Molecular changes in hepatocellular dysplastic nodules on microdissected liver biopsies

Hepatic Precancerous Lesions and Early Hepatocellular Carcinoma

This review discusses the diagnostic challenges of diagnosing and treating precursor lesions of hepatocellular carcinoma (HCC) in both cirrhotic and non-cirrhotic livers. The distinction of high-grade dysplastic nodule (the primary precursor lesion in cirrhotic liver) from early HCC is emphasized based on morphologic, immunohistochemical, and genomic features. The risk factors associated with HCC in hepatocellular adenomas (precursor lesion in non-cirrhotic liver) are delineated, and the risk in different subtypes is discussed with emphasis on terminology, diagnosis, and genomic features.

Characterisation of dysplastic liver nodules using low-pass DNA sequencing and detection of chromosome arm-level abnormalities in blood-derived cell-free DNA

High-grade dysplasia carries significant risk of transformation to hepatocellular carcinoma (HCC). Despite this, at the current standard of care, all non-malignant hepatic nodules including high-grade dysplastic nodules are managed similarly. This is partly related to difficulties in distinguishing high-risk pathology in the liver. We aimed to identify chromosome arm-level somatic copy number alterations (SCNAs) that characterise the transition of liver nodules along the cirrhosis-dysplasia-carcinoma axis. We validated our findings on an independent cohort using blood-derived cell-free DNA. A repository of non-cancer DNA sequences obtained from patients with HCC (n = 389) was analysed to generate cut-off thresholds aiming to minimise false-positive SCNAs. Tissue samples representing stages from the multistep process of hepatocarcinogenesis (n = 184) were subjected to low-pass whole genome sequencing. Chromosome arm-level SCNAs were identified in liver cirrhosis, dysplastic nodules, and HCC to assess their discriminative capacity. Samples positive for 1q+ or 8q+ arm-level duplications were likely to be either HCC or high-grade dysplastic nodules as opposed to low-grade dysplastic nodules or cirrhotic tissue with an odds ratio (OR) of 35.5 (95% CI 11.5-110) and 16 (95% CI 6.4-40.2), respectively (p < 0.0001). In an independent cohort of patients recruited from Nottingham, UK, at least two out of four alterations (1q+, 4q-, 8p-, and 8q+) were detectable in blood-derived cell-free DNA of patients with HCC (n = 22) but none of the control patients with liver cirrhosis (n = 9). Arm-level SCNAs on 1q+ or 8q+ are associated with high-risk liver pathology. These can be detected using low-pass sequencing of cell-free DNA isolated from blood, which may be a future early cancer screening tool for patients with liver cirrhosis. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Clinicopathological Significance of Overall Frequency of Allelic Loss (OFAL) in Lesions Derived from Thyroid Follicular Cell

Background

Loss of heterozygosity (LOH) and microsatellite instability (MSI) are frequent molecular events in thyroid tumor etiopathogenesis occurring in several chromosomal critical areas, including 3p12–25.3, 7q21–31, 10q22–24, and 15q11–13, with loci of tumor suppressor genes.

Objective

We evaluated the usefulness of LOH/MSI as a diagnostic/prognostic biomarker in lesions derived from thyroid follicular cells: follicular thyroid carcinoma (FTC); follicular adenoma (FA), papillary thyroid carcinoma (PTC), and nodular goiter (NG).

Methods

We performed allelotyping (GeneMapper Software v. 4.0.) of ten microsatellite markers linked to the 1p31.2, 3p21.3, 3p24.2, 9p21.3, 11p15.5, and 16q22.1 region on DNA from 93 primary thyroid lesions then evaluated the LOH/MSI frequency and overall frequency of allelic loss (OFAL).

Results

We found regions with significantly increased frequency of LOH/MSI for specific histotypes: the 3p24.2 region for FA and 1p31.2 for FTC. LOH/MSI in 3p21.3 was significantly elevated in PTC and FTC. LOH/MSI in 3p21.3 was increased for small size tumors (T1a + T1b), tumors with no regional lymph node involvement (N0 + Nx), American Joint Committee on Cancer (AJCC) stage I tumors, and tumor diameter (Td) < 10 mm; in 1p31.2 for T2–3, N1, stage II–IV, and Td 10–30 mm; in 11p15.5 for T2–3, N1, stage II–IV, and Td > 30 mm. OFAL values were significantly higher in younger patients (< 40 years), in men, in those with T2–3 stage tumors, in those with increased Td, and in FA and FTC compared with NG and PTC.

Conclusions

We confirmed the occurrence of LOH/MSI in 3p21.3 at an early stage of tumorigenesis and mapped 1p31.2 and 11p15.5 as characteristic for advanced-stage tumors. The results of our study may enable consideration of OFAL, defined as LOH/MSI coincidence in various chromosomal regions, as a tumor progression marker. OFAL values were significantly higher in follicular neoplasms (FA and FTC) than in PTC or NG; hence, increased OFAL values can be regarded as a characteristic feature of the follicular phenotype.

Transcriptome analysis identifies metallothionein as biomarkers to predict recurrence in hepatocellular cacinoma

Background

Liver cancer is the fifth most common cancer, and hepatocellular carcinoma (HCC) is the major liver tumor type seen in adults. HCC is usually caused by chronic liver disease such as hepatitis B virus or hepatitis C virus infection. One of the promising treatments for HCC is liver transplantation, in which a diseased liver is replaced with a healthy liver from another person. However, recurrence of HCC after surgery is a significant problem. Therefore, it is important to discover reliable cellular biomarkers that can predict recurrence in HCC.

Methods

We analyzed previously published HCC RNA‐Seq data that includes 21 paired tumor and normal samples, in which nine tumors were recurrent after orthotopic liver transplantation and 12 were nonrecurrent tumors with their paired normal samples. We used both the reference genome and de novo transcriptome assembly based analyses to identify differentially expressed genes (DEG) and used RandomForest to discover biomarkers.

Results

We obtained 398 DEG using the Reference approach and 412 DEG using de novo assembly approach. Among these DEG, 258 genes were identified by both approaches. We further identified 30 biomarkers that could predict the recurrence. We used another independent HCC study that includes 50 patients normal and tumor samples. By using these 30 biomarkers, the prediction accuracy was 100% for normal condition and 98% for tumor condition. A group of Metallothionein was specifically discovered as biomarkers in both reference and de novo assembly approaches.

Conclusion

We identified a group of Metallothionein genes as biomarkers to predict recurrence. The metallothionein genes were all down‐regulated in tumor samples, suggesting that low metallothionein expression may be a promoter of tumor growth. In addition, using de novo assembly identified some unique biomarkers, further confirmed the necessity of conducting a de novo assembly in human cancer study.

Genomic structures of dysplastic nodule and concurrent hepatocellular carcinoma

Although high-grade dysplastic nodule (HGDN) is a preneoplastic lesion that precedes hepatocellular carcinoma (HCC), the genomic structures of HGDN in conjunction with HCC remain elusive. The objective of this study was to identify genomic alterations of HGDN and its difference from HCC that may drive HGDN progression to HCC. We analyzed 16 regions of paired HGDN and HCC from 6 patients using whole-exome sequencing to find somatic mutation and copy number alteration (CNA) profiles of HGDN and HCC. The numbers of mutations, driver mutations, and CNAs of HGDNs were not significantly different from those of HCCs. We identified that the CNA gain of 1q25.3-1q42.13 was predominant in the HCCs compared with that in the HGDNs. Two cases (one nodule-in-nodule case and another case with closely attached HCC and HGDN) showed several overlapped driver mutations (CTNNB1 and CEBPA) and CNAs (losses of CDKN2A, RB1, and TP53) between HGDNs and HCCs, suggesting their roles in the early HCC development. The other 4 cases with spatially separated HCCs and HGDNs showed few overlapped alterations between the paired HCCs and HGDNs. Mutations in ERBB2 and CCND1, and CNAs (gains of CTNNB1, MET, and SMO and losses of PTEN, TP53, and SETD2) were identified as "HCC predominant," suggesting their roles in the progression of HGDN to HCC. Our data show that HCCs are direct descendants of HGDNs in some cases, but there is no direct evidence of such relationship in spatially separated cases. Genomic features of HGDN identified in this study provide a useful resource for dissecting clues for the genetic diagnosis of HGDN and HCC.

