Geographic variation of p53 mutational profile in nonmalignant human liver

Fifty Years of Aflatoxin Research in Qidong, China: A Celebration of Team Science to Improve Public Health

The Qidong Liver Cancer Institute (QDLCI) and the Qidong Cancer Registry were established in 1972 with input from doctors, other medical practitioners, and non-medical investigators arriving from urban centers such as Shanghai and Nanjing. Medical teams were established to quantify the extent of primary liver cancer in Qidong, a corn-growing peninsula on the north side of the Yangtze River. High rates of liver cancer were documented and linked to several etiologic agents, including aflatoxins. Local corn, the primary dietary staple, was found to be consistently contaminated with high levels of aflatoxins, and bioassays using this corn established its carcinogenicity in ducks and rats. Observational studies noted a positive association between levels of aflatoxin in corn and incidence of liver cancer across townships. Biomarker studies measuring aflatoxin B1 and its metabolite aflatoxin M1 in biofluids reflected the exposures. Approaches to decontamination of corn from aflatoxins were also studied. In 1993, investigators from Johns Hopkins University were invited to visit the QDLCI to discuss chemoprevention studies in some townships. A series of placebo-controlled clinical trials were conducted using oltipraz (a repurposed drug), chlorophyllin (an over-the-counter drug), and beverages prepared from 3-day-old broccoli sprouts (rich in the precursor phytochemical for sulforaphane). Modulation of biomarkers of aflatoxin DNA and albumin adducts established proof of principle for the efficacy of these agents in enhancing aflatoxin detoxication. Serendipitously, by 2012, aflatoxin exposures quantified using biomarker measurements documented a many hundred-fold reduction. In turn, the Cancer Registry documents that the age-standardized incidence rate of liver cancer is now 75% lower than that seen in the 1970s. This reduction is seen in Qidongese who have never received the hepatitis B vaccination. Aflatoxin mitigation driven by economic changes switched the dietary staple of contaminated corn to rice coupled with subsequent dietary diversity leading to lower aflatoxin exposures. This 50-year effort to understand the etiology of liver cancer in Qidong provides the strongest evidence for aflatoxin mitigation as a public health strategy for reducing liver cancer burden in exposed, high-risk populations. Also highlighted are the challenges and successes of international team science to solve pressing public health issues.

Blood biomarkers of hepatocellular carcinoma: a critical review

Hepatocellular Carcinoma (HCC) is a malignant tumor with high morbidity and mortality worldwide, which represents a serious threat to human life, health and quality of life. Blood-based detection is essential for HCC screening, early diagnosis, prognosis evaluation, and surveillance. Current non-invasive detection strategy including serum alpha-fetoprotein (AFP), ultrasound, computerized tomography, and magnetic resonance imaging. The limited specificity of an AFP and the dependence on operator experience and diagnostic personnel for ultrasound have constrained their utility in early HCC diagnosis. In recent years, with the development of various detection technologies, there has been an increasing focus on exploring blood-based detection markers for HCC. The types of markers include protein markers, DNA mutation, DNA epigenetic modification, mRNA, miRNA, and so on. However, numerous methodological and biological factors limit the clinical sensitivity and generalization performance of these new biomarkers. In this review, we describe the state-of-the-art technologies for cfDNA analysis, and discuss outstanding biological and technical challenges that, if addressed, would substantially improve HCC diagnostics and patient care.

Role of p53 suppression in the pathogenesis of hepatocellular carcinoma

In the world, hepatocellular carcinoma (HCC) is among the top 10 most prevalent malignancies. HCC formation has indeed been linked to numerous etiological factors, including alcohol usage, hepatitis viruses and liver cirrhosis. Among the most prevalent defects in a wide range of tumours, notably HCC, is the silencing of the p53 tumour suppressor gene. The control of the cell cycle and the preservation of gene function are both critically important functions of p53. In order to pinpoint the core mechanisms of HCC and find more efficient treatments, molecular research employing HCC tissues has been the main focus. Stimulated p53 triggers necessary reactions that achieve cell cycle arrest, genetic stability, DNA repair and the elimination of DNA-damaged cells’ responses to biological stressors (like oncogenes or DNA damage). To the contrary hand, the oncogene protein of the murine double minute 2 (MDM2) is a significant biological inhibitor of p53. MDM2 causes p53 protein degradation, which in turn adversely controls p53 function. Despite carrying wt-p53, the majority of HCCs show abnormalities in the p53-expressed apoptotic pathway. High p53 in-vivo expression might have two clinical impacts on HCC: (1) Increased levels of exogenous p53 protein cause tumour cells to undergo apoptosis by preventing cell growth through a number of biological pathways; and (2) Exogenous p53 makes HCC susceptible to various anticancer drugs. This review describes the functions and primary mechanisms of p53 in pathological mechanism, chemoresistance and therapeutic mechanisms of HCC.

Pathogenesis and Current Treatment Strategies of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most frequent liver cancer with high lethality and low five-year survival rates leading to a substantial worldwide burden for healthcare systems. HCC initiation and progression are favored by different etiological risk factors including hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, non-/and alcoholic fatty liver disease (N/AFLD), and tobacco smoking. In molecular pathogenesis, endogenous alteration in genetics (TP53, TERT, CTNNB1, etc.), epigenetics (DNA-methylation, miRNA, lncRNA, etc.), and dysregulation of key signaling pathways (Wnt/β-catenin, JAK/STAT, etc.) strongly contribute to the development of HCC. The multitude and complexity of different pathomechanisms also reflect the difficulties in tailored medical therapy of HCC. Treatment options for HCC are strictly dependent on tumor staging and liver function, which are structured by the updated Barcelona Clinic Liver Cancer classification system. Surgical resection, local ablative techniques, and liver transplantation are valid and curative therapeutic options for early tumor stages. For multifocal and metastatic diseases, systemic therapy is recommended. While Sorafenib had been the standalone HCC first-line therapy for decades, recent developments had led to the approval of new treatment options as first-line as well as second-line treatment. Anti-PD-L1 directed combination therapies either with anti-VEGF directed agents or with anti-CTLA-4 active substances have been implemented as the new treatment standard in the first-line setting. However, data from clinical trials indicate different responses on specific therapeutic regimens depending on the underlying pathogenesis of hepatocellular cancer. Therefore, histopathological examinations have been re-emphasized by current international clinical guidelines in addition to the standardized radiological diagnosis using contrast-enhanced cross-sectional imaging. In this review, we emphasize the current knowledge on molecular pathogenesis of hepatocellular carcinoma. On this occasion, the treatment sequences for early and advanced tumor stages according to the recently updated Barcelona Clinic Liver Cancer classification system and the current algorithm of systemic therapy (first-, second-, and third-line treatment) are summarized. Furthermore, we discuss novel precautional and pre-therapeutic approaches including therapeutic vaccination, adoptive cell transfer, locoregional therapy enhancement, and non-coding RNA-based therapy as promising treatment options. These novel treatments may prolong overall survival rates in regard with quality of life and liver function as mainstay of HCC therapy.

