Association between HBX status, aflatoxin-induced R249S TP53 mutation and risk of hepatocellular carcinoma in a case-control study from Thailand. Cancer Lett. 2013;331:46-51. [PMID: 23200676 DOI: 10.1016/j.canlet.2012.11.012]

The Use of ctDNA in the Diagnosis and Monitoring of Hepatocellular Carcinoma-Literature Review

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and is one of the leading causes of cancer-related deaths worldwide. Despite advances in medicine, it is still a cancer with a very poor prognosis. Both imaging and liver biopsy still have important limitations, especially in very small nodules and those which show atypical imaging features. In recent years, liquid biopsy and molecular analysis of tumor breakdown products have become an attractive source of new biomarkers. Patients with liver and biliary malignancies, including hepatocellular carcinoma (HCC), may greatly benefit from ctDNA testing. These patients are often diagnosed at an advanced stage of the disease, and relapses are common. Molecular analysis may indicate the best cancer treatment tailored to particular patients with specific tumor DNA mutations. Liquid biopsy is a minimally invasive technique that facilitates the early detection of cancer. This review summarizes the knowledge of ctDNA in liquid biopsy as an indicator for early diagnosis and monitoring of hepatocellular cancer.

First Molecular Characterization of Chronic Hepatitis B Carriers in Timbuktu, Mali

In Mali, hepatocellular carcinoma (HCC) is the third and sixth most common cancer in men and women, respectively. Mali comprises several distinct climato-ecological zones. Most studies to date have been conducted in the sub-Sahelian zone of southern Mali, including the capital city Bamako. In this part of the country, the main risk factors for HCC are chronic hepatitis B virus (HBV) carriage and dietary exposure to aflatoxins, a well-known hepatocarcinogen. Data are scarce for other ecological zones, but our preliminary data from 721 blood donors in the area of Timbuktu, presented in this study, suggest that chronic HBV carriage is also endemic in the northern Saharan zone of Mali. For further study, 29 healthy HBV chronic carrier volunteers were recruited from the blood transfusion center in Timbuktu. Successful viral genotyping in 20 volunteers revealed HBV genotype E in 13 cases and D in 7 cases, suggesting that this geographical and anthropological transition zone may also represent a transition zone between HBV genotypes that dominate sub-Saharan and northern Africa, respectively. Sequencing of circulating cell-free plasma DNA (cfDNA) from donors did not reveal the presence of the TP53 R249S mutation in these donors, a marker of dietary exposure to aflatoxins in sub-Saharan Africa. These results suggest that the geo-epidemiological distribution of the risk factors for HCC is not uniform across Mali, but is dependent upon climatic, socioeconomic and anthropological factors that might have an impact on patterns of chronic liver disease and cancer.

Prognostic Value of Postoperative Circulating Tumor DNA in Patients With Early- and Intermediate-Stage Hepatocellular Carcinoma

Majority of patients with resected early- and intermediate-stage liver cancer will experience postoperative recurrence. This study aimed to investigate the application of ctDNA sequencing in the postoperative period of hepatocellular carcinoma. A total of 96 patients with liver cancer were enrolled in this study. Postoperative peripheral blood samples were collected from all patients after surgery and analyzed using hybridization capture-based next-generation sequencing. Identification of at least one somatic mutation in the peripheral blood was defined as ctDNA+. Five genetic features in tumor tissues were associated with disease-free survival (DFS) using Lasso-Cox model. The area under the receiver operating characteristic curve was 0.813 and 0.882 in training and validation cohorts, respectively. The recurrence rate in ctDNA+ and ctDNA- groups was 60.9% and 27.8%, respectively. Multivariate Cox regression analysis showed that the postoperative ctDNA was an independent prognostic predictor of DFS (HR [hazard ratio]: 6.074, 95% Cl [confidence interval]: 2.648-13.929, P<0.001) and overall survival (OS) (HR: 4.829, 95% CI: 1.508-15.466, P=0.008). Combined ctDNA with AFP improved prediction performance. The median DFS was 2.0, and 8.0 months in ctDNA+/AFP-H and ctDNA+/AFP-L groups, respectively; while ctDNA-/AFP-H and ctDNA-/AFP-L groups had not reached the median time statistically (Log-rank test, P < 0.0001). Furthermore, ctDNA- patients had better prognosis than ctDNA+ patients irrespective of tumor stage. Postoperative ctDNA sequencing has great prognostic value in patients with liver cancer. Patients with positive ctDNA should receive more intensive disease monitoring and more aggressive treatment strategies to improve the survival time.

