Telomerase activity in human ovarian carcinoma.

Telomeres fulfill the dual function of protecting eukaryotic chromosomes from illegitimate recombination and degradation and may aid in chromosome attachment to the nuclear membrane. We have previously shown that telomerase, the enzyme which synthesizes telomeric DNA, is not detected in normal somatic cells and that telomeres shorten with replicative age. In cells immortalized in vitro, activation of telomerase apparently stabilizes telomere length, preventing a critical destabilization of chromosomes, and cell proliferation continues even when telomeres are short. In vivo, telomeres of most tumors are shorter than telomeres of control tissues, suggesting an analogous role for the enzyme. To assess the relevance of telomerase and telomere stability in the development and progression of tumors, we have measured enzyme activity and telomere length in metastatic cells of epithelial ovarian carcinoma. We report that extremely short telomeres are maintained in these cells and that tumor cells, but not isogenic nonmalignant cells, express telomerase. Our findings suggest that progression of malignancy is ultimately dependent upon activation of telomerase and that telomerase inhibitors may be effective antitumor drugs.     

Telomerase activity in gastric cancer

OBJECTIVE : To examine telomerase activity and its clinical significance in human gastric carcinoma and to evaluate the feasibility of non‐radioisotopic TRAP (telomeric repeat amplification protocol) assays to detect telomerase activity. METHODS : Telomerase activity in tissue samples from 58 gastric carcinomas (and their matched normal tissues), 12 gastric adenomas and nine gastric ulcers was examined by using a modified non‐ radioisotopic PCR (polymerase chain reaction)‐based TRAP assay. RESULTS : Forty‐nine of 58 gastric cancer specimens were positive for telomerase activity, with a positive rate of 84.5%. In contrast, none of the normal tissues exhibited telomerase activity (P < 0.001). One of each of the 12 gastric adenomas and nine gastric ulcers was also positive. The prevalence of telomerase activity in gastric carcinoma tissues was not correlated with age, tumor diameter, histological grade, tumor invasion depth, lymph node metastasis or tumor node metastasis (TNM) stage. CONCLUSIONS : Telomerase activity could be a good diagnostic marker for the detection of gastric carcinoma. The non‐radioisotopic TRAP assay is a feasible method for detecting telomerase activity.     

Telomerase activity in normal and malignant hematopoietic cells.

Bone marrow and peripheral blood leukocytes from 19 leukemia patients were found to contain telomerase activity detectable by a PCR-based assay. Telomerase was also detectable in nonmalignant bone marrow and peripheral blood leukocytes from normal donors, including fractions enriched for granulocytes, T lymphocytes, and monocytes/B cells. Semiquantitative comparison revealed considerable overlap between telomerase activities in samples from normal subjects and leukemia patients, confounding evaluation of the role of telomerase in this disease. These data indicate that human telomerase is not restricted to immortal cells and suggest that the somatic expression of this enzyme may be more widespread than was previously inferred from the decline of human telomeres.     

Telomerase activity in benign and malignant adrenal tumors.

Histological analysis of surgically removed adrenal masses often fails to differentiate between benign and malignant tumors. In normal cells, the telomeric ends of the chromosomes are shortened with each cell division, leading to chromosome destabilization and cellular senescence after a critical number of cell cycles. In tumor cells, telomere shortening is prevented by a specific DNA polymerase, called telomerase. In an effort to clarify the role of telomerase in the pathogenesis of adrenal tumors, and to test whether its activity could serve as marker of malignancy, we measured telomerase activity in 41 human adrenal tissue samples that were classified both by the clinical course and by histological examination. Telomerase activity was determined by TRAP ELISA and expressed as high (>50% of positive control telomerase activity), medium (31-50%), low (11-30%), very low (< or = 10%), or absent (0%). The 8 normal adrenal tissue samples showed very low levels of telomerase activity. Mean telomerase activity also very low in 3/3 incidentalomas, 6/6 Cushing adenomas, 6/6 Conn adenomas, 7/7 adrenocortical carcinomas, 8/8 benign pheochromocytomas, and 2/3 malignant pheochromocytomas. In contrast, one malignant pheochromocytoma showed high telomerase activity. These data indicate that telomerase activity may not be a suitable marker for malignancy in the adrenal gland. Our results also challenge the current dogma of close correlation between cell dedifferentiation and telomerase activity.     

