泌尿系肿瘤端粒酶研究现状及应用前景

近年来，对肿瘤端粒及端粒酶的研究表明其在肿瘤发生发展起着重要作用［１］。肿瘤细胞端粒酶活性检测及活性抑制具有潜在的诊治应用前景。一、端粒与端粒酶的结构与功能端粒是真核细胞染色体末端的特殊结构，是由端粒ＤＮＡ和与端粒ＤＮＡ特异结合的端粒结合蛋白组成的核...     

端粒酶与骨质疏松

端粒、端粒酶是当今生物学、医学研究的热点之一，端粒是一种封闭了真核染色体末端的脱氧核糖核酸。它与端粒结合蛋白结合在一起，对染色体起到了保护的作用。端粒酶是一种特异的染色体末端转移酶，它的存在解决了染色体末端复制引缩问题。为了探讨端粒酶与骨质疏松之间的关系，笔者通过检索有关端粒、端粒酶的结构、功能及活性与骨质疏松的相关文献并进行综述。文章阐明了端粒酶激活机制在骨质疏松的发生发展中起着重要作用，而利用分子生物学技术改变端粒酶尤其是hTERT的基因表达水平，将在防治骨质疏松方面具有广泛的应用前景及实际意义。     

端粒、端粒酶及其与泌尿系肿瘤相关性研究进展

端粒(telomere)是位于染色体末端的碱基片段,呈帽状在染色体两端从而阻止染色体之间融合,防止细胞畸变。端粒酶(telomerase)能以内源性RNA(核糖核酸)为模板合成端粒序列片段。因而端粒的长短及端粒酶的活性与肿瘤细胞增殖有关。本文就端粒及端粒酶与泌尿系肿瘤中的应用进展进行综述。     

端粒及端粒酶在膀胱癌中的研究进展

端粒是位于染色体末端的DNA片段 ,具有稳定染色体结构的功能 ,它随细胞的增殖而缩短。端粒酶是重新合成端粒DNA片段的一种核糖核酸蛋白酶 ,其活化可维持端粒的长度和功能 ,使细胞永生化或成为癌细胞。本文在对端粒和端粒酶认识的基础上综述了膀胱癌、癌旁组织中端粒酶活性的研究和脱落细胞中端粒酶活性表达在膀胱癌诊断中的研究进展以及膀胱癌的抗端粒酶治疗。     

端粒酶和端粒酶逆转录酶与男性生殖

端粒(Telomer)和端粒酶(Telomerase)是近几年来生命科学研究中的热点之一。绝大多数生物细胞DNA的端粒随着细胞分裂而缩短，当缩短到一定长度，即达到一危机点时，细胞不再分裂而衰老、死亡。少数细胞逃逸危机点，激活端粒酶，从而永生化或恶变。目前普遍认为，绝大部分正常人体细胞中没有端粒酶活性，而在90％的恶性肿瘤细胞、生殖细胞和干细胞中端粒酶却特异性的表达，其中端粒酶在生殖细胞中的活性被认为是在生理状态下合理存在的。端粒酶与男性生殖细胞的相关性成为人们关注的方向，现就端粒酶的结构功能以及与男性生殖关系的研究现状作一综述。     

端粒及端粒酶在膀胱癌中的研究进展

端粒是位于染色体末端的DNA片段，具有稳定染色体结构的功能，它随细胞的增殖而缩短。端粒酶是重新合成端粒DNA片段的一种核糖核酸蛋白酶，其活化可维持端粒的长度和功能，使细胞永生化或成为癌细胞。本文在对端粒和端粒酶认识的基础上综述了膀胱癌、癌旁组织中端粒酶活性的研究和脱落细胞中端粒酶活性表达在膀胱癌诊断中的研究进展以及膀胱癌的抗端粒酶治疗。     

端粒和端粒酶与永生化软骨细胞

关节软骨细胞凋亡与增殖在正常情况下处于动态平衡,维持着关节软骨的细胞数量及其形态和功能的稳定.软骨细胞凋亡过盛可能是关节软骨退变发展成骨关节炎的重要原因之一.关节软骨细胞凋亡主要与细胞的端粒长短和端粒酶活性密切相关,细胞的"末端复制问题"使端粒不可避免地随着复制逐渐缩短,端粒缩短达到临界长度时细胞将无法进行分裂而凋亡.端粒酶的逆转录反应弥补细胞分裂过程的端粒丢失,实现细胞永生化.有效地调控软骨细胞端粒长短、端粒酶的活性,抑制关节软骨细胞过度凋亡,意味着部分软骨细胞功能得以保护,延缓或减轻关节软骨的退变,促进软骨修复,从而缓解症状,改善关节功能,可能为骨关节炎的防治开辟一条新途径.     

