Frequency and Association Of GSTM1 and GSTT1 Gene Polymorphisms with Survival in Breast Cancer Patients

Objective:

Glutathione S-transferase M1 and T1 (GSTM1 and GSTT1) are the key detoxification enzymes of xenobiotics, including chemotherapeutic drugs. The deletion polymorphisms of GSTM1 and GSTT1 genes are associated with reduced enzyme activity that influenced clinical outcomes of chemotherapeutic agents in breast cancer. However, there is limited information among Thai patients. This research aims to explore the frequency and role of GSTM1 and GSTT1 polymorphisms on survival among Thai patients with breast cancer.

Methods:

The retrospective cohort study was performed. Demographic data and clinicopathology characteristics were collected from hospital base registry data and medical records. A multiplex qualitative real-time PCR method was used to detect the presence or absence of the GSTM1 and GSTT1 gene in the genomic DNA samples of the participants.

Results:

The frequencies of the GSTM1 and GSTT1 null genotypes in 198 breast cancer patients were 65.70% and 33.30%, respectively. The overall survival at 1, 3 and 5 years were 95.00%, 83.00%, 71.00% respectively. The log rank test and Cox proportional hazards revealed a significant different in the 5-years overall survival according to lymph node metastasis and tumor stage (P = 0.014 and P < 0.001). No associations between overall survival and GSTM1 or GSTT1 genotype were found in single or combined genotypes analyses (P = 0.76 and P= 0.15).

Conclusion:

The results of our study provided the epidemiological information for prognostic of survival in breast cancer patients treated with chemotherapy.

Doxorubicin-conjugated dexamethasone induced MCF-7 apoptosis without entering the nucleus and able to overcome MDR-1-induced resistance

Background

Doxorubicin (DOX) is the most widely used chemotherapeutic agent that has multimodal cytotoxicity. The main cytotoxic actions of DOX occur in the nucleus. The emergence of drug-resistant cancer cells that have the ability to actively efflux DOX out of the nucleus, and the cytoplasm has led to the search for a more effective derivative of this drug.

Materials and methods

We created a new derivative of DOX that was derived via simple conjugation of the 3' amino group of DOX to the dexamethasone molecule.

Results

Despite having a lower cytotoxic activity in MCF-7 cells, the conjugated product, DexDOX, exerted its actions in a manner that was different to that of DOX. DexDOX rapidly induced MCF-7 cell apoptosis without entering the nucleus. Further analysis showed that Dex-DOX increased cytosolic oxidative stress and did not interfere with the cell cycle. In addition, the conjugated product retained its cytotoxicity in multidrug resistance-1-overexpressing MCF-7 cells that had an approximately 16-fold higher resistance to DOX.

Conclusion

We have synthesized a new derivative of DOX, which has the ability to overcome multidrug resistance-1-induced resistance. This molecule may have potential as a future chemotherapeutic agent.

Association between ERCC1 Polymorphism and the Risk and Clinicopathological Features of Breast Cancer in Thai Women in the Lower Northeastern Region

Background:

Breast cancer is a major public health problem around the world, including Thailand and it has the highest ranking among female cancer. Currently, the diversity or polymorphism of ERCC1 gene (excision repair cross-complementary group 1 gene or ERCC1) was reported to associate with an increased risk of breast cancer. This study aims to investigate the relationship between ERCC1 polymorphism and the breast cancer risk in the lower northeastern region women of Thailand.

Materials and Methods:

One hundred fifty one samples from breast cancer patients and 120 samples from healthy control group were analysed. Genomic DNA was extracted from white blood cell of all samples. The real-time polymerase chain reaction (qPCR) was used to demonstrate genetic polymorphism of ERCC1.

Results:

The results showed that the ERCC1 rs11615 polymorphism variant AG was associated with an increased risk of breast cancer. This study demonstrated that the frequency of ERCC1 rs11615 in patients with breast cancer was higher than healthy control group. The ERCC1 polymorphism variant AG carrier presented 3.53-folds high risk of breast cancer [odds ratio (OR) = 3.53, 95% CI = 1.61-7.74, P = 0.001]. In addition, when age, menopause period, number of child, smoking and alcohol drinking were adjusted, the ERCC1 rs11615 variant AG carrier was associated with increased breast cancer risk to 3.97 folds, with OR = 3.79, 95% CI = 1.62-8.84, P = 0.002.

Conclusions:

This study showed that ERCC1 rs11615 genotype AG was associated with breast cancer risk in the lower northeastern region women of Thailand.

Clinicopathological significance of BRCA1 promoter hypermethylation in Thai breast cancer patients

Breast cancer susceptibility gene 1 (BRCA1), mapped on chromosome 17q21, is implicated in the mechanisms of cellular DNA repair. Inactivation of this gene is involved in the development of many human cancers, including breast cancer. This study aimed to investigate the prognostic value of BRCA1 promoter hypermethylation and expression in breast cancer cases. Sixty-one breast cancers were examined for BRCA1 hypermethylation by methylation-specific polymerase chain reaction (PCR), and 45 paired normal breast tissues were analyzed for altered BRCA1 mRNA levels by quantitative real-time reverse transcription-polymerase chain reaction (qRT- PCR). Aberrant methylation status in BRCA1 was detected in 15 of 61 cases (24.6%), while reduced expression was found in 7 of 45 (15.6%). BRCA1 hypermethylation was statistically associated with tumor grade III (p=0.04), a high frequency of stage IIB (p=0.02), and triple-negative phenotype (OR= 3.64, 95%CI =1.1-12.3, p=0.03). Our findings indicated that BRCA1 promoter hypermethylation is a useful prognostic marker for breast cancer.

