端粒酶活性检测方法研究进展

端粒是真核细胞染色体的线性DNA分子末端,有着重要的生物学功能,对维持染色体稳定、防止染色体末端融合和保证DNA完整复制起着重要作用。端粒酶(telom-erase)是使端粒延伸的反转录DNA合成酶,是一种核糖核酸蛋白复合体。端粒酶以其RNA组份为模板,以端粒3′末端为引物,在其具有逆转录酶活性的蛋白组份的催化下合成端粒重复序列。近年来大量研究表明,端粒酶广泛表达于各类恶性肿瘤细胞,但人正常细胞一般阴性,是目前应用最广、最特异的肿瘤标志物。有文献报道,端粒酶     

端粒、端粒酶与皮肤肿瘤

端粒 (telomere)是真核细胞染色体末端的特殊结构 ,具有保护染色体、维持染色体稳定性的重要作用。端粒的不断缩短或丢失 ,可阻止细胞的增殖 ,活化的端粒酶则以自身 RNA为模板 ,不断合成端粒。通常正常体细胞无端粒酶活性 ,端粒酶的活化与细胞衰老、永生化和癌变密切相关。本文     

端粒/端粒酶--抗肿瘤药物设计的新靶点

端粒是染色体末端具有TTAGGG重复序列的特殊结构，它对维护染色体完整并在细胞老化和肿瘤中起着重要作用。端粒酶是一种带有内源RNA及蛋白组分的特殊逆转录酶，研究证实它在80％－90％的肿瘤细胞中呈高水平表达，而在正常体细胞中检测不到。因此端粒／端粒酶已成为抗肿瘤药物的新靶点，综述端粒／端粒酶的结构和功能、各种有效抑制端粒／端粒酶的途径及其研究现状。     

端粒酶hTERT基因反义RNA表达载体的构建及其对肝癌细胞SMMC-7721的作用

端粒是真核细胞线性染色体末端特殊的DNA-蛋白质结构,具有维持染色体的结构稳定和生物功能的作用[1].端粒酶的催化亚基具有逆转录酶活性,能向染色体末端添加端粒序列而阻止端粒缩短.据统计,大部分恶性肿瘤中端粒酶检测为阳性,而周围癌组织和正常组织的端粒酶阳性率分别为12.1%和4.2%或更低[2],端粒酶激活可能是细胞癌变或永生化的一个必然通路,因此抑制其活性可作为肿瘤基因治疗的一个理想的新靶点.本研究构建端粒酶hTERT基因反义表达载体,研究其对肝癌细胞SMMC-7721的生长等方面的影响.     

端粒酶与肿瘤治疗的研究进展

细胞分裂中染色体因其末端的ＤＮＡ不能完全复制，导致的端粒ＤＮＡ序列的丢 失，与细胞的寿命控制有关，端粒酶激活可以维持端粒的长度而使肿瘤细胞获得增殖分裂的能力，从而避锣细胞死亡。本了端粒和端粒酶的构成和功能及其与肿瘤的相关性，通过抑制端粒酶活性治疗肿瘤的可能性，以及作用于端粒酶的药物。     

端粒酶在肿瘤分子靶向治疗中的研究进展

端粒酶（Telomerase）是一种能延长端粒末端的特异性逆转录酶,以自身RNA为模板,反转录合成端粒DNA重复序列,对细胞增殖、衰老、永生化和癌变起重要作用。端粒酶在各类原发肿瘤中的特异性高表达,针对端粒酶的治疗比单纯针对某个癌基因或抑癌基因的治疗具有更为广阔的应用前景,为肿瘤治疗提供了新的思维。现将端粒酶的生物学特性以及目前针对抑制端粒酶活性的研究综述如下。     

肿瘤细胞凋亡与端粒酶调控

端粒是真核细胞染色体末端由重复的DNA序列组成的特殊结构，能维持染色体的完整和稳定。端粒酶是由RNA和蛋白质组成的一种特殊逆转录酶，能以自身的RNA为模板合成端粒的DNA片断，补充因细胞分裂造成的端粒序列的丢失。在端粒酶的作用下，可使必死细胞转化成永生细胞。大多数正常细胞端粒酶处于低活性状态，而肿瘤细胞的端粒酶活性较高，故基于调节端粒酶为目的的基因治疗而引起的肿瘤细胞凋亡，为抗肿瘤开辟了新的途径。     