端粒,端粒酶与膀胱癌的研究进展

端粒随细胞的增殖缩短,端粒酶的激活可维持端粒的长度和功能,肿瘤细胞中有端粒酶的表达,并在不同肿瘤,不同期级有不同程度的表达。本文在对端粒和端粒酶认识的基础上综述了膀胱癌中端粒长度的变化端粒酶活性表达的研究进展,以及脱落细胞端粒酶活性表达在膀胱癌诊断中应用的进展。     

大便脱落细胞端粒酶活性与结直肠癌的早期诊断的临床应用前景

端粒酶（telomerase）是一种逆转录酶，它以自身RNA为模板，逆转录合成端粒DNA，可以避免因DNA复制时端粒缩短所致的细胞衰亡，使细胞获得无限增殖的能力。大多数恶性肿瘤中可检测到端粒酶的活性，而正常体细胞不表达或微弱表达端粒酶活性，可知端粒酶激活是肿瘤形成的重要机制之一^[1]。     

端粒、端粒酶与膀胱癌的研究进展

端粒随细胞的增殖缩短，端粒酶的激活可维持端粒的长度和功能，肿瘤细胞中有端粒酶的表达，并在不同肿瘤、不同期级有不同程度的表达，本文在对端粒和端粒酶认识的基础上综述了膀胱癌中端粒长度的变化端粒酶活性表达的研究进展，以及脱落细胞端粒酶活性表达在膀胱癌诊断中应用的进展     

端粒酶活性和端粒长度在大肠癌组织中的表达及其意义

目的　探讨端粒长度及端粒酶活性在大肠癌发生发展中作用。方法　采用Southernblot及端粒重复扩增 (TRAP)法检测端粒长度和端粒酶活性水平。结果　大肠癌端粒酶活性明显高于癌旁组织及正常大肠黏膜组织 ;大肠癌组织端粒长度较癌旁组织及正常大肠黏膜明显缩短 ,且随大肠癌Dukes分期的进展进一步缩短。结论　端粒的短缩和端粒酶的激活可能对大肠癌的发生发展起重要作用.     

乳腺癌端粒长度与端粒酶活性变化的相关性研究

目的　检测乳腺癌及其癌旁组织中的端粒 (TLM )长度、端粒酶 (TLMA )活性的表达 ,探讨乳腺癌端粒长度与端粒酶活性的关系。方法　采用端粒酶重复扩增实验 (TRAP) 银染法检测端粒酶活性 ,以地高辛标记的Southern杂交的方法检测端粒长度。结果　端粒酶活性在乳腺癌TNM分期的进展中由Ⅰ期的 5 9.1%增高到Ⅳ期的 92 .9% ,而端粒长度在乳腺癌TNM分期的进展中不断缩短 ,由Ⅰ期的 (7.5 4± 0 .95 )kb缩短到Ⅳ期的 (5 .0 3± 0 .5 3 )kb。恶性乳腺肿瘤癌旁组织中的平均端粒长度皆位于正常水平。乳腺癌中端粒酶阳性表达组的端粒长度为 (4 .45± 1.3 9)kb显著短于端粒酶阴性组的 (5 .70± 1.2 3 )kb。结论　恶性乳腺肿瘤将端粒酶激活并没有绝对延长其染色体末端的端粒长度 ,而且 ,随着肿瘤的发展端粒片段还会缩短 ,并与端粒酶活性似乎存在着反向的关系。     

Antitumor effects of telomerase inhibitor TMPyP4 in osteosarcoma cell lines

Telomere studies in carcinomas have been extensively reported for prognostic utility and effective methods for targeting telomerase therapy has been described, but efficacy of telomerase inhibitor remained unknown in sarcoma cells. In this study, we investigated the effects of telomerase inhibitor cationic porphyrin TMPyP4 on telomerase activity, telomere length, cell growth, and apoptosis in osteosarcoma cell lines. TMPyP4 significantly inhibited telomerase activity in telomerase positive HOS and Saos‐2, but not in MG‐63. TMPyP4 significantly induced telomere shortening, and inhibition of the cell growth in HOS and Saos‐2 with over 17% apoptosis rates. In terms of MG‐63, TMPyP4 did not induce inhibition of both telomerase activity and cell growth, although it induced significant telomere shortening. Telomere length after treatment was 5.60 kb in HOS, 4.00 kb in Saos‐2, and 9.89 kb in MG‐63. These results may suggest that both telomerase activity loss and sufficient telomere shortening are necessary to inhibit cell growth in telomerase positive osteosarcoma cells. TMPyP4 did not induced telomere shortening but significantly inhibited the growth with 22.6% apoptosis rate in telomerase negative with extremely longer telomere‐U2OS, may indicating the antitumor effect of TMPyP4 may be related to DNA damage including telomere dysfunction through G‐quadruplex stabilization, independent on telomere length. © 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:1707–1711, 2011     