Hypermethylation of suppressor of cytokine signaling 1 in hepatocellular carcinoma patients

Hepatocellular carcinoma (HCC), the most common primary hepatic tumor, is highly prevalent in the Asia-Pacific region, including Thailand. Many genetic and epigenetic alterations in HCC have been elucidated. The aim of this study was to determine whether aberrant methylation of the suppressor of cytokine signaling 1 gene (SOCS1) occurs in HCCs. Methylation specific-PCR assays were performed to identify the methylation status of SOCS1 in 29 tumors and their corresponding normal liver tissues. An abnormal methylation status was detected in 17 (59%), with a higher prevalence of aberrant SOCS1 methylation significantly correlating with HCC treated without chemotherapy (OR=0.04, 95%CI=0.01-0.31; P=0.001). This study suggests that epigenetic aberrant SOCS1 methylation may be a predictive marker for HCC patients.

Epstein-Barr virus strains defined by the latent membrane protein 1 sequence characterize Thai ethnic groups

Epstein-Barr virus (EBV) is ubiquitous in the human population and seroepidemiological studies have revealed that more than 90% of adults are infected with the virus in Thailand. It has been suggested that latent membrane protein 1 (LMP1) variants may differ in their tumorigenicity and geographical localization. The distribution of LMP1 variants of EBV in the Thai population was studied. A total of 259 LMP1 sequences from ten Thai ethnic groups (Lahu, Lisu, Shan, Red Karen, White Karen, Hmong, Akha, Mlabri, Moken and Urak Lawoi) were studied using direct PCR sequencing. Nucleotide sequences corresponding to the C terminus of the LMP1, including previously published sequences from central and southern Thais, were used in the phylogenetic analysis. Five strains--the B95-8 prototype, China 1, China 2, Mediterranean (Med) and SEA 2--were identified in ethnic groups in Thailand. The major strain and the distribution pattern differed by group and location. When the ethnic groups were classified by linguistic group, the prevalence of the SEA 2 strain was significantly different between Austro-Thais and other linguistic groups (P=0.0001), whereas, among Tibeto-Burman linguistic groups, the prevalence of the Med strain was different between matrilocal and patrilocal groups (P=0.0245). The distribution of LMP1 strains in ethnic minorities in Thailand is associated with ethnogeographical factors and the social/marriage system. This study thus provides evidence for the importance of interactions between populations in virus diversity.

Real-time PCR assay for rapid detection of GSTM1 polymorphism in nasopharyngeal carcinoma patients

Nasopharyngeal carcinoma (NPC) is a common public health problem in Thailand. Glutathione S-transferase M1 gene deletion (GSTM1 null genotype) carriers have been reported to be at increased risk and therefore this parameter is a potential marker for screening of NPC high-risk individuals. However, the conventional polymerase chain reaction (C-PCR) assay commonly used for GSTM1 null genotype detection is not suitable for mass screening since it is inconvenient, time consuming and unsafe due to the use of a toxic chemical. Currently, real-time PCR (R-PCR) assay is recommended for quicker and safer detection of various genetic polymorphisms. The aim of this study was to develop a SYBR green I R-PCR assay combined with melting curve analysis for GSTM1 polymorphism detection in Thai NPC patients. The results were compared to those from the C-PCR assay using DNA samples from peripheral blood leukocytes of 120 Thai NPC patients. The frequencies of GSTM1 polymorphism detected by the R-PCR and the C-PCR were the same. Forty-eight individuals that were GSTM1+ in the R-PCR assay showed 2 peaks with melting points of 82.5 and 87.5 that correlated with the appearance of 2 DNA bands in the C-PCR assay (i.e., one for GSTM1 at 215 base pairs (bp) and one for ?-globin at 268 bp). By contrast, 72 individuals that were GSTM1?- in the R-PCR assay showed 1 peak with a melting point of 87.5C that correlated with the appearance of 1 DNA band for -globin at 268 bp in the C-PCR assay. The R-PCR assay using SYBR Green I and melting curve analysis for GSTM1 polymorphism detection was as reliable as C-PCR assay but was quicker and safer and more amenable to large scale screening in Thai NPC cases.

Cytochrome P450 2A6 polymorphism in nasopharyngeal carcinoma

Nitrosamine has been identified as a carcinogen for nasopharyngeal carcinoma (NPC). Here, we investigated if a nitrosamine metabolizing gene, cytochrome P450 2A6 (CYP2A6) played an important role in NPC development. Relationships between the disease and the CYP2A6 were studied in 74 NPC patients and 137 age-matched healthy controls by using PCR-RFLP assay to distinguish between a wide type allele, *1A, and two mutant alleles, *1B and *4C. Overall, a significant association between CYP2A6 polymorphism and NPC development was observed (P<0.05). Individual with mutant alleles had an increased risk for NPC when compared to those with *1A/*1A (OR=2.37, 95% CI=1.27-4.46). In addition, males who carried mutant alleles of CYP2A6 had a fivefold increased risk for NPC when compared with those who carried *1A/*1A genotype (OR=5.02, 95% CI=1.82-14.14). It is thus suggested that CYP2A6 polymorphism may play a crucial role in NPC susceptibility and it may be used as a risk marker for NPC.

