TP53 mutations and hepatocellular carcinoma: insights into the etiology and pathogenesis of liver cancer

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and the major risk factors include chronic infections with the hepatitis B (HBV) or C (HCV) virus, and exposure to dietary aflatoxin B(1) (AFB(1)) or alcohol consumption. Multiple genetic and epigenetic changes are involved in the molecular pathogenesis of HCC, for example, somatic mutations in the p53 tumor suppressor gene (TP53) and the activation of the WNT signal transduction pathway. AFB(1) frequently induces G:C to T:A transversions at the third base in codon 249 of TP53 and cooperates with HBV in causing p53 mutations in HCC. The detection of TP53 mutant DNA in plasma is a biomarker of both AFB(1) exposure and HCC risk. Chronic infection with HBV and HCV viruses, and oxyradical disorders including hemochromatosis, also generate reactive oxygen/nitrogen species that can both damage DNA and mutate cancer-related genes such as TP53. Certain mutant p53 proteins may exhibit a 'gain of oncogenic function'. The p53 biological network is a key responder to this oxidative and nitrosative stress. Depending on the extent of the DNA damage, p53 regulates the transcription of protective antioxidant genes and with extensive DNA damage, transactivates pro-oxidant genes that contribute to apoptosis. The X gene of HBV (HBx) is the most common open reading frame integrated into the host genome in HCC and the integrated HBx is frequently mutated. Mutant HBx proteins still retain their ability to bind to p53, and attenuate DNA repair and p53-mediated apoptosis. In summary, both viruses and chemicals are implicated in the etiology of TP53 mutations during the molecular pathogenesis of HCC.

Viruses in the mammalian male genital tract and their effects on the reproductive system

This review describes the various viruses identified in the semen and reproductive tracts of mammals (including humans), their distribution in tissues and fluids, their possible cell targets, and the functional consequences of their infectivity on the reproductive and endocrine systems. The consequences of these viral infections on the reproductive tract and semen can be extremely serious in terms of organ integrity, development of pathological and cancerous processes, and transmission of diseases. Furthermore, of essential importance is the fact that viral infection of the testicular cells may result not only in changes in testicular function, a serious risk for the fertility and general health of the individual (such as a fall in testosteronemia leading to cachexia), but also in the possible transmission of virus-induced mutations to subsequent generations. In addition to providing an exhaustive account of the data available in these domains, this review focuses attention on the fact that the interface between endocrinology and virology has so far been poorly explored, particularly when major health, social and economical problems are posed. Our conclusions highlight the research strategies that need to be developed. Progress in all these domains is essential for the development of new treatment strategies to eradicate viruses and to correct the virus-induced dysfunction of the endocrine system.

Multiple hepatitis viruses in multiple attacks of acute viral hepatitis

We evaluated the causes of 30 episodes of acute viral hepatitis in 13 patients who had multiple attacks. Two (seven per cent) of 30 bouts were caused by hepatitis A virus, and 12 (40%) by hepatitis B virus. No patient, however, had more than one attack with the serologic characteristics of Type A or Type B disease. Thus, there were 16 bouts (53 per cent) not attributable to either of the two recognized hepatitis viruses. None of these "non-A, non-B" episodes, evaluated for infectious mononucleosis and cytomegalovirus infection, could be ascribed to either. From this evidence, therefore, it appears that the clinical syndrome of viral hepatitis is produced not only by the two viruses (hepatitis A virus and hepatitis B virus) recognized since the 1940's but also, in all probability, by two non-A, non-B agents.

HISTOCHEMICAL STUDIES OF LYSOSOMES AND LYSOSOMAL ENZYMES IN VIRUS-INFECTED CELL CULTURES

The appearance of lysosomes and the distribution of lysosomal enzymes have been studied in a number of cell cultures exposed to viruses. Lysosomes were shown by fluorescence microscopy after vital staining with aminoacridines and light microscopy after vital staining with neutral red. The lysosomal enzymes studied histochemically in unfixed and fixed cells were acid phosphatase and 5-bromo-4-chloro-indoxyl acetate esterase. Activation of lysosomal enzymes was found to take place in three stages. The first is characterized by permeability of lysosomal membranes without release of enzymes. This is demonstrable by staining of lysosomal enzymes in unfixed cells and by increased uptake of aminoacridine fluorochromes and neutral red into lysosomes. In cell sheets initially stained with neutral red this gives rise to red plaques. This stage can be fully reversible; cells infected with, and yielding, the red-plaque strain of NDV, recover fully afterwards. In the second stage lysosomal enzymes are released into the cytoplasm, the cells round up and there is decreased uptake of aminoacridines and neutral red into lysosomes. In cell monolayers this results in the formation of white plaques. In the third stage, not usually seen in cell cultures, lysosomal enzymes are released from or inactivated in the cells and are not seen in either fixed or unfixed preparations. The possible roles of lysosomal enzymes in production of cytopathic effects, polykaryocytosis and malignant cell transformation are discussed.