Low Levels of Microsatellite Instability at Simple Repeated Sequences Commonly Occur in Human Hepatocellular Carcinoma

BACKGROUND/AIM

The aim of this study was to assess the incidence of MSI in a large series of human hepatocellular carcinomas (HCC) with various etiologies.

MATERIALS AND METHODS

The MSI status was determined by polymerase chain reaction (PCR) using 5 mononucleotide and 13 CAn dinucleotide repeats.

RESULTS

None of the 122 HCC samples displayed an MSI-High phenotype, as defined by the presence of alterations at more than 30% of the microsatellite markers analyzed. Yet, limited microsatellite instability consisting in the insertion or deletion of a few repeat motifs was detected in 32 tumor samples (26.2%), regardless of the etiology of the underlying liver disease. MSI tended to be higher in patients with cirrhosis (p=0.051), possibly reflecting an impact of the inflammatory context in this process.

CONCLUSION

Based on a large series of HCC with various etiologies, our study allowed us to definitely conclude that MSI is not a hallmark of HCC.

Selective Retention of an Inactive Allele of the DKK2 Tumor Suppressor Gene in Hepatocellular Carcinoma

In an effort to identify the functional alleles associated with hepatocellular carcinoma (HCC), we investigated 152 genes found in the 4q21-25 region that exhibited loss of heterozygosity (LOH). A total of 2,293 pairs of primers were designed for 1,449 exonic and upstream promoter regions to amplify and sequence 76.8–114 Mb on human chromosome 4. Based on the results from analyzing 12 HCC patients and 12 healthy human controls, we discovered 1,574 sequence variations. Among the 99 variants associated with HCC (p < 0.05), four are from the Dickkopf 2 (DKK2) gene: three in the promoter region (g.-967A>T, g.-923C>A, and g.-441T>G) and one in the 5’UTR (c.550T>C). To verify the results, we expanded the subject cohort to 47 HCC cases and 88 healthy controls for conducting haplotype analysis. Eight haplotypes were detected in the non-tumor liver tissue samples, but one major haplotype (TAGC) was found in the tumor tissue samples. Using a reporter assay, this HCC-associated allele registered the lowest level of promoter activity among all the tested haplotype sequences. Retention of this allele in LOH was associated with reduced DKK2 transcription in the HCC tumor tissues. In HuH-7 cells, DKK2 functioned in the Wnt/β-catenin signaling pathway, as an antagonist of Wnt3a, in a dose-dependent manner that inhibited Wnt3a-induced cell proliferation. Taken together, the genotyping and functional findings are consistent with the hypothesis that DKK2 is a tumor suppressor; by selectively retaining a transcriptionally inactive DKK2 allele, the reduction of DKK2 function results in unchecked Wnt/β-catenin signaling, contributing to HCC oncogenesis. Thus our study reveals a new mechanism through which a tumor suppressor gene in a LOH region loses its function by allelic selection.

Liver cancer is one of the most lethal human cancers. Identifying functional alleles associated with liver cancer can provide new insights into the disease’s pathogenesis and help to advance the development of new therapeutic approaches. We conducted re-sequencing of the 4q21-25 region that frequently showed loss of heterozygosity (LOH) in liver cancer. Among the 99 variants associated with liver cancer, four are found within the Dickkopf 2 (DKK2) gene. We conducted haplotype analysis of the DKK2 promoter sequence and found that a transcriptionally inactive DKK2 allele was selectively retained in the tumor tissues. Additionally, by sequencing individual molecular clones, we detected 7-mer CCTCCCT sites within the DKK2 promoter region that are involved in PRDM9 binding, pinpointing hotspots for recombination and genome instability. Furthermore, we demonstrated that DKK2 functioned as an antagonist within the Wnt/β-catenin signaling pathway. Our findings have led to the discovery of a new mechanism whereby a tumor suppressor gene in a LOH region loses its function by allelic selection.

Loss of heterozygosity at D8S262: an early genetic event of hepatocarcinogenesis

BACKGROUND

Hepatocellular carcinoma (HCC) is a multi-factor, multi-step, multi-gene and complicated process resulting from the accumulation of sequential genetic and epigenetic alterations. An important change among them is from precancerous lesions to HCC. However, only few studies have been reported about the sequential genetic changes during hepatocarcinogenesis.

METHODS

We observed firstly molecular karyotypes of 10 matched HCC using Affymetrix single-nucleotide polymorphism (SNP) 6.0 arrays, and found chromosomal fragments with high incidence (more than 70%) of loss of heterozygosity (LOH). Then, we selected 28 microsatellite markers at some gene spanning these chromosomal fragments, and examined the frequency of LOH of 128 matched HCC and 43 matched precancerous lesions-dysplastic nodules (DN) by a PCR-based analysis. Finally, we investigated the expression of proteins encoded by these genes in HCC, DN and the surrounding hepatic tissues.

RESULTS

The result of Affymetrix SNP6.0 arrays demonstrated that more than 70% (7/10) cases had chromosomal fragment deletion on 4q13.3-35.1, 8p23.2-21.2, 16q11.2-24.3, and 17p13.3-12. Among 28 microsatellite markers selected, LOH frequencies at D8S262 for DN and HCC were found to be the highest, 51.2% and 72.7%, respectively. Immunohistochemically, the positive rate of its adjacent gene CSMD1 in HCC, DN, and the surrounding hepatic tissues were 27.3% (35/128), 75% (33/44), and 82% (105/128), respectively.

CONCLUSIONS

LOH at D8S262 may be associated with an early genetic event of hepatocarcinogenesis, and a predictor for the monitor and prevention of HCC.

VIRTUAL SLIDES

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1557074981159099 .

Anatomic pathology of hepatocellular carcinoma: histopathology using classic and new diagnostic tools

Hepatocellular carcinoma can be diagnosed on a needle biopsy of the liver; however, uncertainty may arise because of the inherent complexity of liver histology. This article aims to provide practicing pathologists with tools for the approach to mass-directed liver biopsies clinically concerning for hepatocellular carcinoma. The examination of routine hematoxylin-eosin stains and the use of ancillary histochemical and immunohistochemical stains are discussed. Sections reviewing liver carcinoma with biphenotypic differentiation and the challenge of dysplastic nodules are included.

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.

Involvement of DNA damage response pathways in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has been known as one of the most lethal human malignancies, due to the difficulty of early detection, chemoresistance, and radioresistance, and is characterized by active angiogenesis and metastasis, which account for rapid recurrence and poor survival. Its development has been closely associated with multiple risk factors, including hepatitis B and C virus infection, alcohol consumption, obesity, and diet contamination. Genetic alterations and genomic instability, probably resulted from unrepaired DNA lesions, are increasingly recognized as a common feature of human HCC. Dysregulation of DNA damage repair and signaling to cell cycle checkpoints, known as the DNA damage response (DDR), is associated with a predisposition to cancer and affects responses to DNA-damaging anticancer therapy. It has been demonstrated that various HCC-associated risk factors are able to promote DNA damages, formation of DNA adducts, and chromosomal aberrations. Hence, alterations in the DDR pathways may accumulate these lesions to trigger hepatocarcinogenesis and also to facilitate advanced HCC progression. This review collects some of the most known information about the link between HCC-associated risk factors and DDR pathways in HCC. Hopefully, the review will remind the researchers and clinicians of further characterizing and validating the roles of these DDR pathways in HCC.

