Complexity of PEComas : Diagnostic approach, molecular background, clinical management.

Perivascular epithelioid cell neoplasms (PEComas) are a family of mesenchymal neoplasms with features of both melanotic and smooth muscle differentiation. PEComa morphology is highly variable and encompasses epithelioid to spindle cells often with clear cytoplasm and prominent nucleoli. Molecularly, most PEComas are defined by a loss of function of the TSC1/TSC2 complex. Additionally, a distinct small subset of PEComas harboring rearrangements of the TFE3 (Xp11) gene locus has been identified. By presenting a series of three case reports with distinct features, we demonstrate diagnostic pitfalls as well as the importance of molecular work-up of PEComas because of important therapeutic consequences.

[Complexity of PEComas : Diagnostic approach, molecular background, clinical management (German version)]. / Komplexität von PEComen : Diagnose, Molekulargenetik, klinisches Management.

Perivascular epithelioid cell neoplasms (PEComas) are a family of mesenchymal neoplasms with features of both melanotic and smooth muscle differentiation. PEComa morphology is highly variable and encompasses epithelioid to spindle cells often with clear cytoplasm and prominent nucleoli. Molecularly, most PEComas are defined by a loss of function of the TSC1/TSC2 complex. Additionally, a distinct small subset of PEComas harboring rearrangements of the TFE3 (Xp11) gene locus has been identified. By presenting a series of three case reports with distinct features, we demonstrate diagnostic pitfalls as well as the importance of molecular work-up of PEComas because of important therapeutic consequences.

[Nuclear Her2 expression in hepatocytes in liver disease]. / Nukleäre HER2/neu-Expression in Hepatozyten bei Lebererkrankungen.

BACKGROUND: Her2 is a well-known member of the epidermal growth factor receptor (EGFR) superfamily, a group of transmembrane receptors that mediate effects of proliferation and survival and thus play an important role in tumorigenesis. EGFRs can translocate to the nucleus and may mediate DNA repair and cell cycle arrest. OBJECTIVES: The aim of this study was to characterize hepatocellular Her2 expression in different liver diseases. MATERIALS AND METHODS: Her2 expression was analyzed by immunohistochemistry in 674 liver biopsies. RESULTS: Hepatocytes often revealed a nuclear and cytoplasmic Her2 expression in different liver diseases with the strongest association to alcoholic steatohepatitis. The histologic parameters of hepatocellular ballooning and the presence of Mallory-Denk bodies strongly correlated with Her2 positivity. Interestingly, in hepatocellular carcinomas (HCC) nuclear Her2 expression was frequently observed. Furthermore, Her2 positive hepatocytes showed a loss of estrogen receptor expression and increased expression of p21, a cell cycle regulator, and pSTAT3, a downstream effector of nuclear Her2. CONCLUSIONS: Nuclear Her2 expression in hepatocytes with further metabolic and cell cycle alterations may imply a so far unknown mechanism of a stress response. So far, the effects on disease course and a possible role of nuclear Her2 in progression to HCC are unclear and the subject of future research.

[Molecular and metabolic changes in human clear cell liver foci]. / Molekulare und metabolische Veränderungen in humanen klarzelligen Leberherden.

Activation of the AKT/mTOR and Ras/MAPK pathways and the lipogenic phenotype are evident both in human hepatocellular carcinoma and in the rat model of insulin-induced hepatocarcinogenesis in the earliest preneoplastic lesions, i.e. clear cell foci (CCF) of altered hepatocytes. These CCFs have also been described in the human liver but characterization of molecular and metabolic changes are still pending. In this study, human sporadic CCFs were investigated in a collection of human non-cirrhotic liver specimens using histology, histochemistry, immunohistochemistry, electron microscopy and molecular pathological analysis. Human CCFs occurred in approximately 33 % of non-cirrhotic livers and stored masses of glycogen in the cytoplasm, largely due to reduced activity of glucose-6-phosphatase. Hepatocytes revealed an upregulation of the AKT/mTOR and the Ras/MAPK pathways, the insulin receptor, glucose transporters and enzymes of glycolysis and de novo lipogenesis. Proliferative activity was 2-fold higher than in extrafocal tissue. The CCFs of altered hepatocytes are metabolically and proliferatively active lesions even in humans. They resemble the well-known preneoplastic lesions from experimental models in terms of morphology, glycogen storage, overexpression of protooncogenic signaling pathways and activation of the lipogenic phenotype, which are also known in human hepatocellular carcinoma. This suggests that hepatic CCFs also represent very early lesions of hepatocarcinogenesis in humans.