Somatic Mutations in Circulating Cell-Free DNA and Risk for Hepatocellular Carcinoma in Hispanics

Hispanics are disproportionally affected by liver fibrosis and hepatocellular carcinoma (HCC). Advanced liver fibrosis is a major risk factor for HCC development. We aimed at identifying somatic mutations in plasma cell-free DNA (cfDNA) of Hispanics with HCC and Hispanics with advanced liver fibrosis but no HCC. Targeted sequencing of over 262 cancer-associated genes identified nonsynonymous mutations in 22 of the 27 HCC patients. Mutations were detected in known HCC-associated genes (e.g., CTNNB1, TP53, NFE2L2, and ARID1A). No difference in cfDNA concentrations was observed between patients with mutations and those without detectable mutations. HCC patients with higher cfDNA concentrations or higher number of mutations had a shorter overall survival (p < 0.001 and p = 0.045). Nonsynonymous mutations were also identified in 17 of the 51 subjects with advanced liver fibrosis. KMT2C was the most commonly mutated gene. Nine genes were mutated in both subjects with advanced fibrosis and HCC patients. Again, no significant difference in cfDNA concentrations was observed between subjects with mutations and those without detectable mutations. Furthermore, higher cfDNA concentrations and higher number of mutations correlated with a death outcome in subjects with advanced fibrosis. In conclusion, cfDNA features are promising non-invasive markers for HCC risk prediction and overall survival.

Pan-cancer circulating tumor DNA detection in over 10,000 Chinese patients

Circulating tumor DNA (ctDNA) provides a noninvasive approach to elucidate a patient's genomic landscape and actionable information. Here, we design a ctDNA-based study of over 10,000 pan-cancer Chinese patients. Using parallel sequencing between plasma and white blood cells, 14% of plasma cell-free DNA samples contain clonal hematopoiesis (CH) variants, for which detectability increases with age. After eliminating CH variants, ctDNA is detected in 73.5% of plasma samples, with small cell lung cancer (91.1%) and prostate cancer (87.9%) showing the highest detectability. The landscape of putative driver genes revealed by ctDNA profiling is similar to that in a tissue-based database (R² = 0.87, p < 0.001) but also shows some discrepancies, such as higher EGFR (44.8% versus 25.2%) and lower KRAS (6.8% versus 27.2%) frequencies in non-small cell lung cancer, and a higher TP53 frequency in hepatocellular carcinoma (53.1% versus 28.6%). Up to 41.2% of plasma samples harbor drug-sensitive alterations. These findings may be helpful for identifying therapeutic targets and combined treatment strategies.

Preoperative evaluation of microvascular invasion with circulating tumour DNA in operable hepatocellular carcinoma

BACKGROUND & AIMS

Microvascular invasion (MVI) is a critical prognostic factor for operable hepatocellular carcinoma (HCC). This study aimed to explore the performance of circulating tumour DNA (ctDNA) in evaluating MVI status preoperatively.

METHODS

Seventy-three HCC patients were enrolled and randomly divided into a training cohort and a validation cohort in a 2:1 ratio, and preoperative blood and surgical tissue samples were obtained. Genomic alterations were analysed using targeted deep sequencing with a 1021-gene panel.

