Semi-quantitative analysis of telomerase in pancreatic ductal adenocarcinoma

Understanding, diagnosing, and treating pancreatic cancer from the perspective of telomeres and telomerase

Telomerase is associated with cellular aging, and its presence limits cellular lifespan. Telomerase by preventing telomere shortening can extend the number of cell divisions for cancer cells. In adult pancreatic cells, telomeres gradually shorten, while in precancerous lesions of cancer, telomeres in cells are usually significantly shortened. At this time, telomerase is still in an inactive state, and it is not until before and after the onset of cancer that telomerase is reactivated, causing cancer cells to proliferate. Methylation of the telomerase reverse transcriptase (TERT) promoter and regulation of telomerase by lactate dehydrogenase B (LDHB) is the mechanism of telomerase reactivation in pancreatic cancer. Understanding the role of telomeres and telomerase in pancreatic cancer will help to diagnose and initiate targeted therapy as early as possible. This article reviews the role of telomeres and telomerase as biomarkers in the development of pancreatic cancer and the progress of research on telomeres and telomerase as targets for therapeutic intervention.

Telomerase activity as a marker for differential diagnosis of pancreatic adenocarcinoma: a systematic review and meta-analysis

BACKGROUND

Studies evaluating the role of telomerase activity in pancreatic adenocarcinoma are inconsistent and a systemic review of the available literature may shed new light on this issue.

OBJECTIVE

To systematically review the usefulness of telomerase activity in distinguishing pancreatic cancer from other pancreatic diseases.

METHODS

A comprehensive search of the PubMed and Embase databases was conducted to identify eligible studies. Only studies evaluating telomerase activity in patients with suspected or previously diagnosed pancreatic adenocarcinomas versus nonpancreatic adenocarcinomas and published in English with a sufficient number of cases were included. The hierarchical summary receiver operating characteristic (HSROC) model was used to establish the potential value of telomerase activity in the diagnosis of pancreatic adenocarcinoma.

RESULTS

A total of 19 studies qualified for this meta-analysis. In distinguishing pancreatic adenocarcinoma from benign diseases, the pooled sensitivity and specificity of telomerase activity were 0.81 (95% CI, 0.68-0.90) and 0.97 (95% CI, 0.93-0.98), respectively; the diagnostic odds ratio (DOR) was 126.62 (95% CI, 49.94-320.99); beta was -1.16 (95% CI, -3.62-1.29), Z was -0.93, p was 0.35>0.1, and lambda was 6.86 (95% CI, 1.01-12.70). In distinguishing pancreatic adenocarcinoma from chronic pancreatitis, the pooled sensitivity and specificity of telomerase activity were 0.77 (95% CI, 0.61-0.88) and 0.97 (95% CI, 0.91-0.99), respectively; DOR was 117.28 (95% CI, 32.25-426.53); beta was -0.38 (95% CI, -1.89-1.13), Z was -0.49, p was 0.62>0.1, and lambda was 5.30 (95% CI, 3.37-7.24).

CONCLUSIONS

The present meta-analysis demonstrates that telomerase activity could be a useful biomarker for the differential diagnosis of pancreatic adenocarcinoma and benign pancreatic diseases.

Positive regulation of human telomerase reverse transcriptase gene expression and telomerase activity by DNA methylation in pancreatic cancer

AIM

We sought to determine the role of telomerase and its catalytic subunit hTERT in pancreatic cancer and evaluate the epigenetic regulation of hTERT by promoter methylation.

METHODS

Thirty paired samples of pancreatic ductal adenocarcinomas and adjacent normal tissue and 12 chronic pancreatitis samples were studied. Reverse transcriptase polymerase chain reaction, telomeric repeat amplification protocol assay, and methylation-specific polymerase chain reaction were performed to analyze hTERT expression, telomerase activity, and methylation status of gene promoters, respectively.

RESULT

hTERT and telomerase activity were upregulated in pancreatic cancer compared with paired normal tissues and samples of pancreatitis. hTERT expression correlated with telomerase activity (P \ .05) and in turn correlated positively with hTERT promoter methylation (P \ .001) and p16 promoter methylation. hTERT transcript expression and telomerase activity both conferred a worse outcome by univariate and multivariate analysis (P \ .05).

CONCLUSION

hTERT expression and telomerase activity are predictors of poor outcome in pancreatic cancer. hTERT gene expression is positively regulated by promoter methylation.

