In situ nucleic acid detection of human telomerase in intrahepatic cholangiocarcinoma and its preneoplastic lesion

Telomere length and risk of cirrhosis, hepatocellular carcinoma, and cholangiocarcinoma in 63,272 individuals from the general population

BACKGROUND AND AIMS

Inherited short telomeres are associated with a risk of liver disease, whereas longer telomeres predispose to cancer. The association between telomere length and risk of HCC and cholangiocarcinoma remains unknown.

APPROACH AND RESULTS

We measured leukocyte telomere length using multiplex PCR in 63,272 individuals from the Danish general population. Telomere length and plasma ALT concentration were not associated (β = 4 ×10 -6 , p -value = 0.06) in a linear regression model, without any signs of a nonlinear relationship. We tested the association between telomere length and risk of cirrhosis, HCC, and cholangiocarcinoma using Cox regression. During a median follow-up of 11 years, 241, 76, and 112 individuals developed cirrhosis, HCC, and cholangiocarcinoma, respectively. Telomere length and risk of cirrhosis were inversely and linearly associated ( p -value = 0.004, p for nonlinearity = 0.27). Individuals with telomeres in the shortest vs. longest quartile had a 2.25-fold higher risk of cirrhosis. Telomere length and risk of HCC were nonlinearly associated ( p -value = 0.009, p -value for nonlinearity = 0.01). This relationship resembled an inverted J-shape, with the highest risk observed in individuals with short telomeres. Individuals with telomeres in the shortest versus longest quartile had a 2.29-fold higher risk of HCC. Telomere length was inversely and linearly associated with the risk of cholangiocarcinoma. Individuals with telomeres in the shortest versus longest quartile had a 1.86-fold higher risk of cholangiocarcinoma.

CONCLUSIONS

Shorter telomere length is associated with a higher risk of cirrhosis, HCC, and cholangiocarcinoma.

The Hallmarks of Liver Fluke Related Cholangiocarcinoma: Insight into Drug Target Possibility

Cholangiocarcinoma (CCA) is a malignant tumor of the biliary tree that is classified into three groups based on its anatomic location: intrahepatic (iCCA), perihilar (pCCA), and distal (dCCA). Perihilar CCA is the most common type and accounts for 50-60% of CCA cases. It is followed by distal CCA and then intrahepatic CCA that account for 20-30% and 10-20% of cases, respectively. This chapter discusses the hallmarks of liver fluke related CCA and explores insights into drug target possibilities.

Preneoplastic lesions in the liver: Molecular insights and relevance for clinical practice

Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) are the most frequent primary liver cancers, accounting for approximately 80% and 15%, respectively. HCC carcinogenesis occurs mostly in cirrhosis and is a complex multi-step process, from precancerous lesions (low-grade and high-grade dysplastic nodules) to progressed HCC. During the different stages of liver carcinogenesis, there is an accumulation of pathological, genetic and epigenetic changes leading to initiation, malignant transformation and finally tumour progression. In contrast, a small subset of HCC occurs in normal liver from the transformation of hepatocellular adenoma (HCA), a benign hepatocellular tumour. The recent molecular classification enables to stratify HCAs according to their risk of complication, in particular malignant transformation, associated with mutations in exon 3 of the catenin beta 1 (CTNNB1) gene. Cholangiocarcinoma (CCA) derives from the multistep malignant transformation of preneoplastic lesions, like biliary intraepithelial neoplasia (BilIN) and intraductal papillary neoplasm of the bile duct (IPNB), for which a pre-operative diagnosis remains difficult. Different genetic alterations are involved in BilIN and IPNB progression, leading to the development of tubular or intestinal adenocarcinoma. The aims of this review are to describe the main clinical and molecular features of preneoplastic lesions leading to the development of HCC and CCA, their implications in clinical practice and the perspectives for future research.

Telomerase reactivation is associated with hepatobiliary and pancreatic cancers

BACKGROUND

Human telomerase reverse transcriptase (hTERT) and its components play a significant role in cancer progression, but recent data demonstrated that telomeres and telomerase alterations could be found in other diseases; increasing evidence suggests a key role of this enzyme in the fields of hepatobiliary and pancreatic diseases.