RESULTS

In training cohort, 260 somatic mutations were identified in 40 blood samples (81.6%). CtDNA mutation was verified in paired tissue sample in 39 patients (97.5%). In univariate analysis, ctDNA allele frequency (AF) and largest tumour diameter were associated with the presence of MVI, but ctDNA AF was the only independent risk factor in multivariate analysis. With the cut-off value of 0.83%, ctDNA AF determined the presence of MVI with the sensitivity of 89.7% and specificity of 80.0% in the training cohort, and the sensitivity of 78.6% and the specificity of 81.8% in the validation cohort. In preoperative evaluation, ctDNA AF, AFP level and BCLC staging were associated with recurrence-free survival in both univariate and multivariate analysis.

CONCLUSIONS

CtDNA can serve as an independent risk factor of MVI for operable HCC and help determining precise treatment strategies. The integration of ctDNA in the management of operable HCC may achieve better clinical outcomes.

Mode of action-based risk assessment of genotoxic carcinogens

The risk assessment of chemical carcinogens is one major task in toxicology. Even though exposure has been mitigated effectively during the last decades, low levels of carcinogenic substances in food and at the workplace are still present and often not completely avoidable. The distinction between genotoxic and non-genotoxic carcinogens has traditionally been regarded as particularly relevant for risk assessment, with the assumption of the existence of no-effect concentrations (threshold levels) in case of the latter group. In contrast, genotoxic carcinogens, their metabolic precursors and DNA reactive metabolites are considered to represent risk factors at all concentrations since even one or a few DNA lesions may in principle result in mutations and, thus, increase tumour risk. Within the current document, an updated risk evaluation for genotoxic carcinogens is proposed, based on mechanistic knowledge regarding the substance (group) under investigation, and taking into account recent improvements in analytical techniques used to quantify DNA lesions and mutations as well as "omics" approaches. Furthermore, wherever possible and appropriate, special attention is given to the integration of background levels of the same or comparable DNA lesions. Within part A, fundamental considerations highlight the terms hazard and risk with respect to DNA reactivity of genotoxic agents, as compared to non-genotoxic agents. Also, current methodologies used in genetic toxicology as well as in dosimetry of exposure are described. Special focus is given on the elucidation of modes of action (MOA) and on the relation between DNA damage and cancer risk. Part B addresses specific examples of genotoxic carcinogens, including those humans are exposed to exogenously and endogenously, such as formaldehyde, acetaldehyde and the corresponding alcohols as well as some alkylating agents, ethylene oxide, and acrylamide, but also examples resulting from exogenous sources like aflatoxin B1, allylalkoxybenzenes, 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), benzo[a]pyrene and pyrrolizidine alkaloids. Additionally, special attention is given to some carcinogenic metal compounds, which are considered indirect genotoxins, by accelerating mutagenicity via interactions with the cellular response to DNA damage even at low exposure conditions. Part C finally encompasses conclusions and perspectives, suggesting a refined strategy for the assessment of the carcinogenic risk associated with an exposure to genotoxic compounds and addressing research needs.

Circulating Tumor Cells Undergoing EMT Provide a Metric for Diagnosis and Prognosis of Patients with Hepatocellular Carcinoma

