Molecular aspects of hepatic carcinogenesis

The Chemopreventive Activity of Indonesia Medicinal Plants Targeting on Hallmarks of Cancer

Cancer remains a complex disease with increasing global mortality and morbidity. Numerous theories have been established to understand the biological mechanism underlying cancer. One of the most renowned frameworks is the hallmark of cancer proposed by Hanahan and Weinberg that covers ten eminent characteristics of cancer: (i) genome instability and mutation, (ii) sustaining proliferative signaling, (iii) evading growth suppressor, (iv) enabling replicative immortality, (v) resisting cell death, (vi) inducing angiogenesis, (vii) activating invasion and metastasis, (viii) avoiding immune destruction, (ix) tumor-promoting inflammation, and (x) deregulating cellular energetics. These hallmarks provide a rational approach to design an anticancer therapy. In the current review, we summarized specific target molecules on each hallmark of cancer. Further, we evaluated the biological activity of several Indonesia medicinal plants against those specific targets. We explicated the anticancer and chemopreventive activities of some medicinal plants that have been used for centuries by local communities in Indonesia, including Curcuma genus, Brucea javanica, Boesenbergia pandurata, Caesalpinia sappan, and Nigella sativa. Interestingly, these medicinal plants target several hallmarks of cancer, and even Curcuma genus exhibited biological activities that target all hallmarks of cancer. Further, we also discuss several strategies to develop those medicinal plants and/or their active compounds as anticancer and chemopreventive agents.

Quantitative methylation analysis reveals gender and age differences in p16INK4a hypermethylation in hepatitis B virus-related hepatocellular carcinoma

BACKGROUND

Frequent promoter hypermethylation of the inhibitors in either Rb or p53 pathways is associated with the hepatocellular carcinoma (HCC) development.

OBJECTIVE

To quantitatively assess the gradual changes of the promoter methylation of p14ARF, p15INK4b, p16INK4a and CCND2 genes in hepatitis B virus (HBV) infection-related HCC.

METHODS

A total of 118 pairs of tumour and their corresponding non-tumour tissues were collected from HCC patients with evidence of HBV infection. The promoter methylation status was analysed by combined DNA methylation-sensitive and methylation-dependent restriction endonuclease digestion, followed by subsequential quantitative PCR assay.

RESULTS

Promoter hypermethylation frequencies were gradually increased from 6.25% in normal liver tissues to 21.19% in adjacent non-tumour and to 40.68% in tumour tissues for p16INK4a (P = 0.000), and from none to 10.20% and to 29.59% for CCND2 (P = 0.001). The hypermethylation intensities in HCC tissues were also significantly increased (P = 0.0018 for p16INK4a, P = 0.0001 for CCND2). Altogether, 48.93% cases were found with increased hypermethylation intensity of either p16INK4a and/or CCND2 promoter in tumour tissues, compared with their matched non-tumour tissues. In addition, tumour tissue p16INK4a promoter hypermethylation was significantly higher in male than that in female gender patients in frequency (P = 0.041) and was significantly increased in patients older than 50 years of age in intensity (P = 0.0021). No hypermethylation of p14ARF or p15INK4b was found.

CONCLUSION

Our study demonstrated that from normal liver to the adjacent cirrhotic liver and to the HCC tissues, p16INK4a hypermethylation was gradually increased both in frequency and in intensity, such increase might be gender and age related.

Mutations in TP53 and CTNNB1 in Relation to Hepatitis B and C Infections in Hepatocellular Carcinomas from Thailand

Hepatocellular carcinoma (HCC) may develop according to two major pathways, one involving HBV infection and TP53 mutation and the other characterized by HCV infection and CTNNB1 mutation. We have investigated HBV/HCV infections and TP53/CTNNB1 mutations in 26 HCC patients from Thailand. HBV DNA (genotype B or C) was detected in 19 (73%) of the cases, including 5 occult infections and 3 coinfections with HCV. TP53 and CTNNB1 mutations were not mutually exclusive, and most of TP53 mutations were R249S, suggesting a significant impact of aflatoxin-induced mutagenesis in HCC development.

Genomic and immunophenotypical differences between hepatocellular carcinoma with and without cirrhosis

AIMS

To compare the expression of genes involved in p53, Wnt/beta-catenin, and retinoblastoma (Rb) 1 pathways between cirrhosis-associated hepatocellular carcinoma (HCC-C) and hepatocellular carcinoma arising in non-cirrhotic liver (HCC-NC).

