Expression of telomerase component genes in hepatocellular carcinomas

Prognostic analysis and risk assessment based on RNA editing in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality, and prognosis assessment is crucial for guiding treatment decisions. In this study, we aimed to develop a personalized prognostic model for HCC based on RNA editing. RNA editing is a post-transcriptional process that can affect gene expression and, in some cases, play a role in cancer development. By analyzing RNA editing sites in HCC, we sought to identify a set of sites associated with patient prognosis and use them to create a prognostic model. We gathered RNA editing data from the Synapse database, comprising 9990 RNA editing sites and 250 HCC samples. Additionally, we collected clinical data for 377 HCC patients from the Cancer Genome Atlas (TCGA) database. We employed a multi-step approach to identify prognosis-related RNA editing sites (PR-RNA-ESs). We assessed how patients in the high-risk and low-risk groups, as defined by the model, fared in terms of survival. A nomogram was developed to predict the precise survival prognosis of HCC patients and assessed the prognostic model's utility through a receiver operating characteristic (ROC) analysis and decision curve analysis (DCA). Our analysis identified 33 prognosis-related RNA editing sites (PR-RNA-ESs) associated with HCC patient prognosis. Using a combination of LASSO regression and cross-validation, we constructed a prognostic model based on 13 PR-RNA-ESs. Survival analysis demonstrated significant differences in the survival outcomes of patients in the high-risk and low-risk groups defined by this model. Additionally, the differential expression of the 13 PR-RNA-ESs played a role in shaping patient survival. Risk-prognostic investigations further distinguished patients based on their risk levels. The nomogram enabled precise survival prognosis prediction. Our study has successfully developed a highly personalized and accurate prognostic model for individuals with HCC, leveraging RNA editing data. This model has the potential to revolutionize clinical evaluation and medical management by providing individualized prognostic information. The identification of specific RNA editing sites associated with HCC prognosis and their incorporation into a predictive model holds promise for improving the precision of treatment strategies and ultimately enhancing patient outcomes in HCC.

Correlation between the expression of hTERT gene and the clinicopathological characteristics of hepatocellular carcinoma

The aim of the present study was to detect the expression levels of the human telomerase reverse transcriptase (hTERT) gene in hepatocellular carcinoma (HCC), and investigate its significance in the incidence and development of the cancer. HCC tissues and corresponding para-carcinoma liver tissues were surgically collected from 78 patients with HCC who presented to Shandong Provincial Hospital (Jinan, Shandong, China). hTERT expression at the protein and mRNA levels were detected by immunohistochemistry (streptavidin peroxidase method) and reverse transcription polymerase chain reaction, respectively, in the HCC tissues and corresponding para-carcinoma liver tissues of 78 HCC patients and in 12 samples of normal liver tissue. The data were analyzed using SPSS 17.0 statistical software, and employing χ² tests and t-tests. hTERT protein was mainly expressed in the HCC cell cytoplasm, but was occasionally observed in the cell nucleus. The positive rates of hTERT protein and mRNA expression in the HCC patients were 84.62% (66/78) and 78.21% (61/78), respectively, which was significantly higher compared with the rates of 10.26% (8/78) and 8.97% (7/78) in the paired para-carcinoma liver tissues (P<0.01). hTERT protein and mRNA were not expressed in the normal liver tissues (0/12). χ² test and t-test analysis revealed that hTERT gene expression was correlated with tumor grade, the presence/absence of a portal vein tumor thrombus, hepatitis B surface antigen positivity and a high α-fetoprotein level (P<0.05) rather than patient age, gender or tumor size. Expression of the hTERT gene may play a pivotal role in the incidence and development of HCC. The hTERT gene potentially serves as an important molecular and biological index for diagnosing and predicating the biological behavior of HCC.

From chronic liver disorders to hepatocellular carcinoma: Molecular and genetic pathways

Hepatocarcinogenesis is a process attributed to progressive genomic changes that alter the hepatocellular phenotype producing cellular intermediates that evolve into hepatocellular carcinoma (HCC). During the preneoplastic phase, the liver is often the site of chronic hepatitis and/or cirrhosis, and these conditions induce liver regeneration with accelerated hepatocyte cycling in an organ that is otherwise proliferatively at rest. Hepatocyte regeneration is accelerated by upregulation of mitogenic pathways involving molecular and genetic mechanisms. Hepatic growth factors, inhibitors and triggers may also play a role. This process leads to the production of monoclonal populations of aberrant and dysplastic hepatocytes that have telomerase re-expression, microsatellite instability, and occasionally structural aberrations in genes and chromosomes. Development of dysplastic hepatocytes in foci and nodules and the emergence of HCC are associated with the accumulation of irreversible structural alterations in genes and chromosomes even if the genomic basis of the malignant phenotype is largely heterogeneous. Therefore, a malignant hepatocyte phenotype may be produced by changes in genes acting through different regulatory pathways, thus producing several molecular variants of HCC. On these bases, a key point for future research will be to determine whether the deletions are specific, due to particular loci in the minimally deleted regions of affected chromosome arms, or whether they are non-specific with loss of large portions of chromosomes or entire chromosome arms leading to passive deletion of loci. The final aim is the possibility of identifying a step where carcinogenetic processes could be terminated.