Telomerase activity in pancreatic endocrine tumors

OBJECTIVES: Pancreatic endocrine tumors (PETs) have variable prognoses, and predictors of survival are lacking. PETs can be difficult to distinguish histologically from aggressive pancreatic neoplasms such as acinar cell carcinoma. Telomerase is a ribonuclear protein that maintains the length of the telomere and induces cell immortality. Telomerase is present in 95% of pancreatic adenocarcinoma and is associated with aggressive tumor behavior. Our aim is to determine telomerase activity in PETs and investigate its potential role as a prognostic indicator. METHODS: Telomerase detection using the telomeric repeat amplification protocol was performed on frozen surgical archived pancreatic endocrine tissue from 30 patients with PETs identified by light microscopy (hematoxylin-eosin stain). All results were confirmed with internal controls. A patient's survival was measured from the time of surgery. Acinar cell differentiation (presence of zymogen granules) was determined by electron microscopy. Follow-up data were acquired via telephone interview, medical record review, and death certificates. RESULTS: Three of 30 PETs diagnosed by light microscopy were telomerase positive: three were considered nonfunctional, and two of these three patients had extrapancreatic disease. All three telomerase-positive cases were reclassified as either acinar cell carcinoma (two cases) or mixed acinar-endocrine cell carcinoma (one case). All three patients (mean age = 63 yr) died from tumor progression within 2 yr of surgery (mean = 1.6 yr +/- 0.5 SD). The remaining PETs were telomerase negative: 13 insulinomas, four nonfunctional, two sporadic glucagonomas, one gastrinoma, one vipoma, one carcinoidlike PET, and five PETs from three patients with multiple endocrine neoplasm syndrome type I and two patients with von Hippel-Lindau syndrome. Excluding insulinomas, 12 of 14 patients with telomerase-negative PETs had extrapancreatic disease. Nevertheless, Kaplan-Meier survival estimates for these 12 patients were significantly longer than for patients with telomerase-positive acinar cell carcinoma (92% vs 0% at 2 yr, p = 0.001, log rank test). The survival of all telomerase-negative PETs (n = 27) was significantly longer than that of the patients with telomerase-positive acinar cell carcinoma (93% vs 0% at 2 yr, p = 0.0001). CONCLUSIONS: Telomerase activity helps to identify acinar cell carcinomas that histologically resemble PETs, which accounts for the poor prognosis demonstrated in these patients. The absence of telomerase activity in most PETs may be responsible for their indolent clinical course. Telomerase may identify potentially progressive tumors, such as acinar cell carcinoma, and may be useful in selecting patients for more aggressive treatment.     

Telomerase activity in small cell esophageal carcinoma

Small cell carcinoma of the esophagus is a rare and aggressive malignant tumor. Telomerase activation is common in human cancers. There is a lack of data on telomerase activity in esophageal small cell cancers. The present report studied the role of telomerase activity in esophageal small cell carcinoma. The clinicopathologic data of five patients with small cell carcinoma of the esophagus who underwent primary surgical treatment between 1991 and 2000 were studied. Telomeric repeat amplification protocol assays were used to investigate telomerase activity in these tumors. The proliferative activity (MIB-1) and p53 expression of these tumors were also studied using immunohistochemistry and correlated with the telomerase activity. All five small cell carcinomas showed detectable telomerase activity in the primary tumor. Two out of the five morphologically normal esophageal mucosae adjacent to the primary tumor had detectable telomerase activity. There was no correlation between the p53 expression, tumor stage, survival of patients, and the presence of telomerase activity. High MIB-1 expression in esophageal small cell carcinomas was associated with high telomerase activity. Telomerase activation is common in small cell carcinoma of the esophagus. This fact may find application in anti-telomerase treatment for this aggressive tumor.     