DATA SOURCES

We performed a PubMed search with the following keywords: telomerase, hepatocellular carcinoma, cholangiocarcinoma, pancreatic adenocarcinoma by December 2019. We reviewed the relevant publications that analyzed the correlation between telomerase activity and hepatobiliary and pancreatic diseases.

RESULTS

Telomerase reactivation plays a significant role in the development and progression of hepatobiliary and pancreatic tumors and could be used as a diagnostic biomarker for hepatobiliary and pancreatic cancers, as a predictor for prognosis and a promising therapeutic target.

CONCLUSIONS

Our review summarized the evidence about the critical role of hTERT in cancerous and precancerous lesions of the alteration and its activity in hepatobiliary and pancreatic diseases.

Telomeres and Telomerase in the Development of Liver Cancer

Liver cancer is one of the most common cancer types worldwide and the fourth leading cause of cancer-related death. Liver carcinoma is distinguished by a high heterogeneity in pathogenesis, histopathology and biological behavior. Dysregulated signaling pathways and various gene mutations are frequent in hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA), which represent the two most common types of liver tumors. Both tumor types are characterized by telomere shortening and reactivation of telomerase during carcinogenesis. Continuous cell proliferation, e.g., by oncogenic mutations, can cause extensive telomere shortening in the absence of sufficient telomerase activity, leading to dysfunctional telomeres and genome instability by breakage-fusion-bridge cycles, which induce senescence or apoptosis as a tumor suppressor mechanism. Telomerase reactivation is required to stabilize telomere functionality and for tumor cell survival, representing a genetic risk factor for the development of liver cirrhosis and liver carcinoma. Therefore, telomeres and telomerase could be useful targets in hepatocarcinogenesis. Here, we review similarities and differences between HCC and iCCA in telomere biology.

Prognostic value of DNA alterations on chromosome 17p13.2 for intrahepatic cholangiocarcinoma

AIM

To characterize and evaluate DNA alterations among intrahepatic cholangiocarcinoma (ICC) patients.

METHODS

DNA from tumor and corresponding normal tissues of 52 patients was amplified with 33 arbitrary primers. The DNA fragment that alters most frequently in ICC was cloned, sequenced, and identified by comparison with known nucleotide sequences in the genome database (www.ncbi.nlm.nih.gov). The DNA copy numbers of the allelic alterations in cholangiocarcinoma were determined by quantitative real-time PCR and interpreted as allelic loss or DNA amplification by comparison with the reference gene. Associations between allelic imbalance and clinicopathological parameters of ICC patients were evaluated by chi2-test. The Kaplan-Meier method was used to analyze survival rates.

RESULTS

From 33 primers, an altered DNA fragment (518 bp) amplified from BC17 random primer was found frequently in the tumors analyzed and mapped to chromosome 17p13.2. Sixteen of 52 (31%) cases showed DNA amplification, while 7 (13%) showed allelic loss. Interestingly, DNA amplification on chromosome 17p13.2 was associated with a good prognosis, median survival time (wk) of amp vs no amp was 44.14 vs 24.14, P = 0.002; whereas allelic loss of this DNA sequence corresponded with a poor prognosis, median survival time (wk) of loss vs no loss was 18.00 vs 28.71, P = 0.019). Moreover, Kaplan-Meier curves comparing the DNA alterations with survival depicted highly significant separation that the median survival time equal to DNA amplification, allelic loss, and normal was 44.14 wk, 18.00 wk, and 24.29 wk, respectively (P = 0.005).

CONCLUSION

Alterations in the DNA sequence on chromosome 17p13.2 may be involved in cholangio-carcinogenesis, and could be used as a prognostic marker in the treatment of ICC patients.

Molecular pathology of biliary tract cancers

The molecular mechanisms underlying the development, growth and metastatic diffusion of biliary tract cancers are still undefined. The increase in worldwide incidence and mortality of cholangiocarcinoma justifies the impellent need to clarify the intracellular mechanisms triggering the malignant transformation of the biliary epithelium and growth of biliary malignancies. A more complete characterization of the molecular pathology of bile duct cancers could lead to the identification of valid targets for the diagnosis and therapy of these devastating malignancies. This review describes the scientific progress made over the past decades with regard to the understanding of the molecular processes of cholangiocarcinogenesis.