A novel biomarker TERTmRNA is applicable for early detection of hepatoma

Backgrounds

We previously reported a highly sensitive method for serum human telomerase reverse transcriptase (hTERT) mRNA for hepatocellular carcinoma (HCC). α-fetoprotein (AFP) and des-γ-carboxy prothrombin (DCP) are good markers for HCC. In this study, we verified the significance of hTERTmRNA in a large scale multi-centered trial, collating quantified values with clinical course.

Methods

In 638 subjects including 303 patients with HCC, 89 with chronic hepatitis (CH), 45 with liver cirrhosis (LC) and 201 healthy individuals, we quantified serum hTERTmRNA using the real-time RT-PCR. We examined its sensitivity and specificity in HCC diagnosis, clinical significance, ROC curve analysis in comparison with other tumor markers, and its correlations with the clinical parameters using Pearson relative test and multivariate analyses. Furthermore, we performed a prospective and comparative study to observe the change of biomarkers, including hTERTmRNA in HCC patients receiving anti-cancer therapies.

Results

hTERTmRNA was demonstrated to be independently correlated with clinical parameters; tumor size and tumor differentiation (P < 0.001, each). The sensitivity/specificity of hTERTmRNA in HCC diagnosis showed 90.2%/85.4% for hTERT. hTERTmRNA proved to be superior to AFP, AFP-L3, and DCP in the diagnosis and underwent an indisputable change in response to therapy. The detection rate of small HCC by hTERTmRNA was superior to the other markers.

Conclusions

hTERTmRNA is superior to conventional tumor markers in the diagnosis and recurrence of HCC at an early stage.

Serum messenger RNA as a biomarker and its clinical usefulness in malignancies

A number of biomarkers are used clinically and many protein-based assay methods are available. Improvements in the method to utilize specific antibodies have led to remarkable progress in clinical diagnosis using biomarkers. Proteomics studies to identify better biomarkers have been performed worldwide by using a protein-based comprehensive method. The detection rate of conventional biomarkers can not improve further. Now is a time that a breakthrough is needed. We previously proposed mRNA, which is circulating in the body, as a novel material for biomarkers. mRNA is an unexpectedly useful molecule, not only because it can detect genes with a low expression level in protein, but also because it can detect the expression from non-coding RNA precursor genes or gene products with limited secretion from the cells. Circulating mRNA has been thought to be unstable in blood containing RNase. We confirm that mRNA remains at the same level for 24 hours after blood sampling. Unlike DNA, the RNA molecule can reflect events in the human body which occurred within a day, resulting in an early diagnosis of diseases. We report the possibility to detect and quantify cancer-derived mRNAs circulating in human vessels. We introduce the detection of serum mRNA as a useful biomarker of human malignancies.

High telomerase activity and long telomeres in advanced hepatocellular carcinomas with poor prognosis

Telomerase reactivation and telomere maintenance are crucial in carcinogenesis and tumor progression. In this study, the relationships between telomere parameters, chromosomal instability and clinicopathological features were evaluated in hepatocellular carcinomas (HCCs). Telomere length (TL), telomerase activity (TA) and human telomerase reverse transcriptase (hTERT) mRNA levels were measured in 49 hepatitis B virus (HBV)-related HCCs and corresponding non-tumorous tissues. The results were compared with clinicopathological data, including differentiation, multipolar mitosis (MM), anaphase bridge, immunohistochemical stain results for cytokeratin 19 (CK19) and patient outcome. TL of HCCs ranged from 4.7 to 13.1 kb, and 44.4% of HCCs showed telomere lengthening. hTERT mRNA levels and TA were closely related (P=0.008), and were significantly higher in HCCs than non-tumorous tissues. TL was significantly higher in HCCs with strong TA (P=0.048), high hTERT mRNA levels (P=0.001) and poor differentiation (P=0.041). Frequent MM was associated with poor differentiation (P=0.007) and advanced stage (P<0.001). TA was positively correlated with MM, anaphase bridges and advanced stage (P=0.019, P=0.017 and P=0.029). Thirteen (28.3%) HCCs were CK19+ and demonstrated longer telomeres than CK19- HCCs (P=0.046). Overall survival was poor in HCCs with MM >0.4 per field (P=0.016), high TA (P=0.009) and high TL ratio (HCC/non-HCC) >0.8 (P=0.044). Our results show that long telomeres, high TA and high mitotic instability are poor prognostic markers for HBV-related HCCs and their close association suggests that telomere maintenance may be important for the progression of HCCs with high chromosomal instability to more aggressive ones.