METHODS AND RESULTS

The gene expression profile was analysed using oligo-DNA arrays, and then validated at protein level in a tissue microarray using immunohistochemistry. Compared with their background non-neoplastic liver tissue, HCC-C showed a significantly higher rate of p53, beta-catenin (protein only) and cyclin D1 expression, whereas HCC-NC showed a significantly higher rate of p21(Waf1/cip1) and p27(Kip1) expression. HCC-C had a significantly higher rate of p53 expression and a significantly lower rate of p21(waf1/cip1) expression than HCC-NC. There was no statistically significant association between the expression of genetic markers and tumour histological grade, underlying aetiology, or lymphovascular invasion. Aberrant beta-catenin expression was more commonly seen in single tumours in comparison with multiple tumours. Increased p16(INK4) and p21(waf1/cip1) expression was more commonly observed in large-sized tumours (>50 mm) than small-sized tumours.

CONCLUSIONS

Alteration of the p53 pathway plays a more important role in the pathogenesis of HCC-C, whereas alterations in cell cycle regulators p21(waf1/cip1) and p27(Kip1) play a more important role in the pathogenesis of HCC-NC.

249 TP53 mutation has high prevalence and is correlated with larger and poorly differentiated HCC in Brazilian patients

Background

Ser-249 TP53 mutation (249^Ser) is a molecular evidence for aflatoxin-related carcinogenesis in Hepatocellular Carcinoma (HCC) and it is frequent in some African and Asian regions, but it is unusual in Western countries. HBV has been claimed to add a synergic effect on genesis of this particular mutation with aflatoxin. The aim of this study was to investigate the frequency of 249^Ser mutation in HCC from patients in Brazil.

Methods

We studied 74 HCC formalin fixed paraffin blocks samples of patients whom underwent surgical resection in Brazil. 249^Ser mutation was analyzed by RFLP and DNA sequencing. HBV DNA presence was determined by Real-Time PCR.

Results

249^Ser mutation was found in 21/74 (28%) samples while HBV DNA was detected in 13/74 (16%). 249^Ser mutation was detected in 21/74 samples by RFLP assay, of which 14 were confirmed by 249^Ser mutant-specific PCR, and 12 by nucleic acid sequencing. All HCC cases with p53-249ser mutation displayed also wild-type p53 sequences. Poorly differentiated HCC was more likely to have 249^Ser mutation (OR = 2.415, 95% CI = 1.001 – 5.824, p = 0.05). The mean size of 249^Ser HCC tumor was 9.4 cm versus 5.5 cm on wild type HCC (p = 0.012). HBV DNA detection was not related to 249^Ser mutation.

Conclusion

Our results indicate that 249^Ser mutation is a HCC important factor of carcinogenesis in Brazil and it is associated to large and poorly differentiated tumors.

Involvement of cell junctions in hepatocyte culture functionality

In liver, like in other multicellular systems, the establishment of cellular contacts is a prerequisite for normal functioning. In particular, well-defined cell junctions between hepatocytes, including adherens junctions, desmosomes, tight junctions, and gap junctions, are known to play key roles in the performance of liver-specific functionality. In a first part of this review article, we summarize the current knowledge concerning cell junctions and their roles in hepatic (patho)physiology. In a second part, we discuss their relevance in liver-based in vitro modeling, thereby highlighting the use of primary hepatocyte cultures as suitable in vitro models for preclinical pharmaco-toxicological testing. We further describe the actual strategies to regain and maintain cell junctions in these in vitro systems over the long-term.

Hepatitis B virus X protein sensitizes UV-induced apoptosis by transcriptional transactivation of Fas ligand gene expression