Interleukin-6 decreases senescence and increases telomerase activity in malignant human cholangiocytes

BACKGROUND/AIMS

Cellular senescence results in irreversible growth arrest. In malignant cells, senescence is prevented by maintenance of chromosomal length by telomerase activity. Telomerase activity is increased in malignant, but not in normal cholangiocytes. Interleukin-6 (IL-6) is an autocrine promoter of cholangiocarcinoma growth. Our aims were to assess the relationship between IL-6 activated p38 mitogen-activated protein kinase (MAPK) pathways and senescence in malignant cholangiocytes.

METHODS

Cell senescence and telomerase activity was assessed in Mz-ChA-1 malignant human cholangiocytes. The effect of inhibitors of p38 MAPK and telomerase activity on cell proliferation was assessed, and the interaction between these inhibitors was quantitated by median effects analysis.

RESULTS

Mz-ChA-1 cells rapidly underwent senescence during repeated passaging. IL-6 increased telomerase activity and decreased cellular senescence during repeated passaging. However, basal telomerase activity was increased by inhibition of p38 MAPK. Inhibition of telomerase activity decreased IL-6 induced proliferation and had a synergistic effect with p38 MAPK inhibitors. Thus, IL-6 increases telomerase activity independent of p38 MAPK signaling and maintenance of telomerase activity promotes cholangiocarcinoma growth.

CONCLUSION

Enhanced telomerase activity in response to IL-6 stimulation can prevent cellular senescence and thereby contribute to cholangiocarcinoma growth. Inhibition of telomerase activity may therefore be therapeutically useful in biliary tract malignancies.

Cholangiocarcinoma: molecular targeting strategies for chemoprevention and therapy

Cholangiocarcinomas are devastating cancers that are increasing in both their worldwide incidence and mortality rates. The challenges posed by these often lethal biliary tract cancers are daunting, with conventional treatment options being limited and the only hope for long-term survival being that of complete surgical resection of the tumor. Unfortunately, the vast majority of patients with cholangiocarcinoma typically seek treatment with advanced disease, and often these patients are deemed poor candidates for curative surgery. Moreover, conventional chemotherapy and radiation therapy have not been shown to be effective in prolonging long-term survival, and although photodynamic therapy combined with stenting has been reported to be effective as a palliative treatment, it is not curative. Thus, there is a real need to develop novel chemopreventive and adjuvant therapeutic strategies for cholangiocarcinoma based on exploiting select molecular targets that would impact in a significant way on clinical outcome. This review focuses on potential preventive targets in cholangiocarcinogenesis, such as inducible nitric oxide synthase, cyclooxygenase-2, and altered bile acid signaling pathways. In addition, molecular alterations related to dysregulation of cholangiocarcinoma cell growth and survival, aberrant gene expression, invasion and metastasis, and tumor microenvironment are described in the context of various clinical and pathological presentations. Moreover, an emphasis is placed on the importance of critical signaling pathways and postulated interactions, including those of ErbB-2, hepatocyte growth factor/Met, interleukin-6/glycoprotein130, cyclooxygenase-2, vascular endothelial growth factor, transforming growth factor-beta, MUC1 and MUC4, beta-catenin, telomerase, and Fas pathways as potential molecular therapeutic targets in cholangiocarcinoma.

In situ detection of TGF betas, TGF beta receptor II mRNA and telomerase activity in rat cholangiocarcinogenesis

AIM: Initial report on the in situ examination of the mRNA expression of transforming growth factor betas (TGFβs), TGFβ type II receptor (TβRII) and telomerase activity in the experimental rat liver tissue during cholangiocarcinogenesis.

METHODS: Rat liver cholangiocarcinogenesis was induced by 3’-methyl 4-dimethylazobenzene (3’Me-DAB). In situ hybridization was used to examine the TGFβs) and TGFβ type II receptor (TβRII) mRNA, in situ TRAP was used to check the telomerase activity in the tissue samples.