A Pleiotropic Role of the Hepatitis B Virus Core Protein in Hepatocarcinogenesis

Chronic hepatitis B virus (HBV) infection is one of the most common factors associated with hepatocellular carcinoma (HCC), which is the sixth most prevalent cancer among all cancers worldwide. However, the pathogenesis of HBV-mediated hepatocarcinogenesis is unclear. Evidence currently available suggests that the HBV core protein (HBc) plays a potential role in the development of HCC, such as the HBV X protein. The core protein, which is the structural component of the viral nucleocapsid, contributes to almost every stage of the HBV life cycle and occupies diverse roles in HBV replication and pathogenesis. Recent studies have shown that HBc was able to disrupt various pathways involved in liver carcinogenesis: the signaling pathways implicated in migration and proliferation of hepatoma cells, apoptosis pathways, and cell metabolic pathways inducing the development of HCC; and the immune system, through the expression and production of proinflammatory cytokines. In addition, HBc can modulate normal functions of hepatocytes through disrupting human host gene expression by binding to promoter regions. This HBV protein also promotes HCC metastasis through epigenetic alterations, such as micro-RNA. This review focuses on the molecular pathogenesis of the HBc protein in HBV-induced HCC.

Aflatoxin B1 interferes with embryonic liver development: Involvement of p53 signaling and apoptosis in zebrafish

Aflatoxin B₁ (AFB₁), a naturally occurring mycotoxin, is present in human placenta and cord blood. AFB₁ at concentrations found in contaminated food commodities (0.25 and 0.5 μM) did not alter the spontaneous movement, heart rate, hatchability, or morphology of embryonic zebrafish. However, around 86 % of 0.25 μM AFB₁-treated embryos had livers of reduced size, and AFB₁ disrupted the hepatocyte structures, according to histological analysis. Additionally, AFB₁ treatment that begins at any stage before 72 h post-fertilization (hpf) effectively reduced the size of embryonic livers. In hepatic areas, AFB₁ suppressed the expression of Hhex and Prox1, which are two critical transcriptional factors for initiating hepatoblast specification. KEGG analysis based on transcriptome profiling indicated that p53 signaling and apoptosis are the only observed pathways in AFB₁-treated embryos. AFB₁ at 0.5 μM significantly activated the expression of tp53, mdm2, puma, noxa, pidd1, and gadd45aa genes that are related to the p53 pathway and also that of baxa, casp 8 and casp 3a in the apoptotic process. TUNEL staining demonstrated that AFB₁ triggered the apoptosis of embryonic hepatocytes in a dose-dependent manner. These results indicate that the deficiency of both hhex and prox1 as well as hepatocyte apoptosis via the p53-Puma/Noxa-Bax axis may contribute to the embryonic liver shrinkage that is caused by AFB_1.

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.

Obesity and cancer: A mechanistic overview of metabolic changes in obesity that impact genetic instability

Obesity, defined as a state of positive energy balance with a body mass index exceeding 30 kg/m2 in adults and 95th percentile in children, is an increasing global concern. Approximately one-third of the world's population is overweight or obese, and in the United States alone, obesity affects one in six children. Meta-analysis studies suggest that obesity increases the likelihood of developing several types of cancer, and with poorer outcomes, especially in children. The contribution of obesity to cancer risk requires a better understanding of the association between obesity-induced metabolic changes and its impact on genomic instability, which is a major driving force of tumorigenesis. In this review, we discuss how molecular changes during adipose tissue dysregulation can result in oxidative stress and subsequent DNA damage. This represents one of the many critical steps connecting obesity and cancer since oxidative DNA lesions can result in cancer-associated genetic instability. In addition, the by-products of the oxidative degradation of lipids (e.g., malondialdehyde, 4-hydroxynonenal, and acrolein), and gut microbiota-mediated secondary bile acid metabolites (e.g., deoxycholic acid and lithocholic acid), can function as genotoxic agents and tumor promoters. We also discuss how obesity can impact DNA repair efficiency, potentially contributing to cancer initiation and progression. Finally, we outline obesity-related epigenetic changes and identify the gaps in knowledge to be addressed for the development of better therapeutic strategies for the prevention and treatment of obesity-related cancers.

Aflatoxin B₁⁻Formamidopyrimidine DNA Adducts: Relationships between Structures, Free Energies, and Melting Temperatures

Thermal stabilities of DNA duplexes containing Gua (g), α- (a) or β-anomer of formamidopyrimidine-N7-9-hydroxy-aflatoxin B₁ (b) differ markedly (T_m: a<g<b), but the underlying molecular origin of this experimentally observed phenomenon is yet to be identified and determined. Here, by employing explicit-solvent molecular dynamics simulations coupled with free-energy calculations using a combined linear-interaction-energy/linear-response-approximation approach, we explain the quantitative differences in Tm in terms of three structural features (bulkiness, order, and compactness) and three energetical contributions (non-polar, electrostatic, and preorganized-electrostatic), and thus advance the current understanding of the relationships between structures, free energies, and thermal stabilities of DNA double helices.

Qidong: a crucible for studies on liver cancer etiology and prevention

Qidong (Jiangsu, China) has been of interest to cancer epidemiologists and biologists because, until recently, it was an endemic area for liver cancer, having amongst the highest incidence rates in the world. The establishment of the Qidong Cancer Registry together with the Qidong Liver Cancer Institute in 1972 has charted the patterns of liver cancer incidence and mortality in a stable population throughout a period of enormous economic, social, and environmental changes as well as of improvements in health care delivery. Updated incidence trends in Qidong are described. Notably, the China age-standardized incidence rate for liver cancer has dropped by over 50% in the past several decades. Molecular epidemiologic and genomic deep sequencing studies have affirmed that infection with hepatitis B virus as well as dietary exposure to aflatoxins through contamination of dietary staples such as corn, and to microcystins – blue-green algal toxins found in ditch and pond water – were likely important etiologic factors that account for the high incidence of liver cancer in this region. Public health initiatives to facilitate universal vaccination of newborns against HBV and to improve drinking water sources in this rural area, as well as economic and social mandates serendipitously facilitating dietary diversity, have led to precipitous declines in exposures to these etiologic factors, concomitantly driving substantive declines in the liver cancer incidence seen now in Qidong. In this regard, Qidong serves as a template for the global impact that a package of intervention strategies may exert on cancer burden.

A Review of Circulating Tumor DNA in Hepatobiliary Malignancies

Circulating tumor DNA (ctDNA) is released into circulation (blood) specifically from tumor cells undergoing metabolic secretion, apoptosis, or necrosis, carries tumor-specific genetic or epigenetic alterations. Technologies enabling clinical evaluation of ctDNA continue to advance rapidly and allow for the assessment of patient-specific tumoral genetic and epigenetic alterations. This holds great potential for earlier detection of disease, serial monitoring of tumor heterogeneity, identification of therapeutic targets, and evaluation of treatment response and mechanisms of resistance. Hepatobiliary malignancies are often diagnosed late, recur commonly, yield limited available tumor on biopsy, and harbor several genomic alterations with potential therapeutic impacts. Patients suffering from or at risk for these diseases thus stand to benefit immensely from this technology. Herein, we review the limited literature pertaining to the potential for ctDNA technologies in such patients. Patients with these cancers stand to benefit greatly from the application of ctDNA technologies, and concerted efforts at further investigation of such are ongoing and greatly needed.