Telomerase deletion limits progression of p53-mutant hepatocellular carcinoma with short telomeres in chronic liver disease

BACKGROUND & AIMS

During early stages of carcinogenesis most human epithelial cancers including hepatocellular carcinoma (HCC) have been observed to transit through a "crisis" stage characterized by telomere shortening, loss of p53 checkpoint function, and a sharp increase in aneuploidy. The function of telomerase during in vivo hepatocarcinogenesis has not been studied in this genetic context.

METHODS

Here we generated a mouse model in which HCC was induced by chronic organ damage (HBs-AG transgene) in the presence of telomere shortening and p53 deletion. Tumor development was analyzed in late-generation telomerase knockout mice (mTERC(-/-)) and littermates, genetically rescued for telomerase gene expression (mTERC(+/-)).

RESULTS

The formation of HCCs was strongly suppressed in mTERC(-/-) mice compared to mTERC(+/-) siblings correlating with reduced rates of tumor cell proliferation and elevated rates of tumor cell apoptosis. Although the prevalence of short telomeres was similar in chronically damaged liver of both cohorts, mTERC(-/-) HCC developed increased levels of DNA damage and aneuploidy compared to mTERC(+/-) HCC.

CONCLUSIONS

This study provides direct evidence that telomerase is a critical component for in vivo progression of p53 mutant HCC with short telomeres in the chronically damaged liver. In this molecular context, telomerase limits the accumulation of telomere dysfunction, the evolution of excessive aneuploidy, and the activation of p53-independent checkpoints suppressing hepatocarcinogenesis.

Small-molecule c-Myc inhibitor, 10058-F4, inhibits proliferation, downregulates human telomerase reverse transcriptase and enhances chemosensitivity in human hepatocellular carcinoma cells

c-Myc oncogene is critical for the development of hepatocellular carcinoma. Given the successful use of small-molecule inhibitors on cancers, targeting c-Myc with small-molecule inhibitors represents a promising approach. The potential of using small-molecule c-Myc inhibitor, 10058-F4, was evaluated on hepatocellular carcinoma cell lines, HepG2 and Hep3B cells. HepG2 cells were more sensitive to 10058-F4 than Hep3B cells, as demonstrated by reduced cell viability, marked morphological changes and decreased c-Myc levels. 10058-F4 arrested the cell cycle (at G0/G1 phase) and induced apoptosis upon extended treatment. These observations might be attributable to the increased cyclin-dependent kinase inhibitor, p21, and decreased cyclin D3 levels. Besides, 10058-F4 also significantly decreased the alpha-fetoprotein levels, an indicator for hepatocellular carcinoma differentiation. We further found that 10058-F4 inhibited the transactivation of human telomerase reverse transcriptase, downregulated human telomerase reverse transcriptase expression and abrogated telomerase activity. In addition, pretreatment with 10058-F4 increased the chemosensitivity of HepG2 cells to low-dose doxorubicin, 5-fluorouracil and cisplatin. Therefore, small-molecule c-Myc inhibitors might represent a novel agent, alone or in combination with conventional chemotherapeutic agents, for anti-hepatocellular carcinoma therapy.

[Mechanism of cell proliferation--cell cycle, oncogenes, and senescence]

Cell proliferation is regulated through a transition between the G0 phase and cell cycle. We isolated a mammalian temperature-sensitive mutant cell line defective in the function from the G0 phase to cell cycle. Senescent human somatic cells fail to enter into the cell cycle from the G0 phase with stimulation by any growth factor. Telomere shortening was found to be a cause of cellular senescence, and reexpression of telomerase immortalized human somatic cells. Immortalized human somatic cells showed normal phenotypes and were useful not only for basic research but also for clinical and applied fields. The importance of p53 and p21 activation/induction i now well accepted in the signal transduction process from telomere shortening to growth arrest, but the precise mechanism is largely unknown as yet. We found that the MAP kinase cascade and histone acetylase have an important role in the signaling process to express p21. Tumor tissues and cells were found to have strong telomerase activity, while most normal somatic human tissues showed very weak or no activity. Telomerase activity was shown to be a good marker for early tumor diagnosis because significant telomerase activity was detected in very early tumors or even in some precancerous tissues compared with adjacent normal tissues. Telomere/telomerase is a candidate target for cancer chemotherapeutics, and an agent that abrogated telomere functions was found to kill tumor cells effectively by inducing apoptosis whereas it showed no effect on the viability of normal cells.