Telomere Length in Peripheral Blood Mononuclear Cells of Patients on Chronic Hemodialysis Is Related With Telomerase Activity and Treatment Duration

Telomere shortening to a critical limit is associated with replicative senescence. This process is prevented by the enzyme telomerase. Oxidative stress and chronic inflammation are factors accelerating telomere loss. Chronic hemodialysis, typically accompanied by oxidative stress and inflammation, may be also associated with replicative senescence. To test this hypothesis, we determined telomere length and telomerase activity in peripheral blood mononuclear cells (PBMCs) in a cross‐sectional study. Hemodialysis patients at the University Hospital Larissa and healthy controls were studied. Telomere length was determined by the TeloTAGGG Telomere Length Assay and telomerase activity by Telomerase PCR‐ELISA (Roche Diagnostics GmbH, Mannheim, Germany). We enrolled 43 hemodialysis patients (17 females; age 65.0 ± 12.7 years) and 23 controls (six females; age 62.1 ± 15.7 years). Between the two groups, there was no difference in telomere length (6.95 ± 3.25 vs. 7.31 ± 1.96 kb; P = 0.244) or in telomerase activity (1.82 ± 2.91 vs. 2.71 ± 3.0; P = 0.085). Telomere length correlated inversely with vintage of hemodialysis (r = ?0.332, P = 0.030). In hemodialysis patients, positive telomerase activity correlated with telomere length (r = 0.443, P = 0.030). Only age, and neither telomere length nor telomerase activity, was an independent survival predictor (hazard ratio 1.116, 95% confidence interval 1.009–1.234, P = 0.033). In this study, telomere length and telomerase activity in PBMCs are not altered in hemodialysis patients compared with healthy controls. Long duration of hemodialysis treatment is associated with telomere shortening and positive telomerase activity with an increased telomere length in PBMCs of hemodialysis patients. The underlying mechanism and clinical implications of our findings require further investigation.     

Telomere biology in neuroblastoma: telomere binding proteins and alternative strengthening of telomeres

Purpose

Neuroblastoma (NBL) shows remarkable biologic heterogeneity, resulting in favorable or unfavorable prognoses. Previously, we reported that most unfavorable NBLs express high telomerase activity to maintain telomere length. Recently, telomere binding proteins (TBPs) and alternative lengthening of telomeres (ALTs) have been identified as key factors of telomere maintenance.

Methods

To evaluate the correlation between telomerase activity, telomere length, and the expression levels of TBPs in NBL, we analyzed and quantified these factors in 121 untreated NBLs.

Results

Shortened and elongated telomeres were detected in 21 (17.3%) and 11 cases (9.0%), respectively, and there was a significant correlation between telomere length and the length of the 3′-overhang. The tumors with shortened or elongated telomeres showed significant lower expression of TBPs, except for RAP1. Although telomerase activity did not correlate with telomere length, 16 of 22 cases with high telomerase activity and 5 of 9 cases (ALT tumors) that showed long telomeres without high telomerase activity resulted in death. High-dose chemotherapy did not have much effect on these deceased ALT cases, but their survival periods were more than 2 years and relatively long compared with the deceased cases with nonelongated telomeres, suggesting that chemoresistance in ALT tumors may be related to slow growth rates.

Conclusions

High telomerase activity is a poor prognostic factor in NBL. In the cases without high telomerase activity, those with elongated telomere also showed poor outcomes because of chemoresistance. Therefore, ALT and TBPs may be biomarkers for chemosensitivity in NBL. Thus, a better understanding of telomere biology may help define the characteristics of individual NBLs.     

Telomerase Activity in Giant Cell Tumors of Bone

Background A giant cell tumor of bone (GCT) is a histologically benign neoplasma that has an unpredictable pattern of biological aggressiveness. In the present study, we investigated whether there was a correlation between telomere length or the levels of telomerase activity and other clinical features of GCTs, for the possible use of these factors as parameters of aggressiveness or prognosis. Methods In 16 surgically resected GCTs specimens, telomere length was assessed by terminal restriction fragments by Southern blot analysis. Telomerase activity was measured by a semiquantitative polymerase chain reaction–based telomeric repeat amplification protocol assay. Results Telomere length reduction was observed in 69% of the GCT samples. The telomere lengths of tumors were significantly shorter than those of normal tissue (P = .008). The mean telomere length of grade 3 tumors was significantly shorter than those of grade 1 and 2 tumors (P = .038). Telomerase activity was detected in 81% of tumor samples. The level of telomerase activity in tumors with local recurrence was significantly higher than in tumors without local recurrence (P = .011). Conclusions These results suggest that telomere length correlates with roentgenographic grade as a result of the frequency of cell division, and high telomerase activity indicates the aggressiveness of GCTs.     

