Telomerase activity and its clinicopathological significance in gastric cancer

Clinical Significance of Lymph Node Micrometastasis in pN0 Gastric Cancer Patients

Purpose

To investigate the relationship between lymph node micrometastasis (LNMM) and clinicopathological factors and to evaluate the prognostic effects of LNMM in pN0 gastric cancer (GC) patients.

Methods

One hundred and seventy-two GC patients who received radical gastrectomy with D2 lymph node dissection were enrolled in the present study. 1371 negative lymph nodes from level 2 station confirmed by pathology were examined. The LNMM was diagnosed by telomeric repeat amplification protocol/enzyme-linked immunosorbent assay (TRAP-ELISA). The relationship between clinicopathological factors and LNMM was investigated by multivariate analysis. Survival analysis was performed to evaluate the effects of LNMM on prognosis.

Results

LNMM was detected in 423 lymph nodes from 72 patients. The results showed that invasion depth (OR = 3.755, P = 0.004), TNM staging (OR = 3.152, P = 0.002), lymphatic invasion (OR = 2.178, P = 0.009), and tumor differentiation (OR = 1.266, P = 0.013) were independent risk factors associated with LNMM. Survival analysis showed that patients with LNMM had significantly worse 5-year survival compared with those without LNMM (42% vs. 76.4%, P < 0.05). Multivariate analysis demonstrated that LNMM, tumor size, Lauren type, invasion depth, and lymphatic invasion (P < 0.05) were independently factors associated with 5-year survival.

Conclusions

The findings showed that tumor invasion depth, TNM staging, lymphatic invasion, and tumor differentiation were independent risk factors associated with LNMM occurrence. Moreover, LNMM is a clinically negative prognostic factor in pN0 GC patients.

Mechanisms of human telomerase reverse transcriptase (hTERT) regulation: clinical impacts in cancer

Background

Limitless self-renewal is one of the hallmarks of cancer and is attained by telomere maintenance, essentially through telomerase (hTERT) activation. Transcriptional regulation of hTERT is believed to play a major role in telomerase activation in human cancers.

Main body

The dominant interest in telomerase results from its role in cancer. The role of telomeres and telomere maintenance mechanisms is well established as a major driving force in generating chromosomal and genomic instability. Cancer cells have acquired the ability to overcome their fate of senescence via telomere length maintenance mechanisms, mainly by telomerase activation.

hTERT expression is up-regulated in tumors via multiple genetic and epigenetic mechanisms including hTERT amplifications, hTERT structural variants, hTERT promoter mutations and epigenetic modifications through hTERT promoter methylation. Genetic (hTERT promoter mutations) and epigenetic (hTERT promoter methylation and miRNAs) events were shown to have clinical implications in cancers that depend on hTERT activation. Knowing that telomeres are crucial for cellular self-renewal, the mechanisms responsible for telomere maintenance have a crucial role in cancer diseases and might be important oncological biomarkers. Thus, rather than quantifying TERT expression and its correlation with telomerase activation, the discovery and the assessment of the mechanisms responsible for TERT upregulation offers important information that may be used for diagnosis, prognosis, and treatment monitoring in oncology. Furthermore, a better understanding of these mechanisms may promote their translation into effective targeted cancer therapies.

Conclusion

Herein, we reviewed the underlying mechanisms of hTERT regulation, their role in oncogenesis, and the potential clinical applications in telomerase-dependent cancers.

Design and development of PCR-free highly sensitive electrochemical assay for detection of telomerase activity using Nano-based (liposomal) signal amplification platform

Telomerase, which has been detected in almost all kinds of cancer tissues, is considered as an important tumor marker for early cancer diagnostics. In the present study, an electrochemical method based on liposomal signal amplification platform is proposed for simple, PCR-free, and highly sensitive detection of human telomerase activity, extracted from A549 cells. In this strategy, telomerase reaction products, which immobilized on streptavidin-coated microplate, hybridized with biotinylated capture probes. Then, dopamine-loaded biotinylated liposomes are attached through streptavidin to biotinylated capture probes. Finally, liposomes are ruptured by methanol and the released-dopamine is subsequently measured using differential pulse voltammetry technique by multi-walled carbon nanotubes modified glassy carbon electrode. Using this strategy, the telomerase activity extracted from 10 cultured cancer cells could be detected. Therefore, this approach affords high sensitivity for telomerase activity detection and it can be regarded as an alternative to telomeric repeat amplification protocol assay, having the advantages of simplicity and less assay time.