Deregulation of DNA-dependent protein kinase catalytic subunit contributes to human hepatocarcinogenesis development and has a putative prognostic value.

BACKGROUND: The DNA-repair gene DNA-dependent kinase catalytic subunit (DNA-PKcs) favours or inhibits carcinogenesis, depending on the cancer type. Its role in human hepatocellular carcinoma (HCC) is unknown. METHODS: DNA-dependent protein kinase catalytic subunit, H2A histone family member X (H2AFX) and heat shock transcription factor-1 (HSF1) levels were assessed by immunohistochemistry and/or immunoblotting and qRT-PCR in a collection of human HCC. Rates of proliferation, apoptosis, microvessel density and genomic instability were also determined. Heat shock factor-1 cDNA or DNA-PKcs-specific siRNA were used to explore the role of both genes in HCC. Activator protein 1 (AP-1) binding to DNA-PKcs promoter was evaluated by chromatin immunoprecipitation. Kaplan-Meier curves and multivariate Cox model were used to study the impact on clinical outcome. RESULTS: Total and phosphorylated DNA-PKcs and H2AFX were upregulated in HCC. Activated DNA-PKcs positively correlated with HCC proliferation, genomic instability and microvessel density, and negatively with apoptosis and patient's survival. Proliferation decline and massive apoptosis followed DNA-PKcs silencing in HCC cell lines. Total and phosphorylated HSF1 protein, mRNA and activity were upregulated in HCC. Mechanistically, we demonstrated that HSF1 induces DNA-PKcs upregulation through the activation of the MAPK/JNK/AP-1 axis. CONCLUSION: DNA-dependent protein kinase catalytic subunit transduces HSF1 effects in HCC cells, and might represent a novel target and prognostic factor in human HCC.

[De novo lipogenesis: role in hepatocellular carcinoma]. / De-novo-Lipogenese: Bedeutung beim hepatozellulären Karzinom.

Hepatocellular carcinoma (HCC) is one of the most frequent and lethal tumors worldwide. Thus, there is an urgent need to elucidate its molecular pathogenesis in order to develop novel diagnostic, preventive and therapeutic strategies for this deadly disease. Mounting evidence implies a pivotal role of proteins involved in lipid biosynthesis in the development and progression of human HCC. This review summarizes the data available on the pathogenetic relevance of lipogenic proteins in the growth of liver cancer cells, the mechanisms responsible for unrestrained lipid biosynthesis in HCC and the possible clinical implications arising from these discoveries. Altogether the data implicate the AKT-mTORC1-RPS6 signaling pathway as the main inducer of aberrant lipid synthesis in HCC and are indicative of therapeutic strategies aimed at inhibiting de novo lipogenesis for the treatment of human liver cancer.

Repeated exposure of the oral mucosa over 12 months with cold plasma is not carcinogenic in mice.

Peri-implantitis may result in the loss of dental implants. Cold atmospheric pressure plasma (CAP) was suggested to promote re-osseointegration, decrease antimicrobial burden, and support wound healing. However, the long-term risk assessment of CAP treatment in the oral cavity has not been addressed. Treatment with two different CAP devices was compared against UV radiation, carcinogen administration, and untreated conditions over 12 months. Histological analysis of 406 animals revealed that repeated CAP exposure did not foster non-invasive lesions or squamous cell carcinoma (SCCs). Carcinogen administration promoted non-invasive lesions and SCCs. Molecular analysis by a qPCR screening of 144 transcripts revealed distinct inflammatory profiles associated with each treatment regimen. Interestingly, CAP treatment of carcinogen-challenged mucosa did not promote but instead left unchanged or reduced the proportion of non-invasive lesions and SCC formation. In conclusion, repeated CAP exposure of murine oral mucosa was well tolerated, and carcinogenic effects did not occur, motivating CAP applications in patients for dental and implant treatments in the future.