RESULTS: There was no TGFβs, TβRII mRNA expression or telomerase activity in the control rat cholangiocytes. The expression of TGFβ1, TβRII was increased in regenerative, hyperplastic, dysplastic cholangiocytes and cholangiocarcinoma (CC) cells. The expression of TGFβ2 mRNA was observed in only a part of hyperplastic, dysplastic cholangiocytes. TGFβ3 expression was very weak, only in hyperplastic lesion. There was positive telomerase activity in the regenerative, hyperplastic, dysplastic cholangiocytes, and CC cells. Stroma fibroblasts of these lesions also showed positive TGFβs, TβRII mRNA expression and telomerase activity.

CONCLUSION: There were TGFβs, TβRII expression and telomerase activity in hyperplastic, dysplastic cholangiocytes, cholangiocarcinoma cells as well as in stroma fibroblasts during cholangiocarcinogenesis. Their expression or activity is important in cholangiocarcinogenesis andstroma formation.

Cholangiocarcinoma: recent progress. Part 2: molecular pathology and treatment

Part 2 of this review discusses DNA damage in biliary epithelial cells in the development of cholangiocarcinoma, alterations in cell kinetics of biliary epithelial cells, biliary epithelial mitoinhibition, and apoptosis that includes the role of Bcl-2, transforming growth factor-beta, telomerase activities and deregulation of Ras and p53, cancer-associated antigens in cholangiocarcinoma, precancerous lesions, stroma formation and angiogenesis, cancer invasion, cell-cell and cell-matrix interactions, and the mechanism of evasion from immune surveillance. These discussions are followed briefly by treatments such as photodynamic therapy, and surgical approaches comparing resection and liver transplantation.

Telomerase in human tumors: molecular diagnosis and clinical significance

Shortening of structures known as telomeres, which cap the ends of chromosomes, is postulated to limit the lifespan of human cells. Activation of telomerase, an enzyme that synthesizes telomeric DNA, is an essential step in cell immortalization. Telomerase is ordinarily inactive in most somatic cells, but can be detected in nearly all tumors. The activation of telomerase in malignant cancers seems to be an important step in tumorigenesis, whereby the cell gains the ability of indefinite proliferation. Due to the association between telomerase expression and malignancy, the enzyme is expected to be a useful tumor marker and a new anticancer therapeutic target. However, recent results scale down to some extent the initial enthusiastic expectations for telomerase as the ideal malignancy marker.

Clinical implications of telomerase detection

In 1994 a sensitive method for the detection of telomerase was described. This assay, which was based on the polymerase chain reaction, suggested that telomerase activity was associated with immortal and cancer cells. Since then more than a thousand studies have documented the expression and activity of the enzyme in diseased tissues, primarily tumours. This review gives an overview of the biological significance of telomerase expression and methods for detecting its activity. This is followed by an organ system-based discussion of expression in normal tissues and disease states. We finish with speculation as to the future role of telomerase detection in diagnostic histopathology.

Hepatocellular carcinoma

The incidence of hepatocellular carcinoma (HCC) appears to be declining in Taiwan and potentially in other high-prevalence areas as a consequence of vaccination for hepatitis B virus (HBV). However, there is evidence that the incidence of HCC is increasing in North America and Europe. This appears to be related to the increasing prevalence and duration of hepatitis C virus (HCV) infection in these countries. There is also growing evidence to support an increase in the risk of HCC in patients with HCV who are coinfected with occult HBV (patients who have lost HBV surface antigen but still have detectable HBV DNA either in blood or liver). Occult HBV infection in patients with HCV may be more common than previously thought, and HCC that occurs in this setting appears to have a worse prognosis. There is continuing interest in the effect of interferon therapy on the incidence of HCC in patients with HCV. Several studies from Japan have shown a benefit in patients without cirrhosis, although there are a number of potentially confounding variables that may partly explain these results. Prospective randomized studies are needed to investigate this important question. The molecular biology of HCC and the events of malignant transformation in the liver continue to be areas of intense study. Recently, there has been considerable interest in telomeres, the repeat units on the ends of chromosomes, and the enzyme that maintains these, telomerase. Telomeres shorten with each cell division and can be used to determine the number of divisions a cell has undergone. Eventually they reach a critical length, with further loss resulting in cellular senescence. Telomerase restores telomere length and may help malignant cells escape senescence. Nearly all HCCs have telomerase activity and assessments of telomeres and telomerase may be clinically useful.