Hepatocarcinogenesis: imaging-pathologic correlation

Rapid advances in liver surgery, including liver transplantation, radiology, and pathology, have created a need for clinically relevant nomenclature for premalignant and early lesions of hepatocellular carcinoma (HCC). Precancerous lesions include dysplastic foci and dysplastic nodules (DNs) characterized by cytologic or structural atypia. Although imaging diagnosis is playing a crucial role in the evaluation of hepatocarcinogenesis and early diagnosis of HCC, it is still challenging to accurately characterize borderline nodules such as small arterially enhancing lesions or hypovascular nodules. This article discusses pathological and radiological features of these small nodular lesions and offers insights into the multistep process of hepatocarcinogenesis by describing the progression of pathologic change linking DNs to HCC.

Update on precursor and early lesions of hepatocellular carcinomas

CONTEXT

There is increasing evidence to support a multistep model of the process of human hepatocarcinogenesis. Precursor lesions are characterized by the appearance of dysplastic lesions in the form of microscopic dysplastic foci and macroscopic dysplastic nodules. There are 2 types of small hepatocellular carcinoma (HCC) (≤2 cm in diameter): (1) early HCC with an indistinct margin and (2) progressed HCC with a distinct margin. Pathologic diagnostic criteria for early HCC have recently been set up based on a consensus between Eastern and Western pathologists.

OBJECTIVE

To review the nomenclature, pathology, and biomarkers of precursor and early lesions of HCC.

DATA SOURCES

Literature review and illustrations from case materials were used.

CONCLUSIONS

Dysplastic foci are composed of large and small cell changes. Small cell change is considered to be a more advanced precursor lesion than large cell change, and large cell change is a rather heterogeneous lesion that may represent both reactive change and true dysplasia. Dysplastic nodules can be categorized as low or high grade according to the degree of atypia. High-grade dysplastic nodules have been reported to show molecular changes similar to HCC and have a high risk of malignant transformation. Early HCC, which may correspond to microinvasive carcinomas of other organs, is a well-differentiated HCC, and differential diagnosis between early HCC and high-grade dysplastic nodule is difficult. Identification of stromal invasion and application of a panel of markers (glypican-3, heat shock protein 70, and glutamine synthetase) is helpful for diagnosis of early HCC. Detection of precursor lesions of HCC is important in recognizing patients with higher risk of developing HCC, and diagnosis of early HCC can improve patient survival by allowing for early and adequate treatment.

Evolution of genomic instability in diethylnitrosamine-induced hepatocarcinogenesis in mice

Diethylnitrosamine (DEN) is a hepatic procarcinogen which is frequently used as an inducer of hepatocellular carcinoma (HCC) in mice. Although mice after DEN exposure are among the most widely used models for liver tumorigenesis, a detailed, mechanistic characterization of the longitudinal changes in the respective tumor genomes has never been performed. Here we established the chronological order of genetic alterations during DEN carcinogenesis by examining mice at different points in time. Tumor samples were isolated by laser microdissection and subjected to array-comparative genomic hybridization (array-CGH) and sequencing analysis. Chromosomal gains and losses were observed in tumors by week 32 and increased significantly by week 56. Loss of distal chromosome 4q, including the tumor suppressors Runx3 and Nr0b2/Shp, was a frequent early event and persisted during all tumor stages. Surprisingly, sequencing revealed that β-catenin mutations occurred late and were clearly preceded by chromosomal instability. Thus, contrary to common belief, β-catenin mutations and activation of the Wnt/β-catenin pathway are not involved in tumor initiation in this model of chemical hepatocarcinogenesis.

CONCLUSION

Our study suggests that the majority of the current knowledge about genomic changes in HCC is based on advanced tumor lesions and that systematic analyses of the chronologic order including early lesions may reveal new, unexpected findings.

[Epidemiology, natural history and pathogenesis of hepatocellular carcinoma]

Hepatocellular carcinoma (HCC) is the main type of primary liver cancers and the third most common cause of cancer mortality worldwide. In France, rising number between 5000 and 6000 cases are diagnosed each year. The major risk factor for hepatocellular carcinoma is chronic hepatitis: viral hepatitis B, viral hepatitis C, consumption of alcohol, hemochromatosis. Hepatocellular carcinoma is closely associated to liver cirrhosis, which is a true precancerous state. Because hepatocarcinogenesis is a long and heterogeneous process, there is still much to understand. Many genetic and epigenetic alterations are described leading to changes in cellular signalling cascades involved in regulation of growth, differentiation, apoptosis, motility. Hepatitis viruses play a direct oncogenic role through the interaction between viral and cellular proteins, which control cell homeostasis, or by the integration of hepatitis B virus genome into the host genome. Furthermore, hepatitis viruses play an indirect oncogenic role by causing chronic inflammation and hepatocyte regeneration related to viral hepatopathy. In expectation of a better understanding of hepatocarcinogenesis and new treatments, prevention from risk factors and ultrasonographic screening of patients with cirrhosis should increase prognosis.

Radiofrequency ablation of hepatocellular carcinoma: The feasibility of magnetic resonance imaging with gadolinium ethoxybenzyl diethylene triamine pentaacetic acid for evaluating the ablative margin

AIM

  The aim of this study was to evaluate the feasibility of gadolinium ethoxybenzyl diethylene triamine pentaacetic acid (Gd-EOB-DTPA) in magnetic resonance imaging (MRI) to assess the ablative margin of radiofrequency (RF) ablation to hepatocellular carcinoma (HCC).

METHODS

  RF ablation was performed in the livers of six pigs after the i.v. administration of Gd-EOB-DTPA 20 min before ablation. Three pigs were killed 2 h after administration (group A), and the other pigs were killed 7 days after ablation (group B). Thereafter, correlation between pathological findings and MRI was investigated. Moreover, the Gd concentrations were examined in ablated and non-ablated regions. An initial clinical evaluation was conducted for 28 HCC nodules. Percutaneous RF ablation was performed 20 min after administration, and T(1)-weighted images were taken 2, 24 and 72 h post-treatment.

RESULTS

  On T(1)-weighted images of the porcine liver, the RF ablated lesions showed hyperintense regions with hypointense rims, which histopathologically corresponded to sinusoidal congestion. The Gd concentrations in ablated regions in group A were significantly higher than those in non-ablated regions, while the concentrations in both regions in group B fell to nearly undetectable levels. In 27 of the 28 HCC nodules, the treated area consisted of a hypointense region, indicative of the tumor, and a surrounding hyperintense rim 2 h after ablation. Subsequently, a thin hypointense region was observed in the outermost layer 24 and 72 h after ablation.

CONCLUSION

  Administration of Gd-EOB-DTPA in conjunction with RF ablation of HCC may be feasible for the assessment of an accurate ablative margin.

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

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

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.

Chromosomal instability, telomere shortening, and inactivation of p21(WAF1/CIP1) in dysplastic nodules of hepatitis B virus-associated multistep hepatocarcinogenesis

Systemic analysis for chromosomal instability and inactivation of cell cycle checkpoints are scarce during hepatocarcinogenesis. We studied 24 patients with chronic B viral cirrhosis including 30 cirrhotic regenerative nodules, 35 low-grade dysplastic nodules, 15 high-grade dysplastic nodules, 7 dysplastic nodules with hepatocellular carcinoma foci, and 18 hepatocellular carcinomas. Eight normal livers were studied as the control group. Telomere length and micronuclei were detected by Southern blot and Feulgen-fast green dyeing technique, respectively, and p21(WAF1/CIP1) expression was studied by immunohistochemistry. Micronuclei >1 per 3000 hepatocytes were found in 17% of low-grade dysplastic nodules, 87% of high-grade dysplastic nodules, and 100% of high-grade dysplastic nodules with hepatocellular carcinoma foci and hepatocellular carcinomas in contrast to those of all normal livers, and 90% of cirrhosis showed no micronuclei. The micronuclei index showed a gradual increase during hepatocarcinogenesis and there was a significant increase between cirrhosis and low-grade dysplastic nodules, low-grade dysplastic nodules and high-grade dysplastic nodules, and high-grade dysplastic nodules and hepatocellular carcinomas. Telomere length showed a gradual shortening during hepatocarcinogenesis and a significant reduction was found in high-grade dysplastic nodules (P=0.024) and hepatocellular carcinomas (P=0.031) compared with normal and cirrhotic livers. The micronuclei index was correlated with telomere shortening (P=0.016). The p21(WAF1/CIP1) labeling index was significantly higher in cirrhosis than in normal livers (P=0.024) and markedly decreased in low-grade dysplastic nodules, high-grade dysplastic nodules, and hepatocellular carcinomas compared with cirrhosis (P<0.05). The p21(WAF1/CIP1) labeling index was associated with telomere length (P<0.001) but not micronuclei index. This study shows that telomere shortening, chromosomal instability, and inactivation of p21(WAF1/CIP1) checkpoint function occur in low-grade dysplastic nodules as well as in high-grade dysplastic nodules, and their cooperation is considered to be critical for malignant transformation during hepatitis B virus associated-multistep hepatocarcinogenesis.