Real-time quantification of human telomerase reverse transcriptase mRNA in liver tissues from patients with hepatocellular cancer and chronic viral hepatitis

We determined, for the first time, the human telomerase reverse transcriptase (hTERT) mRNA expression, using real-time quantitative PCR, in liver tissues from patients with hepatocellular cancer (HCC; n = 13), chronic hepatitis B (n = 19) and C (n = 13). Liver tissues from the 45 patients and 17 patients without liver disease in whom liver biopsy was performed during cholecystectomy (control group), were investigated for telomerase activity (TA) and hTERT mRNA expression using the LightCycler technology. TA was detected in all HCC tissues compared with 15.6% of chronic hepatitis (P < 0.001) and none of controls (P < 0.001). TA levels and hTERT mRNA were higher in HCC compared with chronic hepatitis (P < 0.001) and normal livers (P < 0.001). hTERT mRNA expression was correlated with TA (P < 0.05). Chronic hepatitis patients who tested negative for TA and hTERT mRNA had significantly lower disease duration (58 +/- 85 months) compared with those tested positive (144 +/- 50 months; P < 0.05). Detection of TA and quantification of hTERT mRNA expression in liver tissues could be useful and additional markers for HCC diagnosis and may serve as prognostic markers for HCC development in chronic viral hepatitis patients. However, we were not able to draw general conclusions at this moment, as the number of chronic hepatitis patients positive for hTERT mRNA was relatively small. Real-time quantification of hTERT mRNA expression as a diagnostic/prognostic marker in patients with chronic hepatitis B and C and its relationship with hepatocarcinogenesis needs further evaluation.

Dynamic alteration of telomerase expression and its diagnostic significance in liver or peripheral blood for hepatocellular carcinoma

AIM: To investigate the dynamic alteration of telomerase expression during development of hepatocellular carcinoma (HCC) and its diagnostic implications in liver tissues or peripheral blood mononuclear cells for HCC.

METHODS: Dynamic expressions of liver telomerase during malignant transformation of hepatocytes were observed in Sprague-Dawly (SD) rats fed with 0.05% of 2-fluoenyacetamide (2-FAA). Total RNA and telomerase were extracted from rat or human liver tissues. The telomerase activities in livers and in circulating blood were detected by a telomeric repeat amplification protocol-enzyme-linked immunosorbent assay (TRAP-ELISA), and its diagnostic value was investigated in patients with benign or malignant liver diseases.

RESULTS: The hepatoma model displayed the dynamic expression of hepatic telomerase during HCC development. The telomerase activities were consistent with liver total RNA levels (r = 0.83, P < 0.01) at the stages of degeneration, precancerosis, and cancerization of hepatocytes. In HCC patients, the telomerase levels in HCC tissues were significantly higher than in their adjacent non-cancerous tissues, but liver total RNA levels were lower in the former than in the latter. Although the circulating telomerase of HCC patients was abnormally expressed among patients with chronic liver diseases, the telomerase activity was a non-specific marker for HCC diagnosis, because the incidence was 15.7% in normal control, 25% in chronic hepatitis, 45.9% in liver cirrhosis, and 85.2% in HCC, respectively when absorbance value of telomerase activity was more than 0.2. If the value was over 0.6, the incidence was 60% in HCC group and 0% in any of the others (P < 0.01) except in two cases with liver cirrhosis. However, the combination of circulating telomerase with serum alpha-fetoprotein level could increase the positive rate and the accuracy (92.6%, 125 of 135) of HCC diagnosis.

CONCLUSION: The overexpression of telomerase is associated with HCC development, and its abnormality in liver tissues or in peripheral blood could be a useful marker for diagnosis and prognosis of HCC.