Molecular Diagnosis of Solid and Cystic Lesions of the Pancreas

Pancreatic cancer presents at a clinically advanced stage. Diagnosis often is delayed in those who undergo several negative investigations, and at times, the diagnosis ultimately is made at surgery. Tumor suppressor-linked microsatellite allelic loss analysis appears to improve the diagnostic accuracy of inconclusive cytology specimens. Science, however, still suffers from the lack of a reliable biomarker for the purpose of screening and early detection. The continued study of sera and pancreatic juice hopefully will lead to the discovery of molecular biomarkers capable of diagnosing preclinical disease in at-risk groups.The ability to predict the underlying biologic behavior of pancreatic cystic neoplasia is less than ideal. Tumor suppressor-linked microsatellite allelic loss and telomerase analysis show promise, but they have not been studied extensively. Proteomic analysis of pancreatic cyst fluid, although not yet reported, also may prove valuable in guiding clinical management.

Molecular diagnosis of solid and cystic lesions of the pancreas

Pancreatic cancer presents at a clinically advanced stage. Diagnosis often is delayed in those who undergo several negative investigations, and at times, the diagnosis ultimately is made at surgery. Tumor suppressor-linked microsatellite allelic loss analysis appears to improve the diagnostic accuracy of inconclusive cytology specimens. Science, however, still suffers from the lack of a reliable biomarker for the purpose of screening and early detection. The continued study of sera and pancreatic juice hopefully will lead to the discovery of molecular biomarkers capable of diagnosing pre-clinical disease in at-risk groups. The ability to predict the underlying biologic behavior of pancreatic cystic neoplasia is less than ideal. Tumor suppressor-linked microsatellite allelic loss and telomerase analysis show promise, but they have not been studied extensively. Proteomic analysis of pancreatic cyst fluid, although not yet reported, also may prove valuable in guiding clinical management.

Quantitative analysis of hTERT mRNA expression in colorectal cancer

OBJECTIVES

Telomerase is highly activated in a variety of malignant neoplasms including colon cancer. Among the major components of telomerase, human telomerase reverse transcriptase (hTERT) is thought to regulate telomerase activity. To assess the importance of telomerase for the diagnosis of colorectal cancer, we measured the expression of hTERT mRNA and telomerase activity in a large series of 140 colorectal cancers, 140 adjacent normal tissues, and 20 adenomas.

METHODS

The expression level of hTERT was measured quantitatively by competitive reverse transcriptase-polymerase chain reaction (RT-PCR), and telomerase activity was examined by telomeric repeat amplification protocol (TRAP) assay in the same samples.

RESULTS

The median expression level of hTERT mRNA in carcinomas was significantly higher than that in either adenomas or normal tissues. The median level of hTERT in adenomas was significantly higher than that in normal tissues. Telomerase activities in carcinomas were significantly higher than those in either adenomas or normal tissues. Telomerase activities in adenomas were also significantly higher than those in normal tissues. Furthermore, the relative expression levels of hTERT mRNA in adenomas and carcinomas were significantly correlated with the relative telomerase activities; the Spearman rank correlation was 0.53 (p = 0.021) and 0.18 (p = 0.031), respectively.

CONCLUSIONS

Our data suggest that determination of hTERT mRNA by competitive RT-PCR is superior in quantitative accuracy and sensitivity and would support the importance of telomerase activity for the diagnosis of colorectal cancer.

Possible role of telomerase activation in the multistep tumor progression of periampullary lesions in patients with familial adenomatous polyposis

OBJECTIVES

The role of telomerase in periampullary tumor progression in patients with familial adenomatous polyposis (FAP) was investigated.

METHODS

Relative telomerase activity was measured using a telomerease amplification protocol in periampullary biopsy specimens of normal mucosa and adenoma obtained from patients with FAP, and was compared with that of periampullary normal mucosa and cancer specimens from patients without FAP.

RESULTS

None of normal mucosa from the non-FAP patients showed a telomerase ladder. Telomerase was positively detected in three of seven normal mucosa (42.9%) and in five of seven adenoma from FAP patients (62.5%). In papillary cancer from the non-FAP patients, seven of nine tissue specimens (77.8%) showed positive activity. When semiquantitatively analyzed, the relative telomerase activity increased in accordance with the progression of the diseases.

CONCLUSIONS

Telomerase is activated even in normal mucosa of FAP patients, and the intensities of telomerase may reflect the malignant potential of periampullary neoplasms.

Telomerase activity in pure pancreatic juice for the diagnosis of pancreatic cancer may be complementary to K-ras mutation

BACKGROUND

The usefulness of K-ras mutation in pancreatic juice for the diagnosis of pancreatic cancer is questionable. Telomerase is positive in pancreatic cancer but rarely in benign pancreatic diseases. We conducted this study to determine the usefulness of K-ras mutation and telomerase activity in pancreatic juice for the diagnosis of pancreatic cancer.

METHODS

Pancreatic juice collected during endoscopic retrograde cholangiopancreatography was examined in 31 patients: 12 with pancreatic cancer, 11 with chronic pancreatitis, and 8 control patients. The K-ras gene was detected by using the restriction fragment length polymorphism method. Telomerase activity was detected by using the telomeric repeat amplification protocol.