Participation of liver stem cells in cholangiocarcinogenesis after aflatoxin B1 exposure of glutathione S-transferase A3 knockout mice

Aflatoxin B1, arguably the most potent human carcinogen, induces liver cancer in humans, rats, trout, ducks, and so on, but adult mice are totally resistant. This resistance is because of a detoxifying enzyme, mouse glutathione S-transferase A3, which binds to and inactivates aflatoxin B1 epoxide, preventing the epoxide from binding to DNA and causing mutations. Glutathione S-transferase A3 or its analog has not been detected in any of the sensitive species, including humans. The generation of a glutathione S-transferase A3 knockout (represented as KO or -/-) mice has allowed us to study the induction of liver cancer in mice by aflatoxin B1. In contrast to the induction of hepatocellular carcinomas in other species, aflatoxin B1 induces cholangiocarcinomas in GSTA3-/- mice. In other species and in knockout mice, the induction of liver cancer is preceded by extensive proliferation of small oval cells, providing additional evidence that oval cells are bipolar stem cells and may give rise to either hepatocellular carcinoma or cholangiocarcinoma depending on the nature of the hepatocarcinogen and the species of animal. The recent development of mouse oval cell lines in our laboratory from aflatoxin B1-treated GSTA3-/- mice should provide a new venue for study of the properties and potential of putative mouse liver stem cells.

Dual Role of Dietary Curcumin Through Attenuating AFB1-Induced Oxidative Stress and Liver Injury via Modulating Liver Phase-I and Phase-II Enzymes Involved in AFB1 Bioactivation and Detoxification

It is well understood that liver cytochrome p450 enzymes are responsible for AFB1 bioactivation, while phase-II enzymes regulated by the transcription factor nuclear factor-erythroid-2-related factor 2 (Nrf2) are involved in detoxification of AFB1. In this study, we explored the potential of curcumin to prevent AFB1-induced liver injury by modulating liver phase-I and phase-II enzymes along with Nrf2 involved in AFB1 bioactivation and detoxification. Arbor Acres broiler were divided into four groups including control group (G1; fed only basal feed), curcumin alone-treated group (G2; 450 mg/kg feed), AFB1-fed group (G3; 5 mg/kg feed), and curcumin plus AFB1 group (G4; 5 mg AFB1+450 mg curcumin/kg feed). After 28 days, liver and blood samples were collected for different analyses. Histological and phenotypic results revealed that AFB1-induced liver injury was partially ameliorated by curcumin supplementation. Compared to AFB1 alone-treated group, serum biochemical parameters and liver antioxidant status showed that curcumin supplementation significantly prevented AFB1-induced liver injury. RT-PCR and western blot results revealed that curcumin inhibited CYP enzymes-mediated bioactivation of AFB1 at mRNA and protein level. Transcription factor Nrf2, its downstream genes such as GSTA3, and GSTM2 mRNA, and protein expression level significantly upregulated via dietary curcumin. In addition, GSTs enzyme activity was enhanced with dietary curcumin which plays a crucial role in AFB1-detoxification. Conclusively, the study provided a scientific basis for the use of curcumin in broiler's diet and contributed to explore the multi-target preventive actions of curcumin against AFB1-induced liver injury through the modulation of phase-I and phase-II enzymes, and its potent anti-oxidative effects.

A General Overview of the Process of Carcinogenesis

A general synthetic overview of the process of carcinogenesis is presented. The following points are discussed: the uniqueness of tumor disease with respect to other pathologies; tumors viewed as a pathology of the transduction system of signals that regulate the communal life of the cells of multicell organisms; the tumor as a genetic disease of somatic cells; carcinogenesis as a multistage event; the fundamental role of physiologic and pathologic rhythms of cell proliferation in the modulation of tumor incidence; mechanisms entailed in the maintenance of genome integrity; mechanisms involved in the protection of genome integrity from exogenous and endogenous causes of degradation of the genetic message.

MDM2-p53 Interactions in Human Hepatocellular Carcinoma: What Is the Role of Nutlins and New Therapeutic Options?

Human hepatocellular carcinoma (HCC) is the fifth most common cancer and is associated with poor prognosis worldwide. The molecular mechanisms underlying the pathogenesis of HCC have been an area of continuing interest, and recent studies using next generation sequencing (NGS) have revealed much regarding previously unsettled issues. Molecular studies using HCC samples have been mainly targeted with the aim to identify the fundamental mechanisms contributing to HCC and identify more effective treatments. In response to cellular stresses (e.g., DNA damage or oncogenes), activated p53 elicits appropriate responses that aim at DNA repair, genetic stability, cell cycle arrest, and the deletion of DNA-damaged cells. On the other hand, the murine double minute 2 (MDM2) oncogene protein is an important cellular antagonist of p53. MDM2 negatively regulates p53 activity through the induction of p53 protein degradation. However, current research has shown that the mechanisms underlying MDM2-p53 interactions are more complex than previously thought. Microarray data have added new insight into the transcription changes in HCC. Recently, Nutlin-3 has shown potency against p53-MDM2 binding and the enhancement of p53 stabilization as well as an increment of p53 cellular accumulation with potential therapeutic effects. This review outlines the molecular mechanisms involved in the p53-MDM2 pathways, the biological factors influencing these pathways, and their roles in the pathogenesis of HCC. It also discusses the action of Nutlin-3 treatment in inducing growth arrest in HCC and elaborates on future directions in research in this area. More research on the biology of p53-MDM2 interactions may offer a better understanding of these mechanisms and discover new biomarkers, sensitive prognostic indicators as well as new therapeutic interventions in HCC.

Whole genome sequencing of matched tumor, adjacent non-tumor tissues and corresponding normal blood samples of hepatocellular carcinoma patients revealed dynamic changes of the mutations profiles during hepatocarcinogenesis

Hepatocellular carcinoma (HCC) has become the third most deadly disease worldwide and HBV is the major factor in Asia and Africa. We conducted 9 WGS (whole genome sequencing) analyses for matched samples of tumor, adjacent non-tumor tissues and normal blood samples of HCC patients from three HBV positive patients. We then validated the mutations identified in a larger cohort of 177 HCC patients. We found that the number of the unique somatic mutations (average of 59,136) in tumor samples is significantly less than that in adjacent non-tumor tissues (average 83, 633). We discovered that the TP53 R249S mutation occurred in 7.7% of the HCC patients, and it was significantly associated with poor diagnosis. In addition, we found that the L104P mutation in the VCX gene (Variable charge, X-linked) was absent in white blood cell samples, but present at 11.1% frequency in the adjacent tissues and increased to 14.6% in HCC tissues, suggesting that this mutation might be a tumor driver gene driving HCC carcinogenesis. Finally, we identified a TK1-RNU7 fusion, which would result in a deletion of 103 amino acids from its C-terminal. The frequencies of this fusion event decreased from the adjacent tissues (29.2%) to the tumors (16.7%), suggesting that a truncated thymidine Kinase1 (TK1) caused by the fusion event might be deleterious and be selected against during tumor progression. The three-way comparisons allow the identification of potential driver mutations of carcinogenesis. Furthermore, our dataset provides the research community a valuable dataset for identifying dynamic changes of mutation profiles and driver mutations for HCC.