Serum human telomerase reverse transcriptase messenger RNA as a novel tumor marker for hepatocellular carcinoma

PURPOSE

We previously reported the usefulness of a qualified highly sensitive detection method for human telomerase reverse transcriptase (hTERT) mRNA in serum with 89.7% sensitivity for hepatocellular carcinoma (HCC). In this study, we developed a quantitative detection method for serum hTERT mRNA and examined the clinical significance in HCC diagnosis. EXPERIMENTAL BACKGROUND: In 64 patients with HCC, 20 with liver cirrhosis, 20 with chronic hepatitis, and 50 healthy individuals, we measured serum hTERT mRNA by using the newly developed real-time quantitative reverse transcription-PCR with SYBR Green I. We examined its sensitivity and specificity in HCC diagnosis, clinical significance in comparison with other tumor markers, and its correlations with the clinical variables by using multivariate analyses.

RESULTS

Serum hTERT mRNA showed higher values in patients with HCC than those with chronic liver diseases. hTERT mRNA expression was shown to be independently correlated with clinical variables such as tumor size, number, and degree of differentiation (P < 0.001, each). The sensitivity/specificity of hTERT mRNA and alpha-fetoprotein (AFP) mRNA in HCC diagnosis were 88.2%/70.0% for hTERT and 71.6%/67.5% for AFP, respectively. hTERT mRNA proved to be superior to AFP mRNA, AFP, and des-gamma-carboxy prothrombin in HCC diagnosis. Furthermore, hTERT mRNA in serum was associated with that in HCC tissue.

CONCLUSIONS

The usefulness of hTERT mRNA expression in HCC diagnosis and its superiority to conventional tumor markers were shown. Therefore, serum hTERT mRNA is a novel and available marker for HCC diagnosis.

Fumagillin treatment of hepatocellular carcinoma in rats: An in vivo study of antiangiogenesis

AIM: To investigate the effect and possible mechanisms of antiangiogenesis therapy for HCC in rats.

METHODS: Adult male LEW/SsN rats were divided into 3 groups, 25 animals each. Group A was the control group. Groups B and C were given diethylnitrosamine, 5 mg/kg/d. In addition, group C rats received an intraperitoneal injection of fumagillin, 30 mg/(kg·d). Five animals in each group were killed at 6^th, 12^th, 18^th, 20^th and 24^th wk to evaluate the development of HCC and metastasis. Weight of the rats, liver tumors, and number of organs involved by HCC were measured at each stage. We compared methionine aminopeptidase-2 (MetAP-2) mRNA, Bcl-2 mRNA, telomerase mRNA, and telomerase activity at 24^th wk in the liver tissue of group A rats and tumor tissue of HCC from group B and C rats.

RESULTS: No HCC developed in group A, but tumors were present in group B and C rats by the 18^th wk. At wk 20 and 24, the median liver weight in group B was 0.64 g (range: 0.58-0.70 g) and 0.79 g (range: 0.70-0.90 g) (P = 0.04), and that in group C was 0.37 g (range: 0.35-0.42 g) and 0.39 g (range: 0.35-0.47 g) (P = 0.67). The liver weight in group C rats was significantly lower than that in group B rats (P = 0.009). At the same time, the median metastasis score (number of organ systems involved) was 3 (range 2-3) in group B, and 1 (range 1-2) in group C, a significant difference between the groups (P = 0.007, 0.004). The levels of MetAP-2 mRNA were significantly higher in groups B and C than in group A (P = 0.025), and significantly higher in group C than in group B (P = 0.047). The level of Bcl-2 mRNA was significantly higher in group B than in group A (P = 0.024), but lower in group C than in group B, although not significantly (P = 0.072). Telomerase mRNA was significantly higher in group B than in group A (P = 0.025), but significantly lower in group C than in group B (P = 0.016). The same inter-group relationship was also true for telomerase activity (P = 0.025 and 0.046).

CONCLUSION: Fumagillin effectively inhibits both liver tumor growth and metastasis in rats in vivo. A possible mechanism is fumagillin-induced inhibition of MetAP-2, which plays an essential role in endothelial cell proliferation. Inhibition of MetAP-2 also results in inhibition of Bcl-2 and telomerase activity.

Telomerase reverse transcriptase gene amplification in hepatocellular carcinoma

BACKGROUND AND AIM

Telomerase activation is essential for the immortality of cancer cells. The expression of telomerase reverse transcriptase (hTERT), the catalytic component of the telomerase complex, regulates telomerase activity in human cancers. Amplification of the hTERT gene, located at chromosome 5p, is thought to be a potential genetic event contributing to telomerase activation in sporadic tumors.

METHODS

The amplification of the hTERT gene was examined in 46 surgically resected hepatocellular carcinomas (HCC) by real-time polymerase chain reaction and the status was compared with the expression of hTERT mRNA and clinicopathological parameters.