端粒酶与肿瘤关系的研究进展

端粒是染色体末端膨大的粒状结构,由简单重复的端粒DNA序列和结合蛋白组成。人端粒DNA重复序列为TTAGGG,长度5～20kb。端粒长度随着细胞分裂而缩短,当缩短到一定程度即不能维持染色体的稳定,细胞最终死亡。人端粒酶由模板RNA、端粒相关蛋白和人端粒酶逆转录酶（hTERT）构成。人端粒酶以其分子RNA为模板,在hTERT的作用下,不断合成新重复序列添加到染色体DNA的3＇末端,从而阻止端粒DNA序列的缩短。正常人体细胞除一些更新较快的组织细胞如生殖细胞等外,一般无端粒酶活性,而肿瘤细胞由于端粒酶的激活,使端粒维持在一定的长度不再缩短,成为无限增殖的“永生性”细胞。本文就端粒酶与肿瘤关系的研究进展作一综述。     

端粒、端粒酶与胃癌关系研究

胃癌的发生是一个多因素、多基因变化、多步骤的演进过程 ,通常认为是由于细胞癌基因的激活和抑癌基因的失活 ,扰乱了正常细胞的增殖、分化的调控 ,导致细胞增殖过度、分化不足所致。近年来研究发现 ,端粒及端粒酶的表达异常在胃粘膜癌变发生、发展中具有重要作用 ,两者高度相关。1　端粒与端粒酶的结构与功能端粒 (telom ere)是真核细胞染色体末端的一种特殊异质化结构 ,由一简单重复的 DAN及其相关蛋白质组成。不同物种的端粒 DAN序列各异 ,人类染色体端粒平均长度为 (8～1 4 )× 1 0 3bp,其核心序列为 5 - TTAGGG- 3 ,它为染色体末…     

端粒酶在肿瘤疾病中的表达及研究进展

端粒酶是近年来发现的与肿瘤发生发展密切相关的一种逆转录酶 ,已成为肿瘤研究的热点。目前的研究表明[1 ] ,已知 85 %的人肿瘤组织发现了端粒酶活性的表达 ,而与肿瘤相邻的正常组织或良性病变仅为 4%左右 ,这种显著的相关性提示端粒酶在肿瘤细胞恶性状态的形成和发展中起着关键作用。现将端粒、端粒酶与肿瘤发生的机制、端粒酶的检验方法 ,近年来端粒酶在肿瘤疾病中的表达及研究进展以及治疗前景加以综述如下。1　端粒、端粒酶与肿瘤发生的机制端粒是真核细胞染色体末端的特殊结构 ,像二顶帽子盖在染色体两端 ,在染色体复制及保护染色体稳…     

Prospects for anti-neoplastic therapies based on telomere biology

The maintenance of specialized nucleoprotein structures at the ends of human chromosomes called telomeres is essential for chromosome stability, and plays a fundamental role in the regulation of cellular lifespan. Without new synthesis of telomeres, chromosome ends shorten with progressive cell division, eventually triggering either replicative senescence or apoptosis when telomere length becomes critically short. The regulation of telomerase activity in human cells plays a significant role in the development of cancer. Telomerase is tightly repressed in the vast majority of normal human somatic cells but becomes activated during cell immortalization and in cancers. Recent work has demonstrated that inhibiting or targeting telomerase shows promise as a novel anti-neoplastic strategy; however, the biology of telomeres and telomerase predict that such approaches will differ in important ways from traditional cytotoxic drug therapies. Understanding telomerase biology may eventually lead to several types of clinically effective, telomerase-based therapies for neoplastic disease.     

Telomerase - strategies to exploit an important chemotherapeutic target

Telomeres, unique protein-DNA complexes located at the chromosome ends, have important functions involving both DNA protection and cellular signalling. Telomere structure is very dynamic yet tightly controlled. One important factor is the presence of telomerase, a telomere-specific DNA polymerase activated in a majority of cancer cells. Cancer and normal cell telomeres may have dissimilar structures due to variances in telomere length, telomerase activity and levels of telomere binding proteins. In designing compounds to strictly target cancer cells, these distinctions should be investigated. Much of the recent focus has been on the development of highly effective telomerase inhibitors. Another novel group of small molecules target telomere DNA, thereby disrupting both telomerase activity and telomere structure. This class of compounds should have an immediate impact on cell growth and viability. Since many molecular characteristics of telomeres are unknown, small molecules should also be useful in probing differences in telomere dynamics unique to cancer cells.     