Aflatoxin B1 invokes apoptosis via death receptor pathway in hepatocytes

The fungal metabolites produced by Aspergillus flavus and Aspergillus parasiticus cause detrimental health effects on humans and animals. Particularly aflatoxin B1 (AFB1) is the most studied and a well-known global carcinogen, producing hepatotoxic, genotoxic and immunotoxic effects in multiple species. AFB1 is shown to provoke liver dysfunctioning by causing hepatocytes apoptosis and disturbing cellular enzymatic activities. In liver, AFB1 causes apoptosis via extrinsic mechanism because of high expression of death receptor pathway. The detailed mechanism of AFB1 induced hepatocytes apoptosis, via death receptor pathway still remains elusive. So the present study was conducted to explore apoptotic mechanism initiated by death receptors and associated genes in aflatoxin B1 induced liver apoptosis in chickens fed with AFB1 for 3 weeks. Results from the present study displayed histopathological and ultrastructural changes in liver such as hydropic degeneration, fatty vacuolar degeneration and proliferation of bile duct in hepatocytes in AFB1 group, along with imbalance between reactive oxygen species (ROS) and antioxidant defense system upon AFB1 ingestion. Moreover, AFB1 intoxicated chickens showed upregulation of death receptors FAS, TNFR1 and associated genes and downregulation of inhibitory apoptotic proteins XIAP and BCL-2. The results obtained from this novel and comprehensive study including histopathological, ultrastructural, flow cytometrical and death receptor pathway gene expression profiles, will facilitate better understanding of mechanisms and involvement of death receptor pathway in hepatocytes apoptosis induced by AFB1 and ultimately may be helpful in bringing down the toxigenic potential of AFB1.

Aflatoxin B1 affects apoptosis and expression of death receptor and endoplasmic reticulum molecules in chicken spleen

Aflatoxin B₁ (AFB₁) is a natural product of the Aspergillus genus of molds, which grow on several foodstuffs stored in hot moist conditions, and is among the most potent hepatocarcinogens and immunosuppression presently known. The latter was related to the up-regulated apoptosis of immune organs. However, the effect of expression of death receptor and endoplasmic reticulum molecules in AFB₁-induced apoptosis of chicken splenocytes was largely unknown. The objective of this study was to investigate this unknown field. One hundred and forty four one-day-old chickens were randomly divided into control group (0 mg/kg AFB₁) and AFB₁ group (0.6 mg/kg AFB₁), respectively and fed with AFB₁ for 21 days. Histological observation demonstrated that AFB₁ caused slight congestion and lymphocytic depletion in the spleen. TUNEL and flow cytometry assays showed the excessive apoptosis of splenocytes provoked by AFB₁. Moreover, quantitative real-time PCR analysis revealed that AFB₁ induced the elevated mRNA expression of Fas, FasL, TNF-α, TNF-R₁, Caspase-3, Caspase-8, Caspase-10, Grp78 and Grp94 in the spleen. These findings suggested that AFB₁ could lead the excessive apoptosis and alter the expression of death receptor and endoplasmic reticulum molecules in chicken spleen.

Human Biomonitoring of DNA Adducts by Ion Trap Multistage Mass Spectrometry

Humans are continuously exposed to hazardous chemicals in the environment. These chemicals or their electrophilic metabolites can form adducts with genomic DNA, which can lead to mutations and the initiation of cancer. The identification of DNA adducts is required for understanding exposure and the etiological role of a genotoxic chemical in cancer risk. The analytical chemist is confronted with a great challenge because the levels of DNA adducts generally occur at <1 adduct per 10(7) nucleotides, and the amount of tissue available for measurement is limited. Ion trap mass spectrometry has emerged as an important technique to screen for DNA adducts because of the high level sensitivity and selectivity, particularly when employing multi-stage scanning (MS(n) ). The product ion spectra provide rich structural information and corroborate the adduct identities even at trace levels in human tissues. Ion trap technology represents a significant advance in measuring DNA adducts in humans. © 2016 by John Wiley & Sons, Inc.

Circulating tumor DNA in hepatocellular carcinoma: trends and challenges

Molecular characterization of individual patients’ tumor cells is becoming increasingly important in offering effective treatment for patients in clinical practice. Recent advances in the field have indicated that circulating tumor DNA (ctDNA) has huge potential to serve as a biomarker for early detection and precision treatment as well as prognosis of hepatocellular carcinoma (HCC). As ctDNA in HCC patients harbors the molecular characteristics of HCC tumor cells, ctDNA analysis in the blood may be sufficient for convenient, non-invasive and accurate detection, providing information for HCC diagnosis, treatment and prognosis. In this review, we will summarize and discuss current trends and challenges of ctDNA application in HCC.

Th1/Th2 cytokines and their genotypes as predictors of hepatitis B virus related hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the predominant type of primary liver cancer, is one of the most serious life-threatening malignancies, worldwide. In majority of the cases, HCC develops after prolonged and persistent chronic liver disease. hepatitis B virus (HBV) or HCV infection is prominent etiological factors, attributing to this condition. It has been well documented that HBV, being the inducer of chronic inflammation, is the main causative agent in causing HCC, particularly in Asian countries. The HBV infection leads to a wide range of clinical symptoms from carrier state to malignancy. Cytokines being immune-modulatory molecules, are the key mediators in the defense mechanism against viral infection. In this regard, this review will detail the substantial role of key Th1: interleukin 1 (IL-1), IL-2, IL-12, tumor necrosis factor-α, interferon-γ; Th2: IL-4, IL-10 and non Th1/Th2: IL-6, transforming growth factor-β1 cytokines genotypes in analyzing the variability in the clinical manifestations in an HBV-afflicted individual, which might finally, culminates into HCC. Since cytokine production is regulated genetically, the cytokine promoter region single-nucleotide polymorphisms induced changes, greatly affects the cytokine production, thus resulting into differential outcome of immune balance.

p53 in liver pathologies-taking the good with the bad

The distinct physiology of the liver makes it a unique ground with respect to its cross talk with p53, the "guardian of the genome." The stressful environment in the liver frequently leads to the activation of p53, which is associated with alterations in metabolic pathways and induction of apoptosis. The latter serves as a mechanism that controls the deposal of DNA-damaged cells. However, accentuated apoptosis may eventually lead to liver pathologies, mainly steatosis, which can develop into a more severe disease such as steatohepatitis, fibrosis, and cirrhosis. These pathologies, together with other apoptosis outcome such as chronic inflammation, may pave the way toward cancer development. In addition to this unique scenario that connects the ongoing response of wild-type (WT) p53 to stress and cancer development, hepatocarcinoma may develop in other well-described mechanisms involving p53. One such example is hepatitis virus-induced liver cancer whereby p53 is inactivated upon the binding of a specific viral protein, leading to the loss of its tumor suppressive activity. Furthermore, the accumulations of carcinogens such as aflatoxin were shown to yield an oncogenic mutated p53 protein. In this review, we will demonstrate the diverse activities of p53 in the liver. Interestingly, some of these activities may protect the liver from cancer in the short term, yet in the long term, p53 may lead to malignant transformation. A better understanding of the complex clinical outcome of p53 function in the liver may shed light on future therapies.