RESULTS

Amplified hTERT genes were found in 21.7% (10/46) of HCC. The incidence of amplified hTERT genes in poorly differentiated HCC (6/12, 50%) was significantly higher than that in highly to moderately differentiated HCC (4/34, 11.8%; P = 0.012). Tumor size in those cases with hTERT gene amplification was larger compared to those cases with no amplification (P = 0.047). Amplification of the hTERT gene was not observed in non-cancerous tissues. The hTERT mRNA level did not correlate with the number of hTERT genes.

CONCLUSIONS

Based on these results, it is thought that hTERT gene amplification is a cancer-specific event, and may furthermore contribute to the dedifferentiation and development of HCC. However, hTERT gene overexpression was rarely due to an increased hTERT gene copy number in HCC.

Telomerase and c-myc expression in hepatocellular carcinomas

BACKGROUND

Telomerase is activated in the majority of cancer tissues and immortalized cell lines. The hTERT (human telomerase reverse transcriptase-major component of telomerase) gene promoter has been cloned and contains many c-myc binding sites that mediate hTERT transcriptional activation. Thus far, the role of hTERT in tumorigenesis in hepatocellular carcinoma (HCC) has been little studied using RNA in situ hybridization. The relationship between c-myc and telomerase in human HCC tissue is undetermined.

MATERIALS AND METHODS

The telomerase activity was assayed using TRAP in specimens from 23 HCC patients, hTERTmRNA was detected using in situ hybridization from 57 HCC patients. The immunohistochemistry for c-myc and DNA sequence for hTERT promoter, and tumour differentiation in relation to hTERT and c-myc expression were determined in 57 specimens.

RESULT

hTERTmRNA was found in 47/57 (82.5%) HCC specimens using in situ hybridization. The hTERT expression paralleled telomerase activity, but hTERTmRNA regulation was not significantly associated with c-myc level ( P<0.954) The DNA sequence analysis of the hTERT promoter in specimens from 17 HCC revealed 15 cases of nucleotide transition (T-->C) over 5'-end of distal E-box and one case of nucleotide transversion (G-->C) over 5'-end of proximal E-box. Neither the hTERT expression (P< 0.890) nor c-myc level (P < 0.348) were related to HCC differentiation.

CONCLUSIONS

The hTERT expression paralleled telomerase activity. The telomerase activity in HCC was not only regulated by c-myc. Another pathways might contribute to hTERT and telomerase activity regulation. The lack of telomerase activity in specimens from 17.4% of HCC cases might indicate an alternative pathway for maintaining telomere length. Furthermore, both the telomerase activity and c-myc had no significant role in HCC differentiation.

Telomerase activity in tuberculous peritonitis and malignant ascites

AIM

To determine telomerase activity of exfoliated cells in tuberculous peritonitis and malignant ascites, and study the diagnostic value of telomerase activity in differentiating tuberculous peritonitis from malignant ascites.

METHODS

TRAP-PCR-ELISA and TRAP-PCR-silver staining were employed to determine telomerase activity in 18 specimens of malignant ascites and 13 specimens of tuberculous peritonitis. Telomerase activities in tuberculous peritonitis and malignant ascites were analysed.

RESULTS

Telomerase activity in malignant ascites (0.387±0.023)was significantly higher than that in tuberculous peritonitis(0.023±0.004, P<0.01). The positive rate of telomerase activity in malignant ascites was significantly higher than that in tuberculous peritonitis, 88.9% (16/18) vs 7.7% (1/13), P<0.01. The sensitivity, specificity and accuracy of determination of telomerase activity in diagnosis of malignant ascites were 88.9%, 92.3%, and 90.3%, respectively.

CONCLUSION

Telomerase activity is positive in malignant ascites and may serve as a useful indicator for differentiating between tuberculous peritonitis and malignant ascites.

Expressions of human telomerase mRNA component (hTERC) and telomerase reverse transcriptase (hTERT) mRNA in effusion cytology

Telomerase is a ribonucleoprotein enzyme that synthesizes telomeric DNA onto chromosomal ends. Its activity has been reported to be a novel diagnostic marker of malignant potential. However, no study has investigated the diagnostic importance of the expressions of human telomerase mRNA component (hTERC) and telomerase reverse transcriptase (hTERT) mRNA in effusion cytology. We investigated the expressions of hTERC and hTERT using in situ hybridization in 20 malignant cytologic specimens from 20 patients with adenocarcinomas disseminating into the pleura or peritoneum, and 16 benign cytologic specimens in pleural or peritoneal fluid (including reactive mesothelial cells) from 16 patients with non-neoplastic diseases. Expressions of hTERC and hTERT mRNA were detected in 95% and 90% of the 20 malignant cytology specimens, respectively, and were apparent within the cytoplasm of malignant cells. However, no expression was detected in reactive mesothelial cells in the 16 benign cytologic specimens. The expressions of hTERC and hTERT mRNA would appear to be a useful addition to cytology examination for diagnosis based on effusion cytology.