Prognostic role of telomerase activity in gastric adenocarcinoma: A meta-analysis

Activation of telomerase is involved in carcinogenesis in most types of cancers. However, the prognostic value of telomerase activity (TA) in patients with gastric carcinoma (GC) remains controversial. We conducted a meta-analysis to assess the relationship between TA and the clinical outcome of GC. A meta-analysis of 18 studies (886 patients) was performed to evaluate the association between TA and metastasis-related parameters in GC patients by searching databases, including PubMed, MEDLINE, EMBASE, Web of Science databases, Cochrane Library and the Chinese Biomedical Literature database (CBM) (last search updated in October 2011). We used the odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association between TA and metastasis of GC. Our analysis results indicated that high telomerase activity expression tended to be associated with the presence of lymph node metastasis (866 patients) (OR=2.03, 95% CI 1.21-3.39, p=0.007), the depth of invasion (886 patients) (OR=1.87, 95% CI 1.30-2.70, p=0.0007), distant metastasis (407 patients) (OR=2.71, 95% CI 1.59-4.63, p=0.0002), tumor size (466 patients) (OR=2.14, 95% CI 1.31-3.50, p=0.002) and TNM stage (711 patients) (OR=2.39, 95% CI 1.30-4.41, p=0.005). However, high TA expression was not associated with the presence of histologic differentiation (791 patients) (OR=1.51, 95% CI 0.73-3.11, p=0.26). In conclusion, telomerase overexpression not only plays a key role in primary initiation, but also promotes invasion and metastatic progression of GC. These findings raise the possibility of using TA to screen for the prognosis of gastric cancer.

Prevalence of telomerase activity in human cancer

Telomerase activity has been measured in a wide variety of cancerous and non-cancerous tissue types, and the vast majority of clinical studies have shown a direct correlation between it and the presence of cancerous cells. Telomerase plays a key role in cellular immortality and tumorigenesis. Telomerase is activated in 80-90% of human carcinomas, but not in normal somatic cells, therefore, its detection holds promise as a diagnostic marker for cancer. Measurable levels of telomerase have been detected in malignant cells from various samples: tissue from gestational trophoblastic neoplasms; squamous carcinoma cells from oral rinses; lung carcinoma cells from bronchial washings; colorectal carcinoma cells from colonic luminal washings; bladder carcinoma cells from urine or bladder washings; and breast carcinoma or thyroid cancer cells from fine needle aspirations. Such clinical tests for telomerase can be useful as non-invasive and cost-effective methods for early detection and monitoring of cancer. In addition, telomerase activity has been shown to correlate with poor clinical outcome in late-stage diseases such as non-small cell lung cancer, colorectal cancer, and soft tissue sarcomas. In such cases, testing for telomerase activity can be used to identify patients with a poor prognosis and to select those who might benefit from adjuvant treatment. Our review of the latest medical advances in this field reveals that telomerase holds great promise as a biomarker for early cancer detection and monitoring, and has considerable potential as the basis for developing new anticancer therapies.

Thyroid cancer in children

In 1996, the authors were asked to review the subject of thyroid cancer in children. Over the subsequent decade, much has been learned about the treatment and outcome of these uncommon tumors. We now recognize quantitative and perhaps qualitative differences in genetic mutations and growth factor expression patterns in childhood thyroid cancers compared with those of adults. We also know that thyroid cancers induce a robust immune response in children that might contribute to their longevity. Patients under 10 years of age probably represent a unique subset of children at particularly high risk for persistent or recurrent disease; the management of these patients is under evaluation. We remain limited in our knowledge of how to stratify children into low- and high-risk categories for appropriate long-term follow-up and in our knowledge of how to treat children who have detectable serum thyroglobulin but negative imaging studies. In this article, the authors update our understanding of thyroid cancers in children with special emphasis on how these data relate to the current guidelines for management of thyroid cancer developed by the American Thyroid Association Taskforce. The limited data regarding management of children who have detectable serum thyroglobulin but negative whole-body scans are also reviewed.