To clarify the significance of circulating tumor cells (CTC) undergoing epithelial-mesenchymal transition (EMT) in patients with hepatocellular carcinoma (HCC), we used an advanced CanPatrol CTC-enrichment technique and in situ hybridization to enrich and classify CTC from blood samples. One hundred and one of 112 (90.18%) patients with HCC were CTC positive, even with early-stage disease. CTCs were also detected in 2 of 12 patients with hepatitis B virus (HBV), both of whom had small HCC tumors detected within 5 months. CTC count ≥16 and mesenchymal-CTC (M-CTC) percentage ≥2% prior to resection were significantly associated with early recurrence, multi-intrahepatic recurrence, and lung metastasis. Postoperative CTC monitoring in 10 patients found that most had an increased CTC count and M-CTC percentage before clinically detectable recurrence nodules appeared. Analysis of HCC with high CTC count and high M-CTC percentage identified 67 differentially expressed cancer-related genes involved in cancer-related biological pathways (e.g., cell adhesion and migration, tumor angiogenesis, and apoptosis). One of the identified genes, BCAT1, was significantly upregulated, and knockdown in Hepg2, Hep3B, and Huh7 cells reduced cell proliferation, migration, and invasion while promoting apoptosis. A concomitant increase in epithelial marker expression (EpCAM and E-cadherin) and reduced mesenchymal marker expression (vimentin and Twist) suggest that BCAT1 may trigger the EMT process. Overall, CTCs were highly correlated with HCC characteristics, representing a novel marker for early diagnosis and a prognostic factor for early recurrence. BCAT1 overexpression may induce CTC release by triggering EMT and may be an important biomarker of HCC metastasis.Significance: In liver cancer, CTC examination may represent an important "liquid biopsy" tool to detect both early disease and recurrent or metastatic disease, providing cues for early intervention or adjuvant therapy. Cancer Res; 78(16); 4731-44. ©2018 AACR.

Prevalence of Aflatoxin-Associated TP53R249S Mutation in Hepatocellular Carcinoma in Hispanics in South Texas

We aimed to determine whether aflatoxin dietary exposure plays a role in the high incidence of hepatocellular carcinoma (HCC) observed among Hispanics in South Texas. We measured TP53R249S somatic mutation, hallmark of aflatoxin etiology in HCC, using droplet digital PCR and RFLP. TP53R249S mutation was detected in 3 of 41 HCC tumors from Hispanics in South Texas (7.3%). We also measured TP53R249S mutation in plasma cell-free DNA (cfDNA) from 218 HCC patients and 96 Hispanic subjects with advanced fibrosis or cirrhosis, from South Texas. The mutation was detected only in Hispanic and Asian HCC patients, and patients harboring TP53R249S mutation were significantly younger and had a shorter overall survival. The mutation was not detected in any Hispanic subject with advanced fibrosis or cirrhosis. Genes involved in cell-cycle control of chromosomal replication and in BRCA1-dependent DNA damage response were enriched in HCCs with TP53R249S mutation. The E2F1 family members, E2F1 and E2F4, were identified as upstream regulators. TP53R249S mutation was detected in 5.7% to 7.3% of Hispanics with HCC in South Texas. This mutation was associated with a younger age and worse prognosis. TP53R249S was however not detected in Hispanics in South Texas with cirrhosis or advanced fibrosis. Aflatoxin exposure may contribute to a small number of HCCs in Hispanics in South Texas, but the detection of TP53R249S mutation in plasma cfDNA is not a promising biomarker of risk assessment for HCC in subjects with cirrhosis or advanced fibrosis in this population. Cancer Prev Res; 11(2); 103-12. ©2017 AACR.

Genetic alterations in hepatocellular carcinoma: An update

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. Although recent advances in therapeutic approaches for treating HCC have improved the prognoses of patients with HCC, this cancer is still associated with a poor survival rate mainly due to late diagnosis. Therefore, a diagnosis must be made sufficiently early to perform curative and effective treatments. There is a need for a deeper understanding of the molecular mechanisms underlying the initiation and progression of HCC because these mechanisms are critical for making early diagnoses and developing novel therapeutic strategies. Over the past decade, much progress has been made in elucidating the molecular mechanisms underlying hepatocarcinogenesis. In particular, recent advances in next-generation sequencing technologies have revealed numerous genetic alterations, including recurrently mutated genes and dysregulated signaling pathways in HCC. A better understanding of the genetic alterations in HCC could contribute to identifying potential driver mutations and discovering novel therapeutic targets in the future. In this article, we summarize the current advances in research on the genetic alterations, including genomic instability, single-nucleotide polymorphisms, somatic mutations and deregulated signaling pathways, implicated in the initiation and progression of HCC. We also attempt to elucidate some of the genetic mechanisms that contribute to making early diagnoses of and developing molecularly targeted therapies for HCC.