Clinic-based ultrasound can predict malignancy in pediatric thyroid nodules

Background: Thyroid nodules in pediatric patients may carry a greater risk for malignancy than in adults. Most nodules >1?cm in patients ≤21 years of age may require thyroidectomy for definitive diagnosis and treatment. Although clinic-based ultrasound (CBUS) has been shown useful in the evaluation of thyroid nodules in adults, its utility in evaluating nodules in the pediatric population remains unclear. Methods: Prospectively collected data regarding 50 patients ≤21 years who underwent preoperative CBUS and initial thyroidectomy at a single institution were retrospectively reviewed. All CBUS were performed by endocrine surgeons certified in basic and cervical ultrasonography. Preoperative CBUS characteristics of pediatric thyroid nodules were analyzed with respect to final pathology. Results: Of the 50 patients ≤21 years of age who underwent surgical resection for a dominant thyroid nodule, there were 45 females and 5 males with an average age of 17.4 years (range: 10-21 years). On univariate analysis, microcalcifications (p<0.001), abnormal lymph nodes (p<0.001), and dimensions taller more than wide (p=0.033) were individual CBUS characteristics predictive of thyroid malignancy. All nine patients with abnormal lymph nodes on CBUS had malignant disease on final pathology. Multiple thyroid nodules, a cystic component, and echogenicity did not predict malignancy; regular borders trended toward predicting a benign nodule (p=0.066). When malignant ultrasound features were considered (i.e., hypoechoic, irregular borders, microcalcifications, abnormal lymph nodes, and shape taller more than wide), having one malignant feature predicted malignancy with an odds ratio of 2.0 while having ≥2 features held even greater significance (p=0.004, OR 4.0). All patients with ≥3 malignant ultrasound features had thyroid cancer on final pathology. Conclusion: CBUS is a useful diagnostic modality in determining malignancy status of thyroid nodules in patients ≤21 years of age. CBUS should be employed as part of an initial assessment of any pediatric patient presenting with thyroid nodules to help further guide management and treatment.     

Rectilinear thyroid scanning as a predictor of malignancy

Rectilinear scan findings were correlated with the surgically documented size, location, and histology of thyroid carcinoma in 67 patients. At the site of the carcinoma, 36 (54%) had hypofunction, associated with a palpable abnormality in all but one patient; 16 (24%) had an abnormality on palpation but not on scanning; 11 (16%) had both a normal clinical examination and a normal scan, associated with a benign abnormality in another part of the thyroid; and four (6%) had a patchy uptake. A literature review established that use of the gamma camera with pinhole collimator does not increase the specificity of carcinoma predictability, despite the enhanced sensitivity. The scan may still be used in evaluating the clinically solitary module that is not obviously malignant. However, unless that module is hyperfunctioning, clinical criteria rather than appearance of the scan should contribute most to the decision of whether to treat surgically.     

Telomerase activity in normal leukocytes and in hematologic malignancies

Telomeres are essential for function and stability of eukaryotic chromosomes. In the absence of telomerase, the enzyme that synthesizes telomeric DNA, telomeres shorten with cell division, a process thought to contribute to cell senescence and the proliferative crisis of transformed cells. We reported telomere stabilization concomitant with detection of telomerase activity in cells immortalized in vitro and in ovarian carcinoma cells, and suggested that telomerase is essential for unlimited cell proliferation. We have now examined the temporal pattern of telomerase expression in selected hematologic malignancies. We found that, unlike other somatic tissues, peripheral, cord blood, and bone marrow leukocytes from normal donors expressed low levels of telomerase activity. In leukocytes from chronic lymphocytic leukemia (CLL) patients, activity was lower than in controls in early disease, and comparable with controls in late disease. Relative to bone marrow, telomerase activity was enhanced in myelodysplastic syndrome (MDS) and more significantly so in acute myeloid leukemia (AML). Regardless of telomerase levels, telomeres shortened with progression of the diseases. Our results suggest that early CLL and MDS cells lack an efficient mechanism of telomere maintenance and that telomerase is activated late in the progression of these cancers, presumably when critical telomere loss generates selective pressure for cell immortality.     

