Differential expression of telomerase activity in neuroendocrine lung tumours: correlation with gene product immunophenotyping

Telomerase activity was examined by the telomeric repeat amplification protocol (TRAP) assay in 38 neuroendocrine (NE) lung tumours. A significantly (p = 0.001) different frequency of telomerase positivity was observed among different histological tumour types. Specifically, a positive TRAP signal was observed in 14 of 15 (93%) small cell lung cancers (SCLCs), 7 of 8 (87%) large-cell NE carcinomas (LCNECs), and only 1 of 15 (7%) typical carcinoid tumours. When telomerase activity was correlated with the gene product-based immunophenotypic profile of individual tumours, it was found that the absence of telomerase activity was associated with a lack of bcl-2, p53, and c-kit expression, and characterized by a low proliferation index consistent with the absence of cdk-4 expression and the presence of the cdk inhibitor Rb. Such a phenotype was appreciable in most of the carcinoid tumours. Conversely, telomerase-positive tumours generally showed an immunophenotype consistent with gene product alterations (including high expression of bcl-2, p53, and c-kit, and loss of Rb) and were characterized by a high proliferation index. These telomerase data support the previously reported evidence for two genetically unrelated groups of NE lung tumours (SCLC, and to some extent LCNEC, versus carcinoid tumours) that have distinct phenotypic profiles.     

Telomerase expression shows differences across multiple regions of oligodendroglioma versus high grade astrocytomas but shows correlation with Mib-1 labelling.

AIMS/BACKGROUND: Telomerase is an enzyme that is expressed in most human neoplasms and is associated with tumour immortality. Determination of the point in neoplastic transformation at which telomerase is expressed may aid the understanding of tumour pathogenesis and progression. Despite numerous reports on telomerase, few studies have investigated its expression in high grade glial tumours. These studies, performed on archival banked, single brain tumour specimens, have shown conflicting results for oligodendrogliomas and unexpectedly negative results for telomerase expression in high grade astrocytomas, with one third to one half of glioblastoma multiformes being negative. METHODS: 34 rapidly banked glioma specimens taken from patients undergoing gross total surgical resection of their tumours were studied. Telomerase expression was assessed across 3-8 sampled regions from each tumour by the telomeric repeat amplification protocol (TRAP) assay. Matched mirror image tissue samples were taken for histological analysis of tissue adequacy, statistical correlation of telomerase with tumour histological features, Mib-1 (a marker for cell cycling) labelling, and p53 immunohistochemistry. RESULTS: All five well differentiated oligodendrogliomas were homogeneously telomerase negative and two of three untreated anaplastic oligodendrogliomas were homogeneously positive. In contrast, 10 of 14 high grade astrocytomas showed heterogeneity for telomerase expression across the multiple regions sampled. All glioblastoma multiformes and two of three anaplastic astrocytomas showed at least one region positive for telomerase. When test samples were individually assessed in both oligodendrogliomas and high grade astrocytomas, telomerase expression was associated with Mib-1 labelling (p < 0.001). For the entire group, telomerase expression was associated with grade of tumour, age of patient, and vascular endothelial proliferation (all p < 0.001). CONCLUSIONS: This regional study clarifies that all glioblastoma multiformes are at least focally positive and that telomerase expression correlates with tumour grade in oligodendrogliomas. Homogeneity versus heterogeneity for telomerase expression across multiple regions of oligodendrogliomas versus high grade astrocytomas may provide important preclinical data on the use of antitelomerase agents in these adult glial tumours.     

Telomerase activity in pancreatic endocrine tumours: a potential marker for malignancy.

AIMS: Telomerase activation is known to be a common event in human cancer and may be a useful marker for malignancy. In general, the histological features of pancreatic endocrine tumours cannot be used to determine their malignant potential. The aim of this study was to investigate the role of testing telomerase activity in pancreatic endocrine tumours. METHODS: Prospectively collected fresh frozen tissue specimens from 10 patients with pancreatic endocrine tumours (nine insulinomas, one adrenocorticotrophin producing pancreatic endocrine tumour) were examined by a highly sensitive polymerase chain reaction (PCR) based telomerase repeat protocol (TRAP). RESULTS: Of the 10 pancreatic endocrine tumours, three had telomerase activity. The positive cases included two frankly malignant tumours with liver metastases and one pancreatic endocrine tumour occurring in the setting of multiple endocrine neoplasia type 1. The latter had an infiltrative border. Vascular and perineural tumour infiltration was noted. In the two malignant pancreatic endocrine tumours with liver metastases, telomerase activity was noted in the tumour and the adjacent morphologically non-neoplastic pancreas. CONCLUSION: To our knowledge, this is the first report of the role of telomerase activity in pancreatic endocrine tumours. Telomerase activity might be useful for distinguishing between benign and malignant pancreatic endocrine tumours.     