Forkhead box M1B is a determinant of rat susceptibility to hepatocarcinogenesis and sustains ERK activity in human HCC.

BACKGROUND AND AIMS: Previous studies indicate unrestrained cell cycle progression in liver lesions from hepatocarcinogenesis-susceptible Fisher 344 (F344) rats and a block of G(1)-S transition in corresponding lesions from resistant Brown Norway (BN) rats. Here, the role of the Forkhead box M1B (FOXM1) gene during hepatocarcinogenesis in both rat models and human hepatocellular carcinoma (HCC) was assessed. METHODS AND RESULTS: Levels of FOXM1 and its targets were determined by immunoprecipitation and real-time PCR analyses in rat and human samples. FOXM1 function was investigated by either FOXM1 silencing or overexpression in human HCC cell lines. Activation of FOXM1 and its targets (Aurora Kinose A, Cdc2, cyclin B1, Nek2) occurred earlier and was most pronounced in liver lesions from F344 than BN rats, leading to the highest number of Cdc2-cyclin B1 complexes (implying the highest G(2)-M transition) in F344 rats. In human HCC, the level of FOXM1 progressively increased from surrounding non-tumorous livers to HCC, reaching the highest levels in tumours with poorer prognosis (as defined by patients' length of survival). Furthermore, expression levels of FOXM1 directly correlated with the proliferation index, genomic instability rate and microvessel density, and inversely with apoptosis. FOXM1 upregulation was due to extracellular signal-regulated kinase (ERK) and glioblastoma-associated oncogene 1 (GLI1) combined activity, and its overexpression resulted in increased proliferation and angiogenesis and reduced apoptosis in human HCC cell lines. Conversely, FOXM1 suppression led to decreased ERK activity, reduced proliferation and angiogenesis, and massive apoptosis of human HCC cell lines. CONCLUSIONS: FOXM1 upregulation is associated with the acquisition of a susceptible phenotype in rats and influences human HCC development and prognosis.

Hepatocellular carcinoma as a complex polygenic disease. Interpretive analysis of recent developments on genetic predisposition.

The different frequency of hepatocellular carcinoma (HCC) in humans at risk suggests a polygenic predisposition. However, detection of genetic variants is difficult in genetically heterogeneous human population. Studies on mouse and rat models identified 7 hepatocarcinogenesis susceptibility (Hcs) and 2 resistance (Hcr) loci in mice, and 7 Hcs and 9 Hcr loci in rats, controlling multiplicity and size of neoplastic liver lesions. Six liver neoplastic nodule remodeling (Lnnr) loci control number and volume of re-differentiating lesions in rat. A Hcs locus, with high phenotypic effects, and various epistatic gene-gene interactions were identified in rats, suggesting a genetic model of predisposition to hepatocarcinogenesis with different subset of low-penetrance genes, at play in different subsets of population, and a major locus. This model is in keeping with human HCC epidemiology. Several putative modifier genes in rodents, deregulated in HCC, are located in chromosomal segments syntenic to sites of chromosomal aberrations in humans, suggesting possible location of predisposing loci. Resistance to HCC is associated with lower genomic instability and downregulation of cell cycle key genes in preneoplastic and neoplastic lesions. p16(INK4A) upregulation occurs in susceptible and resistant rat lesions. p16(INK4A)-induced growth restraint was circumvented by Hsp90/Cdc37 chaperons and E2f4 nuclear export by Crm1 in susceptible, but not in resistant rats and human HCCs with better prognosis. Thus, protective mechanisms seem to be modulated by HCC modifiers, and differences in their efficiency influence the susceptibility to hepatocarcinogenesis and probably the prognosis of human HCC.

Underserved populations and bacterial and protozoal sexually transmitted infections: a lost health-care opportunity.

