A case-control study on liver cancer with special emphasis on the possible aetiological role of schistosomiasis

Biliary Parasitic Diseases Associated with Hepatobiliary Carcinoma

Background

Despite long-term preventative efforts by local public health authorities, the prevalence of fluke infection remains high in specific areas in eastern and southeastern Asia. Recently increasing travel or migration activities have led to the transfer and spread of such infections from endemic areas to other regions.

Summary

The epidemiology, clinical signs, and symptoms for three common blood and liver flukes, namely Schistosoma japonicum, Clonorchis sinensis, and Opisthorchis viverrini, are described in this review, and their current diagnosis and management strategy are reviewed. These flukes are considered clinically important because of the increased risk of liver or biliary cancer.

Key Messages

Early treatment and prevention of disease spread can reduce the incidence of related hepatobiliary cancer. Recognition of these fluke infection is essential for a correct diagnosis and early treatment to prevent the development of deadly cancers.

Identification of a Schistosoma japonicum MicroRNA That Suppresses Hepatoma Cell Growth and Migration by Targeting Host FZD4 Gene

Previous studies have demonstrated miRNAs derived from plants and parasites can modulate mammalian gene expression and cell phenotype in a cross-kingdom manner, leading to occurrence of diseases or strengthening resistance of host to diseases such as cancer. In this study, we identified a schistosome miRNA (named Sja-miR-71a) through screening of 57 Schistosoma japonicum miRNAs that exerts antitumor activity in vitro and in vivo models. We demonstrated presence of this parasite miRNA in liver cells during infection. We showed that Sja-miR-71a arrested cell cycle at G0/G1 phase of hepatoma cell lines and inhibited cell proliferation in vitro. The HepG2 transfected with Sja-miR-71a mimics displayed significant reduction of migration and colony formation. Further, growth of the tumor cells transfected with the Sja-miR-71a mimics was obviously suppressed in a xenograft mouse model. Mechanically, we found the antitumor activity of Sja-miR-71a was through targeting a host gene encoding Frizzled Class Receptor 4 (FZD4), as FZD4 small interfering RNAs (siRNAs) generated a similar inhibitory effect on the tumor. These data indicated that Sja-miR-71a is a tumor suppressor miRNA and suggested this parasite-derived miRNA as a potential therapeutic target for cancer.

