抑癌基因PTEN的研究进展

第10号染色体同源缺失性磷酸酶-张力蛋白基因(phosphataseandtensinhomologdeletedonchromosometen,PTEN)在多种肿瘤中存在突变。PTEN基因产物具有蛋白磷酸酶活性和脂质磷酸酶活性,其C端可调节PTEN在膜上的靶向定位。结合到质膜上的PTEN通过催化磷脂酰肌醇3,4,5-三磷酸(phosphatidylinositol3,4,5-triphosphate,PIP3)的降解来调节细胞内PIP3水平,对PKB/Akt途径进行负调控。在细胞内,PTEN与许多细胞表面受体相互作用,对一些受体介导的信号转导途径进行负调节,从而调控细胞的增殖、迁移和侵袭。PTEN也通过与p53蛋白结合,调节基因转录,进而对细胞生长或细胞凋亡进行调控。     

PTEN蛋白在喉鳞癌中表达的研究

<正>PTEN抑癌基因是迄今为止发现的第1个具有磷酸酶活性的抑癌基因,定位于人类染色体10q23,全长200kb。PTEN蛋白定位于细胞质,具有双特异性磷酸酶活性,在酪氨酸磷酸酶和丝氨酸/苏氨酸磷酸酶介导的信号传递过程中具有重要作用。PTEN基因异常表达与肿瘤的侵袭、转移和生长有关。本研究采用免疫组织化学技术对喉鳞状细胞癌中PTEN蛋白的表达情况进行研究,旨在探讨PTEN蛋白在喉鳞癌的发生、发展中的临床意义。     

PTEN基因的研究进展

PTEN基因是迄今发现的第一个具双特异性磷酸酶活性的抑癌基因 ,其突变失活与人类多种恶性肿瘤发生、发展及预后密切相关 ,PTEN蛋白在细胞的生长发育、信号传导和细胞凋亡过程中起重要作用。     

紫杉醇对PTEN不同状态的子宫内膜癌细胞株的作用及其机制探讨

目的研究紫杉醇对不同PTEN状态子宫内膜癌细胞株中的作用及其相关机制。方法利用慢病毒载体系统,分别转染PTEN野生型的HEC-1A细胞和PTEN突变型的Ish-ikawa细胞,建立PTEN基因敲除(HEC-1-RNAi)细胞及过表达(Ishikawa-PTEN)的细胞模型。采用MTT法检测细胞增殖抑制率,流式细胞术检测细胞凋亡率,Western blot观察磷酸化AKT蛋白和Caspase-3蛋白的表达。结果紫杉醇对不同PTEN状态的细胞株均有明显的生长抑制作用,抑制率与时间、剂量成正相关。紫杉醇处理不同PTEN状态的细胞24h后,PTEN阳性细胞的IC50和磷酸化AKT蛋白水平明显低于PTEN阴性细胞,PTEN阳性细胞的凋亡率、Caspase-3的蛋白水平明显高于PTEN阴性细胞。结论 PTEN基因能增加子宫内膜癌细胞株对紫杉醇的敏感性,其可能与抑制PI3K/AKT信号通路,增强Caspase-3蛋白表达有关。     

肿瘤抑制基因PTEN/MMAC1/TEP1的研究现状及展望

PTEN基因是具有双特异性磷酸酶活性的抑癌基因,在细胞的生长发育、凋亡、迁移及信号传导等方面起着重要的调控作用.PTEN在人类多种肿瘤中存在突变、缺失及甲基化,如前列腺癌、乳腺癌、胶质瘤等,并与肿瘤的发生、发展密切相关.因此,研究PTEN的信号传导机制及相关调节因子,将会对研究肿瘤的致癌机制、早期诊断、预后判断及基因治疗具有一定作用.     