A non-isotopic method for the detection of telomerase activity in tumour tissues: TRAP-silver staining assay.

Telomerase activity has been observed in a high proportion of specimens from a wide variety of human malignant tumours, but not in non-neoplastic tissues. Measurement of telomerase activity is a possible diagnostic maker for malignant tumours. A non-isotopic telomeric repeat amplification protocol (TRAP) silver staining method for the detection of telomerase activity in human bone tumour tissues is described. The TRAP-silver staining method was quick, safe, and effective, and can be used as a routine diagnostic method for the detection of telomerase activity in bone tumours.     

Chondrosarcoma is not characterized by detectable telomerase activity

Reactivation of telomerase, an enzyme which elongates human telomeres, is associated with cell immortilization. In approximately 90% of malignant tumours telomerase activity can be demonstrated, whereas in benign tumours it is mostly absent. Chondrosarcomas are relatively rare malignant cartilaginous neoplasms. A small number of chondrosarcomas located centrally in bone arise secondarily to an enchondroma, while the majority of chondrosarcomas developing from the surface arise within the cartilage cap of an osteochondroma. The histological distinction between a benign lesion and low-grade chondrosarcoma is generally considered difficult. To investigate whether the progression towards chondrosarcoma is characterized by reactivation of telomerase activity, this study determined telomerase activity in ten enchondromas, five osteochondromas, and 37 chondrosarcomas using the TRAP assay. In all tumour samples except one, telomerase activity was absent. By adding tumour lysates to the positive control, an increasing inhibition of telomerase activity was found with an increasing chondroid matrix, suggesting that it may contain inhibitory factors. Inhibition due to endogenous RNAse or Taq-polymerase inhibitors was excluded. The lack of detectable telomerase activity in the high-grade component of a dedifferentiated chondrosarcoma without matrix favours the possibility that telomerase is truly absent. Either its true absence or inhibitory effects disabling telomerase detection exclude the telomerase TRAP assay as a diagnostic tool in the differential diagnosis of benign and low-grade malignant cartilaginous tumours.     

Evaluation of telomerase in the development and progression of colon cancer

Telomerase activity, a cardinal requirement for immortalization, is a crucial step in the development of cancer and has been studied in many kinds of malignant tumours for clinical diagnostic and/or prognostic utilities. Using a PCR-based TRAP assay, we investigated telomerase activity in 8 adenomatous polyps, 9 dysplastic polyps, and in 36 paired cancer-normal mucosa specimens, one liver and one spleen metastasis from patients resected for sporadic colorectal cancer. Telomerase was absent or very low in normal mucosa and in adenomatous polyps. Dysplastic polyps and adenocarcinoma samples showed telomerase activity, with higher levels in cancer tissues compared to dysplastic lesions. A high telomerase activity was shown to be associated with late-staged cancers and metastasis, providing arguments supporting the role of telomerase not only in the development but also in the progression of colorectal carcinoma. Moreover, telomerase evaluation may help to confirm the malignant transformation in polypoid colorectal lesions with different levels of dysplastic alterations.     

In situ detection of telomerase enzymatic activity in human hepatocellular carcinogenesis

Telomerase enzymatic activity has been detected in most human malignant tumours including hepatocellular carcinoma. In order to assess the cellular source, the topographic distribution, and the chronology of telomerase re-expression during human liver carcinogenesis, an in situ technique derived from the standard TRAP (telomeric repeat amplification protocol) assay was set up that allowed the detection of telomerase enzyme activity at the cellular level on frozen liver tissue sections. In situ TRAP (ISTRAP) was performed on 27 hepatocellular carcinomas (HCCs) and 57 non-tumour livers, including normal liver without HCC, liver samples adjacent to tumour with and without hepatic cirrhosis, and biopsies of chronic hepatitis. In HCC, telomerase was detected in the nuclei of liver tumour cells in 23/27 cases (85%), with a heterogeneous distribution within the tumour. This signal was also detected in clusters of hepatocytes in 16/26 (61%) samples of liver adjacent to HCC, in 10/23 (43%) cases of chronic viral hepatitis without adjacent HCC, and in scattered nuclei of 2/8 histologically normal livers. Comparison of the results obtained with ISTRAP and standard TRAP assays on tissue extracts suggests a gain in sensitivity with the in situ technique. This study confirms that telomerase is expressed in most HCCs and suggests that focal telomerase reactivation is an early event during human liver carcinogenesis. ISTRAP is a sensitive technique that allows the study of telomerase expression in the morphological context.     