Coinfection of Schistosoma Species with Hepatitis B or Hepatitis C Viruses

Although a considerable number of studies have been undertaken to date, it is still controversial as to whether or not coinfection with schistosomiasis increases the susceptibility to or progression from Hepatitis B virus (HBV) or Hepatitis C virus (HCV) infection. This review is a closer examination of the key studies conducted on human populations on clinical factors that were published in English between 1975 and January 2015. Our review is mainly based on tables containing the salient information, which are arranged first by study population, country of study and publication date. We provide further explanation, clarification and discussion in the text. As such, it includes both studies that have been conducted on general populations who are largely asymptomatic for clinical disease (Table 3), as well as those focussing on special populations, which are usually comprised of clinical patients. These special populations have been presented as follows: subjects with chronic liver disease or related conditions such as cirrhosis, Table 4; subjects with primary liver cancer, Table 5; subjects with schistosomiasis, Table 6; subjects with acute or chronic hepatitis resulting from HBV, Table 7 and, subjects with HCV, Table 8. We have presented studies that compared two mono-infected groups with one that is coinfected separately in Table 9, as these offer us the best basis from which to evaluate if any synergistic effects accompany coinfection. A number of factors contributed to the results reported in our tables. These included, but are not limited to: subject selection (i.e. asymptomatic cases typically drawn from the general population vs subjects presenting to a hospital or clinic with clinical disease); study design, which directly impacts our ability to infer causality (i.e. case series, cross-sectional, case-control, cohort study); use and choice of control population (i.e. apparently healthy subjects vs other hospital patients vs none); sample size, which directly impacts statistical power and can result in a Type II error; geographic area, which may reflect differences in population genetics, public health history, environmental differences or any number of other important factors (i.e. Egypt, Brazil, China); method of testing for schistosomal infections (i.e. stool vs antibody test); method of testing to determine if advanced schistosomal disease was present (i.e. ultrasound, liver biopsy vs none); method of serological testing for HBV (i.e. use of HBsAg alone or with other markers or DNA testing); method of serological testing for HCV (i.e. use of anti-HCV alone or with RNA testing) and, year of the study, which reflects among other things, technological improvements between tests as well as possible changes in the frequency of exposure in the populations under study (i.e. use of parenteral antischistosomal therapy vs the oral antischistosomal medication). Despite all these differences, throughout this review we have observed general patterns that seem largely consistent with one another. Studies conducted on general, largely asymptomatic populations tend to support the view that having one of the diseases in question (i.e. schistosomiasis) does not necessarily predispose one to becoming coinfected with another (i.e. HBV or HCV). Rather, the probability of becoming coinfected seems most closely associated with modes of transmission for either HBV or HCV in schistosome-endemic areas, such as the past use of parenteral antischistosomal therapy or frequent blood transfusion. Once coinfected, however, the clinical course of illness for those with Schistosoma-HBV or Schistosoma-HCV infections are typically much more severe than for mono-infected subjects. The strongest evidence for this was found in the half-dozen or so prospective cohort studies that systematically monitored disease progression in their subjects. With respect to HBV infection, coinfection with Schistosoma prolonged the carriage state and more often resulted in chronic hepatitis with greater cirrhosis as well as higher mortality. Much of the same was also observed with respect to HCV, where coinfection with Schistosoma was associated with a reduced ability to spontaneously resolve the viral infection and more often resulted in rapid fibrosis as well as higher mortality. Furthermore, two of these studies which were fully comparative in nature, support the supposition that there is a synergistic association between Schistosoma-HCV for both liver fibrosis and mortality. Immunological studies, all conducted on HCV, also generally seem to support this. The results of our research argue for greater primary prevention for both HBV and HCV in Schistosoma-endemic populations. Although no vaccine currently exists for HCV as it does for HBV, additional steps can still be taken to reduce transmission in high-risk populations. Greater use of the HBV vaccine is particularly advisable. Finally, additional observational, longitudinal studies conducted on human populations that are fully comparative in nature could help answer some of the remaining questions on both Schistosoma-HBV as well as Schistosoma-HCV coinfections. Some of these include the role of active versus past schistosomal infections, the role of genetic variants, as well as the effect of coinfection on treatment. Future studies should make a particular effort to use a sufficient sample size to ensure adequate statistical power, which was not often properly considered in many of the studies we reviewed for this paper.

Bilharzia: Pathology, Diagnosis, Management and Control

More than one billion people travel internationally each year and approximately 100 million to the tropics. Schistosomiasis is a neglected tropical disease caused by trematode blood flukes of the genus Schistosoma. It currently infects over 250 million people worldwide and results in approximately 25 million disability adjusted life years lost. Clinical manifestations depend on the affected organ. Subtle morbidities have also been documented including: growth retardation, anaemia and poor cognitive function in children. While schistosomiasis has been eradicated from Japan and significantly reduced in parts of China and Egypt, transmission in many other regions remains ongoing due to the wide-spread distribution of the intermediate snail host, poor sanitation, lack of health education and decreasing compliance to mass drug administration. Integrated control has significantly reduced the burden of disease in China but considerable financial capital is needed if similar results are to be duplicated elsewhere. Human vaccination is in various stages of development, and once found, will become an integral part of future control. This comprehensive review examines the epidemiology, pathology, diagnosis, clinical management, prevention and control of the disease.

The application of attributable risk analysis in helminth epidemiology

Estimating the public health impact of endemic helminth infections is an important component of control strategies that aim not only to reduce the number of infections in a community, but also to improve community health. This is not straightforward, as the risk of morbidity in an infected individual can be influenced by a number of factors, and different infections can cause similar symptoms. Here, Mark Booth describes how attributable risk analysis techniques based on 232 tables can be used to address these problems, and how they were applied to estimate the public health impact of Schistosoma japonicum infections in three villages in China.

Alcohol drinking and liver cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population

BACKGROUND

Although alcohol consumption has been recognized as a risk factor for primary liver cancer, it will be informative to summarize relevant epidemiologic data in the Japanese who have characteristic environmental determinants (e.g. hepatitis C virus infection) and genetic traits (e.g. presence of poor acetaldehyde metabolizers).