Telomerase activity in peripheral blood for diagnosis of hepatoma

BACKGROUND: Telomerase activity may be used as a molecular marker for the detection of circulating hepatoma cells in blood of patients with hepatoma. METHODS: Telomerase activity in peripheral blood from hepatocellular carcinoma (HCC) patients was assessed by using a highly sensitive and non-radioisotope telomerase polymerase chain reaction (PCR) ELISA. Initially, tissue telomerase activity was measured in the hepatoma and non-tumour portions by using PCR ELISA within the same specimen, to compare its sensitivity with the conventional telomeric repeat amplification protocol (TRAP) method. Second, telomerase activity was measured in the peripheral blood obtained from patients with HCC, patients with chronic liver disease and in healthy controls. RESULTS: Of the 17 HCC patients, telomerase activity was found to be positive in 14 (82%) by using TRAP and 15 (88%) by using PCR ELISA, indicating that PCR ELISA is a reliable tool for the measurement of telomerase activity. By using the Telomerase PCR ELISA assay, telomerase activities in the peripheral blood of 20 HCC patients was 1.65 +/- 0.78 units. This was significantly greater than the results obtained for 20 chronic liver disease patients (0.43 +/- 0.36 units) and 20 healthy controls (0.39 +/- 0.14 units; P < 0.0001).When the arbitrary cut-off level was set at 0.7 units (maximum value of healthy controls + 0.1), the positive frequency of telomerase activity was 25% for chronic liver disease and 80% for HCC patients (sensitivity 80%, specificity 75%). Among the HCC patients, high telomerase activity in the peripheral blood was shown at stage III HCC with vascular invasion (2.10 +/- 0.62 units, n = 9). This was significantly higher than patients at stage II of HCC (1.28 +/- 0.72 units, n = 11, without vascular invasion; P = 0.012). CONCLUSION: These results suggest that peripheral blood telomerase activity, which may reflect haematogenous micrometastasis, is potentially a practical diagnostic/predictive marker of HCC.     

Prevalence and prediction of malignancy in cytologically indeterminate thyroid nodules

OBJECTIVE: Controversy surrounds the evaluation of nodules with indeterminate cytology results. Malignancy rates in these nodules are not low. We examined the malignancy rates in nodules that showed follicular neoplasm or atypical cells on cytology and attempted to predict malignancy based on ultrasonographic features. DESIGN AND PATIENTS: We retrospectively analysed 5 years' cytopathology results of fine-needle aspiration biopsy (FNAB) specimens of indeterminate follicular thyroid lesions prior to thyroidectomy. The prevalence of malignancy on final histology was determined. The sonographic features of the thyroid nodules with respect to size, echogenicity, echo structure, border shape and presence of calcification were analysed. RESULTS: A total of 86 patients (15 men, 61 women; mean age 52.1 +/- 12.5 years) with indeterminate cytology underwent thyroidectomy and had histopathological diagnoses. The average nodule was 18.9 +/- 12.3 mm. The prevalence of malignancy in patients with atypical cell cytology was 51.7% (30 of 59), and the prevalence of malignancy in patients with follicular neoplasm cytology was 15% (4 of 27). Malignancy prevalence was higher in patients who had follicular neoplasm cytology with atypical cells than in those without atypical cells (2 of 7 and 2 of 20, respectively). We found no significant correlations between sonographic or clinical features and malignancy in this patient group. Sonographic features and nodule size are not useful predictors of malignancy. CONCLUSION: Until better molecular markers for malignancy are developed, surgical consultation remains necessary after examination of cytologically indeterminate FNAB specimens in patients with follicular thyroid lesions. But in follicular lesions without atypical cells the malignancy rate is low and reassessment later on could be an alternative approach.