Telomerase activity of needle-biopsied liver samples: its usefulness for diagnosis and judgement of efficacy of treatment of small hepatocellular carcinoma

The proliferation of atypical hepatocytes and CDT1 expression in noncancerous tissue are associated with the postoperative recurrence of hepatocellular carcinoma

Recently, we reported that extent of proliferation of atypical hepatocytes (atypical hepatocytes) was most important histological risk factor for development of hepatocellular carcinoma (HCC) from chronic hepatitis C or liver cirrhosis. Here, we aimed to clarify whether the atypical hepatocytes in noncancerous sections is also involved in postoperative recurrence. Furthermore, we investigated significant genes involved in the atypical hepatocytes. Association between the extent of atypical hepatocytes in noncancerous tissue and postoperative recurrence was validated in 356 patients with HCC. Next, we identified putative signature genes involved in extent of atypical hepatocytes. First, atypical hepatocytes or hepatocytes other than the atypical hepatocyte in noncancerous sections of 4 HCC patients were selectively collected by laser capture microdissection (LCM). Second, the gene expression profiles of the selected hepatocyte populations were compared using Ion AmpliSeq Transcriptome Human Gene Expression Kit (Thermo Fisher SCIENTIFIC, Waltham, MA, USA) analysis. Finally, we validated the mRNA expression of the extracted genes in noncancerous frozen liver tissue from 62 patients with HCC by RT-qPCR to identify the signature genes involved in both the extent of atypical hepatocytes and postoperative recurrence. Furthermore, the extent of atypical hepatocytes and CDT1 expression in noncancerous sections from 8 patients with HCC were also validated by selectively collecting samples using LCM. The extent of atypical hepatocytes was associated with postoperative recurrence. Of the genes that showed significant differences in expression levels between two populations, the expression of the chromatin licensing and DNA replication factor 1 (CDT1) gene was most strongly associated with the extent of atypical hepatocytes and was also associated with postoperative recurrence. Furthermore, CDT1-positive cells that exhibited stronger expression resembled those morphologically considered to be atypical hepatocytes. CDT1 and Ki-67 were colocalized in the nuclei of both hepatocytes and cancer cells. The hepatocytes in noncancerous livers were not uniform in each hepatocyte population, suggesting that the accumulation of genetic abnormalities was variable. We found that the strong degree of atypical hepatocytes and high CDT1 mRNA expression represent a high carcinogenic state of the liver. Thus, we consider the evaluation of degree of these could support the personalized medicine.

Forced activation of β-catenin signaling supports the transformation of hTERT-immortalized human fetal hepatocytes

Hepatocarcinogenesis is a multistep process driving the progressive transformation of normal liver cells into highly malignant derivatives. Unlimited proliferation and telomere maintenance have been recognized as prerequisites for the development of liver cancer. Moreover, recent studies identified illegitimate β-catenin signaling as relevant hit in a considerable subset of patients. To further investigate the currently not well-understood malignant evolution driven by telomerase and β-catenin, we monitored cytogenetic and phenotypic alterations in untransformed telomerase-immortalized human fetal hepatocytes following forced activation of β-catenin signaling. As expected, constitutive activation of β-catenin signaling significantly enhanced proliferation with decreasing serum dependence. Previously intact contact inhibition was almost completely eliminated. Interestingly, after several passages in cell culture, immortalized clones with dominant-positive β-catenin signaling acquired additional chromosomal aberrations, in particular translocations, anchorage-independent growth capabilities, and formed tumors in athymic nude mice. In further support for the driving role of β-catenin during hepatocarcinogenesis, improved colony growth in soft agar and accelerated tumor formation was also confirmed in Huh7 cells following stable expression of the constitutively active S33Y β-catenin mutant. Telomerase inhibition showed that short-term expansion of transformed clones was not telomerase dependent. Finally, cancer pathway profiling in derived tumors revealed upregulation of characteristic genes associated with invasion and angiogenesis. In conclusion, illegitimate activation of β-catenin signaling enhances the transformation from immortalization to malignant growth in human fetal hepatocytes. Our data functionally confirm a permissive role for β-catenin signaling in the initial phase of hepatocarcinogenesis.

Androgen activates PEG10 to promote carcinogenesis in hepatic cancer cells

The molecular mechanism of striking higher prevalence of hepatocellular carcinoma (HCC) in male subjects has not yet been fully elucidated. Here, we report that androgen receptor (AR) is differentially expressed in different HCC cell lines. AR agonist dihydrotestosterone (DHT) enhances HCC cell growth and apoptotic resistance. Antagonist flutamide (FLU) blocks the effects of DHT on the HCC cell lines. Paternally expressed gene 10 (PEG10) is expressed in HCC cell lines at substantial high level. Using small interfering RNAs against AR and PEG10 in AR- and PEG10-expressing BEL-7404 hepatoma cells and HuH7 hepatoma cells (HuH7) cells, and AR-transfection technique in AR-lacking and PEG10-expressing HepG2 cells, we have confirmed that through upregulation and activation of PEG10, DHT enhances HCC cell growth and apoptotic resistance. We have further demonstrated that DHT upregulates expression of human telomerase reverse transcriptase (hTERT) in HCC cell lines in a PEG10-dependent manner. Moreover, AR directly interacts in vivo with androgen-responsive elements in the regions of promoter and exon 2 of PEG10 gene in HCC cell lines. DHT promotes the hepatoma formation in vivo nude mice through PEG10 activation. AR antagonists (FLU and valproate) inhibit the hepatoma formation. These findings suggest that PEG10 plays an essential role in hepatocarcinogenesis. The PEG10 inhibition can be a novel approach for therapy of HCC.

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.

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.

Long-term high-dose interferon-alpha therapy delays Hepadnavirus-related hepatocarcinogenesis in X/myc transgenic mice

The role of interferon-alpha (IFN-alpha) remains unclear in prevention of virus-induced hepatocellular carcinoma in humans. We have investigated it herewith in the X/myc transgenic mouse model of Hepadnavirus-related hepatocarcinogenesis because of upregulation of c-myc oncogene in the liver. We have demonstrated that IFN-alpha can downregulate dose-dependently hepatocyte proliferation and c-myc overexpression at early premalignant stages, while it does not affect either hepatocyte apoptosis or telomerase activity at these steps. However, continuous and long-term administration of IFN-alpha dose-dependently delays tumor onset in dysplastic livers and increases overall survival of animals, more efficiently whether started before the onset of dysplasia. The present study therefore highlights that early preventive administration of IFN-alpha can slow down evolution towards hepatocellular carcinoma via repression of c-myc and hepatocyte proliferation at premalignant steps in experimental c-myc-induced hepatocarcinogenesis. However, the transient effect observed in this study emphasizes a need to clarify the possible mechanisms of acquired resistance and subsequent therapeutic escape. Our experimental model may be a pertinent tool to explore antioncogenic properties of IFN-alpha in human cirrhotic livers showing c-myc upregulation.

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.

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.