PTEN和PS2在乳腺癌中的表达及意义

<正>PTEN是第一个被发现具有磷酸酶活性的抑癌基因,在细胞的生长发育、信号转导和细胞凋亡过程中起重要作用。PS2基因又称乳腺癌雌激素诱导基因(BCEI),PS2受雌激素调节和控制,在雌激素诱发和控制下才能转录,而产生PS2蛋白依赖于ER的存在。作为乳     

肝癌中骨形成蛋白2对PTEN蛋白水平影响的研究

目的用骨形成蛋白2(BMP2)干预肝癌细胞系HepG2细胞,从而观察肝癌细胞中PTEN蛋白水平的变化,观察BMP2对PTEN蛋白表达的影响,探讨BMP2与PTEN蛋白水平之间的关系,探索肝癌治疗的新途径。方法将受试对象分为3个组:对照组、BMP2100ng/ml组、BMP2300ng/ml组,作用时间为3个水平:6、12、24h。用免疫组织化学方法测定细胞中PTEN蛋白水平。结果免疫组织化学结果显示在不同浓度BMP2组中HepG2细胞中PTEN蛋白表达差异有统计学意义。不同时间组中PTEN蛋白表达差异有统计学意义。PTEN蛋白阳性表达率在300ng/ml组与100ng/ml组、对照组之间差异有统计学意义(P<0.05),在6h组与12h组、24h组之间差异有统计学意义(P<0.05)。在300ng/ml、24h组中PTEN蛋白阳性表达最高。浓度与时间之间无交互作用。结论在肝癌中BMP2可以增加PTEN蛋白水平,且呈浓度时间依赖。     

PTEN,Survivin与卵巢恶性肿瘤关系的研究进展

1997年首次发现PTEN基因,是迄今为止发现的唯一具有磷酸酶活性、抑制细胞凋亡和调节细胞有丝分裂的双重功能,且具有控制生长或负调控、抑制转化细胞的恶性表达的基因。     

NHERF-1介导雌激素调节PTEN蛋白表达的研究

目的：研究雌激素调节PTEN蛋白表达的分子机制。方法：利用蛋白质芯片筛选PTEN的结合蛋白，发现了NHERF-1与PTEN的相互作用；应用GST pull-down、over-lay和免疫共沉淀等方法确认了其二者的相互作用。通过瞬时转染、免疫印迹分析、RT-PCR、RNAi以及蛋白降解速度检测等方法检测NHERF-1对细胞内PTEN稳定性的影响。结果：发现了PTEN与NHERF-1的相互作用，该相互作用是通过PTEN羧基末端与NHERF-1的第一个PDZ结构域相结合而实现的。将PTEN羧基末端的4个氨基酸分别突变为丙氨酸，都会明显抑制二者的结合。利用免疫共沉淀确认了细胞内完整的PTEN与NHERF-1蛋白分子的相互作用。发现NHERF-1的表达可以提高细胞内PTEN的蛋白表达量，而其mRNA表达水平没有增加。利用环己酮抑制新蛋白合成后，检测到NHERF-1的表达可以抑制PTEN蛋白的降解速度；RNAi抑制内源性NHERF-1的表达导致IYFEN的蛋白表达量显著下降。雌激素可以明显增高NHERF-1与PTEN的蛋白表达，RNAi干扰NHERF-1表达后，雌激素不再调节PTEN的蛋白的表达。结论：PTEN与NHERF-1可以特异结合。NHERF-1与PTEN结合显著提高PTEN蛋白的稳定性；雌激素并不直接调节PTEN蛋白的表达而是通过诱导NHERF-1的表达，引起PTEN蛋白稳定性的增强而导致PTEN蛋白含量的提高。     

pIRES-IL-24-PTEN双表达载体的构建及鉴定

目的构建携带人IL-24和10号染色体缺失的磷酸脂酶与PTEN双基因的真核表达载体,为研究其表达产物的抑癌机制提供基础。方法通过PCR方法获得PTEN、IL-24基因片段,进行T-A克隆,再酶切亚克隆到pIRES载体,酶切、测序鉴定正确后命名为pIRES-IL-24-PTEN载体。脂质体转染A549细胞,提取细胞的总蛋白,Western blot检测IL-24和PTEN蛋白的表达。结果酶切、测序显示pIRES-IL-24-PTEN载体序列正确,Western blot检测到IL-24和PTEN蛋白表达。结论成功构建pIRES-IL-24-PTEN载体,为后续研究奠定基础。     