METHODS

We systematically reviewed epidemiologic studies on alcohol drinking and liver cancer among Japanese populations. Original data were obtained through searches of the MEDLINE (PubMed) and Ichushi databases, complemented with manual searches. The evaluation was performed in terms of the magnitude of association ('strong', 'moderate', 'weak' or 'no association') in each study and the strength of evidence ('convincing', 'probable', 'possible' or 'insufficient'), together with biological plausibility as previously assessed by the International Agency for Research on Cancer.

RESULTS

Among 22 cohort studies identified, 14 (64%) reported weak to strong positive associations between alcohol and liver cancer risk, 3 (14%) reported no association and five (23%) reported weak to moderate inverse associations; such inverse associations were found mostly in follow-up studies of patients with chronic liver disease (particularly, cirrhotic patients), yet recent studies on patients with chronic hepatitis C presented fairly consistent positive associations. Of 24 case-control studies identified, 19 (79%) showed weak to strong positive associations, whereas the remainder demonstrated no association (n = 4) or a moderate inverse association (n = 1).

CONCLUSION

We conclude that there is 'convincing' evidence that alcohol drinking increases the risk of primary liver cancer among the Japanese population.

Novel adenine adducts, N7-guanine-AFB1 adducts, and p53 mutations in patients with schistosomiasis and aflatoxin exposure

INTRODUCTION

The most frequent mutation in human hepatocellular carcinoma (HCC) in populations exposed to a high dietary intake of aflatoxin B1 (AFB1) is a mutation in codon 249 of the p53 gene. Schistosomiasis is known to cause p53 mutation. We hypothesized that the combination of schistosomiasis and aflatoxin B1 increases the incidence of p53 gene mutation.

METHODS

Liver tissue from 21 patients with schistosomiasis and 5 patients without schistosomiasis were analyzed for occurrence of mutations of the p53 gene and levels of N7-guanine-AFB1 adducts.

RESULTS

The presence of mutations in codon 249 of p53 gene was higher in patients infected with Schistosoma haematobium (S. haematobium) than in those infected with Schistosoma mansoni (S. mansoni) or a combination of both strains (p < 0.01), compared to control subjects. No mutations were detected in p53 gene in liver DNA from schistosomiasis-free patients. Significant amounts of N7-guanine-AFB1 adducts and novel adenine-adducts (p < 0.01) were detected in patients with schistosomiasis, mostly in patients infected with S. haematobium or a combination of both strains, compared to control subjects.

CONCLUSION

These data suggest that schistosomiasis and exposure to aflatoxin B1 act synergistically to increase the incidence of p53 gene mutation. The increase in p53 mutations may enhance progression of HCC at an early age in patients with schistosomiasis.

A matched, case-control study of the association between Schistosoma japonicum and liver and colon cancers, in rural China

A study of liver and colon cancers and their association with a previous diagnosis of schistosomiasis was performed in rural Sichuan, China. The data analysed came from 127 liver-cancer and 142 colon-cancer patients, each matched, by age, gender, hospital and township, with one or two controls. The cancer cases were identified from the hospital records of three Sichuan counties (all of which have some level of endemic schistosomiasis japonicum): Meishan (66 liver and 54 colon cases), Pujiang (16 liver and 22 colon cases) and Xichang (45 liver and 66 colon cases). Each control was selected using the hospital records for the same year the matched case of cancer was diagnosed, when the control had been found to have an illness other than cancer. Previous schistosomal infection was determined by examining the medical records at the county hospitals, searching the records at the local schistosomiasis-control stations or health-surveillance units, and, when no written record could be found, by interviews with the subjects or their relatives. Given the extremely strong association between hepatitis and liver cancer in China, only data from hepatitis-negative pairs were used in the analyses. Previous schistosomal infection was found to be significantly associated with both liver cancer (odds ratio = 3.7; 95% confidence interval = 1.0-13) and colon cancer (odds ratio = 3.3; 95% confidence interval = 1.8-6.1). The results indicate a fraction of disease attributable to schistosomiasis of 24% for colon cancer, and (among the hepatitis-negative population) one of 27% for liver cancer.

