEN表达与细胞分化程度的关系。方法:进行细胞株的培养,采用流式细胞仪和共聚焦显微镜检测方法对细胞中PTEN的表达进行定位定量检测。结果:两种细胞株均有PTEN的表达,表达强度和分布与分化程度有关,分化越好,表达越高,流式细胞仪检测PTEN在细胞株中表达强弱顺序为CNE1>CNE2,阳性表达细胞数CNE1>CNE2差异有统计学意义(P<0.01);激光共聚焦扫描显微镜检测PTEN主要表达在细胞核和细胞浆,分布与分化程度有关,细胞核表达强度CNE1相似文献   

抑癌基因LIMD1

抑癌基因LIMD1在肿瘤发生及演进中的作用逐渐受到重视,两者的因果关系较为密切,如与肺癌、乳腺癌、头颈部恶性肿瘤及儿童急性淋巴细胞白血病等相关。本文就LIMD1的发现、结构、生物学功能及在肿瘤中的作用机制等做一综述。     

Alternative splicing of the human PTEN/MMAC1/TEP1 gene

The human tumour suppressor gene PTEN/MMAC1/TEP1 encodes a lipid and protein phosphatase. Using RT-PCR, alternatively spliced forms of PTEN mRNA, encoding full-length PTEN and two forms of the protein truncated at the C-terminal end, were detected in normal human tissue. Cultured tumour and non-tumour cell lines show similar splicing patterns.     

PTEN/MMAC1/TEP1 in signal transduction and tumorigenesis.

The level of phosphorylation within cells is tightly regulated by the concerted action of protein kinases and protein phosphatases [Hunter, T. (1995) Cell 80, 225-236]. Disregulation in the activity of either of these players can lead to cellular transformation. Many protein tyrosine kinases are proto-oncogenes and it has been postulated that some protein phosphatases may act as tumor suppressors. Herein we will review the recent findings addressing the roles the candidate tumor suppressor PTEN/MMAC1/TEP1 (PTEN, phosphatase and tensin homologue deleted from chromosome 10; MMAC 1, mutated in multiple advanced cancers 1; TEP1, TGF beta regulated and epithelial cell enriched phosphatase 1) plays in signal transduction and tumorigenesis. PTEN is a dual specificity protein phosphatase (towards phospho-Ser/Thr and phospho-Tyr) and, unexpectedly, also has a phosphoinositide 3-phosphatase activity. PTEN plays an important role in the modulation of the 1-phosphatidylinositol 3-kinase (PtdIns 3-kinase) pathway, by catalyzing the degradation of the PtdIns(3,4,5)P3 generated by PtdIns 3-kinase; this inhibits the downstream functions mediated by the PtdIns 3-kinase pathway, such as activation of protein kinase B (PKB, also known as Akt), cell survival and cell proliferation. Furthermore, PTEN modulates cell migration and invasion by negatively regulating the signals generated at the focal adhesions, through the direct dephosphorylation and inhibition of focal adhesion kinase (FAK). Growth factor receptor signaling is also negatively regulated by PTEN, through the inhibition of the adaptor protein Shc. While some of the functions of PTEN have been elucidated, it is clear that there is much more to discover about the roles of this unique protein.     

Downregulation of PTEN/MMAC/TEP1 expression in human prostate cancer cell line DU145 by growth stimuli

Genetic alterations and/or deletion of the tumor suppressor gene PTEN/MMAC/TEP1 occur in many types of human cancer including prostate cancer. We describe the production of monoclonal antibody against recombinant human PTEN and the study of PTEN gene and protein expression in three commercially available human prostate cancer cell lines, PC-3, LNCaP, and DU 145. Northern blotting analyses showed that LNCaP and DU145 but not PC-3 cells expressed PTEN mRNA. However, Western blotting analyses using a monoclonal antibody against PTEN demonstrated the expression of PTEN protein in DU145 but not LNCaP cells. In DU145 cells, PTEN expression at both the mRNA and protein levels inversely correlated with serum concentrations and levels of PKB/Akt phosphorylation. In addition, the basal activity of PKB/Akt as indicated by level of phosphorylation was higher in prostate cancer cells which do not express PTEN than that in the cells expressing wild type PTEN. Thus, PTEN may play a critical role in regulating cellular signaling in prostate cancer cells.     