Detection of telomerase activity in gastric lavage fluid: a novel method to detect gastric cancer

BACKGROUND

Telomerase is a ribonucleoprotein polymerase that is essential for cell immortality. Recent studies have demonstrated that a high percentage of gastric cancer tissue expressed telomerase. This study describes the presence of telomerase activity in gastric lavage fluid in patients with gastric cancer.

METHODS

Gastric lavage fluid was collected during esophageogastroduodenoscopy in 70 patients: 25 with gastric cancer, 25 with peptic ulcer disease, and 20 with normal stomach. The fluid and biopsy samples were analyzed for telomerase activity by a polymerase chain reaction-based telomerase repeat amplification protocol. The findings were related to the histological results.

RESULTS

Telomerase activity was present in 24 of the 25 (96%) gastric cancer tissue and in 7 of the 25 tissue specimens from peptic ulcer or gastritis. In the gastric lavage fluid, telomerase was detected in 20 patients (80%) with gastric cancer, 7 patients (28%) with peptic ulcer, and none in normal subjects (P < 0.001). The sensitivity, specificity, positive predictive value, and negative predictive value of gastric fluid telomerase expression in gastric cancer patients was 80%, 84%, 74%, and 88%, respectively.

CONCLUSIONS

The presence of telomerase activity is present in gastric lavage fluid of patients with gastric cancer as compared to those without, may represent a novel method for diagnosis of gastric cancer.

Gene deregulation in gastric cancer

Despite its decreasing frequency in the Western world during recent decades, gastric cancer is still one of the leading causes of cancer-related deaths worldwide. Due to the oligosymptomatic course of early gastric cancer, most cases are diagnosed in the advanced stages of the disease. The curative potential of current standard treatment continues to be unsatisfactory, despite multimodal approaches involving surgery, chemotherapy and radiotherapy. Novel therapeutics including small molecules and monoclonal antibodies are being developed and have been partially introduced into clinical use in connection with neoplastic diseases such as chronic myeloid leukemia, non-Hodgkin's lymphoma and colorectal cancer. Thorough understanding of the changes in gene expression occurring during gastric carcinogenesis may help to develop targeted therapies and improve the treatment of this disease. Novel molecular biology techniques have generated a wealth of data on up- and down-regulation, activation and inhibition of specific pathways in gastric cancer. Here, we provide an overview of the different aspects of aberrant gene expression patterns in gastric cancer.

Expression of telomerase activity, human telomerase RNA, and telomerase reverse transcriptase in gastric adenocarcinomas

Telomerase is an RNA-dependent DNA polymerase that synthesizes TTAGGG telomeric DNA onto chromosome ends to compensate for sequence loss during DNA replication. It has been detected in 85-90% of all primary human cancers, implicating that the telomerase seems to be reactivated in tumors and that such activity may play a role in the tumorigenic process. The purpose of this study was to evaluate telomerase activity, human telomerase RNA (hTR), and telomerase reverse transcriptase (TERT) in stomach cancer and to determine their potential relationships to clinicopathologic parameters. Frozen and corresponding methacarn-fixed paraffin-embedded tissue samples were obtained from 51 patients with gastric adenocarcinoma and analyzed for telomerase activity by using a TRAPeze ELISA kit. Tissue sections of all the samples were further investigated for hTR and TERT by in situ hybridization and a sensitive immunohistochemical technique, respectively. Telomerase activity was detected in 37 (73%) tumors. Telomerase positivity from methacarn-fixed paraffin blocks was found to be 35% of that from frozen tissues. hTR was overexpressed in 46 (90%) samples: 33/37 (89%) with and 13/14 (93%) without telomerase activation. Expression of TERT was demonstrated in 40 (78%) cases: 30/37 (81%) with and 10/14 (71%) without telomerase. Telomerase activity correlated well with depth of invasion (P =.037) and tumor differentiation (P =.022), whereas hTR significantly correlated with nodal metastasis (P=.047) and tumor size (P=.023). These data suggest that reactivated telomerase may play a significant role in the tumorigenesis of gastric cancer and may reflect, along with enhanced hTR, the malignant potential of the tumor. It is noteworthy that methacarn-fixed tissue cannot as yet substitute for the frozen section in the TRAP assay.