Glutathione S-transferase M1 gene polymorphism in Thai nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a serious health problem in Thailand. It is caused by the combined effects of Epstein-Barr virus (EBV), carcinogens and genetic susceptibility. The glutathione S-transferase M1 gene (GSTM1) encodes a phase II enzyme responsible for detoxifying carcinogenic electrophiles. Polymorphic null forms of the gene GSTM1 lack enzyme activity and have been associated with susceptibility to several cancers including NPC. To examine the association between GSTM1 polymorphism and NPC susceptibility in Thais, GSTM1 genotypes (normal and null genotypes) in 78 NPC patients and 145 age-matched healthy controls were determined using PCR assays. Overall, no statistically significant differences were observed in the frequency of GSTM1 genotypes between cases and controls, nor among NPC patients compared on the basis of sex and clinical stage of disease. Carriers with the GSTM1 null genotype had a 2.9-fold increased risk for NPC of WHO type III when compared to those with GSTM1 normal genotype (P < 0.05 with OR =2.9, 95% CI = 1.2-6.8). When cases and controls were categorized into 3 age groups (>40, (>45 and (>50 years), the frequencies of GSTM1 null genotype in cases the (>45 and (>50 age groups were significantly different from controls (P< 0.05). In addition, carriers of the GSTM1 null genotype in age groups (>45 and (>50 years had a 2-fold and 3-fold increased risk for NPC when compared to those with GSTM1 normal genotype (OR = 2.2, 95% CI = 1.1-4.7 and OR = 3.0, 95% CI = 1.2-7.5). We suggest that GSTM1 polymorphism may be associated with NPC susceptibility in Thais, especially for GSTM1 null genotype carriers of age higher than 45 years. The GSTM1 null genotype may be a useful genetic marker for predicting Thai NPC and for screening of early stages of Thai NPC.

Recent origin and cultural reversion of a hunter-gatherer group

Contemporary hunter–gatherer groups are often thought to serve as models of an ancient lifestyle that was typical of human populations prior to the development of agriculture. Patterns of genetic variation in hunter–gatherer groups such as the !Kung and African Pygmies are consistent with this view, as they exhibit low genetic diversity coupled with high frequencies of divergent mtDNA types not found in surrounding agricultural groups, suggesting long-term isolation and small population sizes. We report here genetic evidence concerning the origins of the Mlabri, an enigmatic hunter–gatherer group from northern Thailand. The Mlabri have no mtDNA diversity, and the genetic diversity at Y-chromosome and autosomal loci are also extraordinarily reduced in the Mlabri. Genetic, linguistic, and cultural data all suggest that the Mlabri were recently founded, 500–800 y ago, from a very small number of individuals. Moreover, the Mlabri appear to have originated from an agricultural group and then adopted a hunting–gathering subsistence mode. This example of cultural reversion from agriculture to a hunting–gathering lifestyle indicates that contemporary hunter–gatherer groups do not necessarily reflect a pre-agricultural lifestyle.

Genes, language and culture reveal that the Mlabri reverted from an agricultural to a hunter-gatherer lifestyle, suggesting that hunter-gatherer groups might not always represent the pre- agricultural lifestyle of humans

The p53 codon 72 polymorphism in Thai nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a serious cancer in Thailand. To address on the genetic risk factor for NPC, we investigated association between the p53 codon 72 polymorphism (Pro/Arg) and NPC susceptibility in the Thai. The genotype frequency of this polymorphism in 102 NPC patients and 148 age-matched healthy controls was determined by using a PCR-RFLP assay. No statistically significant difference in the overall genotype frequencies or allele frequencies between cases and controls was observed. Among NPC patients, no statistical significant difference in p53 genotype frequencies between sex, histological types and clinical stages was observed. When cases and controls were categorized into 3 groups of age, >40, >45 and >50 years, the frequencies of p53 genotype in the cases were significantly different from those of the controls (P<0.05). The p53 Pro homozygotes with age of >40 years had twofold to threefold higher risk to develop NPC and the risk was increased with age (Odds Ratio (OR) increased from 2.01 to 2.63 by age >40 to >50 years). Individuals of age >40, >45 and >50 years with an Arg/Arg genotype and of age >45 and >50 years with combined Arg/Arg or Arg/Pro genotype had lower risk to develop NPC than those with Pro/Pro genotype (P<0.05). Collectively, we suggest that the p53 gene polymorphism may associate with NPC susceptibility in Thai population, particularly the Pro/Pro genotype carriers with age of >40 years. The detection of this p53 polymorphism may be a useful tool for screening of early stage and diagnosis of NPC.

Significance of plasma IgA and IgG antibodies to Epstein-Barr virus early and viral capsid antigens in Thai nasopharyngeal carcinoma

Epstein-Barr virus (EBV) is an important causal factor of human nasopharyngeal carcinoma (NPC). High levels of serum IgA and IgG antibodies to EBV early and viral capsid antigens (IgA/EA, IgA/VCA, IgG/EA and IgG/VCA) have been reported in NPC patients. Since specific serum IgA/EA, IgA/VCA and IgG/EA are claimed to be useful serological markers for NPC. In order to evaluate whether plasma IgA/EA, IgA/VCA, IgG/EA and IgG/VCA antibody levels are useful markers for diagnosis and prognosis of Thai NPC, we examined the prevalence of these antibodies in 79 NPC patients, and 127 age-matched controls (47 healthy subjects (HS), 32 cases of other disease (OD) and 48 cases of other cancer (OC)) by using an indirect immunofluorescence assay. The prevalence of plasma IgA/EA, IgA/VCA, and IgG/EA in NPC patients (55.7, 68.4 and 68.4%) was significantly higher than in the HS (0.0, 0.0 and 20.5%,), OD (0.0, 0.0 and 3.1%) and OC (0.0, 0.0 and 20.8%) groups (p<0.05). The prevalence of plasma IgG/VCA in NPC patients (93.7%) was significantly different from those for the OD and OC groups (71.9 and 43.8%) but not for the HS group (89.4%). In NPC patients, the geometric mean titers (GMT) of plasma IgA/EA, IgA/VCA and IgG/EA were increased with an advanced clinical stage of disease but not IgG/VCA. In contrast, GMT of IgG/VCA was increased with aggressive type of disease (histological type) but not IgA/EA, IgA/VCA, and IgG/VCA. The results of our study suggest that plasma IgA/EA, IgA/VCA and IgG/EA antibodies may be useful markers for diagnosis and assessing prognosis of Thai NPC.