Harmonised investigation of the occurrence of human enteric viruses in the leafy green vegetable supply chain in three European countries

Numerous outbreaks have been attributed to the consumption of raw or minimally processed leafy green vegetables contaminated with enteric viral pathogens. The aim of the present study was an integrated virological monitoring of the salad vegetables supply chain in Europe, from production, processing and point-of-sale. Samples were collected and analysed in Greece, Serbia and Poland, from 'general' and 'ad hoc' sampling points, which were perceived as critical points for virus contamination. General sampling points were identified through the analysis of background information questionnaires based on HACCP audit principles, and they were sampled during each sampling occasion where as-ad hoc sampling points were identified during food safety fact-finding visits and samples were only collected during the fact-finding visits. Human (hAdV) and porcine (pAdV) adenovirus, hepatitis A (HAV) and E (HEV) virus, norovirus GI and GII (NoV) and bovine polyomavirus (bPyV) were detected by means of real-time (RT-) PCR-based protocols. General samples were positive for hAdV, pAdV, HAV, HEV, NoV GI, NoV GII and bPyV at 20.09 % (134/667), 5.53 % (13/235), 1.32 % (4/304), 3.42 % (5/146), 2 % (6/299), 2.95 % (8/271) and 0.82 % (2/245), respectively. Ad hoc samples were positive for hAdV, pAdV, bPyV and NoV GI at 9 % (3/33), 9 % (2/22), 4.54 % (1/22) and 7.14 % (1/14), respectively. These results demonstrate the existence of viral contamination routes from human and animal sources to the salad vegetable supply chain and more specifically indicate the potential for public health risks due to the virus contamination of leafy green vegetables at primary production.

AN ELECTRON MICROSCOPE STUDY OF THE DEVELOPMENT OF A MOUSE HEPATITIS VIRUS IN TISSUE CULTURE CELLS

Samples taken at different intervals of time from suspension cultures of the NCTC 1469 line of mouse liver—derived (ML) cells infected with a mouse hepatitis virus have been studied with the electron microscope. The experiments revealed that the viruses are incorporated into the cells by viropexis within 1 hour after being added to the culture. An increasing number of particles are found later inside dense cytoplasmic corpuscles similar to lysosomes. In the cytoplasm of the cells from the samples taken 7 hours after inoculation, two organized structures generally associated and never seen in the controls are observed: one consists of dense material arranged in a reticular disposition (reticular inclusion); the other is formed by small tubules organized in a complex pattern (tubular body). No evidence has been found concerning their origin. Their significance is discussed. With the progression of the infection a system of membrane-bounded tubules and cisternae is differentiated in the cytoplasm of the ML cells. In the lumen of these tubules or cisternae, which are occupied by a dense material, numerous virus particles are observed. The virus particles which originate in association with the limiting membranes of tubules and cisternae are released into their lumen by a "budding" process. The virus particles are 75 mµ in diameter and possess a nucleoid constituted of dense particles or rods limiting an electron transparent core. The virus limiting membrane is sometimes covered by an outer layer of a dense material. In the cells from the samples taken 14 to 20 hours after inoculation, larger zones of the cell cytoplasm are occupied by inclusion bodies formed by channels or cisternae with their lumens containing numerous virus particles. In the samples taken 20 hours or more after the inoculation numerous cells show evident signs of degeneration.

Activation of lysosomal enzymes in virus-infected cells and its possible relationship to cytopathic effects

Activities of the enzymes β-glucuronidase, acid phosphatase, acid DNAase, acid RNAase, and acid protease have been measured in the lysosomal and supernatant fractions of mouse liver cells and monkey kidney cells before and after infection with mouse hepatitis virus and vaccinia virus, respectively. In the infected cells there was easily measurable release of lysosomal enzymes into the supernatant fraction. Evidence was presented that this is not an artefact of homogenization and precedes cell degeneration demonstrable histologically. It is suggested that release of lysosomal enzymes may explain some of the biochemical changes found in infected cells and may contribute to the cytopathic effects of some viruses.

Multicentre study of prevalence of HBV-associated delta infection and liver disease in drug-addicts

To assess the epidemiological and pathogenic effects of infection with the hepatitis-B-virus (HBV)-associated delta agent in addicts who take drugs parenterally, 225 symptomless addicts from Italy and 261 addicts with HBsAg-positive hepatitis from Italy, Denmark, Switzerland, and Ireland were tested for delta antigen (delta-Ag) and its antibody (anti-delta) by radioimmunoassay. 79 liver biopsy specimens from HBsAg-positive addicts were also tested for intrahepatic delta-Ag by immunofluorescence. Anti-delta was found in 9 (27%) of 33 of the symptomless HBsAg-positive addicts, in 13 (8%) of 156 of those without HBsAg but with anti-HBs, and in none of those negative for HBV markers. The prevalence of serum delta-Ag or anti-delta among addicts with HBsAg-positive hepatitis was 64% (104/161) in Italy, 44% (8/18) in Denmark, 33% (11/33) in Switzerland, and 31% (15/49) in Ireland. 32 of the 79 (40%)liver biopsy specimens from HBsAg-positive addicts showed positive delta-Ag immunofluorescence. Delta infection occurring simultaneously with HBV infection is common and possibly a major cause of liver disease in drug addicts who receive drug parenterally. The spread of delta infection in drug-using communities is not confined to one country, and the drug habit may represent the major means by which delta agent spreads in areas of the Western world where this infection is not endemic.