Relationship between the expression of human telomerase reverse transcriptase gene and cell cycle regulators in gastric cancer and its significance

AIM: To investigate the expression of human telomerase reverse transcriptase gene (hTRT) in gastric cancer (GC) and its relevance with cell cycle regulators including P16INK4, cyclin and P53.

METHODS: In situ hybridization (ISH) for hTRT mRNA was performed in 53 cases of gastric cancer and adjacent cancerous tissues. Immunohistochemical staining (S-P method) for hTRT protein, P16INK4, cyclinD1 and P53 was performed in 53 cases of GC and adjacent cancerous tissues.

RESULTS: Of 53 cases of GC, the expression of hTRT mRNA and hTRT protein was significantly higher than the expression of hTRT mRNA and hTRT protein in adjacent canerous tissues (P < 0.01), the positive rates of hTRTmRNA and hTRT protein were 79.2% and 88.6%. There was a stastical difference of the expression of hTRT protein among well differentiated adenocarcinoma, poorly differentiated adenocarcinoma and mucoid carcinoma. And there was a highly significant positive correlation between the expression of hTRT mRNA and hTRT protein (r = 0.625, P < 0.01). However, the expression of hTRT mRNA and its protein in GC were not related with other clinicopathological parameters including gender, age, location and size of neoplasm, invasion depth, lymph node metastasis and clinical stage. There was a significant positive correlation between the expression of hTRT mRNA and cyclinD1 protein (r = 0.350, P < 0.01). There was a significant positive correlation between the expression of cyclinD1 protein and hTRT protein (r = 0.549, P < 0.01), so was between P53 and hTRT protein (r = 0.319, P < 0.05).

CONCLUSION: The expression of hTRT gene is correlated significantly to the specific defects of cell cycle on G1/S check point ; telomerase activity may depend on cell cycle in gastric cancer and it is available to clarify the molecular mechanism of telomerase activity regulation. The expression of hTRT mRNA and hTRT protein in GC is significantly different from the expression of hTRT mRNA and hTRT protein in adjacent cancerous tissue which indicates that these targets are correlated closely to the occurrence of GC and can provide important morphologic index for diagnosis of GC.

The expression of hTERT mRNA and cellular immunity in gastric cancer and precancerosis

AIM: To observe the expression of Human telomerase reverse transcriptase (hTERT) in gastric carcinomas and precancerosis lesions, to evaluate the immune state of such patients, and to then study the clinical significance of hTERT and immune state for the diagnosis, treatment and prognosis of gastric cancer.

METHODS: In situ hybridization was used to detect the expression of hTERT mRNA in 116 endoscopic of gastric mucosa. Analyzed tissue samples were as follows: 30 cases of chronic superficial gastritis (CSG), 44 of precancerosis lesions (including 27 of chronic atrophic gastritis, 8 of adenomatous polyp and 9 of gastric ulcer) and 42 of gastric cancer (GC). In addition, the T lymphocyte subsets (CD3⁺, CD4⁺, CD8⁺, CD4⁺/CD8⁺) and natural killer cells (NK) in peripheral blood were determined by flow cytometric analysis (FCM) in 30 cases of CSG, 27 of precancerosis (chronic atrophic gastritis, CAG), and 42 of GC. The data were compared with those of normal control (NC).