p53 gene mutations in rectal cancer associated with schistosomiasis japonica in Chinese patients

Mutations in p53 tumor suppressor gene were examined in 44 Chinese patients with rectal cancer, including 22 cases with advanced schistosomiasis japonica and 22 cases without schistosomiasis. In schistosomal rectal cancer (SRC), 13 mutations were found in 10 cases, which included 11 base-pair substitutions and two deletions. Of 11 base substitutions, nine were transitions and two were transversions and seven of them were located at CpG dinucleotides. In non-schistosomal rectal cancer (NSRC), 13 mutations were found in nine cases, all of which were base-pair substitutions. Of 13 substitutions, 10 were transitions and three were transversions and three of them were located at CpG dinucleotides. The proportion of base-pair substitutions at CpG dinucleotides was higher in SRC patients than in NSRC patients, although this was not statistically significant (P = 0.054). Point mutation was frequent at codon 248 in SRC. A higher frequency of arginine missense mutations was observed in SRC than in NSRC. These observations suggest that the mutations in SRC are the result of genotoxic agents produced endogenously through the course of schistosomiasis japonica.

Schistosomiasis in women: manifestations in the upper reproductive tract

Female genital schistosomiasis (FGS) is a neglected disease entity which may give rise to considerable suffering among women of child-bearing age in areas where schistosomiasis (especially due to Schistosoma haematobium) is prevalent. The close relation between the vessels in genital organs and the urinary bladder enables the parasite to easily change location to virtually any organs in the female pelvic area. Symptoms concur with the anatomical location of worm pairs and their ova. Lesions of the lower female genital tract can easily be investigated by cytology, histology or direct demonstration of eggs in scrapings or biopsies whereas schistosomiasis of the upper genital tract is clinically indecipherable and less accessible for examination. In the literature there are references to FGS as a cause of infertility, complications of pregnancy, menstrual disorders, problems related to sexual intercourse, diagnostic similarities to STDs and cancer, unspecified complaints related to blood loss, chronic abdominal pain, social segregation and related psychological problems. The diagnosis of female upper genital schistosomiasis is difficult and the authors point out possible diagnostic procedures which might be helpful for further understanding of this complex entity.

Pattern of cancer in Madina Al-Munawara region

This is a retrospective study of 2237 histologically proven cases of cancer over a 12 year period from 1981 to 1993. There were 1687 (75.4%) Saudi and 550 (24.6%) non-Saudi patients. Among both sexes, the most common malignancies were from the gastrointestinal tract (29.3%), lymphoma/leukemia (18.4%), head and neck (8.8%) and breast (8.5%). The most common malignancies among males were lymphoma/leukemia, hepatoma, skin and stomach. Among females, the order of frequency of malignancy was breast, lymphoma/leukemia, esophagus, colon and thyroid. Comparison with other leading studies of the Kingdom has been made. The most common malignancies were discussed with the possible etiological factors.

Cancer in the Gizan province of Saudi Arabia: An eleven year study

The occurrence of histologically diagnosed primary malignant tumors in Saudi and Yemeni patients in Gizan Province over the 11 years from 1982 to 1992 was analyzed. During the study period, 1398 malignancies of known primary site were seen in males and 972 in females. In common with other parts of Saudi Arabia, the overall incidence of malignant disease was low by Western standards with lymphoreticular malignancies relatively common and tumors of lung, bowel, breast and the female genital system relatively uncommon. Some malignancies are more common in Gizan Province as compared to elsewhere in Saudi Arabia. Oral cancer was the most common malignancy in females and the most common overall, probably due to widespread use of oral tobacco preparations. Liver cancer was the most common malignancy in males, reflecting the endemic nature of hepatitis B in the area. The incidence of bladder cancer, and particularly of squamous carcinoma of the bladder, was also more, probably due to the high incidence of schistosomiasis in the area. No significant trends in incidence of specific malignancies were noted over the 11-year study period, even though the period has been marked by dramatic and unprecedented changes in lifestyle and public health.