Hepatitis C virus-associated cancer

Hepatitis C virus (HCV) is one of the major etiologic agents of liver cancer. HCV is an RNA virus that, unlike hepatitis B virus, is unable to integrate into the host genome. Through complex interactions between viral and host proteins that induce host responses and promote inflammation, fibrosis, and ultimately cirrhosis, HCV infection can result in the development of hepatocellular carcinoma (HCC). The HCV oncogenic process involves genetic and epigenetic alterations and oncogenic effects mediated by viral proteins in the activation of cellular oncogenes, inactivation of tumor-suppressor genes, and dysregulation of multiple signal-transduction pathways. Advances in genetics and gene expression profiling have enhanced our current understanding of the pathways involved in HCV-associated liver cancer development. In this review, we summarize the current understanding of mechanisms of hepatocarcinogenesis induced by HCV infection.

Identification of drivers from cancer genome diversity in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers with a dismal outcome. The complicated molecular pathogenesis of HCC caused by tumor heterogeneity makes it difficult to identify druggable targets useful for treating HCC patients. One approach that has a potential for the improvement of patient prognosis is the identification of cancer driver genes that play a critical role in the development of HCC. Recent technological advances of high-throughput methods, such as gene expression profiles, DNA copy number alterations and somatic mutations, have expanded our understanding of the comprehensive genetic profiles of HCC. Integrative analysis of these omics profiles enables us to classify the molecular subgroups of HCC patients. As each subgroup classified according to genetic profiles has different clinical features, such as recurrence rate and prognosis, the tumor subclassification tools are useful in clinical practice. Furthermore, a global genetic analysis, including genome-wide RNAi functional screening, makes it possible to identify cancer vulnerable genes. Identification of common cancer driver genes in HCC leads to the development of an effective molecular target therapy.

Current evidence for the hepatoprotective activities of the medicinal mushroom Antrodia cinnamomea

Antrodia cinnamomea (AC) is an endemic mushroom species of Taiwan, and has been demonstrated to possess diverse biological and pharmacological activities, such as anti-hypertension, anti-hyperlipidemia, anti-inflammation, anti-oxidation, anti-tumor, and immunomodulation. This review focuses on the inhibitory effects of AC on hepatitis, hepatocarcinoma, and alcohol-induced liver diseases (e.g., fatty liver, fibrosis). The relevant biochemical and molecular mechanisms are addressed. Overall, this review summarizes the hepatoprotective activities in vitro and in vivo. However, there is no doubt that human and clinical trials are still limited, and further studies are required for the development of AC-related products.

Hepatocellular carcinoma: epidemiology, biology, diagnosis, and therapies

Hepatocellular carcinoma is the fifth most common cancer in men and the seventh in women, as is diagnosed in more than half a million individuals worldwide every year. In Portugal, its incidence and mortality rates are low compared to other types of cancers. In Brazil, in the city of São Paulo, according to data released by the Brazilian Unified Health System (Sistema Único de Saúde - SUS), the incidence of primary liver cancer was 2.07/100,000 inhabitants. Although the vast majority of cases (85%) mainly affect developing countries, especially where infection by hepatitis B virus (HBV) is endemic, the incidence in developed countries is increasing. This pathology is associated with several risk factors, not only environmental but also genetic, generating an increasing interest in attaining a better understanding of this disease, which is still associated with very late diagnosis and poor prognosis. Of the available treatments, few patients benefit from their scanty advantages, increasingly stimulating research of new forms of treatment against this disease. This review aimed to briefly but fully identify risk factors, molecular and biochemical pathways, pathophysiology, diagnosis, and possible clinical approaches of hepatocellular carcinoma.

Hepatitis B virus X antigen and aflatoxin B1 synergistically cause hepatitis, steatosis and liver hyperplasia in transgenic zebrafish

Aflatoxin B1 (AFB1) and the hepatitis B virus X antigen (HBx) are linked to the formation of liver diseases and hepatocellular carcinoma (HCC). The aim of this study was to investigate the synergistic effects between HBx and AFB1 in causing liver disorders using a transgenic zebrafish animal model. Histopathology, Periodic acid-Schiff (PAS) staining, Sirius red staining, TdT-mediated dUTP Nick End Labeling (TUNEL) assay, immunohistochemistry, and quantitative reverse transcriptase-polymerase chain reaction (Q-RT-PCR) were used to examine the livers of the HBx transgenic fish injected with AFB1. We found that HBx and AFB1 synergistically promoted steatosis as indicated by histopathological examinations and the increased expression of lipogenic factors, enzymes, and genes related to lipid metabolism. Moreover, treatment of AFB1 in HBx transgenic fish accelerated the development of liver hyperplasia and enhanced the expression of cell cycle related genes. PCNA was co-localized with active caspase 3 protein expression in HBx zebrafish liver samples and human HBV positive HCC samples by double fluorescence immunostaining. Finally, we found that in human patients with liver disease, significant glycogen accumulated in the inflammation, cirrhosis stage, and all cases of hepatocellular and cholangiocellular carcinoma showed a moderate cytoplasmic accumulation of glycogen. Our data demonstrated a synergistic effect of AFB1 and HBx on the regulation of lipid metabolism related genes and cell cycle/division-related genes which might contribute to enhanced steatosis and hyperplasia at 5.75months.

Non-viral factors contributing to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide, accounting for over half a million deaths per year. The geographic pattern of HCC incidence is parallel to exposure to viral etiologic factors. Its incidence is increasing, ranging between 3% and 9% annually depending on the geographical location, and variability in the incidence rates correspond closely to the prevalence and pattern of the primary etiologic factors. Chronic infections with hepatitis B viruses or hepatitis C viruses have both been recognized as human liver carcinogens with a combined attributable fraction of at least 75% of all HCC cases. Multiple non-viral factors have been implicated in the development of HCC. Increased body mass index and diabetes with subsequent development of non-alcoholic steatohepatitis represent significant risk factors for HCC. Other non-viral causes of HCC include iron overload syndromes, alcohol use, tobacco, oral contraceptive, aflatoxin, pesticides exposure and betel quid chewing, a prevalent habit in the developing world. Wilson disease, α-1 antitrypsin deficiency, Porphyrias, autoimmune hepatitis, Schistosoma japonicum associated with positive hepatitis B surface antigen, and thorotrast-ray are also contributing hepatocellualar carcinoma. In addition, primary biliary cirrhosis, congestive liver disease and family history of liver cancer increase the risk of HCC incident. In conclusion, clarification of relevant non-viral causes of HCC will help to focus clinicians on those risk factors that are modifiable. The multilevel preventative approach will hopefully lead to a reduction in incidence of non-viral HCC, and a decrease in the patient morbidity and mortality as well as the societal economic burden associated with HCC.