RESULTS: The detected positive rate of hTERT varied as follows: 86% (36/42) in GC, 36% (16/44) in precancerosis lesions and 0% (0/30) in CSG. The expression of hTERT mRNA was not associated with patient gender, tumor location, macroscopic type, lymph node metastasis, or degree of differentiation. It was found that the CD3⁺, CD4⁺ of the CSG group were lower than that of NC (P < 0.05). Meanwhile, the T lymphocyte subsets (CD3⁺, CD4⁺, CD4⁺/CD8⁺ ratio) and NK cells of CAG were remarkably lower than that of NC and CSG groups (P < 0.05-0.01). Values of T cells and NK cells of the GC group were significantly abnormal when compared with the CAG group (P < 0.05-0.01). Furthermore, with tumor progression, the function of T cells was weakened gradually.

CONCLUSION: The expression of telomerase may be a crucial step in gastric carcinogenesis and increased hTERT mRNA may serve as a novel marker for diagnosis of GC. The immune state of patients with GC and precancerosis was somewhat depressed, which indicates the importance of cellular immunological assays in cancer patients.

Immunohistochemical detection of telomerase reverse transcriptase in colorectal adenocarcinoma and benign colonic mucosa

Telomerase activity (TA) is increased in human cancers and cell lines and is thought to contribute to their immortality. High TA has been found to correlate with aggressive tumor behavior. The aim of this study was to determine whether increased TA in colorectal carcinoma (CRC) correlates with survival. Formalin-fixed and paraffin-embedded tissue sections from 82 CRC and 6 cases of benign colon with diverticulosis were immunohistochemically stained for telomerase reverse transcriptase (TRT) using the immunoperoxidase method. The percentage of positive nuclei was determined for each case. Survival analysis was performed using the Kaplan-Meier method. TRT immunoreactivity was always nuclear. In normal colonic mucosa, TRT immunoreactivity was detected in the bottom of crypts. However, in normal colon adjacent to CRC, telomerase immunoreactivity was detected throughout the length of the crypts, including the upper third, and frequently in the surface epithelium. Telomerase immunoreactivity in more than 25% of the cancer cell nuclei was associated with significantly poorer patient survival (P = 0.0081). We conclude that increased TA in CRC, as demonstrated by TRT immunostaining, is associated with poorer survival, and that TA is present in normal colonic mucosa and is increased in colonic mucosa near CRC. Additional studies with larger patient samples and multivariate analysis are needed to determine whether TRT expression is an independent prognostic factor in CRC.

Clinical utility of telomerase in cancer

This review will focus on the clinical utilities of telomerase for human cancer diagnosis. Much attention has been focused on detection of telomerase activity and its essential components (hTR and hTERT) in cancer and noncancerous tissues. Expression of hTR and hTERT is upregulated in almost all human malignant tumors but not in benign or normal tissues with the exception of germline cells, proliferative stem cells, activated lymphocytes, and certain benign tumors. Thus, telomerase is a useful marker for cancer diagnosis and in some instance as a prognostic indicator of outcome. Telomerase detection in cells derived from breast fine needle aspirates, bronchial washes, and pancreatic juices show high sensitivity and specificity for cancer detection. In tissue samples, the level of telomerase activity is a useful prognostic indicator in certain adult cancers such as gastric and colon cancers and in neuroblastomas. Immunohistochemical detection of hTERT will facilitate exact diagnosis of the telomerase positive cells and expand the application of telomerase in cancer diagnosis.

Telomerase activity and patient survival after surgery for gastric and oesophageal cancer

OBJECTIVE

The ribonucleoprotein telomerase extends telomeres in cancer cells and has been proposed as a prognostic marker for cancer. We measured telomerase expression in proximal adenocarcinomas (those arising in the distal oesophagus or at the gastro-oesophageal junction) and distal adenocarcinomas (those arising in the corpus or antrum of the stomach) of the foregut, and correlated telomerase activity with pathological stage and post-operative survival.