抑癌基因PTEN及其假基因PTENP1在子宫内膜癌中的研究进展

子宫内膜癌的发病率在逐年上升,引起了人们的广泛关注,但其发病的分子遗传学机制仍不十分清楚。近年来基因改变致癌的研究成为热点。国内外研究报道发现：PTEN（与张力蛋白同源第10染色体丢失的磷酸酶基因）是目前已知的子宫内膜癌中突变率最高的基因,常发生在子宫内膜癌的早期,对其突变的检测有助于子宫内膜癌的早期诊断、治疗及预后评价,并为子宫内膜癌的基因治疗提供了新的靶点。另外,研究发现,PTENP1（PTEN的假基因）转录调控PTEN的表达,被认为与一些肿瘤的发生有关。本文就PTEN基因的结构、功能及在子宫内膜癌中的突变情况、临床意义及PTENP1的研究现状进行综述。     

Hyper-methylation of RIZ1 tumor suppressor gene is involved in the early tumorigenesis of hepatocellular carcinoma

The retinoblastoma protein-interacting zinc finger gene RIZ1 is a putative tumor suppressor gene, and the inactivation of the RIZ1 is frequently found in tumors through a loss of mRNA expression. In order to understand the role of RIZ1 inactivation in the tumorigenesis of hepatocellular carcinoma (HCC), we detected the RIZ1 promoter methylation status in 39 HCCs using a methylation specific PCR (MSP) method, and carried out LOH study with marker P704. We also assessed the associations between the methylation status and clinicopathological parameters, tumor size, tumor differentiation, and fractional allelic loss (FAL). The results showed that the RIZ1 promoter methylated both in advanced tumors (>3 cm), (18/31, 58.0%) and in early tumors (<3 cm), (4/8, 50.0%). There were 54.6% (12/22) tumors with hyper-methylation in the low FAL group and 45.5% (10/22) in the high FAL group. Moreover, the DNA methylation of the RIZ1 promoter was found not only in the poorly differentiated tumors (12/22, 54.6%), but also in the well differentiated tumors (10/22, 45.5%). Among the 22 HCCs (22/39, 56.4%) that showed hyper-methylation at the RIZ1 promoter region, 3 cases showed biallelic methylation. Interestingly, one case showed hyper-methylation on one allele and a loss of heterozygosity (LOH) on the other allele. In other words, 4 HCCs showed the biallelic inactivation of the RIZ1. These results suggest that the inactivation of the RIZ1 by DNA methylation at its promoter region is involved in the tumorigenesis of HCC, particularly in the early stage of disease.     

Absence of PTEN/MMAC1 pseudogene in mice

The PTEN gene encodes a phosphatase that acts as a tumor-suppressor gene and is mutated in a variety of human cancers. Alterations of the PTEN gene in these tumor samples were identified using exon-by-exon analysis of the gene using single-stranded conformational polymorphism or direct sequencing of PTEN cDNA. However, in humans, mutational analysis of a PTEN cDNA template can produce false results because of a highly conserved PTEN processed pseudogene that shares more than 98% homology with the coding region of functional PTEN. PTEN-knockout mice develop tumors, suggesting that mouse tumor models are useful in vivo model systems to study PTEN function. Any mutational analysis of mouse PTEN cDNA may also produce false results if mice contain a highly conserved PTEN pseudogene. In this paper, we demonstrate the absence of any PTEN pseudogene in the mouse and discuss the significance of this observation for the mutational studies of the PTEN gene in mouse tumor models.     

Arsenic trioxide induces G2/M arrest in hepatocellular carcinoma cells by increasing the tumor suppressor PTEN expression

Arsenic trioxide (As₂O₃), an effective agent against acute promyelocytic leukemia, has been reported to inhibit the viability of solid tumors cell lines recently. The detailed molecular mechanism underlying the As₂O₃‐induced inactivation of the cdc2 and possible functional role of PTEN in the observed G2/M arrest has yet to be elucidated. Here, we assessed the role of PTEN in regulation of As₂O₃‐mediated G2/M cell cycle arrest in Hepatocellular carcinoma cell lines (HepG2 and SMMC7721). After 24 h following treatment, As₂O₃ induced a concentration‐dependent accumulation of cells in the G2/M phase of the cell cycle. The sustained G2/M arrest by As₂O₃ is associated with decreased cdc2 protein and increased phospho‐cdc2(Tyr15). As₂O₃ treatment increased Wee1 levels and decreased phospho‐Wee1(642). Moreover, As₂O₃ substantially decreased the Ser473 and Thr308 phosphorylation of Akt and upregulated PTEN expression. Downregulation of PTEN by siRNA in As₂O₃‐treated cells increased phospho‐Wee1(Ser642) while decreased phospho‐cdc2(Tyr15), resulting in decreased the G2/M cell cycle arrest. Therefore, induction of G2/M cell cycle arrest by As₂O₃ involved upregulation of PTEN. J. Cell. Biochem. 113: 3528–3535, 2012. © 2012 Wiley Periodicals, Inc.     

Mutation analysis of large tumor suppressor genes LATS1 and LATS2 supports a tumor suppressor role in human cancer

In recent years, human cancer genome projects provide unprecedented opportunities for the discovery of cancer genes and signaling pathways that contribute to tumor development. While numerous gene mutations can be identified from each cancer genome, what these mutations mean for cancer is a challenging question to address, especially for those from less understood putative new cancer genes. As a powerful approach, in silico bioinformatics analysis could efficiently sort out mutations that are predicted to damage gene function. Such an analysis of human large tumor suppressor genes, LATS1 and LATS2, has been carried out and the results support a role of hLATS1//2 as negative growth regulators and tumor suppressors.