Non-viral factors contributing to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide, accounting for over half a million deaths per year. The geographic pattern of HCC incidence is parallel to exposure to viral etiologic factors. Its incidence is increasing, ranging between 3% and 9% annually depending on the geographical location, and variability in the incidence rates correspond closely to the prevalence and pattern of the primary etiologic factors. Chronic infections with hepatitis B viruses or hepatitis C viruses have both been recognized as human liver carcinogens with a combined attributable fraction of at least 75% of all HCC cases. Multiple non-viral factors have been implicated in the development of HCC. Increased body mass index and diabetes with subsequent development of non-alcoholic steatohepatitis represent significant risk factors for HCC. Other non-viral causes of HCC include iron overload syndromes, alcohol use, tobacco, oral contraceptive, aflatoxin, pesticides exposure and betel quid chewing, a prevalent habit in the developing world. Wilson disease, α-1 antitrypsin deficiency, Porphyrias, autoimmune hepatitis, Schistosoma japonicum associated with positive hepatitis B surface antigen, and thorotrast-ray are also contributing hepatocellualar carcinoma. In addition, primary biliary cirrhosis, congestive liver disease and family history of liver cancer increase the risk of HCC incident. In conclusion, clarification of relevant non-viral causes of HCC will help to focus clinicians on those risk factors that are modifiable. The multilevel preventative approach will hopefully lead to a reduction in incidence of non-viral HCC, and a decrease in the patient morbidity and mortality as well as the societal economic burden associated with HCC.

Whole-genome sequencing identifies recurrent mutations in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide and has no effective treatment, yet the molecular basis of hepatocarcinogenesis remains largely unknown. Here we report findings from a whole-genome sequencing (WGS) study of 88 matched HCC tumor/normal pairs, 81 of which are Hepatitis B virus (HBV) positive, seeking to identify genetically altered genes and pathways implicated in HBV-associated HCC. We find beta-catenin to be the most frequently mutated oncogene (15.9%) and TP53 the most frequently mutated tumor suppressor (35.2%). The Wnt/beta-catenin and JAK/STAT pathways, altered in 62.5% and 45.5% of cases, respectively, are likely to act as two major oncogenic drivers in HCC. This study also identifies several prevalent and potentially actionable mutations, including activating mutations of Janus kinase 1 (JAK1), in 9.1% of patients and provides a path toward therapeutic intervention of the disease.

DEN+2-AAF-induced multistep hepatotumorigenesis in Wistar rats: supportive evidence and insights

Diethylnitrosamine (DEN), found in many commonly consumed foods, has been reported to induce cancers in animals and humans. Several models have been developed to study multistage carcinogenesis in rat liver; these include the Solt-Farber-resistant hepatocyte model. In the Solt-Farber model, the initiation consists of either a necrogenic dose of a hepatocarcinogen or a non-necrogenic dose in conjunction with partial hepatectomy (PH). We report a novel protocol for tumor induction in liver which eliminates the need for PH. Male Wistar rats were injected with single i.p. dose of DEN (200 mg/kg body weight), controls received saline only. After 1 week of recovery, the DEN-treated animals were administered with the repeated doses of 2-acetyamino fluorine (150 mg/kg body weight) orally in 1 % carboxymethyl cellulose that served as promoting agent. Thirty days after the DEN administration, hepatocellular damage was observed as evident by histopathological analysis. The marker enzyme analysis showed elevated levels of serum AST, ALT, and alkaline phosphatase and a decrease in the levels of liver superoxide dismutase and catalase. The oxidative stress in liver was confirmed by elevated levels of lipid peroxidation and a decrease in antioxidant parameters.

Novel cancerization marker, TP53, and its role in distinguishing normal tissue adjacent to cancerous tissue from normal tissue adjacent to benign tissue

Background

The histopathological and molecular heterogeneity of normal tissue adjacent to cancerous tissue (NTAC) and normal tissue adjacent to benign tissue (NTAB), and the availability of limited specimens make deciphering the mechanisms of carcinogenesis challenging. Our goal was to identify histogenetic biomarkers that could be reliably used to define a transforming fingerprint using RNA in situ hybridization.

Methods

We evaluated 15 tumor-related RNA in situ hybridization biomarkers using tumor microarray and samples of seven tumor-adjacent normal tissues from 314 patients. Biomarkers were determined using comprehensive statistical methods (significance of support vector machine-based artificial intelligence and area under curve scoring of classification distribution).

Results

TP53 was found to be a most reliable index (P <10^-7; area under curve >87%) for distinguishing NTAC from NTAB, according to the results of a significance panel (BCL10, BECN1, BRCA2, FITH, PTCH11 and TP53).

Conclusions

The genetic alterations in TP53 between NTAC and NTAB may provide new insight into the field of cancerization and tumor transformation.

Disruption of Trp53 in livers of mice induces formation of carcinomas with bilineal differentiation

BACKGROUND & AIMS

p53 limits the self-renewal of stem cells from various tissues. Loss of p53, in combination with other oncogenic events, results in aberrant self-renewal and transformation of progenitor cells. It is not known whether loss of p53 is sufficient to induce tumor formation in liver.

METHODS

We used AlfpCre mice to create mice with liver-specific disruption of Trp53 (AlfpCre(+)Trp53(Δ2-10/Δ2-10) mice). We analyzed colony formation and genomic features and gene expression patterns in liver cells during hepatocarcinogenesis in mice with homozygous, heterozygous, and no disruption of Trp53.

RESULTS

Liver-specific disruption of Trp53 consistently induced formation of liver carcinomas that had bilineal differentiation. In nontransformed liver cells and cultured primary liver cells, loss of p53 (but not p21) resulted in chromosomal imbalances and increased clonogenic capacity of liver progenitor cells (LPCs) and hepatocytes. Primary cultures of hepatocytes and LPCs from AlfpCre(+)Trp53(Δ2-10/Δ2-10) mice, but not Cdkn1a(-/-) mice, formed tumors with bilineal differentiation when transplanted into immunocompromised mice. Spontaneous liver tumors that developed in AlfpCre(+)Trp53(Δ2-10/Δ2-10) mice had significant but complex alterations in expression of Rb checkpoint genes compared with chemically induced liver tumors that developed mice with wild-type Trp53.

CONCLUSIONS

Deletion of p53 from livers of mice is sufficient to induce tumor formation. The tumors have bilineal differentiation and dysregulation of Rb checkpoint genes.