Allelic imbalances and homozygous deletion on 8p23.2 for stepwise progression of hepatocarcinogenesis

Early hepatocellular carcinoma (eHCC) originates from the hepatocytes of chronic liver disease and develops into classical hepatocellular carcinoma (HCC). To identify sequential genetic changes in multistep hepatocarcinogenesis, we analyzed molecular karyotypes using oligonucleotide genotyping 50K arrays. First, 1q21.3-44 gain and loss of heterozygosity (LOH) on 1p36.21-36.32 and 17p13.1-13.3 were frequently observed in eHCC, but not in chronic liver diseases, suggesting that such chromosomal aberrations are early, possibly causative events in liver cancer. Next, we detected 25 chromosomal loci associated with liver cancer progression in five HCCs with nodule-in-nodule appearance, in which the inner nodule develops within eHCC lesion. Using these chromosomal regions as independent variables, decision tree analysis was applied on 14 early and 25 overt HCCs, and extracted combination of chromosomal gains on 5q11.1-35.3 and 8q11.1-24.3 and LOH on 4q11-34.3 and 8p11.21-23.3 as distinctive attributes, which can classify early and overt HCCs recursively. In these four altered regions identified as late events of hepatocarcinogenesis, two tumors in 32 overt HCCs analyzed in the present study and one in a set of independent samples of 36 overt HCCs in our previous study harbored a homozygous deletion near the CSMD1 locus on 8p23.2. CSMD1 messenger RNA expression was decreased in HCC without 8p23.2 deletion, possibly due to hypermethylation of the CpG islands in its promoter region.

CONCLUSION

1q gain and 1p and 17p LOH are early molecular events, whereas gains in 5q and 8q and LOH on 4q and 8p only occur in advanced HCC, and inactivation of the putative suppressor gene, CSMD1, may be the key event in progression of liver cancer.

Liver transplantation for hepatocellular carcinoma without preoperative tumor biopsy

BACKGROUND

Progress in liver imaging has made pretransplantation tumor biopsy no longer systematic in patients with hepatocellular carcinoma (HCC).

OBJECTIVES

Our aim was to evaluate the accuracy of a preoperative diagnosis of HCC based on clinical and radiological findings in 102 cirrhotics qualified for liver transplantation (LT) between January 1995 and August 2003 at our institution.

METHODS

The diagnostic accuracy of our policy was assessed by comparing pretransplant diagnosis with the pathologic report of explanted livers.

RESULTS

Sensitivity, specificity, positive, and negative predictive values for the preoperative clinical and radiological diagnosis of HCC were 89%, 94.3%, 77%, and 93.3%, respectively. A false-positive preoperative diagnosis was made in 20 of 102 patients (19.6%) (dysplastic nodules [n=9], regenerative nodules [n=5] cholangiocellular carcinoma [n=1], hemangioma [n=1], and no lesion [n=4]). All tumors larger than 3 cm were correctly diagnosed, irrespective of serum alpha-fetoprotein (sAFP) levels. The risk of overestimating the diagnosis of HCC in the subgroup of patients with tumors less than 3 cm was conversely correlated with preliver transplantation sAFP (sAFP<or=100 ng/L: 28%; sAFP>100: 11%; sAFP>200: 0%).

CONCLUSION

In cirrhotics with nodules larger than 3 cm irrespective of sAFP or nodules less than 3 cm with sAFP greater than 200 ng/L, the pretransplant diagnosis of HCC can be made without performing biopsy. In other cases (i.e., nodules less than 3 cm and sAFP lower than 200 ng/L), histologic confirmation of HCC or a close follow-up imaging should be considered.

Hepatitis B virus-associated multistep hepatocarcinogenesis: a stepwise increase in allelic alterations

Hepatocarcinogenesis is a multistep process, but systematic analysis using a genetic or molecular approach to accurately delineate the different stages of hepatocellular carcinoma (HCC) development is scarce. In this study, we used genome-wide allelotyping to systematically evaluate the allelic alterations in the multisteps of hepatitis B virus-associated hepatocarcinogenesis. The overall fractional allelic loss (FAL) indices of cirrhosis, dysplastic nodules (DN), and HCC were significantly different, with a clear stepwise increase (P < 0.001). Loss of heterozygosity (LOH) was uncommon in cirrhotic livers (n = 24; mean FAL index +/- SD, 0.09 +/- 0.09; median, 0.07). In contrast, LOH was common in our 74 HCC nodules, which were predominantly hepatitis B virus-associated (mean FAL index +/- SD, 0.40 +/- 0.23; median, 0.38). The 18 DNs had FAL index (mean +/- SD, 0.27 +/- 0.19; median, 0.20) in between that of cirrhosis and HCC. Importantly, high-grade DNs had FAL index significantly higher than that of low-grade DNs (P = 0.031) and close to that of HCC, indicating that high-grade DNs were genetically closer to HCC. However, there was no significant difference in FAL indices between primary HCCs and their corresponding intrahepatic metastases, but this absence of major allelic losses in this transformation to a metastatic phenotype does not exclude small-scale chromosomal losses or gene deletions. To conclude, hepatitis B virus-associated hepatocarcinogenesis is a multistep process accompanied by stepwise increase in allelic losses from cirrhosis and low- and high-grade DN to HCC. Such allelic losses contribute to promote tumor development and progression.

Hepatic precancerous lesions and small hepatocellular carcinoma

Precancerous lesions that may be detected in chronically diseased, usually cirrhotic livers, include: clusters of hepatocytes with atypia and increased proliferative rate (dysplastic foci) that usually represent an incidental finding in biopsy or resection specimens; and grossly evident lesions (dysplastic nodules) that may be detected on radiologic examination. There are two types of small hepatocellular carcinoma (HCC) (defined as HCC that measures less than 2 cm): early HCC, which is well-differentiated and has indistinct margins; and distinctly nodular small HCC, which is well- or moderately differentiated, and is usually surrounded by a fibrous capsule. Precise diagnosis of precancerous and early cancerous lesions by imaging methods is often difficult or impossible. Detection of a dysplastic lesion in a biopsy specimen is a marker of increased risk for HCC development, and warrants increased surveillance. High-grade dysplastic nodules and small HCCs should be treated by local ablation, surgical resection, or liver transplantation.