Retention of a mutagen, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), in the liver of mice infected with Schistosoma japonicum

Regarding the mechanism underlying the suspected enhancement of hepatic cancers among Schistosoma japonicum-infected humans, we hypothesized that mutagen exposures in the livers of patients may be enhanced due to the parasitic infection. To explore this possibility, we have done a model experiment using mice and a carcinogenic mutagen, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). Mice infected with Schistosoma japonicum were intravenously administered Trp-P-2, and the mutagenic activities of the mouse serum and of the liver tissue extracts, which were observable during the 6-h period after the administration, were investigated. The level of serum indirect mutagenicity, which probably reflected the amount of unmetabolized Trp-P-2, was higher in the infected animals than in uninfected control animals. Direct mutagenicity in the serum, on the other hand, was higher in the control animals than in the infected mice. Furthermore, the liver tissue extracts from infected mice showed higher indirect-mutagenicity than those from the controls. These data suggest that the infection results in a decreased metabolism and an increased retention of Trp-P-2 in the liver. Consistent with this phenomenon, pigments in the liver formed by the schistosome infection were found to be an efficient adsorbent for Trp-P-2. Thus, the possibility exists that these pigments, which contain hematin as a major constituent, may function as a reservoir for the mutagen, thereby prolonging the exposure period of the liver to the mutagen.

Parasite infection and cancer: with special emphasis on Schistosoma japonicum infections (Trematoda). A review

This article contains a review of current knowledge on the association of parasite infections and cancer formation, especially that of Schistosoma japonicum (Trematoda) in man and experimental animals. The association of S. haematobium infection and bladder cancer is well known and documented. However, S. japonicum infection has also been reported to be associated with cancer, in this case hepatocellular carcinoma and/or colorectal cancer. Pathological records and analyses have shown a correlation between this infection and cancer, and pathohistological descriptions have been numerous, together with clinical case reports. Epidemiological analyses have been conducted in China and Japan and support a role of S. japonicum infection as one of the risk factors in cancer formation, along with others, such as hepatitis virus infection and alcoholic intake. Experimental results have also shown that cancer appears early and in larger numbers in experimentally infected animals given a known carcinogen. In spite of these positive end-point associations, the mechanism of schistosome-mediated enhancement of carcinogenesis is obscure. A suggestive observation is that in S. japonicum-infected mice carcinogen-metabolizing hepatic activity including P-450 was decreased so that an administered carcinogen persisted for a longer period than in uninfected mice. Further studies, both epidemiological and experimental, are needed to firmly establish the relationship between schistosome infection and cancer.

Modified metabolism of a carcinogen, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), by liver S9 from Schistosoma japonicum-infected mice

Schistosoma japonicum infection has been associated with an increased incidence of liver and colorectal cancers in humans. To explore the mechanisms underlying this association, we investigated the carcinogen-metabolizing properties of liver S9 preparations from S. japonicum-infected mice and compared them with those of S9 from uninfected animals. When the carcinogen 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) was incubated with these S9s and the products were analyzed by high-performance liquid chromatography, we observed that the S9 from infected mice had a lower ability to convert Trp-P-2 into 3-hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2(NHOH)), an activated form of promutagenic Trp-P-2, than the S9 from uninfected mice. We found that both of these S9 preparations have a high ability to reduce Trp-P-2(NHOH) into Trp-P-2; however, the infected-mouse S9 showed a significantly greater reducing power than the control S9. This difference appears to be responsible for the observed lower mutagen-activating potential of the infected mouse S9. These results suggest that hepatic enzyme activities of S. japonicum-infected mice are quantitatively different from those of normal mice.

Prospective study of the association of alcohol with cancer of the upper aerodigestive tract and other sites