Screening for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is common throughout the world and most often develops as a late complication of chronic viral hepatitis or cirrhosis of any cause. As a result of the high prevalence rate of chronic hepatitis C, the incidence of HCC is rising in the United States, as well as in European and Asian countries. The overall survival rate of HCC is poor, and surgical resection and liver transplantation are the only curative treatment options. Screening for HCC offers the best hope for early detection, eligibility for treatment, and improved survival. Most physicians routinely screen at-risk patients with chronic viral hepatitis and cirrhosis for HCC, despite the lack of official guidelines. The current consensus recommendations are to screen healthy hepatitis B virus carriers with annual or semiannual serum alpha-fetoprotein; carriers with chronic hepatitis or cirrhosis and patients with cirrhosis of any etiology are surveyed with twice yearly serum alpha-fetoprotein and liver ultrasound. This article will review the current recommendations for HCC screening, the rationale that led to these recommendations, and the challenges of cost-effectiveness research in this area.

Telomerase inhibition and telomere loss in BEL-7404 human hepatoma cells treated with doxorubicin

AIM: To study the effects of doxorubicin on telomerase activity and telomere length in hepatocellular carcinoma.

METHODS: Telomerase activity was assayed with a non-radioisotopic quantitative telomerase repeat amplification protocal-based method. The effect of doxorubicin (DOX) on the growth of BEL-7404 human hepatoma cells was determined by microculture tetrazolium assay. Mean telomere length (terminal restriction fragment) was detected by Southern blot method. The expression of telomerase subunits genes was investigated by RT-PCR. Cell apoptosis and cell cycle distribution were evaluated by flow cytometry.

RESULTS: Telomerase activity was inhibited in a dose and time-dependent manner in BEL-7404 human hepatoma cells treated with DOX for 24, 48 or 72 h in concentrations from 0.156 to 2.5 μM which was crrelated with the inhibition of cell growth. No changes were found in the mRNA expression of three telomerase subunits (hTERT, hTR and TP1) after drug exposure for 72 h with indicated concentrations. The cells treated with DOX showed shortened mean telomere length and accumulated at the G₂/M phase. However, there was almost no effects on cell apoptosis by DOX.

CONCLUSION: The telomerase inhibition and the telomere shortening by DOX may contribute to its efficiency in the treatment in hepatocellular carcinoma.

Expression of human telomerase reverse transcriptase in regenerative and precancerous lesions of cirrhotic livers

BACKGROUND/AIMS

The catalytic subunit of human telomerase (hTERT) is known to be expressed in a variety of malignant tumours, including hepatocellular carcinoma (HCC). We studied hTERT expression in regenerative and precancerous lesions arising in cirrhosis.

METHODS/RESULTS

As shown by in situ hybridisation, hTERT mRNA was absent in normal liver, but present in varying numbers of hepatocytes and HCC cells of diseased livers, as well as in biliary epithelial cells, lymphocytes, sinusoidal-lining cells and tumour endothelial cells. RT-PCR for two hTERT transcript regions demonstrated hTERT expression in 11 out of 15 cirrhotic liver samples, in 20 out of 21 large regenerative nodules/low-grade dysplastic nodules, in 5 out of 5 high-grade dysplastic nodules, and in 4 out of 4 HCCs. The beta-splice variant was identified in all hTERT-positive cases, while the corresponding full-length transcript was found only in 13 out of 29 positive large nodular lesions and in 4 out of 11 positive cirrhotic samples. The full-length transcript was always found in the presence of the beta-splice variant, usually in low relative levels, and tended to correlate with telomerase activity in the samples, while the beta-splice variant did not.

CONCLUSIONS

This study shows that hTERT re-expression takes place both in hepatic regeneration occurring in cirrhosis and in the early steps of hepatocarcinogenesis, and involves mainly the beta-splice variant of this molecule. Additional regulatory mechanisms may be required for the expression of the full-length hTERT transcript.