OBJECTIVE: The purpose of our review is an update about the burden of sexually transmitted infections (STIs) among various types of underserved populations, such as migrants, substance abusers, homeless and incarcerated inmates. First-line test and treatment based on the latest available evidence according to the revised guidelines of Centers for Disease Control and Prevention have also been considered. MATERIALS AND METHODS: We performed a comprehensive research using scientific databases such as Medline and Pubmed, followed by a review of citations and reference list. A consultation with other experts in the management of the various subpopulations was also conducted. RESULTS: Health-care is often influenced by social determinants, which play a vital role in the diffusion of STIs. The consequence is a socio-economical and ethnic disparity in the rate of STIs. Early screening and treatment of STIs should be implemented in clinical practice, starting from marginalized social groups, which are the most affected by this health problem. CONCLUSIONS: In the literature, there are very few papers containing information on STIs prevalence in various types of underserved populations, such as migrants, substance abusers, homeless and incarcerated inmates. The availability of more accurate epidemiological data is needed. In these groups, the most relevant barrier is the lower perception of health-care need, with an underestimation of risk and symptoms of STIs, causing a retard of diagnosis and health-care provision and use. For these populations, targeted interventions are needed, particularly on unaware people, responsible for most STIs transmissions.

The burden of HIV-associated neurocognitive disorder (HAND) in post-HAART era: a multidisciplinary review of the literature.

OBJECTIVE: The purpose of the present multidisciplinary review is to give an updated insight into the most recent findings regarding the pathophysiology, diagnosis and therapeutics of HIV-associated neurocognitive disorder (HAND). MATERIALS AND METHODS: We performed a comprehensive search, through electronic databases (Pubmed - MEDLINE) and search engines (Google Scholar), of peer-reviewed publications (articles and reviews) and conferences proceedings on HAND pathophysiology, diagnosis, and therapy, from 1999 to 2016. RESULTS: It seems to be increasingly clear that neurodegeneration in HIV-1 affected patients is a multi-faceted disease involving numerous factors, from chronic inflammation to central nervous system (CNS) compartmentalization of HIV. Diagnosis of HAND may benefit from both laboratory analysis and advanced specific neuroimaging techniques. As regards HAND therapy, modified HAART combinations and simplification strategies have been tested, while novel exciting frontiers seem to involve the use of nanoparticles with the ability to cross the Blood-Brain Barrier (BBB). CONCLUSIONS: Albeit highly active antiretroviral therapy (HAART) allowed a major decrease in morbidity and mortality for AIDS patients, CNS involvement still represents a challenge in HIV patients even today, affecting up to 50% of patients with access to combination antiretroviral therapy (cART). Future studies will have to focus on CNS compartmentalization, drugs' ability to penetrate and suppress viral replication in this compartment, and on new approaches to reduce HIV-associated neuroinflammation.

Activation of beta-catenin during hepatocarcinogenesis in transgenic mouse models: relationship to phenotype and tumor grade.

Mutations affecting phosphorylation sites in the beta-catenin gene have been implicated in the development of human and rodent hepatocellular carcinomas (HCCs). To further investigate the involvement of this gene in hepatocarcinogenesis, we used several transgenic mouse models of hepatic tumors induced by overexpression of c-myc in the liver either alone or in combination with transforming growth factor (TGF) alpha or TGF-beta1. Activation of beta-catenin, as judged by the presence of mutations and/or nuclear translocation of the protein, was most frequent in liver tumors from c-myc (4/17; 23.5%) and c-myc/TGF-beta1 (6/18; 33.3%) transgenic mice. However, it was very rare in faster growing and histologically more aggressive HCCs developed in c-myc/TGF-alpha mice (1/20; 5%). Administration of diethylnitrosamine, phenobarbital, or 2-amino-3,8-diethylimidazo[4,5-f]quinoxaline did not significantly affect the occurrence of beta-catenin mutations. Notably, nuclear accumulation of beta-catenin was observed only in adenomas and highly differentiated carcinomas with eosinophilic phenotype. Furthermore, preneoplastic lesions with eosinophilic phenotype frequently displayed focal nuclear positivity, colocalized with areas of high proliferation. In contrast, basophilic and clear-cell foci, as well as pseudo-glandular and poorly differentiated HCCs, exhibited a normal or reduced membranous immunoreactivity for beta-catenin. These studies suggest that nuclear translocation of beta-catenin and activation of Wingless/Wnt signaling may represent an early event in liver carcinogenesis, providing a growth advantage in a subset of hepatic tumors with a more differentiated phenotype.