Quantitative detection of telomerase activity by real-time TRAP assay in the body fluids of cancer patients

Real-time TRAP assay was developed to improve the sensitivity and quantitative detection of telomerase activity in the body fluids of cancer patients. The sensitivity and clinical significance of the real-time TRAP assay was investigated. Real-time PCR protocol was modified by using ACX primer and SYBR green mixture from the process of TS primer extension. Real-time TRAP showed high correlation (r2=0.843, p=0.001) and sensitivity (25 times higher) compared to conventional TRAP. Of 164 samples, there were 8 positives in cytology (4.9%), 7 (4.3%) using the conventional TRAP, and 41 (25%) using real-time TRAP. In cytology positive samples, real-time TRAP showed a higher positivity than conventional TRAP (75% vs 63%) suggesting a higher sensitivity in the body fluids. There was a tendency towards a longer progression-free duration in telomerase negative patients than in positive patients, as determined by conventional and real-time TRAP. The diagnostic interval between the first positivity documentation and clinical progression was short in the order of real-time TRAP, conventional TRAP and cytology. In conclusion, real-time TRAP assay can detect telomerase activity at an earlier phase of cancer progression and can replace conventional TRAP assay for detecting the telomerase activity in body fluids.     

Comparison of the telomeric repeat amplification protocol (TRAP) to the new TRAP-eze telomerase detection kit

The ribonucleoprotein, telomerase, is believed to be responsible for the maintenance of telomere length in immortal and cancer cells. A PCR-based assay for the detection of telomerase activity (TRAP assay: telomeric repeat amplification protocol) was developed, allowing fast and efficient detection of telomerase activity when sample amounts are limiting. Of the thousands of primary human tumors examined using the TRAP assay, almost 90% have been shown to exhibit telomerase activity. Thus, for the early detection of cancer and for the rapid screening of compounds and drugs in cancer therapeutics, methods for the detection of telomerase activity are rapidly emerging. The recently developed TRAP-eze^TM kit from Oncor, Inc. gives increased sensitivity with decrease sample processing time, allowing improved detection of telomerase activity in a large number of samples. In the present study, we have addressed some of the technical aspects and limitations of critical importance for reproducibility, reliability, and linearity of the standard TRAP assay and the TRAP-eze^TM kit using cell culture and clinical materials.Abbreviations RP modified reverse primer (CX) for PCR amplification of telomerase products - AEBSF 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride - CHAPS 3-[(3-cholamidopropyl)dimethylammoniol-1-propanesulfonate - CX reverse primer for PCR amplification of telomerase products for standard TRAP - DEPC diethyl pyrocabonate - EGTA ethylene glycol-bis(-aminoethyl ether)-N,N,N',N'-tetraacetic acid - HPLC high pressure liquid chromatography - ITAS internal telomerase assay standard - PCR polymerase chain reaction - T4g32 protein T4 gene 32 protein - TRAP telomeric repeat amplification protocol - TRF terminal restriction fragment - TS primer that serves as a substrate for telomerase     

Telomerase activity and in situ telomerase RNA expression in malignant and non-malignant lymph nodes.

AIMS/BACKGROUND: Telomerase, an enzyme associated with cellular immortality, is expressed by most malignant tumours, but is inactive in normal somatic cells except for male germ cells and proliferating stem cells. Thus, the measurement of telomerase activity in tissue samples may provide useful diagnostic and prognostic information. The aim of this study was to determine whether telomerase expression is useful for the detection of occult malignant cells in lymph nodes. METHODS: Telomerase activity was compared with histological findings in 123 surgically removed lymph nodes submitted for routine or frozen section diagnosis. Telomerase activity was measured using a modified, semi-quantitative PCR-based telomeric repeat amplification protocol (TRAP). The assay was adapted for single 5 microns OCT embedded cryostat sections. In either fresh tissues or cryostat sections, normalised activity was linear when compared with protein concentration. Furthermore, using an in situ hybridisation method, the human telomerase RNA (hTR) component was measured in a subset of negative and positive nodes. RESULTS: Most (96%) of the 97 histologically negative nodes expressed low levels of activity (mean value of positive samples = 3.0 units/microgram protein) which may be derived from activated lymphocytes that express telomerase activity. All 26 malignant nodes (17 metastases, nine lymphomas) expressed telomerase (mean value = 17.8 units/microgram protein). The rank order levels between the two groups differed significantly (p = 0.0002). In situ results showed clearly that the hTR was expressed relatively highly in metastatic cancer cells and at lower levels in germinal centres of secondary follicles. CONCLUSIONS: Although expression of telomerase by activated lymphocytes may limit its usefulness, measurement of enzyme activity combined with detection of hTR using in situ hybridisation may assist in the histopathological diagnosis of lymph nodes.     