Ursolic acid-induced apoptosis in K562 cells involving upregulation of PTEN gene expression and inactivation of the PI3K/Akt pathway

Ursolic acid (UA), a pentacyclic triterpenoid derived from a variety of medicinal plants, exhibits potent anticancer activity against many types of cancer cells. However, the anticancer mechanism of UA is not clearly understood. Suppression of phosphatase and a tensin homolog deleted on chromosome 10 (PTEN) gene expression leading to activation of the phosphatidylinositol-3-OH kinase (PI3K)/Akt pathway has been observed in many cancers including leukemia, making the PTEN gene and PI3K/Akt pathway a central target for cancer therapy. Here, we demonstrated that UA was able to inhibit growth, induce apoptosis in a human chronic myelogenous leukemia cell line (K562 cells) via upregulation of PTEN gene expression, inhibit Akt kinase activity, change mitochondrial transmembrane potential and reduce the release of cytochrome c and the activity of caspases. These results suggest that UA may elicit its strong antitumor effects via upregulation of the PTEN gene and inhibition of the PI3K/Akt pathway.     

Proteasome inhibitor bortezomib increases PTEN expression and enhances trastuzumab-induced growth inhibition in trastuzumab-resistant cells

PTEN (phosphatase and tension homolog deleted on chromosome 10) has been shown to be inactivated in a wide range of cancers and the role of this gene product is associated with the suppression of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway in many cancers. Recently, some reports demonstrated that the degree of PTEN expression could predict trastuzumab chemosensitivity in ErbB2-overexpressing breast cancer. Here, we demonstrate the possible involvement of a proteasome inhibitor (PS341) in PTEN expression and elucidate the influence of PI3K/Akt, one of the main cascades of the ErbB2 downstream pathway, and discuss the role of the proteasome inhibitors in trastuzumab resistance. ErbB2-overexpressing SKBR3 human breast cancer cells and trastuzumab-resistant SKBR3/R cells were analyzed in this study. We show that the expression of phosphorylated Akt was highly increased in trastuzumab-resistant cells, although the expression of PI3K, phosphorylated PI3K and non-phosphorylated Akt was unchanged in comparison with wild-type SKBR3 cells. However, following treatment with PS341, the level of phosphorylated Akt was decreased in a dose-dependent manner. Conversely, the level of PTEN was increased in the same fashion. PS341 showed sufficient cytotoxicity in resistant cells in combination with trastuzumab and the efficacy of trastuzumab was inclined to be better in resistant cells under PS341 treatment. Remarkable activity of Akt was observed in trastuzumab-resistant SKBR3 breast cancer cells and this phenomenon could be associated with the decreased expression of PTEN. The proteasome inhibitor PS341 could increase the level of PTEN and inhibit the downstream pathway of ErbB2, interfering with phosphorylation of Akt.     

The complexity of PTEN: mutation, marker and potential target for therapeutic intervention

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a phosphatase that removes phosphates primarily from lipids. It has also been called mutated in multiple advanced cancers 1 and transforming growth factor-beta regulated epithelial cell-enriched phosphatase 1. The best described substrate of PTEN is phosphatidyliniositol (3,4,5)-tris-phosphate [PtdIns(3,4,5)P3]. PTEN removes the phosphate in PtdIns(3,4,5)P(3) to generate PtdIns(4,5)P(2). PTEN serves to counter-balance the effects of phosphoinositide 3' kinase, which normally adds a phosphate to PtdIns(4,5)P(2) to generate PtdIns(3,4,5)P(3). PtdIns(3,4,5)P(3) recruits kinases such as phosphoinositide-dependent kinase 1, which in turn phosphorylate Akt, which phosphorylates other downstream proteins involved in regulation of apoptosis and cell-cycle progression. PTEN removal of the phosphate from PtdIns(3,4,5)P(3) inhibits this pathway by preventing localisation of proteins with pleckstrin homology domains to the cell membrane. Alterations of the PTEN gene are associated with cancer and other diseases. Novel therapeutic approaches have been developed to counteract the deletion/mutation of PTEN in human cancer. This review will discuss the role of PTEN in signal transduction and cancer as well as pharmacological approaches to combat PTEN loss in human cancer.     