Hepatocellular dysplastic nodules

The multistep process of hepatic carcinogenesis is mirrored by the morphologic classification of lesions detectable in cirrhosis, which include large regenerative nodules (LRN), low grade dysplastic nodules (LGDN), and high grade dysplastic nodules (HGDN). The latter belong to the "bordeline malignancy" category requiring accurate distinction from well-differentiated and early hepatocellular carcinoma (HCC). Nodules in cirrhosis are usually detected by non-invasive imaging techniques, which are unable to discriminate malignant from non-malignant forms, particularly in the 1-2-cm sized group. Liver biopsy is essential in providing practical diagnostic information to hepathologists in the management of cirrhotic patients with ultrasound (US)-detectable nodules. Histologic diagnosis on liver samples is based on the accurate search of a set of cyto-architectural features (e.g. cell atypia, cell crowding, trabecular thickness, microacini) and by a supplement of histochemical (Gomori staining) and immunocytochemical stainings. The latter rely upon the search of both well established and novel markers, targeted to evaluate stromal invasion (CK7/19), the vascular pattern (ASMA and CD34), or tumor markers (including HSP70 and glipican-3). Still, the diagnostic sensitivity is limited by the type and size of sampling and by its representativity of the entire lesion. Thus, the best diagnostic approach requires the integration ofclinical, morphological, and immunocytochemical information with imaging data (i.e. US pattern, perfusional pattern, helical computed tomography/magnetic resonance pattern). Molecular data are still under evaluation as to their diagnostic efficacy in this controversial field. Discrepancies have emerged recently between Eastern and Western interpretation of these lesions, particularly in the category of "borderline" nodules that are mostly labelled as early, well differentiated HCC by Eastern pathologists and as HGDN by Western pathologsts. Novel and more objective phenotypical and molecular markers are needed to discriminate within the grey area of borderline lesions that, epidemiologically, are likely distinct between Eastern and Western geographic areas. These tools might allow a better understanding of the boundaries of the process going from high grade dysplasia to in situ HCC and from the latter to microinvasive HCC and advanced HCC, for proper clinical management and optimal therapy.

Identification of minimal regions of deletion at 8p23.1-22 associated with metastasis of hepatocellular carcinoma

AIMS/BACKGROUND

Loss of heterozygosity (LOH) at 8p is the most frequent chromosomal alteration in tumorigenesis of human cancers. However, the genetic change in metastasis of hepatocellular carcinoma (HCC) still has to be investigated.

METHODS

We used 16 microsatellite markers informative in Japanese patients, selected from among 61 published microsatellite markers at 8p23.2-21 to compare the frequency of LOH in primary tumours (Tps) and metastatic tumours (Tms) in a PCR-based analysis. Sixty-three informative cancerous lesions (26 were Tps, 37 were Tms) from 23 cases of HCC were used.

RESULTS

The frequency of LOH at 8p23.2-21 with at least one marker was 19% in Tps and 68% in Tms. Allelic loss at 8p23.2-21 was significantly more frequent in Tms than in Tps (P=0.0003). More specifically, the frequency of LOH at D8S262, D8S1819, D8S503, D8S1130, D8S552, D8S1109, and D8S261 in Tms was 36-60% respectively.

CONCLUSIONS

In contrast, allelic loss at the same markers in Tp was only detected in 0-17% of the tumour respectively. The significant difference in the frequency of LOH at 8p between primary cancer and metastatic cancer in individual cases of HCC suggests LOH at 8p to be involved in the enhancement of tumour aggressiveness, especially during metastasis.

Hepatitis C virus and malignancy

Hepatitis C virus (HCV) is a hepatotropic virus that causes chronic hepatitis, fibrosis and cirrhosis. HCV is associated with the development of primary liver tumors, namely hepatocellular carcinoma, cholangiocarcinoma and lymphoma. This article reviews HCV-related malignancies, and their prevalence and probable oncogenesis.

Frequent loss of heterozygosity in two distinct regions, 8p23.1 and 8p22, in hepatocellular carcinoma

AIM: To identify the precise location of putative tumor suppressor genes (TSGs) on the short arm of chromosome 8 in patients with hepatocellular carcinoma (HCC).

METHODS: We used 16 microsatellite markers informative in Japanese patients, which were selected from 61 published markers, on 8p, to analyze the frequency of loss of heterozygosity (LOH) in each region in 33 cases (56 lesions) of HCC.

RESULTS: The frequency of LOH at 8p23.2-21 with at least one marker was 63% (20/32) in the informative cases. More specifically, the frequency of LOH at 8p23.2, 8p23.1, 8p22, and 8p21 was 6%, 52%, 47%, and 13% in HCC cases. The LOH was significantly more frequent at 8p23.1 and 8p22 than the average (52% vs 22%, P = 0.0008; and 47% vs 22%, P = 0.004, respectively) or others sites, such as 8p23.2 (52% vs 6%, P = 0.003; 47% vs 22%, P = 0.004) and 8p21 (52% vs 13%, P = 0.001; 47% vs 13%, P = 0.005) in liver cancer on the basis of cases. Notably, LOH frequency was significantly higher at D8S277, D8S503, D8S1130, D8S552, D8S254 and D8S258 than at the other sites. However, no allelic loss was detected at any marker on 8p in the lesions of nontumor liver tissues.

CONCLUSION: Deletion of 8p, especially the loss of 8p23.1-22, is an important event in the initiation or promotion of HCC. Our results should be useful in identifying critical genes that might lie at 8p23.1-22.

Biliary and reticuloendothelial impairment in hepatocarcinogenesis: the diagnostic role of tissue-specific MR contrast media

The development and progression of a hepatocellular carcinoma (HCC) in a chronically diseased liver, i.e., the carcinogenesis, comprise a multistep and long-term process. Morphologically, this process is associated with the presence of distinct nodular lesions in the liver that are called 'preneoplastic lesions.' These preneoplastic lesions are associated with and can precede the growth and progression of well-differentiated HCCs . The characterization of nodular lesions and demonstration of the multistep development of HCC in the cirrhotic liver by imaging modalities represent a challenging issue. The arterial hypervascular supply, depicted by different dynamic studies, represents a fundamental radiological criterion for the diagnosis of HCC in cirrhosis. Magnetic resonance (MR) imaging performed with tissue-specific contrast media can help to investigate the "grey area" of carcinogenesis, in which significant histological changes are already present without any imaging evidence of neoangiogenesis. The purpose of this review is to provide information on the properties of tissue-specific MR contrast agents and on their usefulness in the demonstration of the pathologic changes that take place at the level of the biliary and reticuloendothelial systems during the carcinogenetic process in liver cirrhosis.

Pathological and molecular analysis of sporadic hepatic angiomyolipoma

Hepatic angiomyolipoma (HAML) is an unusual mesenchymal lesion that can be misdiagnosed as hepatocellular carcinoma or sarcoma. We sought to better define the morphological variations and immunohistochemical and molecular features of this unusual tumor. Forty-nine sporadic HAMLs were investigated for immunopathologic characteristics with EnVision Plus. The clonal analysis was based on the methylation pattern of the polymorphic X chromosome-linked human androgen receptor gene, loss of heterozygosity (LOH), and microsatellite instability (MSI) detected with polymerase chain reaction using the MegaBACE 500 automatic system on microdissected tissues. Histologically, HAML is composed of a heterogeneous mixture of blood vessels, smooth muscle, and adipose cells. The myomatous or myoid cells were the most variable. Most of the tumor cells were positive for HMB-45 (100%) and SMA (100%). There was a typical monoclonal pattern in 35 of the 40 tumors. No LOH or MSI was found. Hepatic AML is a benign neoplasm with varied morphology and monoclonal growth. HMB-45 is the best marker available for diagnosis. Neither LOH nor MSI appears to play an important role in the pathogenesis of this tumor.

Overexpression of hepatitis C virus NS5A protein induces chromosome instability via mitotic cell cycle dysregulation

Hepatocellular carcinoma (HCC) is a common primary cancer associated with high incidences of genetic variations including chromosome instability. Moreover, it has been demonstrated that hepatitis C virus (HCV) is one of the major causes of HCC. However, no previous work has assessed whether HCV proteins are associated with the induction of chromosome instability. Here, we found that liver cell lines constitutively expressing full-length or truncated versions of the HCV genome show a high incidence of chromosome instability. In particular, the overexpression of HCV NS5A protein in cultured liver cells was found to promote chromosome instability and aneuploidy. Further experiments showed that NS5A-induced chromosome instability is associated with aberrant mitotic regulations, such as, an unscheduled delay in mitotic exit and other mitotic impairments (e.g. multi-polar spindles). Thus, our results indicate that HCV NS5A protein may be directly involved in the induction of chromosome instability via mitotic cell cycle dysregulation, and provide novel insights into the molecular mechanisms of HCV-associated hepatocarcinogenesis.