Identification of genetic loci controlling hepatocarcinogenesis on rat chromosomes 7 and 10.

Neoplastic liver nodules and hepatocellular carcinomas (HCCs) were induced, by "resistant hepatocyte" model, 32 and 70 weeks after initiation with diethylnitrosamine, respectively, in F344 Brown Norway (BN), and (BNxF344)F1 rats. Nodule number/liver (N) did not significantly differ among rat strains, whereas nodule mean volume (V) and nodule volume fraction (VF) were higher in susceptible F344 than in resistant BN and BFF1 strains and were predictive of subsequent development of HCCs. Genomic scanning of 157 backcross BFF1xF344 rats with 190 polymorphic microsatellites, and linkage analysis, revealed two quantitative trait loci (QTL) on chromosomes 7 and 10, which showed significant linkage with VF, and two QTL on chromosomes 4 and 8, which showed suggestive linkage with V and VF. On the basis of phenotypic patterns of homozygous and heterozygous backcross progeny and of allelic distribution pattern, QTL on chromosomes 10, 8, and 4 were tentatively identified as resistance loci, and QTL on chromosome 7 was identified as susceptibility locus for rat hepatocarcinogenesis. An analysis of interactions allowed us to identify additional putative QTL on chromosomes 5 and 8 and suggested an additive effect of loci on chromosomes 10, 8, and 4 for VF and V. These data are the first to identify chromosomal regions containing putative susceptibility/resistance loci for rat hepatocarcinogenesis, which seems to be highly complex in terms of the number of genetic factors involved.

Jagged 1 is a major Notch ligand along cholangiocarcinoma development in mice and humans.

Intrahepatic cholangiocarcinoma (ICC) is a rare yet deadly malignancy with limited treatment options. Activation of the Notch signalling cascade has been implicated in cholangiocarcinogenesis. However, while several studies focused on the Notch receptors required for ICC development, little is known about the upstream inducers responsible for their activation. Here, we show that the Jagged 1 (Jag1) ligand is almost ubiquitously upregulated in human ICC samples when compared with corresponding non-tumorous counterparts. Furthermore, we found that while overexpression of Jag1 alone does not lead to liver tumour development, overexpression of Jag1 synergizes with activated AKT signalling to promote liver carcinogenesis in AKT/Jag1 mice. Histologically, tumours consisted exclusively of ICC, with hepatocellular tumours not occurring in AKT/Jag1 mice. Furthermore, tumours from AKT/Jag1 mice exhibited extensive desmoplastic reaction, an important feature of human ICC. At the molecular level, we found that both AKT/mTOR and Notch cascades are activated in AKT/Jag1 ICC tissues, and that the Notch signalling is necessary for ICC development in AKT/Jag1 mice. In human ICC cell lines, silencing of Jag1 via specific small interfering RNA reduces proliferation and increases apoptosis. Finally, combined inhibition of AKT and Notch pathways is highly detrimental for the in vitro growth of ICC cell lines. In summary, our study demonstrates that Jag1 is an important upstream inducer of the Notch signalling in human and mouse ICC. Targeting Jag1 might represent a novel therapeutic strategy for the treatment of this deadly disease.

Genetic alterations in liver carcinogenesis: implications for new preventive and therapeutic strategies.