DESIGN

Surgical specimens were collected from patients undergoing resections for gastric and oesophageal carcinomas. Haematoxylin and eosin histology provided data on the pathological tumour stage and pathological node stage.

METHODS

The telomerase activity of cancer specimens was determined using the telomeric repeat amplification protocol. A single pathologist, blinded to the results of the telomerase assays, reviewed all slides of cancers to assign T and N stages.

RESULTS

The cancers exhibited a wide range of telomerase expression. There was no significant difference between the telomerase activity of proximal adenocarcinomas (median, 551 U; 95% confidence interval, 154-2394 U; n = 26) and distal adenocarcinomas (median, 703 U; 95% confidence interval, 139-1618 U; n = 20). Distal adenocarcinomas expressing high telomerase activity (greater than the median) were significantly more advanced with regard to T stage than distal cancers expressing low telomerase levels (less than the median; P = 0.03, Mann-Whitney test). In distal adenocarcinomas, high telomerase activity was associated with poor patient survival (median 3 months) compared to low telomerase activity (median survival 22.4 months; P = 0.01, log-rank test). No such differences were observed for proximal adenocarcinomas.

CONCLUSIONS

There is a difference between gastric and oesophageal/gastro-oesophageal junction adenocarcinomas in terms of the relationship with telomerase expression and clinico-pathological variables. Among patients with distal gastric adenocarcinoma, telomerase activity correlates with markers of advanced disease, whereas this relationship does not hold true in oesophageal/gastro-oesophageal junction adenocarcinomas. Telomerase activation may occur at different stages of the formation of the malignant phenotype in these two cancers and may reflect differences in their pathogenesis. Telomerase could be a prognostic marker in gastric but not in oesophageal adenocarcinoma.

Telomerase, immortality and cancer

Replication of eukaryotic linear chromosomes is incomplete and leaves terminal gaps. The evolutionary widely distributed solution to this "end replication" is twofold: chromosome ends are capped with telomeres, bearing multiple copies of redundant telomeric sequences, and the telomerase enzyme can add (lost) telomeric repeats. Telomerase in humans, as in all mammals, is ubiquitous in all embryonic tissues. In adults, telomerase remains active in germs cells, and, although down-regulated in most somatic tissues, telomerase is active in regenerative tissues and notably, in tumor cells. Telomerase activity is linked to cellular proliferation, and its activation seems to be a mandatory step in carcinogenesis. In contrast to mammals, indeterminately growing multicellular organisms, like fish and crustaceae, maintain unlimited growth potential or 'immortality' in all somatic tissues throughout their entire life. Also this cell immortalization is brought about by maintaining telomerase expression. Disease prognosis for human tumors includes evaluation of cell proliferation, based on the detection of proliferation markers with monoclonal antibodies. The significance of the classical marker Ki-67, and of a novel marker repp-86 are compared with semiquantitative telomerase assays. For tumor therapy, telomerase inhibitors are attractive tools. Results with telomerase knock-out mice have revealed promise, but also risk of this approach. On the other side, telomerase stimulation is attractive for expanding the potential of cellular proliferation in vitro, with possible applications for transplantation of in vitro expanded human cells, for immortalizing primary human cells as improved tissue models, and for the isolation of otherwise intractable products, like genuine human monoclonal antibodies.

Detection of telomerase activity in peritoneal lavage fluid from patients with gastric cancer using immunomagnetic beads

Cytologic examination of peritoneal lavage fluid is a useful predictor of peritoneal recurrence in gastric cancer. However, this technique is not overly sensitive and requires special abilities in the cytologist. In this study, telomerase activity was used to detect free cancer cells in peritoneal lavage fluid from patients with gastric cancer. In the first part, 12 lavage-fluid samples obtained from 12 patients with gastric cancer were analysed using the conventional telomeric repeat amplification protocol (TRAP) assay. Three of five patients with early gastric cancer had positive telomerase activity. These false-positive results may have been due to lymphocyte contamination. Furthermore, polymerase chain reaction inhibitors were also detected in the lavage-fluid samples. Therefore, we developed a novel method for elimination of haematopoietic cell and Taq polymerase inhibitors to increase the accuracy of the TRAP assay using immunomagnetic beads, which bind to most normal and neoplastic human epithelial cells. Telomerase activity was found in 10 of 20 (50%) lavage-fluid samples from patients with serosal or subserosal invasion. Cytologic examination was positive in nine of 20 (45%) samples. Both the telomerase activity and cytology were negative in all 14 patients without serosal or subserosal invasion. These results suggest that the TRAP assay combined with immunomagnetic beads might be useful for detection of free cancer cells in the peritoneal space in gastric cancer without the aid of an experienced cytologist.