Hepatitis B virus X protein (HBx) is a promiscuous transcriptional transactivator of many viral and cellular promoters. HBx plays an important role in hepatitis B virus pathogenesis related with liver diseases including hepatocellular carcinoma (HCC). HBx is also involved in the signal transduction and the apoptosis of HBV-infected cells. However, the exact mechanism of apoptosis by HBx is still controversial. To demonstrate the mechanism of apoptosis by HBx, we induced the apoptosis of HBx-expressing liver cells, HepG2-X, by UV irradiation. We found that HepG2-X was much more sensitive to the UV-induced apoptosis than normal liver cells by analyzing the DNA fragmentation and the cell viability. Very interestingly, when the Fas-associated death domain (FADD)-dominant negative mutant protein was present in HepG2-X, the sensitized apoptotic response of HepG2-X to UV was completely abolished suggesting that there is a close relationship between HBx and Fas pathway in apoptosis. Therefore we examined the transactivation of Fas receptor (Fas) promoter and Fas ligand (FasL) promoter by HBx. We found that HBx strongly transcriptionally transactivated FasL promoter, but not Fas promoter. In addition, it also turned out that the mRNA levels of FasL are higher than those of Fas in HepG2-X. Taken together, HBx sensitizes the apoptosis of UV-irradiated liver cells by transcriptional transactivation of FasL gene.

Genotypic variability of hepatitis viruses associated with chronic infection and the development of hepatocellular carcinoma

At least five hepatitis viruses are known to date. Infection by enterically transmitted viruses (HAV and HEV) is generally benign compared with the disease caused by parenterally transmitted viruses (HBV, HCV, and HDV). Chronic infection by HBV is common and may evolve to cirrhosis and hepatocellular carcinoma (HCC). Eight HBV genotypes (A-H) have been described, with the South American genotype F being the most divergent. Seven clades of HDV have been described; among them, the South American genotype III is associated to a high frequency of fulminant hepatitis. HCV infection leads to a high rate of chronicity and HCC. From the six HCV genotypes, infection with genotype 1 might have the worst prognostic. Chronic infection by HCV and HBV is the major risk factor for HCC, which occurs, in the majority of the cases, as a consequence of cirrhosis. However, there is growing evidence that some HBV and HCV proteins might contribute to the generation of HCC. Some HBV and HCV variants and specific mutations within the viral genomes might be more frequently associated with the evolution to HCC. Although more studies are needed, emerging evidence indicates that it might be important to address the genetic variability of these viruses and their contribution to the development of HCC.

Distinct patterns of gene expression in hepatocellular carcinomas and adjacent non-cancerous, cirrhotic liver tissues in rats fed a choline-deficient, l-amino acid-defined diet

Gene expression profiles of HCC and surrounding non-cancerous tissues in rats fed a CDAA diet for 70 weeks, as well as normal liver tissues, were explored using an oligonucleotide microarray for 3757 genes. A total of 146 genes were identified as differentially expressed; the affected functions including metabolism, apoptosis, cell cycling, RNA splicing, Wnt signaling, reactive oxygen species-induced stress, and fibro/cirrhogenesis. The genes were found to fit into four distinct expression patterns after classification by hierarchical and k-means clustering procedures. Notably, genes within the same functional category tended to be found within the same cluster, thus gene functions appeared to be related to their expression patterns. For example, genes encoding receptors (Fisher's exact test, P < 0.01) and cytokines (Fisher's exact test, P < 0.05) were both enriched in a cluster characterized by low expression in HCC compared to their surrounding tissues. While some of the receptors in this cluster had cell-proliferative potential, others are known to be growth-suppressive. It was noted, however, that four of the 10 receptor genes encode G-protein-coupled receptors, for which growth-suppressive potential has been reported. The seven growth factors in the same cluster included two fibroblast growth factors. The current findings suggest the possibility that genes differentially expressed in this multistep carcinogenic model may be classified into relatively few clusters according to their expression patterns, and that these clusters may be associated with gene functional categories.

p53 immunostaining pattern in Brazilian patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an important type of cancer etiologically related to some viruses, chemical carcinogens and other host or environmental factors associated to chronic liver injury in humans. The tumor suppressor gene p53 is mutated in highly variable levels (0-52%) of HCC in different countries.

OBJECTIVE

The objective of the present study was to compare the frequency of aberrant immunohistochemical expression of p53 in HCC occurring in cirrhotic or in non-cirrhotic patients as well as in liver cell dysplasia and in adenomatous hyperplasia. We studied 84 patients with HCC or cirrhosis.

RESULTS

We detected p53 altered immuno-expression in 58.3% of patients in Grade III-IV contrasting to 22.2% of patients in Grade I-II (p = 0.02). Nontumorous areas either in the vicinity of HCC or in the 30 purely cirrhotic cases showed no nuclear p53 altered expression, even in foci of dysplasia or adenomatous hyperplasia. No significant difference was found among cases related to HBV, HCV or alcohol.