Anthropological implication of the SDF1-3'A allele distribution in Southeast Asia and Melanesia

The distribution of the SDF1-3'A allele among 1848 individuals in Southeast Asia and Melanesia was studied with the polymerase chain reaction-restriction fragment length polymorphism assay. The SDF1-3'A allele frequency in the populations of mainland Southeast Asia ranged from 0.0 to 0.355, whereas in the populations of insular Southeast Asia and Melanesia, it ranged from 0.233 to 0.733, with an increasing cline from west to east. Correlation between SDF1-3'A frequency and longitude values was highly significant for the populations in the Pacific region (r = 0.867, P < 0.001). The geographic distribution of the SDF1-3'A frequencies in the Pacific region was interpreted by an admixture of Austronesians with the aboriginal people in situ. In addition, this study found high proportions of SDF1-3'A/3'A homozygous individuals in several populations, which will enable us to evaluate roles of the SDF1 genotypes in SDF-1 expression.

Prevalence of hepatitis B and C virus infection in rural ethnic populations of Northern Thailand

BACKGROUND

In Thailand, the population is composed of multiethnic stocks. However, many epidemiological studies on HBV and HCV have focused on blood donors with Thai and/or Chinese ethnic background. Available information on HBV and HCV infections among ethnic minorities in Thailand is limited.

OBJECTIVE

So as to contribute to the local public health planning, we have conducted an ethno-epidemiological survey for the HBV and HCV infections among several minorities in a multiethnic center, Northern Thailand.

STUDY DESIGN

A total of 658 individuals from seven ethnic groups, Lahu, Lisu, Shan, Red Karen, White Karen, Hmong and Akha, living in northern Thailand were studied for the prevalence of HBV and HCV infections by the use of particle agglutination tests.

RESULTS

An overall prevalence of HBs-Ag, anti-HBs and anti-HCV in the seven groups was 10.3, 33.0 and 3.8%, respectively. The positivity rate of HBV and HCV infection in each tribe ranged 4.7% (Akha)-22.6% (Lahu) and 2.0% (Hmong and Akha)-8.1% (Shan), respectively. Sexual difference in the prevalence of HBV was not observed, whereas the prevalence of HCV was significantly higher in the males (P<0.05). The prevalence of HBV was significantly different (P<0.005) by the groups but that of HCV was not.

CONCLUSIONS

The prevalence of HBV and HCV infection in Thai ethnic minorities was investigated. We demonstrated that HBV was a more common infectious agent found in this populations than HCV. The prevalence of HBV infection was different by tribe but not by sex. In contrast, the prevalence of HCV infection was not different by tribe but by sex (males were infected more than females). The present study showed that HBV and HCV infection are widely spread in rural ethnic populations of northern Thailand. Thus, a nation wide but community-base epidemiological survey is required for the public health planning to control their related serious diseases.

Human T-lymphotropic retrovirus type-1 in Thailand

Seroprevalence of antibodies to human T-lymphotropic virus type-1 (HTLV-1) was surveyed among the Thai population by the particle agglutination test and Western blotting test. None of a total of 727 individuals from seven ethnic groups were positive for the specific antibody to HTLV-1. Among hospital based 3,427 subjects in Southern Thailand, one patient with a brain tumor showed positivity in the Western blotting test, however, HTLV-1 proviral genome was not identified by PCR. The present data suggest that HTLV-1 is not endemic in the Thai population and that HTLV-1 is not a major public health problem in Thailand because HTLV-1 rarely causes its associated diseases.

Human mtDNA and Y-chromosome variation is correlated with matrilocal versus patrilocal residence

Genetic differences among human populations are usually larger for the Y chromosome than for mtDNA. One possible explanation is the higher rate of female versus male migration due to the widespread phenomenon of patrilocality, in which the woman moves to her mate's residence after marriage. To test this hypothesis, we compare mtDNA and Y-chromosome variation in three matrilocal (in which the man moves to his mate's residence after marriage) and three patrilocal groups among the hill tribes of northern Thailand. Genetic diversity in these groups shows a striking correlation with residence pattern, supporting the role of sex-specific migration in influencing human genetic variation.

Enhancing effects of Thai edible plants on 2-amino-3, 8-dimethylimidazo(4,5-f)quinoxaline-hepatocarcinogenesis in a rat medium-term bioassay

Boesenbergia pandurata (Zingiberaceae), Languas galanga (Zingiberaceae) and Citrus hystrix (Rutaceae) are edible plants that are commonly used as flavors or condiments in various Thai food dishes. They are known to exert strong anti-promoting activity in a test of tumor promoter-induced Epstein-Barr virus (EBV) activation. In the present study their effects on hepatocarcinogenesis were investigated in a medium-term bioassay using F344 male rats. C. hystrix significantly enhanced 2-amino-3,8-dimethylimidazo(4, 5-f)quinoxaline-associated preneoplastic liver cell focus development while B. pandurata and L. galanga had borderline effects. The results suggest that C. hystrix as well as B. pandurata and L. galanga may contain agents augmenting the hepatocarcinogenicity of 2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline.