Growth inhibition of BEL-7404 human hepatoma cells by expression of mutant telomerase reverse transcriptase

Human hepatocellular carcinoma (HCC) is one of the most common malignancies in Asia and Africa. Human telomerase reverse transcriptase (hTERT) is expressed in HCC but absent in normal human liver cells, which is consistent with the expression pattern of telomerase. In the present study, expression of a dominant-negative form of hTERT (DN-hTERT) resulted in inhibition of telomerase activity and decreased mean telomeric length of BEL-7404 human hepatoma cells, whereas expression of wild-type hTERT (WT-hTERT) and control vector had no such effects. Cell growth was inhibited by this mutant (DN-hTERT), which was consistent with the changes in telomerase level. Flattened large cells were found in late generations with the DN-hTERT treatment. When mean telomeric length of DN-hTERT-transfected cells reached a critical length (about 1.7 kb), apoptosis was induced. Tumorigenicity of DN-hTERT-expressing cells was eliminated in vivo. These data indicated that hTERT was essential for the growth of hepatoma cells. hTERT can also be used as an important target for anti-HCC drug screening.

Molecular aspects of hepatic carcinogenesis

Exogenous agents correlated with hepatocellular carcinoma (HCC) have been identified and well characterized. These agents, including the different viruses that cause chronic hepatitis and cirrhosis, can lead to regenerative nodules and dysplastic nodules/adenomatous hyperplasia. These conditions associated with several molecular alterations of hepatocyte ultimately culminate in hepatocellular carcinoma. Recently, there has been a great progress in the identification of somatic and germinative mutations that may be correlated with the development of HCC, justifying a review on the subject. Hence, the factors involved in the process of hepatic carcinogenesis, such as infection by the hepatitis B and C viruses, with a special focus in the molecular alterations described in recent years are discussed herein, pointing out areas potentially relevant for clinical development.

Quantitation of telomerase components and hTERT mRNA splicing patterns in immortal human cells

Telomerase is a reverse transcriptase that adds telomeric repeats to chromosomal ends. In most normal human somatic cells, telomerase is repressed and telomeres progressively shorten, leading to limited proliferative life-span. Telomerase reactivation is associated with cellular immortalization and is a frequent event during tumorigenesis. The telomerase ribonucleoprotein complex consists of two essential components, a catalytic protein subunit [human telomerase reverse transcriptase (hTERT)] and a template RNA (hTR). hTR is constitutively expressed, while hTERT is almost universally absent in telomerase-negative cells. Although repression of telomerase is transcriptional in telomerase-negative cells, post-transcriptional and assembly processes are likely to play important roles in regulating telomerase activity in those that are telomerase-positive. The telomerase transcript can also be alternatively spliced into a variety of non-functional forms. To establish the quantitative relationships between telomerase activity and its various components, we determined the numbers of molecules of hTR and hTERT mRNA, and the levels of alternatively spliced hTERT mRNA variants in normal, in vitro immortalized and cancer cell lines. We report here that there is surprisingly little variation in the proportion of alternatively spliced forms of hTERT in different cell lines. The only variation observed occurred when a change in splicing to non-functional forms appeared in response to conditions that repress telomerase activity in IDH4 cells. We also found that most telomerase-positive cell lines only contain a few molecules of potentially functional hTERT mRNA, and there is a correlation between telomerase activity and the levels of both hTR and hTERT +alpha+beta mRNA.

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.

Immuno-histochemical detection of human telomerase reverse transcriptase in human liver tissues

Although telomerase activity in hepatocellular carcinoma (HCC) increases in accordance with degree of histological undifferentiation, it is unknown whether the level of telomerase activity in HCC reflects of the degree of activity in individual cells or the frequency of telomerase-positive HCC cells. Non-cancerous liver tissues exhibit low but significant levels of telomerase activity, but the nature of telomerase-positive cells in these tissues is unclear. In this study, we performed immunohistochemical staining using specific antibody against telomerase reverse transcriptase (hTERT) protein in 15 HCC samples and 13 adjacent non-cancerous liver tissues. There were hTERT-positive hepatocytes, though very low frequency, in non-cancerous liver tissues. The frequencies in hTERT positive hepatocytes were very well correlated with clinicopathological parameters and telomerase activity levels: the average frequencies of chronic hepatitis was 0.2%, liver cirrhosis 0.2%, well-differentiated HCC 3.0%, moderately differentiated HCC 28%, and poorly differentiated HCC 95%. The intensity of staining varied among cells within a given specimen, and correlation with degree of histological undifferentiation was less obvious. Portions of migrating lymphocytes and biliary epithelial cells were also hTERT-positive. These findings indicate that the upregulation of telomerase activity with degree of undifferentiation of HCC is mainly due to the increase in frequency of hTERT positive HCC cells.