The development of telomerase inhibitors: the G-quartet approach

Human telomeres, which consist of repeated TTAGGG sequences, have recently become the focus of intense and highly competitive biological research. This scientific interest lies in their unique biological functions: telomeres are essential for genome integrity and appear to play an important role in cellular aging and cancer. As telomerase appears to be selectively expressed in tumors versus normal cells, this enzyme represents a good target for inhibition. Different types of telomerase inhibitors have recently been described. We will present briefly the different strategies that have been proposed to achieve efficient telomerase inhibition, with a special emphasis on G-quartet ligands.     

Diagnostics, prognostic and therapeutic exploitation of telomeres and telomerase in leukemias

Telomeres are specialized structures at the end of human chromosomes. Telomere length decreases with each cell division, thus, reflecting the mitotic history of somatic cells. Telomerase, the ribonucleoprotein enzyme which maintains telomeres of eukaryotic chromosomes, is up-regulated in the vast majority of human neoplasia but not in normal somatic tissues. In contrast to other somatic cells, normal primitive human hematopoietic cells and some peripheral blood cells expressed low levels of telomerase activity. This activity is thought to play an important role in self-renewal of hematopoietic stem cells. In malignant disorders, telomere lengths are generally shortened and telomerase expression and activity enhanced with high differences in the levels. Although it is necessary to be cautious in interpreting these data, there are indications that telomere length and telomerase expression and activity can serve as a molecular marker of the clinical progression and prognosis of most leukemias. Approaches that directly target telomerase, telomeres or telomerase regulatory mechanisms have been developed. Some of these anti-telomerase strategies in combination with conventional drugs proved to be promising in some types of leukemias.     

Telomerase and its potential for therapeutic intervention

Telomerase and telomeres are attractive targets for anticancer therapy. This is supported by the fact that the majority of human cancers express the enzyme telomerase which is essential to maintain their telomere length and thus, to ensure indefinite cell proliferation--a hallmark of cancer. Tumours have relatively shorter telomeres compared to normal cell types, opening the possibility that human cancers may be considerably more susceptible to killing by agents that inhibit telomere replication than normal cells. Advances in the understanding of the regulation of telomerase activity and the telomere structure, as well as the identification of telomerase and telomere associated binding proteins have opened new avenues for therapeutic intervention. Here, we review telomere and telomerase biology and the various approaches which have been developed to inhibit the telomere/telomerase complex over the past decade. They include inhibitors of the enzyme catalytic subunit and RNA component, agents that target telomeres, telomerase vaccines and drugs targeting binding proteins. The emerging role of telomerase in cancer stem cells and the implications for cancer therapy are also discussed.     

Telomerase inhibitors as anticancer therapy

Telomerase inhibitors have been touted as a novel cancer specific therapy, as most tumor cells have high expression of telomerase, whereas most normal somatic cells express low or undetectable levels of telomerase. Continued proliferation of tumor cells requires activation of telomerase to maintain chromosomal stability and extend life span, because telomerase elongates telomere length and rewinds the cellular mitotic clock. Conversely, shortening of telomeres by inhibition of telomerase activity induces growth arrest (senescence) and apoptosis in tumor cells. Moreover, it has been reported that inhibition of telomerase increases the susceptibility of tumor cells to apoptosis induced by anticancer agents. Thus, telomerase inhibitors could be used as an adjuvant with conventional therapy. However, there are also several potential limitations of telomerase inhibition as a therapeutic strategy. For example, there is a lag phase between telomerase inhibition and telomere shortening, with growth arrest and cell death. In this review, we will discuss the basic biology of telomeres and telomerase as a platform for the development of treatments based upon inhibition of telomerase activity.     

Telomere length modulates human radiation sensitivity in vitro

The molecular basis of the interindividual differences of normal individuals to ionizing radiation is poorly understood. Several studies in telomerase KO mice with short telomeres have uncovered an inverse relationship between telomere length and radiation sensitivity. The present work aims to determine if chromosome radiosensitivity is correlated with telomere length in healthy individuals. With this purpose, individual radiosensitivity was determined by the micronucleus assay in peripheral blood lymphocytes from two groups of individuals of the same age but with highly heterogeneous telomere length, selected from a population of 181 individuals where we previously measured telomere length. Our study demonstrates that telomere length modulates chromosome in vitro radiosensitivity in healthy individuals as the group with short telomeres presented higher frequencies of ionizing radiation-induced micronuclei when compared to the long telomeres group. This result supports the conclusion that individual telomere length acts as biomarker of individual chromosome instability upon exposure to ionizing radiation.