Hepatocellular carcinoma in ground squirrels persistently infected with ground squirrel hepatitis virus

Although persistent infection with hepatitis B virus and woodchuck hepatitis virus has been associated with development of hepatocellular carcinoma in the host, little has been known of such an association with ground squirrel hepatitis virus (GSHV), which is closely related to the woodchuck virus. Colonies of GSHV-infected and -uninfected Beechey ground squirrels were observed for tumors for a period of 5 years. Tumors developed in seven squirrels after a minimum of 2.4 years of observation per animal; each of the seven animals was over 4 years old when the tumor was detected. The predominant type of tumor was hepatocellular carcinoma, which appeared in 2 of 28 GSHV-bearing animals studied and in 1 of 23 squirrels with antibody to the virus. No hepatocellular carcinoma appeared in 24 GSHV marker-free squirrels. Integrated GSHV DNA was found in the hepatocellular carcinoma tissue of the one carrier animal examined, paralleling the frequent findings of integrated hepatitis B and woodchuck hepatitis viral DNA in human and woodchuck hepatocellular carcinoma. Although the incidence of liver carcinoma reported here in carrier ground squirrels is neither as great as that in carrier woodchucks nor statistically different from the incidence in noncarrier squirrels, the data presented suggest that persistent infection with GSHV may also be associated with hepatocellular carcinoma.

Virus hepatitis with features of prolonged bile retention

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The cellular nature of genetic susceptibility to a virus

Using peritoneal macrophage cultures it was found that both PRI mice and their macrophages in culture were susceptible to mouse hepatitis virus and that C(3)H mice and macrophages were resistant. All F(1) macrophages and some back-cross cell cultures were susceptible. The degeneration of F(1) and back-cross macrophages obtained either from adult mouse peritoneal exudate or newborn mouse liver, occurred more slowly than PRI macrophages. Segregation of susceptibility occurred in the first back-cross generation. Tests of three back-cross generations from susceptible mice yielded about one-quarter of the mice shown to be susceptible either by direct test or test of their macrophages. A clear correlation between susceptibility in vivo and in vitro was established both in the test of the percentage segregation and in tests of individual back-cross mice. A small series of tests, however, indicated that 50 per cent of the back-cross mice had the genetic capacity to transmit susceptibility. Thus a hypothesis of two genes for susceptibility, although not excluded, may yield to a hypothesis of a single dominant gene, incompletely expressed. Resistant cells were converted into susceptible cells by ingestion of a relatively large particle containing a heat-stable substance. This susceptibility, although complete, was temporary. The nature of the factor causing the change has been discussed.

THE APPEARANCE OF A HEPATOTROPHIC VIRUS IN MICE THYMECTOMIZED AT BIRTH

Inbred (C57BL; C3H/Bi), hybrid (C57BL x C3H/Bi), and outbred (TO) mice thymectomized within 24 hours of birth develop wasting symptoms and die prematurely and a proportion of these animals have pathological changes in the liver. The incidence of the liver lesions varies according to the strain of mice used and the lesions tend to occur in animals dying comparatively late. These lesions were shown, by passage of tissue suspensions and of cell-free liver extracts, to be due to a hepatotrophic virus probably mouse hepatitis virus-1 (MHV-1). The part played by the hepatotrophic virus in the premature death of thymectomized mice is discussed but, although neonatal thymectomy apparently alters a normally stable host-virus relationship, it is not thought that the virus is primarily responsible for the death of its host. The role of this virus in the production of the physical wasting is also considered to be problematic.

Viral hepatitis and primates: historical and molecular analysis of human and nonhuman primate hepatitis A, B, and the GB-related viruses

The hepatitis viruses have long been assumed to be highly host-specific, with infection of other nonhuman primates occurring due to inoculation with, or exposure to, human viruses. This paradigm has slowly changed over the last 10 years, as mounting data has revealed nonhuman primate equivalents of hepatitis A virus, hepatitis B virus, and the hepatitis C-related viruses GBV-C and GBV-A. This review summarizes the historical and molecular information for each of these groups and highlights the impact of these nonhuman primate hepatitis viruses on our understanding of the evolution of each of these viruses.