Host nucleotide polymorphism in hepatitis B virus-associated hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is etiologically linked with hepatitis B virus (HBV) and is the leading cause of death amongst 80% of HBV patients. Among HBV affected patients, genetic factors are also involved in modifying the risk factors of HCC. However, the genetic factors that regulate progression to HCC still remain to be determined. In this review, we discuss several single nucleotide polymorphisms (SNPs) which were reportedly associated with increased or reduced risk of HCC occurrence in patients with chronic HBV infection such as cyclooxygenase (COX)-2 expression specifically at COX-2 -1195G/A in Chinese, Turkish and Egyptian populations, tumor necrosis factor α and the three most commonly studied SNPs: PAT-/+, Lys939Gln (A33512C, rs2228001) and Ala499Val (C21151T, rs2228000). In genome-wide association studies, strong associations have also been found at loci 1p36.22, 11q22.3, 6p21 (rs1419881, rs3997872, rs7453920 and rs7768538), 8p12 (rs2275959 and rs37821974) and 22q11.21. The genes implicated in these studies include HLA-DQB2, HLA-DQA1, TCF19, HLA-C, UBE2L3, LTL, FDX1, MICA, UBE4B and PG. The SNPs found to be associated with the above-mentioned genes still require validation in association studies in order to be considered good prognostic candidates for HCC. Screening of these polymorphisms is very beneficial in clinical experiments to stratify the higher or lower risk for HCC and may help in designing effective and efficient HCC surveillance programs for chronic HBV-infected patients if further genetic vulnerabilities are detected.

Hepatitis B virus X protein promotes human hepatoma cell growth via upregulation of transcription factor AP2α and sphingosine kinase 1

AIM

Sphingosine kinase 1 (SPHK1) is involved in various cellular functions, including cell growth, migration, apoptosis, cytoskeleton architecture and calcium homoeostasis, etc. As an oncogenic kinase, SPHK1 is associated with the development and progression of cancers. The aim of this study was to investigate whether SPHK1 was involved in hepatocarcinogenesis induced by the hepatitis B virus X protein (HBx).

METHODS

The expression of SPHK1 in hepatocellular carcinoma (HCC) tissue and hepatoma cells were measured using qRT-PCR and Western blot analysis. HBx expression levels in hepatoma cells were modulated by transiently transfected with HBx or psi-HBx plasmids. The SPHK1 promoter activity was measured using luciferase reporter gene assay, and the interaction of the transcription factor AP2α with the SPHK1 promoter was studied with chromatin immunoprecipitation assay. The growth of hepatoma cells was evaluated in vitro using MTT and colony formation assays, and in a tumor xenograft model.

RESULTS

A positive correlation was found between the mRNA levels of SPHK1 and HBx in 38 clinical HCC samples (r=+0.727, P<0.01). Moreover, the expression of SPHK1 was markedly increased in the liver cancer tissue of HBx-transgenic mice. Overexpressing HBx in normal liver cells LO2 and hepatoma cells HepG2 dose-dependently increased the expression of SPHK1, whereas silencing HBx in HBx-expressing hepatoma cells HepG2-X and HepG2.2.15 suppressed SPHK1 expression. Furthermore, overexpressing HBx in HepG2 cells dose-dependently increased the SPHK1 promoter activity, whereas silencing HBx in HepG2-X cells suppressed this activity. In HepG2-X cells, AP2α was found to directly interact with the SPHK1 promoter, and silencing AP2α suppressed the SPHK1 promoter activity and SPHK1 expression. Silencing HBx in HepG2-X cells abolished the HBx-enhanced proliferation and colony formation in vitro, and tumor growth in vivo.

CONCLUSION

HBx upregulates SPHK1 through the transcription factor AP2α, which promotes the growth of human hepatoma cells.