Post-translational modifications of PTEN and their potential therapeutic implications

PTEN is a tumor suppressor gene localized to human chromosome 10q23.31, a genomic region frequently lost in glioblastoma and prostate cancer. The fact that PTEN encodes a lipid phosphatase with specificity towards phosphatidylinositol-3,4,5-triphosphate renders it a gate-keeper of the phosphatidylinositol 3-kinase pathway. Numerous physiological processes have been ascribed to this evolutionarily conserved molecule including proliferation, cell size determination, survival, differentiation, and cell fate specification. Indeed, mutation in PTEN gene is the genetic cause of Cowden Syndrome. Structurally, the 54-kilodalton protein is composed of two major functional domains crucial for catalytic and membrane binding functions. Additional regulatory regions in both amino- and carboxyl-termini further dictate its structural integrity, catalytic activity, and subcellular localization. Extensive characterization of PTEN primary coding sequence has revealed a multitude of post-translational modifications that fine-tune its biochemical properties. These include phosphorylation, ubiquitination, redox modifications, and acetylation. This article aims to provide an in-depth review of the diverse post-translational modifications of PTEN, focusing on their biological relevance in both normal and cancer cells. The potential applications to cancer therapy by modulating the post-translational modifications of PTEN will also be discussed.     

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) inhibition by 4-hydroxynonenal leads to increased Akt activation in hepatocytes

The production of reactive aldehydes such as 4-hydroxynonenal (4-HNE) is proposed to be an important factor in the etiology of alcoholic liver disease. To understand the effects of 4-HNE on homeostatic signaling pathways in hepatocytes, cellular models consisting of the human hepatocellular carcinoma cell line (HepG2) and primary rat hepatocytes were evaluated. Treatment of both HepG2 cells and primary hepatocytes with subcytotoxic concentrations of 4-HNE resulted in the activation of Akt within 30 min as demonstrated by increased phosphorylation of residues Ser473 and Thr308. Quantification and subsequent immunocytochemistry of phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P(3)[rsqb] resulted in a 6-fold increase in total PtdIns(3,4,5)P(3) and increased immunostaining at the plasma membrane after 4-HNE treatment. Cotreatment of HepG2 cells with 4-HNE and the phosphatidylinositol 3-kinase (PI3K) inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (Ly294002) or the protein phosphatase 2A (PP2A) inhibitor okadaic acid revealed that the mechanism of activation of Akt is PI3K-dependent and PP2A-independent. Using biotin hydrazide detection, it was established that the incubation of HepG2 cells with 4-HNE resulted in increased carbonylation of the lipid phosphatase known as "phosphatase and tensin homolog deleted on chromosome 10" (PTEN), a key regulator of Akt activation. Activity assays both in HepG2 cells and recombinant PTEN revealed a decrease in PTEN lipid phosphatase activity after 4-HNE application. Mass spectral analysis of 4-HNE-treated recombinant PTEN detected a single 4-HNE adduct. Subsequent analysis of Akt dependent physiological consequences of 4-HNE in HepG2 cells revealed significant increases in the accumulation of neutral lipids. These results provide a potential mechanism of Akt activation and cellular consequences of 4-HNE in hepatocytes.     