Mutations in the p53 Tumor Suppressor Gene: Important Milestones at the Various Steps of Tumorigenesis

Inactivation of the p53 tumor suppressor is a frequent event in tumorigenesis. In most cases, the p53 gene is mutated, giving rise to a stable mutant protein whose accumulation is regarded as a hallmark of cancer cells. Mutant p53 proteins not only lose their tumor suppressive activities but often gain additional oncogenic functions that endow cells with growth and survival advantages. Interestingly, mutations in the p53 gene were shown to occur at different phases of the multistep process of malignant transformation, thus contributing differentially to tumor initiation, promotion, aggressiveness, and metastasis. Here, the authors review the different studies on the involvement of p53 inactivation at various stages of tumorigenesis and highlight the specific contribution of p53 mutations at each phase of cancer progression.

Genetic and epigenetic signatures in human hepatocellular carcinoma: a systematic review

Hepatocellular carcinoma (HCC) is the third most common cause of cancer deaths worldwide, and the incidence of this fatal disease is still on rise. The majority of HCCs emerge in the background of a chronic liver disease, such as chronic hepatitis and liver cirrhosis. The current understanding is that majority of HCCs evolve as a consequence of chronic inflammation and due to the presence of infection with hepatitis viruses. These underlying pathogenic stimuli subsequently induce a spectrum of genetic and epigenetic alterations in several cancer-related genes, which are involved in cell-cycle regulation, cell growth and adhesion. Such widespread genomic alterations cause disruption of normal cellular signaling and finally lead to the acquisition of a malignant phenotype in HCC. In general, the type of gene alterations, such as point mutations, deletion of chromosomal regions and abnormal methylation of gene promoters differ according to the individual targeted gene. In HCC, incidence of genetic alterations is relatively rare and is limited to a subset of few cancer-specific genes, such as the tumor suppressor p53, RB genes and oncogenes such as the CTNNB1. In contrast, epigenetic changes that involve aberrant methylation of genes and other post-transcriptional histone modifications occur far more frequently, and some of these epigenetic alterations are now being exploited for the development of molecular diagnostic signatures for HCC. In addition, recent findings of unique microRNA expression profiles also provide an evidence for the existence of novel mechanisms for gene expression regulation in HCC. In this review article, we will review the current state of knowledge on the activation of various oncogenic pathways and the inactivation of tumor suppressor pathways in HCC that result in the disruption of cancer-related gene function. In addition, we will specifically emphasize the clinical implication of some of these genetic and epigenetic alterations in the management of hepatocarcinogenesis.

Targeting the PI3K/Akt/mTOR pathway in hepatocellular carcinoma

Despite recent advances in the understanding of the biologic basis of hepatocellular carcinoma (HCC) development, the clinical management of the disease remains a major challenge. Deregulation of the PI3K/Akt/mTOR pathway, which is a prototypic survival pathway, is increasingly implicated in HCC carcinogenesis. In this article, we detailed the role of this pathway in the pathogenesis of HCC and provide an update on the preclinical and clinical development of various agents targeting this key survival/proliferation pathway, which include various PI3K inhibitors, Akt inhibitors and mTOR inhibitors for HCC. In addition, we highlighted the therapeutic potential of combination strategy for mTOR inhibitors with conventional chemotherapy, in particular, antimicrotubule agents, other molecular targeting agents, as well as radiotherapy.

Serum p53 gene polymorphisms and severity of hepatitis B or C-related chronic liver diseases in Taiwan

BACKGROUND AND AIMS

Polymorphisms of p53 gene are known to play an important role in hepatocarcinogenesis. We aimed to investigate the impact of p53 polymorphisms on disease progression by evaluating their prevalence among chronic hepatitis B (CHB) or hepatitis C (CHC) patients with different stages of liver disease.

METHODS

A total of 215 CHB, 108 CHC patients with different stages of liver disease and 49 healthy controls were consecutively enrolled. The codon 249 p53 mutations as well as codon 72 polymorphisms were assayed by molecular methods, and their prevalence among the enrolled subjects was evaluated.

RESULTS

All patients and controls had codon 249 wild-type sequences. Among codon 72 sequences, Pro/Pro allele frequency of Hepatitis B-related HCC (31.4%), cirrhosis (26.9%), HBV carriers (26.3%), hepatitis C-related cirrhosis (39.1%), and CHC patients (24%) were higher than that of healthy controls (18.4%). After adjustment for sex and age, codon 72 mutant and mixed type were associated with a higher likelihood of asymptomatic carrier state than those with wild type in CHB patients [odd ratio (OR): 2.53, 95% confidence interval (CI) 1.06-6.03, P = 0.037]. However, the prevalence of codon 72 mutant and mixed type were comparable with wild type among CHC patients with HCC (OR 0.70, 95% CI 0.28-1.72, P = 0.433).

CONCLUSIONS

Although serum 249(serine) p53 mutation is rarely found in Taiwanese patients, HBV carriers have a higher prevalence of codon 72 mutants than patients with much severe liver diseases or HCV infection, which implies that codon 72 mutants may affect at an earlier stage of HBV infection. Further studies are necessary to delineate the interactions of p53 mutations with HBV infection.

A locked nucleic acid clamp-mediated PCR assay for detection of a p53 codon 249 hotspot mutation in urine

Hepatocellular carcinoma (HCC) has a 5-year survival rate of <10% because it is difficult to diagnose early. Mutations in the TP53 gene are associated with approximately 50% of human cancers. A hotspot mutation, a G:C to T:A transversion at codon 249 (249T), may be a potential DNA marker for HCC screening because of its exclusive presence in HCC and its detection in the circulation of some patients with HCC. A locked nucleic acid clamp-mediated PCR assay, followed by melting curve analysis (using the SimpleProbe), was developed to detect the TP53 249T mutation. In this assay, the locked nucleic acid clamp suppressed 10(7) copies of wild-type templates and permitted detection of 249T-mutated template, with a sensitivity of 0.1% (1:1000) of the mutant/wild-type ratio, assessed by a reconstituted standard within 2 hours. With an amplicon size of 41 bp, it detects target DNA sequences in short fragmented DNA templates. The detected mutations were validated by DNA sequencing analysis. We then tested DNA isolated from urine samples of patients with HCC for p53 mutations and identified positive TP53 mutations in 9 of 17 samples. The possibility of using this novel TP53 249T assay to develop a urine or blood test for HCC screening is discussed.

Aflatoxin genotoxicity is associated with a defective DNA damage response bypassing p53 activation

BACKGROUND

Hepatocellular carcinoma (HCC) is a leading cause of cancer deaths. Aflatoxins, which may play a causative role in 5-28% of HCCs worldwide, are activated in liver cells and induce principally G→T mutations, including the TP53 codon 249(G→T) hotspot mutation. The DNA damage checkpoint response acts as an antitumour mechanism against genotoxic agents, but its role in aflatoxin-induced DNA damage is unknown.

AIM

We studied the DNA damage checkpoint response of human cells to aflatoxin B1 (AFB1).