Sero- and molecular typing of Duffy blood group in Southeast Asians and Oceanians

Duffy blood group was studied among malaria-endemic Thai and Indonesian populations: Hmong (n = 103), Akha (n = 218), Lisu (n = 44), Bugis (n = 95), Toraja (n = 77), Dani (n = 44), Mee (n = 80) and Irianese (n = 81). Phenotypes were studied by the ordinal indirect Coombs' test and genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) test. DNA analysis was used to type the Duffy blood group system. Deduced allele frequencies of Fya (0.958-1.0) based on the phenotypes were similar to those in other populations in Southeast Asia and Oceania. The study revealed the presence of Fya-antigens showing weak reactivity to antisera as well as a discrepancy between the genotype shown by the PCR-RFLP study and that predicted by the phenotype. The PCR-RFLP study also suggested the presence of an alternative genetic basis for the Fy(a- b-) phenotype, which differs from the African type.

Twenty-seven base pair deletion in erythrocyte band 3 protein gene responsible for Southeast Asian ovalocytosis is not common among Southeast Asians

Screening for a 27-bp deletion in the band 3 protein gene that causes Southeast Asian/Melanesian ovalocytosis (SAO) was carried out using the PCR method among 15 Southeast Asian populations of Thailand (Akha, Hmong, Isaan, Red Karen, White Karen, Black Lahu, Lisu, Manni, Shan, and central Thais) and Indonesia (Bugis, Dayak, Javanese, Madurian, and Toraja). Individuals with the 27-bp deletion were identified only in the Bugis of southern Sulawesi, the Dayak of southern Borneo, and Javanese of central Java. The gene frequency of the 27-bp deletion in the general population was rather low: 0.012 and 0.013 in the Dayak and the Bugis, respectively. This restricted ethnic and geographic distribution of the 27-bp deletion suggests (1) local differentiation in the prevalence of this deletion in a given ethnic group and (2) the presence of molecular heterogeneity of SAO.

Modulation of dihydroxy-di-n-propylnitrosamine-induced liver lesion development in Opisthorchis-infected Syrian hamsters by praziquantel treatment in association with butylated hydroxyanisole or dehydroepiandrosterone administration

The effects of praziquantel coupled with dehydroepiandrosterone (DHEA) or butylated hydroxyanisole (BHA) administration 16 weeks subsequent to dihydroxy-di-n-propylnitrosamine (DHPN) treatment and infection with Opisthorchis viverrini (OV) on lesion development in the liver of Syrian hamsters were investigated. Animals were given 80 OV metacercariae and then two i.p. injections of DHPN (500 mg/kg body weight) 4 and 5 weeks thereafter. At week 16, groups received praziquantel (250 mg/kg, i.g.) and were placed on normal diet or diet supplemented with BHA (1%) or DHEA (0.6%) until they were killed at week 24. Histopathological assessment revealed that, whereas antihelminthic treatment alone resulted in a clear reduction in hepatocellular lesion development, effects on cholangiocellular lesions were equivocal. BHA and DHEA, in contrast, were both associated with a significant reduction in frequency of cholangiofibrosis and cholangiocellular carcinoma. The former chemical, however, increased the numbers of liver nodules while the hormone brought about a decrease as well as a shift in the phenotype of the lesions. The results thus indicate that although cholangiocellular lesion development may, unlike generation of hepatocellular nodules, be to a certain extent independent of the continued presence of parasite, it can be influenced by exogenous treatments.

Modification of the carcinogenic potency of quinoline, a hepatocarcinogen, by fluorine atom substitution: evaluation of carcinogenicity by a medium-term assay

The potent mutagen, 5-fluoroquinoline (5-FQ), and non-mutagenic 3-fluoroquinoline (3-FQ) were tested for hepatocarcinogenicity using a medium-term assay system employing quinoline, a moderately mutagenic hepatocarcinogen, as a reference. F344 male rats were given a single i.p. injection of a submanifestational dose of diethylnitrosamine (DEN, 200 mg/kg). Then, quinoline, 3-FQ, or 5-FQ at two doses (0.1%, and 0.05%) was added to their diet for a period of 6 weeks, starting from 2 weeks after the DEN injection. Control groups were administered DEN alone. All rats were subjected to a partial (two-thirds) hepatectomy at the end of week 3 and sacrificed at the end of week 8. The number and areas of GST-P (placental glutathione S-transferase)-positive foci induced in the liver increased significantly as a result of treatment with 0.1% quinoline, and this increase was dramatic with 5-FQ at both doses, whereas no increases were noted with 3-FQ at either dose. Thus, the results of the medium-term carcinogenicity assay predicted that quinoline, a hepatocarcinogen, would be deprived of carcinogenicity by fluorine atom substitution at position 3, and would conversely be endowed with a higher carcinogenic capacity by substitution at position 5. A semi-quantitative relationship was demonstrated between carcinogenic and mutagenic potencies.

Equivocal evidence of complete carcinogenicity after repeated infection of Syrian hamsters with Opisthorchis viverrini

The effects of repeated infection with Opisthorchis viverrini on liver lesion development in male and female Syrian hamsters were investigated over a 1-yr period. Ten monthly intragastric applications of 50, 25, 13, or 0 parasite metacercariae resulted in pronounced proliferative and inflammatory lesions involving the first- and second-order ducts in response to the presence of adult worms. Despite the development of small numbers of putative preneoplastic areas of cholangiofibrosis and morphologically altered hepatocellular foci, no neoplastic lesions were evident at sacrifice after 1 yr. The results thus suggest that parasite infestation is itself not strongly carcinogenic if at all but, rather, that it exerts a marked promoting influence on cholangiocellular and hepatocellular tumor development in the hamster via chronic irritation and increased cell turnover.