Review of genetic and epigenetic alterations in hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is associated with multiple risk factors and is believed to arise from pre-neoplastic lesions, usually in the background of cirrhosis. However, the genetic and epigenetic events of hepatocarcinogenesis are relatively poorly understood. HCC display gross genomic alterations, including chromosomal instability (CIN), CpG island methylation, DNA rearrangements associated with hepatitis B virus (HBV) DNA integration, DNA hypomethylation and, to a lesser degree, microsatellite instability. Various studies have reported CIN at chromosomal regions, 1p, 4q, 5q, 6q, 8p, 10q, 11p, 16p, 16q, 17p and 22q. Frequent promoter hypermethylation and subsequent loss of protein expression has also been demonstrated in HCC at tumor suppressor gene (TSG), p16, p14, p15, SOCS1, RIZ1, E-cadherin and 14-3-3 sigma. An interesting observation emerging from these studies is the presence of a methylator phenotype in hepatocarcinogenesis, although it does not seem advantageous to have high levels of microsatellite instability. Methylation also appears to be an early event, suggesting that this may precede cirrhosis. However, these genes have been studied in isolation and global studies of methylator phenotype are required to assess the significance of epigenetic silencing in hepatocarcinogenesis. Based on previous data there are obvious fundamental differences in the mechanisms of hepatic carcinogenesis, with at least two distinct mechanisms of malignant transformation in the liver, related to CIN and CpG island methylation. The reason for these differences and the relative importance of these mechanisms are not clear but likely relate to the etiopathogenesis of HCC. Defining these broad mechanisms is a necessary prelude to determine the timing of events in malignant transformation of the liver and to investigate the role of known risk factors for HCC.

Genetic alterations of hepatocellular carcinoma by random amplified polymorphic DNA analysis and cloning sequencing of tumor differential DNA fragment

AIM: To study the genetic alterations and their association with clinicopathological characteristics of hepatocellular carcinoma (HCC), and to find the tumor related DNA fragments.

METHODS: DNA isolated from tumors and corresponding noncancerous liver tissues of 56 HCC patients was amplified by random amplified polymorphic DNA (RAPD) with 10 random 10-mer arbitrary primers. The RAPD bands showing obvious differences in tumor tissue DNA corresponding to that of normal tissue were separated, purified, cloned and sequenced. DNA sequences were analyzed and compared with GenBank data.

RESULTS: A total of 56 cases of HCC were demonstrated to have genetic alterations, which were detected by at least one primer. The detestability of genetic alterations ranged from 20% to 70% in each case, and 17.9% to 50% in each primer. Serum HBV infection, tumor size, histological grade, tumor capsule, as well as tumor intrahepatic metastasis, might be correlated with genetic alterations on certain primers. A band with a higher intensity of 480 bp or so amplified fragments in tumor DNA relative to normal DNA could be seen in 27 of 56 tumor samples using primer 4. Sequence analysis of these fragments showed 91% homology with Homo sapiens double homeobox protein DUX10 gene.

CONCLUSION: Genetic alterations are a frequent event in HCC, and tumor related DNA fragments have been found in this study, which may be associated with hepatocarcin-ogenesis. RAPD is an effective method for the identification and analysis of genetic alterations in HCC, and may provide new information for further evaluating the molecular mechanism of hepatocarcinogenesis.

Clinicopathological significance of loss of heterozygosity and microsatellite instability in hepatocellular carcinoma in China

AIM: To determine the features of microsatellite alterations and their association with clinicopathological characteristics of hepatocellular carcinoma (HCC).

METHODS: Loss of heterozygosity (LOH) and microsatellite instability (MSI) of 55 microsatellite loci were detected with PCR-based microsatellite polymorphism analyses in tumors and corresponding noncancerous liver tissues of 56 surgically resected HCCs using the MegaBACE 500 automatic DNA analysis system.

RESULTS: LOH was found in 44 of 56 HCCs (78.6%) at one or several loci. Frequencies of LOH on 1p, 4q, 8p, 16q, and 17p were 69.6% (39/56), 71.4% (40/56), 66.1% (37/56), 66.1% (37/56), and 64.3% (36/56), respectively. MSI was found in 18 of 56 HCCs (32.1%) at one or several loci. Ten of fifty-six (17.9%) HCCs had MSI-H. Serum HBV infection, alpha-fetoprotein concentration, tumor size, cirrhosis, histological grade, tumor capsule, as well as tumor intrahepatic metastasis, might be correlated with LOH on certain chromosome regions.

CONCLUSION: Frequent microsatellite alterations exist in HCC. LOH, which represents a tumor suppressor gene pathway, plays a more important role in hepatocarcin-ogenesis. MSI, which represents a mismatch repair gene pathway, is a rare event during liver carcinogenesis. Furthermore, LOH on certain chromosome regions may be correlated with clinicopathological characteristics in HCC.

Mutations of beta-catenin and AXIN I genes are a late event in human hepatocellular carcinogenesis

BACKGROUND

Hepatocellular carcinoma (HCC) is a well-known cancer involving the Wnt pathway in its carcinogenesis.

AIMS

However, it is not clear whether these genetic changes are early genetic events in hepatocarcinogenesis or not.

METHOD

In this study, we performed mutational analysis of the beta-catenin and AXIN I genes, and immunohistochemistry for beta-catenin in a series of 114 hepatocellular nodular lesions, including premalignant lesions such as low-grade dysplastic nodules (LGDNs) and high-grade dysplastic nodules (HGDNs).

RESULTS

In the present study, mutations of the beta-catenin and AXIN I genes were detected in 16% (13 out of 81) and 6.2% (five of 81) of the HCCs, respectively. However, no mutations were found in 14 LGDNs and 19 HGDNs. Moreover, abnormal nuclear beta-catenin immunostaining was observed in 30 of 81 HCCs, but not in dysplastic nodules.

CONCLUSION

Taken together, our data suggest that beta-catenin stabilization because of either beta-catenin or AXIN I mutation might be a late event for malignant progression rather than an early genetic event involving the initiation of HCC development.

Preneoplastic lesions in human hepatocarcinogenesis

The early stages of hepatocarcinogenesis in human chronic liver diseases are characterized by the emergence of preneoplastic lesions of which some will eventually develop into hepatocellular carcinoma (HCC). Basic studies on the genetic and epigenetic alterations of these preneoplastic lesions may eventually lead to new therapeutic strategies. Clinicopathological studies are also important in order to determine optimal management of patients with a preneoplastic lesion. This article aims to provide a comprehensive review of the current concepts of preneoplastic lesion in chronic liver diseases. The microscopical small-cell dysplastic focus is the smallest morphologically recognizable precursor lesion of HCC and therefore is a logical target of study to elucidate the earliest events in hepatocarcinogenesis. In contrast, large-cell dysplasia is not a precursor lesion, but appears to be of clinical value because of its good predictive value for development of HCC. Dysplastic nodules (DNs) are macroscopically recognizable precursor lesions of HCC and high-grade DNs (HGDNs) have a risk of malignant transformation. Detection of DNs and correct differentiation from small HCC (<2 cm) is sometimes difficult, especially when only imaging techniques are used. Additional clinicopathological studies on identification and optimal treatment of DNs are necessary. Molecular studies on HGDNs and small HCCs may yield much information on the genetic mechanisms involved in the transition from severe dysplasia to early malignancy. In contrast, currently available data indicate that (large) regenerative nodules do not represent a distinct step in hepatocarcinogenesis. Animal models will be helpful in the further unravelling of human HCC development, provided that studies are performed on models that are good representatives of human hepatocarcinogenesis. We propose three criteria by which good mimickers can be identified.