METHODS AND RESULTS

The treatment of HepG2 hepatoma cells with mutation-inducing doses (3-5 μmol/l) of AFB1 induced DNA adducts, 8-hydroxyguanine lesions and DNA strand breaks that lasted several days. Persistent phospho-H2AX and 53BP1 foci were also detected, but cell growth was not affected. AFB1-exposed HepG2 cells formed phospho-H2AX and 53BP1 foci, but failed to phosphorylate both Chk1 and Chk2. Huh7 hepatoma and HCT116 colorectal cancer cell lines also exhibited a similarly incomplete checkpoint response. p53 phosphorylation also failed, and AFB1-exposed cells did not show p53-dependent G1 arrest or a sustained G2/M arrest. These observations contrasted sharply with the fully functional DNA damage response of cells to Adriamycin. Cotreatment of cells with AFB1 did not inhibit p53 and p21(Cip1) accumulation induced by Adriamycin. Thus, the deficient checkpoint response to AFB1 was not due to an inhibitory effect, but could be explained by an inefficient activation.

CONCLUSION

Genotoxic doses of AFB1 induce an incomplete and inefficient checkpoint response in human cells. This defective response may contribute to the mutagenic and carcinogenic potencies of aflatoxins.

Association of TP53 mutations with stem cell-like gene expression and survival of patients with hepatocellular carcinoma

BACKGROUND & AIMS

Mutations in TP53, a tumor suppressor gene, are associated with prognosis of many cancers. However, the prognostic values of TP53 mutation sites are not known for patients with hepatocellular carcinoma (HCC) because of heterogeneity in their geographic and etiologic backgrounds.

METHODS

TP53 mutations were investigated in a total of 409 HCC patients, including Chinese (n = 336) and white (n = 73) patients, using the direct sequencing method.

RESULTS

A total of 125 TP53 mutations were found in Chinese patients with HCC (37.2%). HCC patients with TP53 mutations had a shorter overall survival time compared with patients with wild-type TP53 (hazard ratio [HR], 1.86; 95% confidence interval [CI]: 1.37-2.52; P < .001). The hot spot mutations R249S and V157F were significantly associated with worse prognosis in univariate (HR, 2.11; 95% CI: 1.51-2.94; P < .001) and multivariate analyses (HR, 1.79; 95% CI: 1.29-2.51; P < .001). Gene expression analysis revealed the existence of stem cell-like traits in tumors with TP53 mutations. These findings were validated in breast and lung tumor samples with TP53 mutations.

CONCLUSIONS

TP53 mutations, particularly the hot spot mutations R249S and V157F, are associated with poor prognosis for patients with HCC. The acquisition of stem cell-like gene expression traits might contribute to the aggressive behavior of tumors with TP53 mutation.

Non-viral causes of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and represents an international public health concern as one of the most deadly cancers worldwide. The main etiology of HCC is chronic infection with hepatitis B and hepatitis C viruses. However, there are other important factors that contribute to the international burden of HCC. Among these are obesity, diabetes, non-alcoholic steatohepatitis and dietary exposures. Emerging evidence suggests that the etiology of many cases of HCC is in fact multifactorial, encompassing infectious etiologies, comorbid conditions and environmental exposures. Clarification of relevant non-viral causes of HCC will aid in preventative efforts to curb the rising incidence of this disease.

Cancer gene discovery in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a deadly cancer, whose incidence is increasing worldwide. Albeit the main risk factors for HCC development have been clearly identified, such as hepatitis B and C virus infection and alcohol abuse, there is still preliminary understanding of the key drivers of this malignancy. Recent data suggest that genomic analysis of cirrhotic tissue - the pre-neoplastic carcinogenic field - may provide a read-out to identify at risk populations for cancer development. Given this contextual complexity, it is of utmost importance to characterize the molecular pathogenesis of this disease, and pinpoint the dominant pathways/drivers by integrative oncogenomic approaches and/or sophisticated experimental models. Identification of the dominant proliferative signals and key aberrations will allow for a more personalized therapy. Pathway-based approaches and functional experimental studies have aided in identifying the activation of different signaling cascades in HCC (e.g. epidermal growth factor, insulin-like growth factor, RAS, MTOR, WNT-betacatenin, etc.). However, the introduction of new high-throughput genomic technologies (e.g. microarrays, deep sequencing, etc.), and increased sophistication of computational biology (e.g. bioinformatics, biomodeling, etc.), opens the field to new strategies in oncogene and tumor suppressor discovery. These oncogenomic approaches are framed within emerging new disciplines such as systems biology, which integrates multiple inputs to explain cancer onset and progression. In addition, the consolidation of sophisticated animal models, such as mosaic cancer mouse models or the use of transposons for mutagenesis screens, have been instrumental for the identification of novel tumor drivers. We herein review some classical as well as some recent fast track approaches for oncogene discovery in HCC, and provide a comprehensive landscape of the currently known spectrum of molecular aberrations involved in hepatocarcinogenesis.

Toxicokinetics of aflatoxin in pregnant mice

Our objective was to study the toxicokinetics of aflatoxin (AF) in pregnant mice. Aflatoxin B1 (AFB1) was administered intraperitoneally (IP) to groups of pregnant mice in single doses of 20 mg/kg on gestation day (GD) 13 and orally at the same gestational age. Controls received (IP and oral) a proportionate volume of solvent only. Maternal blood was collected at 15, 30, 45, 60, 90, 120, and 150 minutes posttreatment. Their AFB1 contents were determined. Aflatoxin B1 concentrations following maternal exposure to AFB1 were highly correlated with time after exposure. The serum concentrations were predictable and the highest serum levels were seen immediately at 15 minutes in mice given AFs IP and at 30 minutes in those given it orally. The absorption was 5.0 microg/min and elimination was 3.0 microg/min. The toxicokinetics of AFB1 have been delineated. Aflatoxins are easily and rapidly absorbed both from the gastrointestinal tract (GI) tract and through the peritoneum.

Proliferative drive and liver carcinogenesis: too much of a good thing?

There have been innumerable studies published in the attempt to identify gene expression signatures in hepatocellular carcinoma (HCC). When all the regulators and targets of the differentially expressed genes are analyzed from larger studies, the most striking theme is upregulation of mitosis-promoting and cell proliferation genes in HCC compared with 'liver-specific gene clusters' in non-tumorous tissue. A major limitation of expression profiling is that it only provides a 'snapshot' of what is an evolving process and thus cannot distinguish the differences in gene expression that are primary effectors of dysregulated growth from those that represent downstream consequences. The development of HCC in a chronically diseased liver, often referred to as hepatocarcinogenesis, is a multistep process characterized by the progressive accumulation and interplay of genetic alterations causing aberrant growth, malignant transformation of liver parenchymal cells, followed by vascular invasion and metastasis. This review will discuss HCC precursor lesions, draw on the 'proliferation cluster' genes highlighted from HCC expression profiling studies, relate them to a selection of regulatory networks important in liver regeneration, cell cycle control and their potential significance in the pathogenesis of HCC or primary liver cancer.