Detection of telomerase activity in breast masses by fine-needle aspiration

Background: Telomerase is an RNA-dependent DNA polymerase that compensates for the telomere shortening that occurs in its absence. Reactivation of telomerase is thought to be an important step in cellular immortalization, and recent studies have indicated that telomerase activity is often detected in primary human malignancies. The clinical implications of telomerase activity in human tumors are currently under investigation. Methods: Eighty-nine samples (46 FNAs and 43 gross tissue biopsies) from 44 patients with breast masses were analyzed prospectively for the presence of telomerase activity by a modification of the telomere repeat amplification protocol (TRAP). All samples were obtained directly from the excised mass at the time of specimen removal in the operating room. Results: Telomerase activity was detected in 17 of 19 (90%) FNA samples and 15 of 18 (83%) invasive breast cancer tissue biopsies. Telomerase was also detected in 9 of 16 (56%) FNAs and 8 of 15 (53%) tissue biopsies from 16 fibroadenomas. Other benign proliferative lesions (n=5) did not have detectable telomerase activity in either FNA or tissue specimens. FNA-TRAP results correlated with the gross tissue specimen TRAP results in 95% of all cases. Conclusion: The FNA-TRAP assay for telomerase detection is a highly sensitive and accurate method for the detection of telomerase activity in breast masses. Future application of these techniques should facilitate evaluation of telomerase as a tumor marker in the clinical management of breast and other solid malignancies. These authors contributed equally to this work.     

Telomerase activity in skeletal sarcomas

Background: Telomerase is a ribonucleoprotein that adds TTAGGG nucleotide repeats onto the ends of eukaryotic chromosomes to maintain telomere integrity. Somatic cells do not express telomerase and stop dividing when the chromosomal ends are shortened critically after many cell divisions. Immortal cell lines and cancer cells apparently have telomerase activity that contributes to an unlimited number of cell cycles. The purpose of our study is to investigate whether telomerase activity is expressed in primary malignant tumors of the skeletal system when compared to adjacent normal tissue. Methods: Fresh tumor and normal tissue was collected from 14 patients (10 males, 4 females; age range, 8 to 76 years) and protein extraction performed. The tumors included seven osteosarcomas (three examined before and after chemotherapy), two chondrosarcomas, two spindle cell tumors, one hemangiopericytoma, one chordoma, and one adamantinoma. Telomerase activity was analyzed by using a highly sensitive polymerase chain reaction (PCR)-based assay (telomere repeat amplification protocol [TRAP]). Results: Telomerase activity was found in 8 of 14 sarcoma patients (57%) using the TRAP assay. Compared to HeLa cell extract (positive control), telomerase activity in the tumor specimen ranged from 0 (in osteosarcoma) to 11.7% (in hemangiopericytoma). There was variation in the number of telomeric repeats generated by telomerase. At least five telomeric bands (e.g. 50, 56, 62, 68, 74 bp) in a ladder pattern had to be present before telomerase activity was considered positive in our analysis. Conclusions: Telomerase activity may be an oncogenic sustaining event helping to maintain the transformed phenotype seen in malignant tumors of the bone. The degree of telomerase activity varies among skeletal malignancies, but was less than that observed in HeLa cells. The majority of osteosarcomas showed no telomerase activity.     

Clinical usefulness of telomerase activation and telomere length in head and neck cancer

BACKGROUND: Telomere shortening at every replication cycle is postulated to limit the life span of human somatic cells. In contrast, activation of telomerase is proposed to be an essential step for cancer cell immortalization. Head and neck cancer is the most common malignancy in the Indian population compared with Western countries. However, there are very few reports on telomerase activity and telomere length in head and neck cancer. METHODS: Telomerase activation and telomere length alterations were studied in tumor and adjacent normal tissues in 110 patients with head and neck cancer and 40 patients with precancerous/benign conditions. Telomerase activity and telomere lengths were determined by Telomeric Repeat Amplification Protocol (TRAP assay) and Southern blot analysis, respectively. RESULTS: Telomerase activation was observed in 78.2% of the malignant tissues, 85% of the precancerous tissues, and 53.1% of the adjacent normal tissues. Peak terminal restriction fragment length (TRF) was observed to be significantly lower in malignant tissues compared with the adjacent normal tissues. No significant correlation could be observed between telomerase activation and clinicopathologic characteristics of the patients. Two-year disease-free survival analysis showed that patients showing telomerase activation in the adjacent normal tissues and patients showing higher telomere length in malignant tissues had poor disease-free survival. CONCLUSIONS: Our results demonstrate the significant clinical usefulness of telomerase activation and telomere length for head and neck cancer patients. These markers may be helpful in predicting the clinical course of the disease and thus in identifying the patients in need of a close follow-up and vigorous adjuvant treatment.