CONCLUSION

The high frequency of p53 immunoexpression in this population is closer to those reported in China and Africa, demanding further studies to explain the differences with European and North American reports.

Correlation of AgNORs, DNA contents and PCNA expression with liver cirrhosis, hyperplastic nodules and hepatocellular carcinoma

AIM: To study the relationship between liver cirrhosis (LC), liver hyperplastic nodules (LHN) and hepatocellular carcinoma (HCC).

METHODS: Silver colloid, image analysis and immunohistochemical technique were used to examine AgNORs counts, DNA contents and the expression of proliferating cell nuclear antigen (PCNA) in LC, LHN and HCC.

RESULTS: In LHN, the AgNORs counts, DNA contents and the expression of PCNA were significantly higher than those in the normal liver and LC (P < 0.01, P < 0.05, P < 0.05, respectively); the AgNORs counts approached those in HCC grade I (P > 0.05), and the DNA contents approached those in HCC (P > 0.05). There was no significant difference of AgNORs counts, DNA contents and the expression of PCNA between LC and the normal liver tissues.

CONCLUSION: LHN and LC are two different cell population with various characteristics; LHN is actively proliferative lesions and should be considered as a preneoplastic lesion of HCC, while LC represents mature liver cells and does not contribute directly to the hepatocarcinogenesis.

Inhibition of the development of hepatocellular carcinomas by phenyl N-tert-butyl nitrone in rats fed with a choline-deficient, l-amino acid-defined diet

Effects of phenyl N-tert-butyl nitrone (PBN), a spin-trapping agent, on the development of frank cancers were examined in male Wistar rats fed with a choline-deficient, l-amino acid-defined (CDAA) diet for 70 weeks. PBN (0.065% in the drinking water) reduced incidences, multiplicities and possibly sizes of both hepatocellular adenomas and carcinomas when administered for all 70 weeks or only for the first 26 weeks, and those of carcinomas but not adenomas, when administered only for the last 44 weeks. These results indicate that PBN can prevent the development of frank HCCs in the CDAA diet model. The anti-carcinogenic effect of PBN may be ascribed to the prevention of both the development of HCAs and their malignant conversion to HCCs. If such findings can be generalized, PBN may be able to serve as a good tool to investigate molecular mechanisms underlying carcinogenic processes.

Antisense oligonucleotide targeting at the initiator of hTERT arrests growth of hepatoma cells

AIM: To evaluate the inhibitory effect of antisense phosphorothioate oligonucleotide (asON) complementary to the initiator of human telomerase catalytic subunit (hTERT) on the growth of hepatoma cells.

METHODS: The as-hTERT was synthesized by using a DNA synthesizer. HepG2.2.15 cells were treated with as-hTERT at the concentration of 10 μmol/L. After 72 h, these cells were obtained for detecting growth inhibition, telomerase activity using the methods of MTT, TRAP-PCR-ELISA, respectively. BALB/c(nu/nu) mice were injected HepG2.2.15 cells and a human-nude mice model was obtained. There were three groups for anti-tumor activity study. Once tumors were established, these animals in the first group were administered as-hTERT and saline. Apoptosis of tumor cells was detected by FCM. In the 2nd group, the animals were injected HepG2.2.15 cells together with as-hTERT. In the third group, the animals were given as-hTERT 24 hours postinjection of HepG2.2.15 cells. The anti-HBV effects were assayed with ELISA in vitro and in vivo.

RESULTS: Growth inhibition was observed in cells treated with as-hTERT in vitro. A significant different in the value of A₅₇₀ - A₆₃₀ was found between cells treated with as-hTERT and control (P < 0.01) by MTT method. The telomerase activity of tumor cells treated with as-hTERT was reduced, the value of A₄₅₀ nm was 0.42 compared to control (1.49) with TRAP-PCR-ELISA. The peak of apoptosis in tumor cells given as-hTERT was 21.12%, but not seen in saline-treated control. A prolonged period of carcinogenesis was observed in the second and third group animals. There was inhibitory effect on the expression of HBsAg and HBeAg in vivo and in vitro.

CONCLUSION: As-hTERT has an anti-tumor activity, which may be useful for gene therapy of tumors.