Genomic instability in hepatocellular carcinoma revealed by using the random amplified polymorphic DNA method

PURPOSE

To investigate the genomic instability and their association with clinicopathological characteristics in hepatocellular carcinoma (HCC).

METHODS

DNA isolated from tumors and corresponding non-cancerous liver tissues of 56 patients with HCC was amplified with ten random 10-mer arbitrary primers by the random amplified polymorphic DNA (RAPD) method.

RESULTS

All the cases of HCC were demonstrated to have genomic instability by at least one primer. The incidence of genomic instability ranged from 20 to 70% in each case, and 17.9-50% in each primer. Serum AFP concentration, HBV infection, tumor size, histological grade, tumor capsule invasion, as well as intrahepatic metastasis were associated with the genomic instability on certain primers.

CONCLUSIONS

Genomic instability is a frequent event in HCC. The RAPD is an effective method for the identification and analysis of genomic instability in HCC, and it may provide new information for further evaluating the molecular mechanism of hepatocarcinogenesis.

Multiple chromosomal abnormalities in human liver (pre)neoplasia

BACKGROUND/AIMS

In human hepatocarcinogenesis the tumor precursor lesions and the sequence of genetic aberrations are not known. We therefore compared genetic alterations of different types of benign liver lesions to those of hepatocellular carcinoma.

METHODS

By comparative genomic hybridisation (CGH) 40 cases, including cirrhotic liver (CL), focal nodular hyperplasia (FNHs), hepatocellular adenoma (HCAs), dysplastic nodules (DNs), primary hepatocellular carcinoma (HCCs), and hepatocellular metastases to the lung were studied.

RESULTS

FNHs and HCAs exhibited few chromosomal abnormalities. Frequency and pattern of genetic alterations in DNs highly resembled those in HCCs: gains of DNA clustered in chromosome arms 1p/q, 7q, 15q, 16p, 17q, and 20q and losses were often found at 3p, 4q, 9p, and 11q. Aberrations on 1p, 6q, 8p/q, and 13q occurred almost exclusively in HCCs; the gain at 8q encompassed amplification of c-myc, as verified by fluorescence in situ hybridisation.

CONCLUSIONS

The pattern of genetic alterations in HCCs resembled more the alterations found in DNs than in FNHs and HCAs, suggesting that DNs may be the actual tumor precursors. Furthermore, alterations at 4q, 9p, 11q, 16p, and 17q appear as early genetic events being crucial for hepatocarcinogenesis.

Genomic instability of murine hepatocellular carcinomas with low and high metastatic capacities

AIM: To investigate the frequency of genomic instability in murine hepatocellular carcinoma (HCC) cell lines Hca/A2-P(P) and Hca/163-F(F) with low and high metastatic capacity, and to explore its association with the occurrence and metastasis of hepatocellular carcinomas.

METHODS: Forty microsatellite markers were randomly selected to examine P and F cells for genomic instability using PCR-simple sequence length polymorphism (PCR-SSLP) analysis.

RESULTS: Allelic genes on the chromosomes of P cell line with thirty informative microsatellite loci were paralleled to those of inbred strain C₃H mouse, while those of F cell line with 28 loci were paralleled to those of inbred strain C₃H mice. The frequency of microsatellite alterations was 37.5% and 42.5% in P cell line and F cell line, respectively. There were different alterations of allelic band 9 at loci between P and F cells, among which, the frequency of microsatellite alterations was most commonly seen on chromosomes 3, 7, 11 and 16.

CONCLUSION: Genomic instability in mouse chromosomes 3, 7, 11 and 16 may play a more important role in the development and progression of HCC in mice. It is suggested that these two sub-clones derived from a same hepatic tumor in homozygous mouse present different genetic features.

Genetic evaluation of the dysplasia-carcinoma sequence in chronic viral liver disease: a detailed analysis of two cases and a review of the literature

Hepatocellular carcinoma (HCC) is one of the most frequent human malignancies, especially in Asia and Africa, but also in the Western world its incidence is increasing. HCC is a complication of chronic liver disease with cirrhosis as the most important risk factor. Viral co-pathogenesis due to hepatitis B virus (HBV) and hepatitis C virus (HCV) infection seems to be an important factor in the development of HCC. Curative therapy is often not possible due to the late detection of HCC. Thus, it is attractive to find parameters which predict malignant transformation in HBV- and HCV-infected livers. In the past decade, preneoplastic lesions, i.e. dysplastic foci or nodules, have gained interest as possible markers for imminent malignancy. Noteworthy, dysplastic liver lesions are increasingly detected by imaging techniques. We describe here two cases of chronic viral liver disease, one HBV-and one HCV-related, in which dysplastic lesions were present adjacent to HCC. In the HBV case, a (smaller) satellite of HCC was present as well. The neoplastic specimens were investigated by comparative genomic hybridization (CGH) and in situ hybridization (ISH). Both methods revealed multiple genetic alterations in the HCCs. The genetic patterns of the HBV-related HCC and the satellite tumor showed many shared alterations suggesting a clonal relationship. A subset of genetic changes were already present in dysplasias illustrating their preneoplastic nature. Surrounding liver cirrhosis samples did not display chromosomal aberrations. A literature survey illustrates the relative paucity of information concerning genetic alterations in preneoplastic liver lesions. However, all the data strongly suggests a role for liver cell dysplasia as a precursor condition of liver cell cancer.

Impact of large regenerative, low grade and high grade dysplastic nodules in hepatocellular carcinoma development

BACKGROUND/AIMS

The natural outcome of ultrasound-detected macronodules in cirrhosis is still poorly understood. In this study we assessed the incidence and predictors of malignant transformation in a prospective study of 90 consecutive ultrasound-detected macronodules in cirrhosis.

METHODS

Macronodules classification was based on recently proposed histological criteria. Extranodular large (LCC) and small cell changes were also evaluated. The follow-up included ultrasound and serum alfa-fetoprotein determination every 3 months. Independent predictors of hepatocellular carcinoma were evaluated by Cox proportional hazards regression analysis.

RESULTS

During a mean follow-up of 33 months, 28 (31%) nodules transformed into hepatocellular carcinoma. The incidence of hepatocellular carcinoma per 100 person-years of follow-up was 11.3%, with a malignant transformation rate of 3.5, 15.5, 31 and 48.5% at 1, 2, 3, and 5 years respectively. High-grade dysplastic nodules (HGDN) (hazard risk=2.4; CI 95%=1.1-5.0) and LCC (hazard risk=3.1; CI 95%=1.2-7.8) were independent predictors of malignant transformation. Eight additional hepatocellular carcinomas developed outside the original lesions raising the overall malignant transformation rate to 40% while 15 macronodules (17%) became undetectable at ultrasound (US).

CONCLUSIONS

Macronodules characterize a cirrhotic subpopulation with high risk of hepatocellular carcinoma. HGDN and LCC are strong predictors of malignant transformation; subjects with simultaneous presence of both these two conditions are at highest risk of cancer development. The management of cirrhotics with macronodules should be based on morphologic features detected on liver microsamples.

Allelic alterations in nontumorous liver tissues and corresponding hepatocellular carcinomas from chinese patients

Allelic imbalance may play an important in tumor progression in hepatocarcinogenesis, but the genetic background of the corresponding nontumorous liver in hepatocellular carcinoma (HCC) is not well defined. We studied the incidence of loss of heterozygosity (LOH) and microsatellite instability (MSI) by microsatellite analysis in both nontumorous livers and the corresponding tumors, by comparing them with the normal DNA from Chinese patients with resected primary HCCs. We also evaluated the pathologic significance of the alterations. We used 18 highly polymorphic microsatellite markers on chromosomes 1, 3, 4, 7, 8, 9, 13, 16, 17, and 18. Our results showed that 70.6% (24 of 34) of the HCCs exhibited LOH at 1 or more loci, and that the overall fractional allelic loss (FAL) was 0.169. MSI was observed in only 1 tumor. In contrast, the nontumorous livers of the HCCs showed a very low incidence of LOH, with only a single LOH detected in 1 of 34 (2.9%) of the nontumorous livers, with an overall FAL index of 0.005. Tumors with LOH at 1 or more loci had significantly more frequent venous invasion (P = 0.019). Allelic loss at locus D9S199 (9p23) was seen more frequently in larger tumors (P = 0.031), and, less significantly, allelic loss at locus D16S516 (16q24.1) was seen more frequently in larger tumors (P = 0.059). LOH was common in predominantly hepatitis B virus-associated HCCs from Chinese patients. However, LOH or MSI in the corresponding cirrhotic or noncirrhotic livers was uncommon.