Association of antibodies to Opisthorchis viverrini with hepatobiliary disease in northeastern Thailand

The association between Opisthorchis viverrini infection and hepatobiliary disease was studied in northeastern Thailand. Positive rates of O. viverrini infection and antibody titers to O. viverrini adult worm extracts, which were determined by enzyme-linked immunosorbent assay (ELISA), were compared among four groups: Thai patients with cholangiocarcinomas (CHCA), those with calculus cholecystitis (CCLT), endemic area victims of traffic accidents, and Japanese individuals used as negative controls. While no difference was observed between cases with CCLT and the accident victims, the CHCA group showed a significantly higher positivity rate for fluke infection and higher antibody titers than the other groups. Comparison of the positivity rates and ELISA titers among intrahepatic and extrahepatic CHCA subgroups showed that only females with intrahepatic tumors had a low positive rate and significantly lower titers, with no other significant variation being evident. From these observations, a strong association between high intensity of past and/or present O. viverrini infection and the genesis of CHCAs was apparent in the majority of cases. However, in addition to the fluke infection, other unknown exogenous or endogenous factor(s) were suggested in the female cases.

Strong promoting effect of Opisthorchis viverrini infection on dimethylnitrosamine-initiated hamster liver

Continuous administration of dimethylnitrosamine (DMN) to Syrian hamsters infected with the liver fluke, Opisthorchis viverrini (OV) results in a 100% incidence of cholangiocellular carcinomas. In a two-stage experiment, however, dosing with liver flukes caused only a few lesions to develop (Flavel, D.J. and Lucus, S.B. (1983) Carcinogenesis, 4, 927]. To clarify this anomaly, Syrian hamsters were initiated with 20 mg/kg DMN injected i.p. 19 days prior to 80 OV metacercaria infection. At 45 weeks, the animals receiving both DMN and the parasite demonstrated a 44% incidence of cholangiocarcinomas, a 93% incidence of cholangiofibrosis, a 35% incidence of mucous cystadenomas and a 98% incidence of hepatocellular nodules with an average number of 9.1 +/- 4.1 per animal. Animals receiving DMN alone developed 85% hepatocellular nodules with an average number of only 3.0 +/- 2.7 and no bile duct lesions. In the parasite alone group, only cholangiofibrosis was detected in a few animals and no lesions were encountered in untreated controls. These results thus demonstrate that the post-initiation influence of Opisthorchiasis is indeed effective in promoting the development of both cholangiolar and hepatocellular lesions initiated by DMN.

Lack of promoting effect of proline on bile duct cancer development in dimethylnitrosamine-initiated hamster livers

Bile duct hyperplasia caused by proline is believed to represent a chemical effect of the liver fluke, Fasciola hepatica, and the resultant cell division might be expected to play a role as a tumor promoter. To investigate the potential promoting effect of proline on bile duct cancer development, Syrian hamsters were therefore divided into 8 treatment groups: dimethylnitrosamine (DMN) + proline intraperitoneally (i.p.); DMN + proline s.c.; DMN + saline i.p.; DMN + saline s.c.; proline i.p.; proline s.c.; saline i.p.; and saline s.c. DMN was injected i.p. at 20 mg/kg to the animals 2 weeks prior to commencement of proline treatment, whereby 1 ml of a 2 M solution was given by i.p. or s.c. injection 3 times a week for 20 weeks. At the end of week 42, assessment of preneoplastic lesion development did not reveal any significant modulating influence of proline on DMN-initiated lesion development nor did it itself cause persistent bile duct hyperplasia.

Number of simultaneously expressed enzyme alterations correlates with progression of N-ethyl-N-hydroxyethylnitrosamine-induced hepatocarcinogenesis in rats

Preneoplastic and neoplastic liver cell lesions, induced by EHEN (N-ethyl-N-hydroxyethylnitrosamine) in rats, were investigated to establish the numbers of simultaneously expressed altered enzyme phenotypes within the lesion cells. The lesions were divided into 5 classes on the basis of altered expression in one or more of the following 5 enzymes: glutathione S-transferase placental form, glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, adenosine triphosphatase, and gamma-glutamyl transpeptidase. Class 1 lesions contained cells expressing one altered enzyme. Similarly, class 2, 3, 4 and 5 lesions had cells simultaneously expressing 2, 3, 4, and 5 enzyme alterations, respectively. Four histopathological categories of lesions, ACF (altered cell foci) (274 lesions), HN (hyperplastic nodules) (47 lesions), HCC (hepatocellular carcinomas) (99 lesions) and THC (transplanted hepatocellular carcinomas) (5 lesions) were studied. Proliferation potential was assessed in terms of 5-bromo-2'-deoxyuridine (BrdU) incorporation. The distribution profiles of classes 1 to 5 showed a clear reciprocal change from low class (1 to 2 enzymes) predominance in ACF to high class (4 to 5 enzymes) predominance in HN. Increase of BrdU labeling indices was clearly correlated with progression from HN to HCC. Only a small population of class 5 ACF showed a high BrdU labeling index, indicating particular potential for further development. Thus, the stages of EHEN-induced neoplasia were found to be characterized by gradual increase in the number of altered enzyme phenotypes, with acquisition of proliferative potential being associated with further progression towards malignant conversion.