Expression of human telomerase catalytic subunit gene in cancerous and precancerous gastric conditions

BACKGROUND AND AIMS

Telomerase activity is thought to be necessary for cellular immortality and carcinogenesis. The mRNA that encodes the telomerase catalytic subunit (hTERT) has recently been identified, and expression of hTERT mRNA is thought to regulate activation of telomerase. To determine at what stage of carcinogenesis cells begin to express hTERT, we analysed hTERT mRNA expression in gastric carcinoma and precancerous conditions, focusing on chronic gastritis with or without intestinal metaplasia.

METHODS

Using reverse transcription-polymerase chain reaction, hTERT gene expression was investigated in 18 gastric cancers and 60 specimens of chronic gastritis. Telomerase activity was evaluated using telomeric repeat amplification protocol.

RESULTS

Sixteen of 18 (89%) gastric carcinomas expressed hTERT mRNA, and this expression was unrelated to histological type or depth of invasion. Telomerase activity was found in seven of eight (88%) gastric cancer tissues, all of which expressed hTERT mRNA. Expression of hTERT mRNA was positive in 14 of 60 (23%) specimens of chronic gastritis, and was most prominent in seven of 15 (47%) specimens of gastric mucosa with intestinal metaplasia. Expression of the hTERT gene was significantly more frequent in chronic gastritis with intestinal metaplasia than in gastritis without intestinal metaplasia (P=0.030). In addition, hTERT gene expression was not correlated with age, sex, biopsy site, histological grade of inflammatory cells, glandular atrophy and lymph follicles, or infection with Helicobacter pylori. None of eight normal gastric mucosa expressed hTERT mRNA.

CONCLUSIONS

Our results indicate that hTERT mRNA is expressed in precancerous conditions as well as in gastric cancer, and that hTERT gene expression is induced at an early stage of gastric carcinogenesis.

Quantification of telomerase activity in sporadic colorectal carcinoma: association with tumor growth and venous invasion

BACKGROUND

Activation of telomerase, a ribonucleoprotein enzyme complex that synthesizes telomere repeats, is associated with acquisition of unlimited cellular proliferation and is commonly detected in human cancer. Measurement of telomerase activity (TA) may provide important information as a diagnostic marker or a prognostic indicator. The authors studied the quantification of TA and assessed its utility as a prognostic marker in sporadic colorectal carcinoma.

METHODS

Sixty surgical specimens, including 30 specimens of cancer tissue and 30 specimens of corresponding normal colorectal mucosa, were examined. TA was measured by a fluorescence-based telomeric repeat amplification protocol assay. The authors determined the telomerase index (TI = log (A-B), where A represented TA of cancer tissues and B represented TA of normal mucosa) and examined the relation between TI and clinicopathologic factors using the Student t test, analysis of variance, the Chi-square test, and the Fisher PLSD as a post hoc test.

RESULTS

TA of cancer and corresponding normal mucosa was 51.87+/-27.38 and 7.14+/-9.85, respectively (P<0.0001). The cutoff value was determined to be 26 in a receiver operating characteristic study, with 90% sensitivity, 96.7% specificity, and 96.4% positive predictive value. TI was closely correlated with depth of invasion (P = 0.0129) but not with age, gender, histologic type, location, lymph node metastasis, lymphatic infiltration, or Dukes stage. There was a significant difference in TI between tumors with and without venous invasion (P = 0.0003). Four of five tumors with synchronous liver metastasis showed high TI (1.555 <TI).