The association of alcohol consumption with cancers of the upper aerodigestive tract, hepato-biliary-pancreatic system, urogenital organs (except for prostate), and lymphohematopoietic tissue was evaluated in a prospective study of 6,701 American men of Japanese ancestry living in Hawaii. Compared with cancer-free subjects, subjects who subsequently developed cancers of the upper aerodigestive tract (oral-pharynx, esophagus, and larynx), liver, biliary tract, and lymphohematopoietic tissue consumed significantly larger amounts of total alcohol--mainly in the form of beer. Subjects who developed oral-pharyngeal and esophageal cancer also consumed larger amounts of wine and spirits. Because the upper aerodigestive tract cancers were associated positively with cigarette smoking, age-adjusted relative risks (RR) were calculated, based on joint exposure to cigarette smoking and heavy alcohol intake (greater than or equal to 30 ml/day) in this population. A markedly increased risk was observed among subjects who were both heavy alcohol drinkers and smokers (RR = 17.3, 95 percent confidence interval [CI] = 6.7-44.2), compared with subjects who who did not smoke and did not drink heavily. The risk for these cancers also was increased among heavy alcohol drinkers who were nonsmokers (RR = 8.6, CI = 2.1-36.0).

Immunohistochemical detection of HBsAg and HBcAg in the liver of patients with schistosomiasis japonica complicated by hepatocellular carcinoma

In liver biopsies from 21 patients with schistosomiasis japonica complicated by hepatocellular carcinoma (HCC), 69 patients with advanced schistosomiasis japonica, and 25 patients with HCC, HBsAg and HBcAg were investigated with peroxidase-antiperoxidase technique. The positive rate of HBAg (i.e. HBsAg and/or HBcAg) in the liver of patients with schistosomiasis japonica complicated by HCC was significantly higher than in the group of advanced schistosomiasis japonica, but similar to that in cases of HCC. The location of carcinoma cells in the liver was not related to the distribution of Schistosoma ova in patients with schistosomiasis japonica complicated by HCC. The results indicated that the complication with hepatitis B virus infection may be one of the major factors involved in the development of HCC in patients with schistosomiasis japonica.

Pattern of cancer at Asir Central Hospital, Abha, Saudi Arabia

Six hundred ninety-seven histologically confirmed cases of cancer were seen in the three-year period, 1987 to 1989, at Asir Central Hospital in Abha, Saudi Arabia. Percentage (crude relative) frequencies of cancer at various sites were determined. The most common cancer sites among males were skin, liver, lymphoid tissue (i.e., non-Hodgkin's lymphomas), bladder,, blood (leukemias), stomach, colon, esophagus, central nervous system, and prostate. Skin cancer was also the most common cancer among females, followed by breast, lymphoid tissue (non-Hodgkin's lymphomas), blood (leukemias), thyroid, stomach, colon, oral cavity, esophagus, and cervix.

International Commission for Protection Against Environmental Mutagens and Carcinogens. ICPEMC publication No. 18. Review of the genotoxicity and carcinogenicity of antischistosomal drugs; is there a case for a study of mutation epidemiology? Report of a task group on mutagenic antischistosomals

One of the interests of ICPEMC is to identify situations in which the possible induction of inherited defects in man by mutagen exposure could actually be studied. The large-scale use of mutagenic drugs in field programmes against schistosomiasis, mainly during the 1970's, was considered a possible case. An ICPEMC task group approached the problem by (1) updating the genetic toxicology data base for antischistosomal drugs, and (2) reviewing possible study areas. Expertise was combined from genetic toxicology, mutation epidemiology and tropical medicine. It was considered that: (a) if any, hycanthone would be the most appropriate candidate drug for study; (b) it would be virtually impossible to meet the basic requirements of an appropriate mutation epidemiology study, in endemic countries; (c) as more defined genetic endpoints would be selected (e.g. sentinel phenotypes) the required large sample sizes would seem prohibitive, since documentation on past programmes is limited and local demography would render the reliable tracking of substantial numbers of offspring of treated persons an almost impossible task; (d) in most endemic countries proper diagnosis and registration of inherited defects is largely lacking; (e) the problems encountered in demonstrating inherited effects in humans after heavy or chronic exposure to established animal mutagens such as ionizing radiation and cancer chemotherapy, in combination with the ambiguous nature of the animal germ cell data with hycanthone, do not particularly warrant large expectations; (f) since non-mutagenic antischistosomal drugs are now in use, the problem is academic and of low priority in the endemic countries whose medical and research resources are often limited. Thus, studying offspring of hycanthone-treated people to demonstrate the mutagenic potential of the drug in man is not a viable enterprise.