Promotion of cholangiocarcinogenesis in the hamster liver by bile duct ligation after dimethylnitrosamine initiation

Administration of hepatocarcinogenic nitrosamines before or after infection with the liver fluke, Opisthorchis viverrini (OV), results in marked development of cholangiocellular and hepatocellular precancerous and cancerous lesions in the hamster liver. The promoting effects of OV are believed to be exerted either mechanically, chemically or immunologically. To test the influence of possible mechanical effects, Syrian hamsters were initiated with a single i.p. injection of dimethylnitrosamine (DMN) 20 mg/kg and subjected 2 weeks later either to a sham operation or to complete ligation of the extrahepatic bile duct to the left lateral lobe. At the end of week 40, the animals receiving DMN-initiation and ligation had a 60.9% incidence of cholangiofibrosis, 21.7% of mucous cystadenomas and 39.1% of cholangiocarcinomas, whereas the group given DMN alone only developed cholangiofibrosis, limited to 5% of the animals. In the latter case neither cystadenomas nor cholangiocarcinomas were observed. The incidence of hepatocellular nodules did not differ between the two groups and no tumorous lesions developed in either the ligated or the untreated groups without DMN pretreatment. Complete ligation of the bile duct itself led to a series of events; obstruction of bile flow being followed by dilatation, cyst formation, and necrosis of the bile duct epithelium and surrounding affected areas leading to regenerative proliferation. The results are in line with the conclusion that parasite-associated proliferation in target cell populations is, at least in part, responsible for the influence of OV on liver tumor development.

Modifying influence of prior treatment with toxic agents on induction of preneoplastic and neoplastic lesions in a medium-term multi-organ carcinogenesis bioassay

The modifying potential of prior administration of toxic agents was investigated in our multi-organ carcinogenesis model using male F344/DuCrj rats with the aim of assessing the link between tissue damage and initiation. Animals were administered one of four toxic agents for 8 wk, and then treated with N-diethylnitrosamine (DEN, 100 mg/kg body weight (b.w.), intraperitoneally (i.p.), single injection), N-methylnitrosourea (MNU, 20 mg/kg b.w., i.p., four times during wk 9 and 10), and dihydroxy-di-N-propylnitrosamine (DHPN, 0.1% in drinking water, during wk 11 and 12) for multi-organ carcinogenesis. All surviving rats were killed at the end of wk 36, and the major organs carefully examined for preneoplastic and neoplastic lesion development. Immunohistochemical demonstration of glutathione S-transferase placental form (GST-P) positive foci was also performed to facilitate quantitative assessment of liver lesion development. D-galactosamine (300 mg/kg b.w., i.p., once a week), a hepatotoxin, significantly inhibited the induction of GST-P positive foci, while 4,4'-diaminodiphenylmethane (DDPM, 0.1% in diet), a bile duct proliferator which is itself a hepatocarcinogen, possessed enhancing activity. DDPM, also a goitrogen, clearly inhibited the development of follicular cell tumors in the thyroid. Uracil (3.0% in diet), which is an inducer of papillomatosis in the urinary bladder, did not exert any enhancing potential on bladder carcinogenesis. Bleomycin (2 mg/kg b.w., i.p., twice a week), which is an alveolar epithelium injuring agent, also did not modify the induction of alveolar epithelium proliferative lesions. These results indicate that prior organ injury by toxic agents does not always act to enhance sensitivity to carcinogenesis.

Suppression of diethylnitrosamine-initiated preneoplastic foci development in the rat liver by combined administration of four antioxidants at low doses

Potential synergism between 4 antioxidants acting at low doses on development of glutathione S-transferase placental form (GST-P)-positive liver cell foci was examined in male rats initially given diethylnitrosamine (200 mg/kg, i.p.). Beginning 2 weeks after the initiation, rats received the antioxidants, individually or in combination, in the diet for 6 weeks. All rats were subjected to two-thirds partial hepatectomy at week 3 and killed at week 8. The numbers and areas of GST-P-positive foci were significantly decreased by single treatment with butylated hydroxyanisole (BHA, 1%), tert-butylhydroquinone (TBHQ, 1%) and catechol (0.8%), but not with sesamol (0.5%). Combined treatments (BHA + TBHQ, catechol + sesamol, or all 4 chemicals) at a quarter of the above dose levels resulted in decrease in numbers and areas of foci to levels less than the sums of individual inhibition data obtained with the one-quarter levels. Although these combined effects were not statistically significant in the additive model, the results indicate possible synergistic suppression of carcinogenesis by low-dose combined treatment with anti-cancer agents and the usefulness of the present protocol for this type of analysis.

Oral toxicity study of tragacanth gum in B6C3F1 mice: development of squamous-cell hyperplasia in the forestomach and its reversibility

Tragacanth gum was administered at dietary levels of 0 (control), 0.625, 1.25, 2.5, and 5.0% to groups of 10 male and 10 female B6C3F1 mice for 13 wk. There were no treatment-associated effects regarding clinical signs, body or organ weights, and urinalysis or hematology data. Significant dose-related, but slight, elevations of plasma gamma-glutamyl transpeptidase (GGT) level were observed in all treated animals except the 0.625% females. Single or small numbers of tiny nodules were observed on the luminal surface of the forestomach in 4 males of the 5.0% group, 2 males of the 2.5% group, and 1 male each from the 1.25 and 0.625% groups. Histopathologically, they were diagnosed as squamous-cell hyperplasia. To investigate the nature of these gross lesions, tragacanth gum was fed to groups of 30 male mice at the dietary level of 5.0% for periods of up to 48 wk; 20 males served as controls. There were no treatment-related increases of plasma GGT levels at wk 24 and 48. Although squamous-cell hyperplasias were seen in 2 out of 10 mice at wk 24, none of these proliferative lesions were apparent at wk 48, after either chronic exposure or 24 wk on basal diet. Furthermore, the levels of DNA synthesis in forestomach epithelium as measured by 5-bromo-2-deoxyuridine (BrdU) immunohistochemistry were comparable to control values at wk 24 and 48. Thus, the oral toxicity of tragacanth gum to B6C3F1 mice was concluded to be negligible.