In this review, genetic changes known to occur in human and experimental animal hepatocarcinogenesis are evaluated comparatively, with the aim of identifying genes that could potentially be targets of new preventive and therapeutic strategies, albeit the fact that although a step-by-step analysis of the premalignant stages has been largely accomplished in experimental hepatocarcinogenesis, this goal is still elusive in the case of humans. Overexpression of several of the genes implicated in the MAPK signaling cascade and cell cycle control appears to be most likely responsible for initiated cells acquiring a proliferating phenotype that facilitates the accumulation of structural changes in additional genes, resulting in the generation of autonomously growing preneoplastic and neoplastic lesions. Several gene abnormalities seen in precancerous lesions of rodents also occur in human hepatocellular carcinomas, suggesting that at least some of them could be present also in human precancerous lesions. Furthermore, there are reports that epigenetic events, such as abnormal DNA methylation, may be critical in hepatocarcinogenesis. DNA hypomethylation is an early event, both in human and experimental hepatocarcinogenesis, and its role in the activation of various genes, has been postulated. In recent years, linkage analysis studies have led to the identification of susceptibility/resistance loci that influence the progression stage of hepatocarcinogenesis in mice and rats. The relevance of these findings, though, will depend on the identification of the genes, and on whether in humans there are genes ortholog with rodent's susceptibility/resistance genes. It is proposed that rodent hepatocarcinogenesis represents a promising model for the identification of genes implicated in the early stages of the process, and that many of these genes may represent key targets for the application of gene therapy in the prevention and treatment of liver cancer.

Analysis of loss of heterozygosity in neoplastic nodules induced by diethylnitrosamine in the resistant BFF1 rat strain.

Loss of heterozygosity (LOH) at specific chromosomal regions is a frequent event in poorly differentiated human hepatocellular carcinomas (HCCs), but rare in mouse HCCs. This behavior could depend on interspecies differences in mechanisms of hepatocarcinogenesis or in developmental stage of lesions. To verify if LOH is involved in rat hepatocarcinogenesis, we studied LOH frequency in slowly growing neoplastic nodules induced by Solt-Farber model in diethylnitrosamine-initiated BFF1 rats. We analyzed, with microsatellites, markers at 67 rat loci dispersed over all chromosomes, corresponding to regions homologous to those lost in human HCCs or containing hepatocellular susceptibility (Hcs) or resistance (Hcr) loci in rat and mouse. In agreement with previous findings with mouse HCCs, but at variance with human HCCs, no detectable LOH was found at any locus in rats, suggesting rare LOH involvement in neoplastic nodules, with low tendency to progress to full malignancy, of BFF1 rats.

Long-term dehydroepiandrosterone and 16alpha-fluoro-5-androsten-17-one administration enhances DNA synthesis and induces expression of c-fos and c-Ha-ras in a selected population of preneoplastic lesions in liver of diethylnitrosamine-initiated rats.

Dehydroepiandrosterone (DHEA) inhibits glucose 6-phosphate dehydrogenase (G6PD) activity and growth of preneoplastic lesions in various tissues, but its administration may also enhance tumorigenesis by genotoxic carcinogens. We have investigated in single preneoplastic liver lesions, induced in diethylnitrosamine-initiated rats by the resistant hepatocyte protocol, the mechanisms underlying these opposite DHEA effects. Administration of DHEA (0.45% in the diet) for 10 and 26 weeks and of its analog 16alpha-fluoro-5-androsten-17-one (FA, 0.25%) for 10 weeks, starting 4 weeks after initiation, induced an apparent decrease in the number of glutathione S:-transferase (placental) (GST-P)-positive lesions and an increase in lesion volume. DHEA administration for 38 weeks enhanced hepatocellular carcinoma multiplicity. Depending on the rise in the number of slowly growing, remodeling GST-P-positive lesions induced by DHEA and FA, overall DNA synthesis decreased slightly in these lesions at 14 weeks, but increased in uniform lesions. Labeling index (LI) in single uniform lesions at 14 weeks ranged between very low (not different from normal liver) to high (>10-fold normal liver). DHEA and FA induced broad increases in lesions with a high LI, which showed a higher number of cells overexpressing c-Ha-ras and/or c-fos than those with a lower LI. High G6PD activity was inhibited by DHEA and FA in only approximately 50% of preneoplastic lesions. These data indicate selection in rats subjected to long-term DHEA and FA treatments of a subpopulation of GST-P-positive cells with high growth and progression potentials. Overall effects of these compounds depends on the relative numbers of lesions in which inhibition of DNA synthesis can counteract their transforming effect.