Real-time quantitative analysis of telomerase activity in breast tumor specimens using a highly specific and sensitive fluorescent-based assay.

Telomerase activity has been associated with almost 90% of malignant human cancers from a variety of tissue sources, making it one of the most prominent molecular cancer markers known to date. As such, telomerase has become a very attractive diagnostic and therapeutic target. The advent of the telomeric repeat amplification protocol (TRAP) has allowed for the semiquantitative detection of telomerase from limiting sample amounts. Both the standard TRAP assay and a real-time assay using Amplifluor technology with primers designed specifically for telomerase activity amplification were used to quantitatively assess telomerase activity in primary tumors and tumor-derived cell lines. We have adapted the recently developed TRAPeze XL telomerase detection kit (Intergen, Gaithersburg, MD) for use with real-time polymerase chain reaction for more accurate quantification and high-throughput capabilities. In doing so, the reliability, assay time, and accuracy of quantitation have all been dramatically improved. A comparison of the quantitative analysis for the standard TRAP assay versus the real-time assay using 19 breast tumors revealed telomerase quantitation and standardization using the real-time assay was superior to the standard assay. Our data suggest that this assay will be useful for clinical and research studies involving detection of telomerase activity as it relates to cancer diagnosis.     

Equine telomeres and telomerase in cellular immortalisation and ageing

To determine the role of telomeres in cellular ageing in equids, we analysed telomere lengths in peripheral blood derived DNA samples from a panel of donkeys (Equus asinus) ranging from 2 to 30 years of age. The average telomere lengths ranged from 7 to 21 kbp and a statistically significant inverse correlation between telomere lengths and donor age was demonstrated. Similarly, telomere lengths in primary fibroblasts isolated from a horse (Equus equus) demonstrated telomeric loss with in vitro ageing when cultured to senescence. We extended this study to evaluate activity of the enzyme telomerase in various equine cell cultures, normal equine tissues and equine benign tumour samples. Initially a panel of equine immortalised and primary cell cultures were evaluated for telomerase activity using a standard telomere repeat amplification protocol (TRAP) assay. High levels of telomerase activity were detected in equine immortalised cells with no activity evident in primary cell cultures. Similarly, no telomerase activity could be detected in normal equine tissues or equine benign tumour samples of the sarcoid or papilloma type. We conclude that telomere attrition may contribute to ageing in equids. However, it would appear that telomerase does not play a major role in the development of the most common benign tumours of the horse.     

Telomerase activity and telomere length in thyroid neoplasia: biological and clinical implications

Despite several recent studies, the biological status and clinical relevance of telomerase expression in tumours derived from the thyroid follicular cell remain controversial. This study has analysed a series of normal, benign, and malignant thyroid samples using two novel approaches: the use of purified epithelial cell fractions to eliminate false-positives due to telomerase-positive infiltrating lymphocytes; and the simultaneous measurement of telomere length to provide a clearer interpretation of telomere dynamics in thyroid neoplasia. The data obtained support the prediction that the epithelial component of non-neoplastic thyroid and of follicular adenomas is telomerase-negative, any positive results being explicable by lymphocyte infiltration. In contrast, many malignant tumours, both follicular and papillary, were telomerase-positive. However, serial dilution of extracts indicated a wide spectrum of activity in these cancers, possibly related to variation in the proportion of telomerase-positive cells. Furthermore, an unexpectedly high proportion were telomerase-negative, a finding which was not explicable by technical problems such as TRAP (telomeric repeat amplification protocol) assay sensitivity. Many of these apparently telomerase-negative tumours had abnormally long telomeres. Correlation of telomerase and telomere length data suggests that thyroid cancers fall into three biological groups: telomerase-positive lesions, consistent with the conventional model of telomere erosion followed by telomerase reactivation; telomerase-negative tumours, which maintain telomere length by a mechanism independent of telomerase; and telomerase-negative tumours which are still undergoing telomere erosion and may therefore be composed of mortal cancer cells. From a clinical standpoint, it is concluded that telomerase detection on unfractionated tissue, such as fine needle aspirates, is of no value as a marker of malignancy in follicular lesions, due to both low sensitivity and specificity.     