How the environment shapes cancer genomes

PURPOSE OF REVIEW

The mutational patterns of cancer genomes allow conclusions or generation of hypotheses as to what mechanisms or environmental, dietary or occupational exposures might have created the mutations and therefore will have contributed to the formation of the cancer. The arguments for cancer causation are particularly convincing when epidemiological evidence can support the theory that a particular exposure is linked to the cancer and when the mutational process can be recapitulated in experimental systems. In this review, I will summarize recent evidence from cancer genome sequencing studies to exemplify how the environment can modulate tumor genomes.

RECENT FINDINGS

Mutation data from cancer genomes clearly implicate the ultraviolet B component of sunlight in melanoma skin cancers, tobacco carcinogen-induced DNA damage in lung cancers and aristolochic acid, a chemical compound found in certain herbal medicines, in urothelial carcinomas of exposed populations. However, large-scale sequencing is beginning to unveil other unique mutational spectra in particular cancers, such as A-to-C mutations at 5'AA dinucleotides in esophageal adenocarcinomas and complex mutational patterns in liver cancer. These datasets can form the basis for future studies aimed at identifying the carcinogens at work.

SUMMARY

The findings have substantial implications for our understanding of cancer causation and cancer prevention.

Molecular characteristics of Hepatitis B and chronic liver disease in a cohort of HB carriers from Bamako, Mali

BACKGROUND

Hepatitis B (HB) infection is common in Mali. However, there is little information on molecular and biochemical characteristics of HB carriers.

METHODS

A group of 1466 adult volunteers was recruited in the district of Bamako. Confirmed HB carriers were tested for HB viral load by quantitative PCR and HBV was genotyped by sequencing of HBS. Fibrosis and hepatitis activity were measured using the Fibrotest-Actitest. A mutation of TP53 at codon 249 (R249S), specific for exposure to aflatoxin, was detected in cell-free DNA extracted from plasma.

RESULTS

Overall, 276 subjects were HBsAg-positive (18.8%). Among 152 subjects tested for HBV load, 49 (32.2%) had over 10(4) copies/mL and 16 (10.5%) had levels below the limit of detection. The E genotype was found in 91.1% of carriers. Fibrotest scores ≥ F2 were observed in 52 subjects (35.4%). Actitest scores ≥ A2 were detected in 15 subjects (10.2%) and were correlated with Fibrotest scores (p = 0.0006). Among 105 subjects tested, 60% had detectable levels of R249S copies (>40 copies/mL plasma).

CONCLUSION

Chronic HB carriage in adults in Bamako district is well over epidemic threshold. About 1/3 of carriers have moderate to severe liver fibrosis and 60% have detectable aflatoxin-related TP53 R249S mutation. These results support introduction of anti-HB therapies to reduce the progression towards severe liver disease.

The p53 mutation spectrum in hepatocellular carcinoma from Guangxi, China : role of chronic hepatitis B virus infection and aflatoxin B1 exposure

BACKGROUND & AIMS

p53 is one of the most frequently mutated human tumour suppressor genes. Chronic infection with hepatitis B virus (HBV) and exposure to aflatoxin B1 (AFB1) induces p53 mutations in hepatocellular carcinoma (HCC) tissue. The aims of present study are to investigate the p53 mutation spectrum in HBV- and AFB1-related hepatocarcinogenesis in patients with hepatocellular carcinoma (HCC) in Guangxi, China.

METHODS

Tumour and adjacent liver tissue were collected from 397 HCC patients who were subdivided into HBV(+)/AFB1(+), HBV(+)/AFB1(-), HBV(-)/AFB1(+) and HBV(-)/AFB1(-) four groups. All 11 exons of the p53 gene were PCR-amplified and sequenced. Immunohistochemistry was used to evaluate the effect of mutations on the expression of p53 protein.