Correlation of c-myc overexpression and amplification with progression of preneoplastic liver lesions to malignancy in the poorly susceptible Wistar rat strain.

Persistent liver nodules (PNs) and hepatocellular carcinomas (HCCs) induced in F344 rats by the resistant hepatocyte (RH) model exhibit c-myc overexpression and amplification. The role of these changes in progression of PN was investigated in nodules with different propensities to evolve to HCC in resistant Wistar rats and, for comparison, in susceptible F344 rats. Initiation of rats with diethylnitrosamine was followed by selection with 2-acetylaminofluorene (AAF) plus partial hepatectomy (RH groups). Two additional Wistar rat groups received a second AAF treatment without (RH+AAF) and with a necrogenic dose of CCl4 (RH+AAF/CCl4) 15 d after selection. The number to liver ratio and volume of glutathione-s-transferase placental form-positive lesions were lower in the Wistar than the F344 RH groups 9 and 32 wk after initiation and increased after a second AAF cycle treatment with and without CCl4. DNA synthesis in glutathione-s-transferase placental form-positive lesions was low in Wistar RH group at 9 wk and was stimulated by additional AAF treatments. HCCs developed at 57-60 wk in F344 RH, Wistar RH+AAF, and RH+AAF/CCl4 rats. Tumor incidence and multiplicity were lower in RH+AAF rats than in RH+AAF/CCl4 and F344 rats. At 32 wk, PN exhibited c-myc overexpression that increased from RH to RH+AAF rats and to RH+AAF/CCl4 Wistar rats. This was associated with c-myc amplification in Wistar RH+AAF/CCl4 rats. These results showed correlation of c-myc overexpression and amplification with nodule propensity to progress to HCC in poorly susceptible Wistar rats and suggested a possible genetic mechanism for susceptibility to hepatocarcinogenesis. The experimental system used in this work may be a valuable tool for studies on molecular mechanisms underlying liver growth and tumorigenesis supported by c-myc overexpression.

Frequent loss of heterozygosity at the Hcr1 (hepatocarcinogenesis resistance) locus on chromosome 10 in primary hepatocellular carcinomas from LFF1 rat strain.

Hepatocarcinogenesis sensitivity (Hcs1, 2) and resistance (Hcr1-3) loci have been identified by linkage analysis on rat chromosomes 7 and 1, and 10, 4, and 8, respectively. Cytogenetic studies documented deletions on chromosomes 3 and 6 of neoplastic rat hepatocytes. Hepatocellular carcinomas (HCCs) were produced in F1 hybrid rats between Long-Evans (LE) and Fisher 344 (F344) rats. Scanning of the above chromosomes for loss of heterozygosity (LOH) showed allelic imbalance (AI) at multiple regions on chromosomes 6, 7, and 10q. Detailed deletion mapping of chromosome 10 localized a putative suppressor Hcr1 gene to within a 3.2-cM interval flanked by D10Rat51 and D10Rat121. Two other distinct regions with frequent AIs were found inside the Hcr1 locus, at marker loci including DNaseI and Mrp genes, and in a segment including 4 consecutive markers (D10Rat64, D10Rat182, D10Rat113, D10Rat216). In 40% of HCCs, AI was seen at the p53 locus. AI on chromosome 7 occurred at the Hcs1 locus, where is located c-myc, which is amplified in HCCs, suggesting allelic gain. Most AIs occurred in poorly/moderately differentiated carcinomas, and a few events were seen in well-differentiated tumors on chromosomes 7 and 10. These data suggest that alteration of a cluster of oncosuppressor genes on 10q is important for HCC progression. The existence of AI on segments of rat chromosomes 6, 7, and 10, syntenic to chromosomal segments of human HCCs where chromosomal gains or deletions occur, suggests a commonality of some molecular events in the pathogenesis of HCCs in rats and humans. Our map provides information toward cloning putative oncosuppressor genes associated with this carcinoma.