RESULTS

K-ras mutation was positive in 75% (9 of 12) of pancreatic cancers and in 27% (3 of 11) of cases of chronic pancreatitis but in none of the control patients. Telomerase activity was detected in 92% (11 of 12) of pancreatic cancers and in 18% (2 of 11) of cases of chronic pancreatitis. The diagnostic value in pancreatic cancer was comparable between K-ras mutation and telomerase when evaluated separately. However, by combining these 2 methods, the specificity rose to 100%.

CONCLUSIONS

For the diagnosis of pancreatic cancer, telomerase activity in pancreatic juice may possibly be complementary to K-ras mutation because it may decrease the rate of false-positive diagnosis.

Activation of telomerase and its diagnostic application in biopsy specimens from biliary tract neoplasms

BACKGROUND

Telomerase activity has been reported to have potential as a useful diagnostic marker for cancer in various organs. The authors previously reported that telomerase activity in pancreatic juice differentiates pancreatic ductal carcinoma from adenoma and pancreatitis. In the current study, the usefulness of semiquantitatively determined telomerase activity in the diagnosis of malignant biliary tract neoplasms was investigated.

METHODS

The samples examined included 61 surgically resected biliary tract tissues (11 gallbladder carcinomas, 5 bile duct carcinomas, 1 gallbladder adenoma, 30 cholecytitis cases, 7 cholesterol polyps, 1 normal gallbladder, and 6 normal common bile duct tissues), 42 bile samples from patients with biliary tract or pancreatic disease (19 cases of malignant biliary tract disease, 11 cases of benign biliary tract disease, 10 cases of malignant pancreatic disease, and 2 cases of benign pancreatic disease), and 14 bile duct biopsy specimens collected by percutaneous transhepatic choledochoscopy or endoscopic retrograde cholangiopancreatography (8 bile duct carcinoma specimens, 1 bile duct adenoma specimen, and 5 hepatolithiasis specimens).

RESULTS

In biliary tract tissues, a telomerase ladder was detected in 73% of gallbladder carcinomas, 40% of bile duct carcinomas, and none of the other biliary tract tissues. One gallbladder adenoma showed a weak telomerase ladder. The telomerase ladder was detected in the bile sample from 1 patient (5.3%) with malignant biliary tract disease, none of the patients with benign biliary tract disease, 5 patients (50%) with malignant pancreatic disease, and none of the patients with benign pancreatic disease. In biopsy specimens, the telomerase ladder was detected in 75% of patients with bile duct carcinoma but not in any of the patients with hepatolithiasis. The median value of relative telomerase activity in the patients with bile duct carcinoma was significantly higher than that in the patients with hepatolithiasis. The diagnosis of bile duct carcinoma was confirmed preoperatively by histopathologic examination in only 25% of the biopsy specimens.

CONCLUSIONS

The results of the current study indicate that telomerase is highly activated in biliary tract carcinomas and that the detection of a telomerase ladder in biopsy samples is an excellent tool for the diagnosis of bile duct carcinomas.

9-Hydroxyellipticine inhibits telomerase activity in human pancreatic cancer cells

There is increasing interest in identifying potent inhibitors of telomerase because the enzyme plays a crucial role in the development of cellular immortality and carcinogenesis. We hypothesized that 9-hydroxyellipticine (9-HE), an antitumor alkaloid, would inhibit telomerase activity because the drug has a unique mechanism of inhibiting phosphorylation of mutant p53 protein via inhibition of protein kinases, thereby restoring wild-type p53 function. This study was conducted to examine the effect of 9-HE on telomerase activity in human pancreatic cancer cells with differing p53 gene status. 9-HE treatment at relatively high concentrations resulted in rapid, complete inhibition of telomerase activity, irrespective of the p53 status. We conclude that 9-HE may exert a strong inhibitory effect on telomerase activity possibly through inhibition of protein kinases rather than through restoration of functional wild-type p53.

Telomerase activity detected in pancreatic juice 19 months before a tumor is detected in a patient with pancreatic cancer

We report a patient with pancreatic cancer in whom telomerase activity had been detected in the pancreatic juice 19 months before he was diagnosed as having pancreatic cancer. A 61-yr-old alcoholic man complaining of epigastric and back pain was diagnosed as having groove pancreatitis based on the presence of inflammation in the pancreatic head and its extension to the duodenal mucosa with an associated elevated serum amylase level. All imaging modalities showed no sign of a tumor. However, high telomerase activity was detected in the pancreatic juice collected during endoscopic retrograde pancreatography. His symptoms subsided due to abstinence from alcohol. A tumor, however, was recognized on computed tomography 19 months later, at which time the patient immediately underwent a pylorus-preserving pancreaticoduodenectomy. The carcinoma was located mainly in the Santorini duct region. High telomerase activity in the pancreatic juice may precede clinical detection of pancreatic cancer and thus could be a useful early diagnostic marker for pancreatic cancer.