RESULTS AND CONCLUSIONS

P53 mutations were detected in 223 HCC samples, 13 adjacent liver tissue samples and only 1 of 68 normal liver tissue samples. The mutation sites concentrated at exon 4, 5, 6, 7, 8, 9 and no mutation was detected in exon 1, 2, 3, 10 and 11. The most frequently occurring mutation was in codon 249 (R249S) in exon 7. Patients in the HBV(+)/AFB1(+) and HBV(-)/AFB1(+) groups had significantly higher mutation rates compared with patients in the HBV(+)/AFB1(-) and HBV(-)/AFB1(-) groups. P53 mutation status and HBV/AFB1 status were independent predictors of tumour recurrence after surgery. Immunohistochemical analysis revealed that p53 gene mutations were correlated with the p53 expression. In Guangxi area, the significant association between AFB1-induced p53 mutations and the expression of p53 protein suggest an important role for p53 mutations in carcinogenesis of HCC.

Association between polymorphisms in tumor suppressor genes and oncogenes and risk of hepatocellular carcinoma: a case-control study in an HCC epidemic area within the Han Chinese population

Data concerning the risk of hepatocellular carcinoma (HCC) and specific single nucleotide polymorphisms (SNPs) in an HBV-free population are currently limited. Therefore, we performed a case-control study to investigate the association between SNPs and the risk of HCC in individuals without chronic HBV infection. A total of 160 Han Chinese patients with HCC and an identical number of healthy controls were enrolled in this study. rs1042522, rs10814325, rs17401966, and rs2279744 genotypes were determined using matrix-associated laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS). CG and GG genotypes in rs1042522 and heterozygote and homozygote in rs2279744 were significantly associated with an elevated risk of HCC. Homozygous mutation of rs1081432 conferred a 2.68-fold risk of HCC (95% CI 1.35-5.34); however heterozygosity was not statistically significant. rs17401966 heterozygosity or homozygosity was not significantly associated with a increased risk of HCC. Several polymorphisms associated with a significantly increased risk of HCC were identified. These may serve as biomarkers in evaluating HCC risk in the general population.

Prevalence of aflatoxin induced p53 mutation at codon 249 (R249s) in hepatocellular carcinoma patients with and without hepatitis B surface antigen (HBsAg)

BACKGROUND

A missense mutation in exon 7 (R249S) of the p53 tumor suppressor gene is characteristic of aflatoxin B1 (AFB1) exposure. AFB1 is believed to have a synergistic effect on hepatitis virus B (HBV) carcinogenesis. However, results of studies comparing R249S prevalence among patients are conflicting. The aim of this study was to determine the prevalence of the R249S mutation in hepatocellular carcinoma (HCC) patients with or without positive HBsAg.

MATERIALS AND METHODS

Paraffin embedded liver tissues were obtained from 124 HCC patients who underwent liver resection and liver biopsy in King Chulalongkorn Memorial Hospital. Restriction fragment length polymorphism (RFLP) was utilized to detect the R249S mutation. Positive results were confirmed by direct sequencing.

RESULTS

Sixty four (52%) patients were positive for HBsAg and 18 (15%) were anti-HCV positive. 12 specimens tested positive by RFLP. Ten HCC patients (8.1%) were confirmed to be R249S positive by Sanger sequencing (AGG to AGT). Out of these 10, six were HBsAg positive, and out of the remaining 4, two were anti-HCV positive. The R249S prevalence among HCC patients with positive HBsAg was 9.4% compared to 6.7% for HBsAg negative samples. Patients with the R249S mutation were younger (55±10 vs 60±13 year-old) and tended to have a more advanced Edmonson-Steiner grade of HCC, although differences did not reach statistical significance.

CONCLUSIONS

Our study shows moderate prevalence of aflatoxin B1-related p53 mutation (R249S) in HCC with or without HBsAg. HBsAg positive status was not associated with R249S prevalence.

DNA markers in molecular diagnostics for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the one of the leading causes of cancer mortality in the world, mainly due to the difficulty of early detection and limited therapeutic options. The implementation of HCC surveillance programs in well-defined, high-risk populations were only able to detect about 40-50% of HCC at curative stages (Barcelona Clinic Liver Cancer stages 0 & 1) due to the low sensitivities of the current screening methods. The advance of sequencing technologies has identified numerous modifications as potential candidate DNA markers for diagnosis/surveillance. Here we aim to provide an overview of the DNA alterations that result in activation of cancer pathways known to potentially drive HCC carcinogenesis and to summarize performance characteristics of each DNA marker in the periphery (blood or urine) for HCC screening.