A case-control study of hepatocellular carcinoma in Osaka, Japan

A case-control study was undertaken to evaluate the roles of hepatitis B virus (HBV), blood transfusion, alcohol drinking and cigarette smoking in the etiology of hepatocellular carcinoma (HCC) in Osaka, Japan. A total of 229 cases and 266 hospital controls were included in our study. The relative risks of HCC obtained after adjustment for age, sex and other important variables were 14.3 (95% confidence interval (CI): 5.7-36.3) for HBsAg positives, 4.3 (95% CI: 1.9-9.6) for blood recipients and 3.2 (95% CI: 2.0-5.1) for heavy drinkers. A statistically significant dose-response relationship was observed between the risk of HCC and total alcohol consumption. The overall risk for HCC was also significantly elevated among smokers; however, there was no consistent dose-response relationship between the risk and cigarette consumption. We conclude that HBV, blood transfusion and excessive alcohol drinking play important roles in the etiology of HCC in Osaka, Japan. Further investigation is needed to clarify the possible etiological role of smoking.

Reduced levels of mutagen processing potential in the Schistosoma japonicum-infected mouse liver

Epidemiological studies have shown the presence of a positive correlation between the infection of Schistosoma japonicum and colorectal and/or liver cancers in the humans. To explore the mechanism underlying this correlation, we have investigated the mutagen-activating potentials of the liver homogenate fraction (S9) from Schistosoma japonicum infected mice and those from control mice, by use of the Ames test with 2-acetylaminofluorene, aflatoxin B1 and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) as test mutagens. Liver S9 prepared from the infected group at the 15th week after the infection showed a potential significantly lower than that from the control group. The hepatic cytochrome P-450 concentration in the infected mice was persistently low, about a half of that in the uninfected mice, during the period of 6-18 weeks after the infection. Thus, in mice bearing chronic schistosomiasis, mutagen-processing potentials are decreased.

Evaluation of the mutagenicity and the tumor-promoting activity of parasite extracts: Schistosoma japonicum and Clonorchis sinensis

In relation to the observed association of carcinogenesis with parasitic infections, the mutagenicity of extracts of Schistosoma japonicum and Clonorchis sinensis was examined. In the bacterial mutagenicity tests using the Ames Salmonella typhimurium strains TA98, TA100, TA97 and TA102, and Escherichia coli WP2 and WP2 uvrA pKM101 Schistosoma soluble egg antigen and a homogenate of adult Schistosoma worms showed no positive responses either in the presence or in the absence of S9 mix. Likewise, adult worm extracts of Clonorchis showed no mutagenicity. The Schistosoma soluble egg antigen showed a weak but significant activity for the induction of Epstein-Barr virus expression in viral genome-carrying human lymphoblastoid cells in culture. This phenomenon suggests that the soluble egg antigen possesses tumor-promoting activity.

Cigarette smoking, alcohol consumption and primary liver cancer: a case-control study in the USA

Cigarette smoking and alcohol consumption were examined as potential risk factors in a case-control study of primary liver cancer (PLC). A total of 165 PLC cases and 465 matched controls from several US hospitals were studied. A weak but statistically significant (p less than 0.05) dose-response relationship was observed between alcohol consumption and PLC in elderly females independent of other major risk factors (adjusted OR = 1.87 and 3.48 for 1-2 and greater than 3 drinks per day, respectively) and a similar trend was evident in elderly males. The risk for PLC was also elevated in elderly females who were current cigarette smokers (adjusted OR = 3.30). Our results suggest that alcohol consumption and cigarette smoking may have minor age- and sex-specific effects on the development of PLC, and underscore the need for further investigations to elucidate major PLC risk factors in US populations.

Abnormalities of chromosome 12p13 and malignant proliferation of eosinophils: a nonrandom association

Four patients representing a spectrum of haematological malignancies are reported. Two patients had Philadelphia chromosome negative myeloproliferative disorders, one had acute lymphoblastic leukaemia and one had eosinophilic leukaemia. In each case eosinophilia was present and demonstrated to be part of the malignancy by the association of clonally abnormal metaphases with eosinophil granules. Abnormalities involving the short arm of chromosome 12 (12p13) were a constant feature in all four cases and therefore a nonrandom association between this chromosome region and malignant eosinophil proliferation is proposed.