Liver pathology and hepatocarcinogenesis in a long-term mouse model of erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is an inherited disease of haem synthesis caused by a mutation in one of the alleles of the enzyme ferrochelatase. This mutation leads to partial deficiency of the enzyme, resulting in increased concentrations of protoporphyrin (PP) in blood, liver, and faeces. Five to ten per cent of patients with EPP develop severe liver disease characterized by the presence of PP deposits. This study used histochemistry and immunohistochemistry to investigate the histopathological features present in the livers of 44 mice with a heterozygous or homozygous point mutation in the ferrochelatase gene (fch/+ and fch/fch mice, respectively). Some fch/+ mouse livers showed mixed steatosis and large cell dysplasia. The livers of fch/fch mice showed periportal or septal fibrosis accompanied by an atypical ductular reaction. These findings suggest that the obstruction and damage of a proportion of large and small bile ducts by PP deposits cause an accumulation of PP in the parenchyma, which leads to damage and loss of hepatocytes due to the toxic effects of PP. The classical stages of hepatocarcinogenesis were observed and hepatic progenitor cells appear to be involved in this process. PP acts as the promoting agent and is probably also the initiating agent.

Focal lesions in cirrhotic explant livers: pathological evaluation and accuracy of pretransplantation imaging examinations

Imaging detection and diagnosis of hepatocellular carcinomas (HCCs) and dysplastic nodules (DNs) in cirrhotic patients is important because the number, size, and type of focal lesions strongly influence patient management. Focal lesions detected by imaging examinations during pretransplantation evaluation were correlated with focal lesions detected during detailed pathological examination of 49 cirrhotic explant livers. Within 6 months before transplantation, color Doppler ultrasonography (US), contrast-enhanced computed tomography (CT), and magnetic resonance (MR) imaging were performed in 94%, 33%, and 55% of patients, respectively. In 2% to 8% of patients, different types of benign focal lesions were present, and a considerable proportion was interpreted as (pre)malignant on imaging examination. US detected only the largest HCCs (patient sensitivity, 40%; specificity, 100%) and no DNs. On a per-patient basis, contrast-enhanced CT and MR imaging had poor sensitivity (20% and 27%, respectively) and good specificity (100% and 94%, respectively) for DNs. Patient sensitivity and specificity of both techniques for HCC were reasonable (50% for CT, 70% for MR imaging) and good (79% for CT, 82% for MR imaging), respectively. Neither technique was able to detect smaller (pre)malignant lesions. As a consequence, 10% of patients underwent transplantation, although they exceeded the tumor number limit. Currently used imaging techniques cannot correctly determine the exact tumor burden in some cirrhotic patients. Regular contrast-enhanced MR examination of cirrhotic patients waiting for liver transplantation is the best tool for the early detection of (pre)malignant lesions.

Molecular pathogenesis of human hepatocellular carcinoma

Hepatocarcinogenesis is a slow process during which genomic changes progressively alter the hepatocellular phenotype to produce cellular intermediates that evolve into hepatocellular carcinoma. During the long preneoplastic stage, in which the liver is often the site of chronic hepatitis, cirrhosis, or both, hepatocyte cycling is accelerated by upregulation of mitogenic pathways, in part through epigenetic mechanisms. This leads to the production of monoclonal populations of aberrant and dysplastic hepatocytes that have telomere erosion and telomerase re-expression, sometimes microsatellite instability, and occasionally structural aberrations in genes and chromosomes. Development of dysplastic hepatocytes in foci and nodules and emergence of hepatocellular carcinoma are associated with the accumulation of irreversible structural alterations in genes and chromosomes, but the genomic basis of the malignant phenotype is heterogeneous. The malignant hepatocyte phenotype may be produced by the disruption of a number of genes that function in different regulatory pathways, producing several molecular variants of hepatocellular carcinoma. New strategies should enable these variants to be characterized.

Methylation framework of cell cycle gene inhibitors in cirrhosis and associated hepatocellular carcinoma

One of the main regulatory pathways reported to be altered in hepatocellular carcinoma (HCC) is that of cell cycle control involving RB1 gene-related cell inhibitors. We investigated p14(ARF), p15(INK4B), p16(INK4A), p18(INK4C), and RB1 genes in a series of HCCs and associated cirrhosis with the goal of ascertaining their pattern of inactivation by gene methylation. Thirty-three HCCs, adjacent nonneoplastic cirrhotic tissues, and 6 HCC cell lines were studied. Cirrhoses (25 of 33, 76%), HCCs (31 of 33, 94%), and 3 of 6 (50%) cell lines showed 1 or more methylated genes. Cirrhoses (17 of 33, 51%) had more frequently than HCCs (11 of 33, 33%, P =.01) only 1 methylated gene. With the exception of p18(INK4C) the genes under study showed promoter methylation with frequency ranging from 82% (p16(INK4A) in HCC) to 33% and 39% (p15(INK4B) and p16(INK4A) in cirrhoses). In cases with only 1 methylated gene, p15(INK4B) in cirrhosis (8 of 17, 47%) and p16(INK4A) in HCC (10 of 11, 91%) were the more frequently altered. An optimal correlation was found between p15 and p16 gene methylation and complete protein loss in HCC detected by immunocytochemistry, whereas a partial loss of the same proteins was a feature of methylated cirrhoses. Inactivation by DNA methylation of several genes of the RB1 pathway is common to cirrhosis and HCC. An early pattern of methylatory events (1 methylated gene) is a feature of cirrhosis rather than HCC, whereas an advanced one (> or = 3 methylated genes) is characteristic of malignancy. Early methylation changes seem to involve p15(INK4B) and p16(INK4A) in cirrhosis and p16(INK4A) in HCC. In conclusion, a stepwise progression of methylating events is a feature of the sequence cirrhosis-HCC and contributes to the process of hepatic carcinogenesis with potential clinical implications.

Chromosomal alterations in hepatocellular nodules by comparative genomic hybridization: high-grade dysplastic nodules represent early stages of hepatocellular carcinoma

Data from experimental hepatocarcinogenesis and recent studies in humans have suggested that the emergence of hepatocellular carcinoma (HCC) is a stepwise process. However, despite abundant experimental data, the precise molecular mechanisms and genetic alterations involved in human liver carcinogenesis are still unclear. Comparative genomic hybridization was used to analyze 26 hepatocellular nodules obtained from patients undergoing liver transplantation or surgical resection for HCC. According to the criteria proposed by the International Working Party, 16 nodules were classified as multiacinar regenerative nodules (MRN), 4 as low-grade dysplastic nodules (LG-DN), and 6 as high-grade dysplastic nodules (HG-DN). Our aim was to investigate the possible genetic differences between MRN, LG-DN, and HG-DN. The whole group of nodules showed only a few aberrations (mean 1.1/case), without any significant pattern. This finding is comparable to what happens in non-neoplastic tissue. On the contrary, in three of six HG-DN, we found deletions of 8p and gains of 1q. LG-DN and MRN did not show these chromosomal imbalances. These results confirm the important role of allelic losses on 8p as well as of gains of 1q in HCC. We conclude that the genes that are important in early stages of hepatocarcinogenesis are probably located on these chromosomal arms.