Hepatitis B virus genetic variation and TP53 R249S mutation in patients with hepatocellular carcinoma in Thailand

Chronic hepatitis B virus (HBV) infection and dietary exposure to aflatoxin B1 (AFB1) are major risk factors for hepatocellular carcinoma (HCC). The aim of this study was to evaluate the role of HBV genetic variation and the R249S mutation of the p53 gene, a marker of AFB1-induced HCC, in Thai patients chronically infected with HBV. Sixty-five patients with and 89 patients without HCC were included. Viral mutations and R249S mutation were characterized by direct sequencing and restriction fragment length polymorphism (RFLP) in serum samples, respectively. The prevalences of T1753C/A/G and A1762T/G1764A mutations in the basal core promotor (BCP) region were significantly higher in the HCC group compared to the non-HCC group. R249S mutation was detected in 6.2% and 3.4% of the HCC and non-HCC groups, respectively, which was not significantly different. By multiple logistic regression analysis, the presence of A1762T/G1764A mutations was independently associated with the risk of HCC in Thai patients.

Liver-specific expressions of HBx and src in the p53 mutant trigger hepatocarcinogenesis in zebrafish

Hepatocarcinogenesis is a multistep process that starts from fatty liver and transitions to fibrosis and, finally, into cancer. Many etiological factors, including hepatitis B virus X antigen (HBx) and p53 mutations, have been implicated in hepatocarcinogenesis. However, potential synergistic effects between these two factors and the underlying mechanisms by which they promote hepatocarcinogenesis are still unclear. In this report, we show that the synergistic action of HBx and p53 mutation triggers progressive hepatocellular carcinoma (HCC) formation via src activation in zebrafish. Liver-specific expression of HBx in wild-type zebrafish caused steatosis, fibrosis and glycogen accumulation. However, the induction of tumorigenesis by HBx was only observed in p53 mutant fish and occurred in association with the up-regulation and activation of the src tyrosine kinase pathway. Furthermore, the overexpression of src in p53 mutant zebrafish also caused hyperplasia, HCC, and sarcomatoid HCC, which were accompanied by increased levels of the signaling proteins p-erk, p-akt, myc, jnk1 and vegf. Increased expression levels of lipogenic factors and the genes involved in lipid metabolism and glycogen storage were detected during the early stages of hepatocarcinogenesis in the HBx and src transgenic zebrafish. The up-regulation of genes involved in cell cycle regulation, tumor progression and other molecular hallmarks of human liver cancer were found at later stages in both HBx and src transgenic, p53 mutant zebrafish. Together, our study demonstrates that HBx and src overexpression induced hepatocarcinogenesis in p53 mutant zebrafish. This phenomenon mimics human HCC formation and provides potential in vivo platforms for drug screening for therapies for human liver cancer.

Association between TP53 R249S mutation and polymorphisms in TP53 intron 1 in hepatocellular carcinoma

Over 100 single nucleotide polymorphisms (SNP) are validated in the TP53 tumor suppressor gene. They define haplotypes, which may differ in their activities. Therefore, mutation in cancer may occur at different rates depending upon haplotypes. However, these associations may be masked by differences in mutations types and causes of mutagenesis. We have analyzed the associations between 19 SNPs spanning the TP53 locus and a single specific aflatoxin-induced TP53 mutation (R249S) in 85 in hepatocellular carcinoma cases and 132 controls from Thailand. An association with R249S mutation (P = 0.007) was observed for a combination of two SNPs (rs17882227 and rs8064946) in a linkage disequilibrium block extending from upstream of exon 1 to the first half of intron 1. This domain contains two coding sequences overlapping with TP53 (WRAP53 and Hp53int1) suggesting that sequences in TP53 intron 1 encode transcripts that may modulate R249S mutation rate in HCC.