Detection of telomerase activity in cultured cells and tumor tissue of lung carcinoma by modified telomeric repeat amplification protocol

Telomerase activity is found in various cell types including stem cells, neoplastic cells, and immortalized cells, suggesting a close association with their proliferation capacity. The telomeric repeat amplification protocol (TRAP) has been traditionally used to detect semi‐quantitatively the telomerase activity by polyacrylamide gel electrophoresis (PAGE), which is difficult to apply for large scale analysis because of laborious post‐PCR manipulation and potential carryover contamination. In the present study, a specific reverse primer was designed and the TRAP protocol was adapted to either PAGE or real‐time PCR assay. Using cultured cell lines, the real‐time TRAP showed a dramatic improvement in the reliability and accuracy of quantitation of telomerase activity and was able to discriminate the A549 cells from hundreds‐fold human embryonic lung cells. Using clinical samples of 60 lung cancers and 8 inflammatory lesions, the real‐time TRAP was also superior in quantitation, high‐throughput capability and standardization. Our modified real‐time TRAP should be applicable for the detection of telomerase activity for the initial screening and progression monitoring of lung cancer patients. Our approach is particularly useful when only limited clinical specimen is available, such as fine needle aspiration or other cytological specimens that may contain only a small number of tumor cells.     

人骨髓间质干细胞中的端粒调控机制

目的：〖HT5"SS〗研究人骨髓来源间充质干细胞(MSCs)端粒长度的调控机制。方法：以贴壁培养法从人骨髓中分离MSCs并用MSCs及造血干细胞相关表面抗体作表型鉴定,用Southern blotting检测MSCs的端粒长度;应用免疫荧光染色技术检测端粒重复序列结合因子1（TRF1）和早幼粒细胞白血病蛋白小体（PML）的定位;以端粒重复序列扩增法（TRAP）和/或Western blotting法检测传代及分化成脂肪细胞的MSCs和经同步化处理被阻断在S期的MSCs的端粒酶表达。结果：与端粒酶阴性ALT细胞株WI-38-2RA细胞相比,MSCs的端粒长度较短并且端粒长度变异度不大;端粒调控相关蛋白TRF1和PML在MSCs中的定位则与端粒酶阳性细胞HeLa细胞相同,两者呈非共定位,而在端粒酶阴性WI-38-2RA细胞中两者呈共定位状态。MSCs中不存在有染色体外端粒重复序列DNA（ECTR DNA）。TRAP法检测传代培养的MSCs端粒酶呈阴性表达,但分化成脂肪的MSCs端粒酶呈阳性表达。Western blotting 检测同步化处理前MSCs端粒酶呈微弱表达,经同步化处理被阻断在S期时,MSCs的端粒酶表达明显增高,并且与S期的细胞比例呈正相关。结论：MSCs中不存在ALT相关的早幼粒细胞白血病蛋白小体(APBs)、染色体外端粒重复序列DNA(ECTR DNA)和端粒长度较长、端粒长度变异度大等ALT机制相关分子特征;非同步化在S期处理的MSCs,端粒酶呈微弱表达,但诱导向脂肪细胞分化或处在S期时,MSCs的端粒酶表达明显增高,并且与S期的细胞比例呈正相关。本研究提示MSCs是通过端粒酶机制而不是端粒延长旁路途径（ALT）机制调控其端粒末端。     

Detection of telomerase expression in fine-needle aspirations and fluids

The cytologic examination of fine-needle aspirates and fluid specimens is plagued by a persistent false negative rate. The rate of false negative results will be decreased if sensitive molecular assays can be developed to detect cytologically malignant cells. The current study investigated telomerase expression as a potential marker of malignancy, using the telomeric repeat amplification protocol (TRAP) in fine-needle aspirates and fluid specimens. TRAP was performed on 24 fine-needle aspirate and 24 fluid specimens from different body sites and of different histological diagnoses. We found that 6 of 12 fine-needle aspirate specimens that were cytologically positive for malignant cells expressed telomerase activity, while no specimens that were cytologically suspicious for malignancy, atypical, or negative tested positive for telomerase activity. Of the fluid specimens, 4 of 6 cytologically positive cases and 1 of 18 cytologically negative cases expressed telomerase. Seven of eight telomerase negative, cytologically positive specimens contained only rare malignant cells in a very bloody background. Peripheral blood contamination is a possible pitfall in the TRAP assay, as applied in the current study, because the assay is standardized to protein concentration that may be derived from lysed red blood cells. We conclude that with further technical refinement, the TRAP assay could become a useful adjunct in the cytologic examination of fine-needle aspirates and fluid samples. Diagn. Cytopathol. 1998;18:431–436. © 1998 Wiley-Liss, Inc.