CONCLUSIONS

High TI may be a risk factor for metastasis of colorectal carcinoma to the liver.

Clinical significance of telomerase activity in biopsy specimens of gastric cancer

Telomerase has been reported to be activated in most immortal cells and human cancers. The purpose of this study was to assess the clinical significance of telomerase activity in biopsy specimens of gastric cancer. Telomerase activity in endoscopic biopsy specimens obtained preoperatively from 31 patients with gastric cancer was determined semiquantitatively using the telomeric repeat amplification protocol assay, a polymerase chain reaction-based assay. Cancer tissues had significantly higher telomerase activity than adjacent normal tissues (13.9 +/-2.0% vs. 7.0 +/- 0.8%; p < 0.05). The ratio of the telomerase activity in cancer tissues to that in normal tissues (telomerase index) was significantly higher in tumors invading the proper muscle layer or deeper or in tumors with moderate or marked lymphatic invasion than in tumors without these invasive factors (4.7 +/- 1.4 vs. 1.1 +/- 0.1 for depth of invasion and 4.4 +/- 1.3 vs. 1.2 +/- 0.2 for lymphatic invasion; p < 0.05 for both). These results suggest that the analysis of telomerase activity in biopsy specimens might contribute to preoperative assessment of the invasive activity or stage of gastric cancer.

Telomerase activity in gastric cancer and its clinical implications

AIM: To study the telomerase expression in gastric carcinoma and its clinical implications.

METHODS: Telomerase activity was examined in gastric cancer an d corresponding normal tissues using a modified TRAP (telomeric repeat amplification protocol) assay (TRAP-eze) in tissue samples from 94 gastric carcinomas an d 58 normal tissues, 12 gastric adenomas and 9 gastric ulcer lesions.

RESULTS: Telomerase activity was present in 81 of the 94 (86.2%) gastric cancer tissues, whereas no telomerase activity was detected in any normal tissues. The incidence of telomerase activity in gastric cancer tissues was unrelated to the tumor diameter, histological grade, tumor invasion in depth, lymph node metastasis and TNM stage.

CONCLUSION: Telomerase plays an important role in carcinogenes is and progression of gastric cancer, and it is suggested to be a useful tumor marker.

Telomeric lengths and telomerase activity in liposarcomas

To assess the role of telomerase in the development of liposarcomas, we measured telomerase activity in 36 malignant and seven benign lipomatous neoplasias from 34 patients. A sensitive polymerase chain reaction-based telomerase assay (the telomeric repeat amplification protocol) was applied. Shortening or elongation of telomeric repeat fragment lengths, as measured by using hybridization with a telomere-specific oligonucleotide probe, was correlated with the presence of telomerase activity. The latter was demonstrable in 69% of malignant tumors. Benign tumors can be distinguished from malignant neoplasias on the basis of telomerase activity. However, telomerase expression seems to be characteristic of poorly differentiated liposarcomas. Myxoid/round cell liposarcomas exhibited a higher telomerase activity level than the classical low-grade variants. Telomerase activity was not correlated with age at the time of diagnosis or with sex. In most cases, telomerase-positive tumors showed higher proliferation indices than did neoplasias lacking telomerase. All eight recurrences expressed telomerase activity, reflecting a close association of telomerase with the biological behavior of liposarcomas. Our findings suggest that telomerase may play a key role in the establishment and progression of malignant lipomatous tumors.

Three molecular determinants of malignant conversion and their potential as therapeutic targets

The past decade has been marked by an explosion of knowledge regarding the dysregulation of cancer at the molecular level. It has become apparent that oncogenes, tumor suppressor genes, and other ancillary molecules interact in complex pathways that govern cellular homeostasis. We review three molecular events that have been implicated in tumorigenesis and define pathways ripe for the development of new therapeutic approaches: 1) activation of telomerase, 2) dysregulation of the patched/sonic hedgehog pathway, and 3) mutation of the INK4 alpha-ARF locus.