The complexity of PTEN: mutation,marker and potential target for therapeutic intervention

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a phosphatase that removes phosphates primarily from lipids. It has also been called mutated in multiple advanced cancers 1 and transforming growth factor-β regulated epithelial cell-enriched phosphatase 1. The best described substrate of PTEN is phosphatidyliniositol (3,4,5)-tris-phosphate [PtdIns(3,4,5)P3]. PTEN removes the phosphate in PtdIns(3,4,5)P₃ to generate PtdIns(4,5)P₂. PTEN serves to counter-balance the effects of phosphoinositide 3′ kinase, which normally adds a phosphate to PtdIns(4,5)P₂ to generate PtdIns(3,4,5)P₃. PtdIns(3,4,5)P₃ recruits kinases such as phosphoinositide-dependent kinase 1, which in turn phosphorylate Akt, which phosphorylates other downstream proteins involved in regulation of apoptosis and cell-cycle progression. PTEN removal of the phosphate from PtdIns(3,4,5)P₃ inhibits this pathway by preventing localisation of proteins with pleckstrin homology domains to the cell membrane. Alterations of the PTEN gene are associated with cancer and other diseases. Novel therapeutic approaches have been developed to counteract the deletion/mutation of PTEN in human cancer. This review will discuss the role of PTEN in signal transduction and cancer as well as pharmacological approaches to combat PTEN loss in human cancer.     

The PTEN/PI3K/AKT signalling pathway in cancer, therapeutic implications

PTEN/PI3K/AKT constitutes an important pathway regulating the signaling of multiple biological processes such as apoptosis, metabolism, cell proliferation and cell growth. PTEN is a dual protein/lipid phosphatase which main substrate is the phosphatidyl-inositol,3,4,5 triphosphate (PIP3), the product of PI3K. Increase in PIP3 recruits AKT to the membrane where it is activated by other kinases also dependent on PIP3. Many components of this pathway have been described as causal forces in cancer. PTEN activity is lost by mutations, deletions or promoter methylation silencing at high frequency in many primary and metastatic human cancers. Germ line mutations of PTEN are found in several familial cancer predisposition syndromes. Activating mutations which have been reported for PI3K and AKT, in tumours are able to confer tumourigenic properties in several cellular systems. Additionally, the binding of PI3K to oncogenic ras is essential for the transforming properties of ras. In summary, the data strongly support the view of the PTEN/PI3K/AKT pathway as an important target for drug discovery.     

Akt as a therapeutic target in cancer

Background: The phosphatidylinositol 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/v-akt murine thymoma viral oncogene homolog (Akt)/mammalian target of rapamycin (mTOR) pathway is central in the transmission of growth regulatory signals originating from cell surface receptors. Objective: This review discusses how mutations occur that result in elevated expression the PI3K/PTEN/Akt/mTOR pathway and lead to malignant transformation, and how effective targeting of this pathway may result in suppression of abnormal growth of cancer cells. Methods: We searched the literature for articles which dealt with altered expression of this pathway in various cancers including: hematopoietic, melanoma, non-small cell lung, pancreatic, endometrial and ovarian, breast, prostate and hepatocellular. Results/conclusions: The PI3K/PTEN/Akt/mTOR pathway is frequently aberrantly regulated in various cancers and targeting this pathway with small molecule inhibitors and may result in novel, more effective anticancer therapies.     

卵巢上皮性肿瘤中PTEN的表达及临床意义

目的 探讨卵巢上皮性肿瘤中蛋白酪胺酸磷酸酶基因(PTEN)的表达及临床意义.方法 采用免疫组织化学法检测PTEN在57例卵巢上皮性癌、20例卵巢良性上皮性肿瘤和10例正常卵巢组织标本中的表达.结果 卵巢上皮性癌中PTEN的阳性表达率为38.6%.明显低于正常卵巢组织的100%及卵巢良性上皮性肿瘤的95.0%(P<0.05);PTEN的阳性表达率与卵巢上皮性痛的临床分期、病理分级呈负相关(P<0.05);浆液性卵巢癌中PTEN的阳性表达率为36.84%(14/38),而8例子宫内膜样卵巢癌中仅有1例表达PTEN.结论 PTEN表达下调可能在卵巢上皮性癌的发生、发展中起重要作用,与子宫内膜样卵巢癌的发生关系尤为密切.