Dose-dependent effects of 2-acetylaminofluorene on hepatic foci development and cell proliferation in rats

Dose-dependent development of pre-neoplastic liver cell foci induced by 2-acetylaminofluorene (2-AAF) was investigated in relation to cell-proliferative activity. Male F344 rats were initially given a single i.p. injection of diethylnitrosamine (DEN, 200 mg/kg) and starting 2 weeks later received diets containing 2-AAF at dose levels of 150, 100, 60, 45, 35 or 30 p.p.m., 500 p.p.m. phenobarbital (PB) or basal diet as a control for 6 weeks. Two-thirds partial hepatectomy (PH) was performed at week 3. The rats were sequentially killed from weeks 0 to 16 and liver sections were analysed by double staining for both BrdU incorporation and glutathione S-transferase placental form (GST-P) expression. 2-AAF increased numbers and areas of GST-P positive (GST-P+) foci in a dose-dependent manner, especially after PH. Proliferation of hepatocytes, as indicated by BrdU labelling indices (LI), was higher in GST-P+ foci than in surrounding hepatocytes in all 2-AAF-treated groups, even after cessation of carcinogen administration. Proliferative response of hepatocytes to PH was delayed in rats treated with the highest dose of 2-AAF in both foci and in surrounding areas possibly due to the 2-AAF toxicity. In the PB treated group, the results were similar to those for the lower dose 2-AAF-treated groups. It is concluded that the development of GST-P+ foci and cell proliferation in GST-P+ foci are directly related to 2-AAF treatment in a dose-dependent manner and the present assay system is reliable for detection of carcinogenicity of chemicals even at low doses.

Modifying effects of various chemicals on preneoplastic and neoplastic lesion development in a wide-spectrum organ carcinogenesis model using F344 rats

Modifying potentials of various chemicals on tumor development were investigated in a wide-spectrum organ carcinogenesis model using male F344/DuCrj rats. The animals were treated with N-nitrosodiethylamine (100 mg/kg body weight, ip, single injection at the commencement of the study), N-methyl-N-nitrosourea (20 mg/kg body weight, ip, 4 times during weeks 1 and 2) and N-bis(2-hydroxypropyl)nitrosamine (0.1% in drinking water, during weeks 3 and 4) for multi-organ initiation and then were given one of 14 test chemicals including 6 hepatocarcinogens, 7 non-hepatocarcinogens and 1 non-carcinogen, or basal diet for 16 weeks. All rats were killed at the end of week 20, and the major organs were carefully examined for preneoplastic and neoplastic lesions. Immunohistochemical demonstration of glutathione S-transferase-positive foci was also used for quantitative assessment of liver preneoplastic lesion development. Modifying effects were shown for 11 out of 14 test agents in the liver, forestomach, glandular stomach, lung, urinary bladder or thyroid, 7 of them targeting more than two organs. This was the first demonstration to our knowledge that clofibrate possesses enhancing potential for urinary bladder carcinogenesis and an inhibiting effect on thyroid carcinogenesis. Caprolactam showed no effect in any organ, in agreement with its established inactivity. The results indicated that the system could be reliably applied as a medium-term multiple organ bioassay for assessment of the modification potential of test agents in unknown target sites.

Level of Opisthorchis infestation and carcinogen dose-dependence of cholangiocarcinoma induction in Syrian golden hamsters

The relationship between different levels of liver fluke, Opisthorchis viverrini infestation and dimethylnitrosamine (DMN) dosage in the induction of cholangiocarcinomas was investigated in Syrian golden hamsters. Two hundred and eighty male, weanling animals were divided into 4 groups: Group 1 served as untreated controls; group 2 received O. viverrini metacercariae only at levels of 100, 50, 25 or 12 per animal; group 3 received DMN only at doses of 12.5, 6.25 or 3.125 ppm; group 4 received various combinations of metacercariae and DMN. Only 2 of 17 animals (12%) in group 3 receiving 12.5 ppm had detectable tumours and no neoplastic lesions were seen in the 6.25 and 3.125 ppm DMN subgroups or in parasite alone or untreated control hamsters. In contrast, high carcinogen and parasite dose-dependent yields of cholangiocarcinomas (incidences up to 93%) and putative preneoplastic cholangiofibrotic lesions were observed in group 4. Thus the results indicate clear dose-dependent synergistic effects for the two agents and reveal the crucial importance of the presence of parasite, even at levels as low as 12 metacercariae, for DMN induction of bile duct carcinogenesis.

Enzyme-linked immunosorbent assay for detection of Opisthorchis viverrini infection

Antibodies to O. viverrini in the sera of people from endemic and non-endemic areas were investigated using indirect ELISA technique. For the patients from the endemic area, 92.8% who passed eggs in the stool were found to be positive for O. viverrini antibody. In addition, 46.5% of the people who did not pass eggs in the stool were also found to have low titer of O. viverrini antibody. On the other hand only 2.4% of the people from the non-endemic area with other intestinal parasite infections were found to have O. viverrini antibody in their sera. It was concluded that positive reaction of O. viverrini antibody is not cause by cross-reaction with other parasites but low liter of antibody is probably due to low-level or past infection. There is a positive correlation between the titer of O. viverrini antibody and intensity of infection as indicated by number of eggs excreted per milligram of feces. Patients with a few O. viverrini eggs in feces, but biopsy-proved-cholangiocarcinoma had very high titer of antibody.