ACTN3 genotype and swimming performance in Taiwan.

Studies have shown that the 577R allele of α-actinin-3 (ACTN3) is more prevalent in sprint athletes than in the general population or in endurance athletes. We examined the distribution of ACTN3 R577X (rs 1815739) genotypes and alleles in the Taiwanese general population (603) and in elite sprint swimmers who had participated in international/national events (168). Additionally, 50 pre-adolescent (age 11-13 years) male students and 38 adult males who completed 12-weeks of swimming training, were included in the present study. We found that the frequencies of the R allele were significantly higher in female international sprint swimmers (67.6%) than in national sprint swimmers (50.0%) or in the general population (53.7%). The 25-m performance was significantly improved across the genotypes after swimming training among the pre-adolescent males but not among the adult males. In addition, pre-adolescents with the RR genotype had the best performance both before and after training although not statistically significant. In conclusion, the frequencies of ACTN3 577R allele were significantly higher in female international sprint swimmers than among national sprint swimmers or the general population. Furthermore, male pre-adolescents with either the ACTN3 RX or XX genotype showed a greater improvement in 25-meter swimming performance than those with the RR genotype.

Germ line MLH1 and MSH2 mutations in Taiwanese Lynch syndrome families: characterization of a founder genomic mutation in the MLH1 gene.

This multicenter study evaluated the mutation spectrum and frequencies of the MLH1 and MSH2 genes and determined the occurrence of large genomic deletions in 93 unrelated Taiwanese families that fulfilled the Amsterdam criteria II by denaturing high-performance liquid chromatography analysis, DNA sequencing for aberrant chromatograms, and multiplex ligation-dependent probe amplification analysis. In total, 38 pathogenic mutations (10 large deletions and 28 point mutations or small deletion/insertions) in the MSH2 or MLH1 gene were identified in 61 of the 93 families (66%). Three of the 10 large deletions and 14 of the 28 point mutations or small insertions/deletions have not been reported elsewhere. Three mutations in the MLH1 gene, the MLH1c.1846_1848delAAG (5 families), deletion exons 11-15 (4 unrelated families), and MLH1c.793C>T (13 unrelated families), accounted for 35% of all cases with pathogenic mutations. Haplotype analysis indicated that mutant c.793C>T alleles were derived from two distinct common founders that might be inherited from a single ancestor of presumably Chinese origin. As a mutation detection strategy for Taiwanese Lynch syndrome patients, we recommend that diagnosis starts with screening for large genomic deletions and continues by screening for common mutations in exons 10 and 16 of the MLH1 gene prior to searching for small mutations in the remaining exons.

Detection of aflatoxin B1-DNA adducts in human placenta and cord blood.

Human placenta and cord blood are readily available specimens that respond to maternal environmental insult and are being used to investigate metabolism, bioactivation, and transplacental transfer of procarcinogens. Enzyme-linked immunosorbent assay was used to quantitate 120 placentas and 56 cord bloods from term, uncomplicated pregnancies at Taipei Chang Gung Memorial Hospital, Taiwan, for the presence of the imidazole ring-opened form of aflatoxin B1-DNA (AFB1-DNA) adducts. Of the 120 samples of placentas, 69 (57.5%) contained AFB1-DNA adducts in levels from 0.6 to 6.3 mumol/mol DNA. Of the 56 samples of cord bloods, 5 (8.9%) contained AFB1-DNA adducts in levels from 1.4 to 2.7 mumol/mol DNA. A higher positive rate was found in samples collected in the summer than in the winter. These results indicate that a significant number of individuals in an area of high liver cancer risk have been exposed to AFB1, and it is possible to transfer AFB1 and its metabolites to the progeny through the transplacental unit. Thus, monitoring adduct levels in human specimens may provide information not only on carcinogen exposure but also on the relationship among infection with hepatitis B/C virus, dietary exposure to AFB1, and liver cancer.

Expression of endogenous retrovirus-like sequences and cellular oncogenes during phenobarbital treatment and regeneration in rat liver.

The expression of two cellular oncogenes (c-myc and c-Ha-ras), the epidermal growth factor receptor gene, and two endogenous retrovirus-like sequences (rat leukemia virus and 30S) was examined in control (nonregenerating) rat livers and at various times after partial hepatectomy. One group of rats had been fed phenobarbital (0.05%) for 16 days prior to the partial hepatectomy. The feeding of phenobarbital (0.05%) itself led to a 65% decrease in the level of epidermal growth factor receptor RNA, but no major change in the level of c-myc, H-ras, rat leukemia virus, or 30S RNAs, in the control rat livers. There was a considerable increase (4- to 5-fold) in the level of c-myc transcripts, at 12 and 48 h after partial hepatectomy in the phenobarbital-treated rats, and at 12 and 24 h in the rats on the control diet. By 72 h, the level of c-myc transcripts returned to normal in both groups of rats. A slight increase (about 1.5-fold) in the level of c-H-ras transcripts was seen at 24 h, which returned to normal levels by 168 h, in the regenerating livers of both the phenobarbital-treated and control diet rats. The regenerating livers displayed a marked decrease (3- to 4-fold) in the level of epidermal growth factor receptor RNA in both the phenobarbital and control diet rats. A marked increase (5- to 6-fold) in the level of transcripts homologous to the endogenous rat leukemia virus-like sequence was seen at 24 h in all of the regenerating livers, but there was no significant change in the level of RNAs homologous to 30S. Thus, the proliferation of normal rat liver cells mimics some but not all of the changes in mRNA levels that we have previously described in rat liver tumors.

Altered expression of retrovirus-like sequences and cellular oncogenes in mice fed methyl-deficient diets.

Methyl-deficient (lipotrope-deficient) diets enhance liver carcinogenesis in rodents. Although the mechanisms responsible for the cancer-promoting activity of such diets have not been identified, they have been observed to cause impaired immune response, alterations in methylation of liver RNA and DNA, and enhanced susceptibility to oxidative damage. Since alterations in gene expression may also play a critical role, the present studies examined the expression of the c-myc, c-H-ras, epidermal growth factor receptor, and ornithine decarboxylase genes, as well as endogenous retrovirus-like sequences, in C57BL/6J x C3H/HeJ F1 mouse liver during the first 2 weeks of feeding of a methyl-deficient diet. The kinetics of liver cell proliferation was investigated in parallel. Increased [3H]thymidine incorporation into liver DNA was found at day 4 and reached a maximum at days 7-11 after commencement of the methyl-deficient diet, when compared to age-matched mice fed a complete diet. Northern blot analysis of polyadenylated liver RNA samples indicated an increase in the levels of RNA homologous to Moloney murine leukemia virus and intracisternal A particle sequences but no significant change in the level of VL30 retrovirus-related RNA in the samples from mice fed methyl-deficient diets. A marked increase in the levels of c-myc and a slight increase in the levels of ornithine decarboxylase and c-H-ras transcripts were seen in the liver RNA samples from the treated mice. Of particular interest was a decrease in the abundance of epidermal growth factor receptor transcripts in the liver RNA samples from the treated mice. These changes in cellular levels of specific RNA resemble, in several respects, those we have previously described in rodent liver during regeneration and tumor promotion and also those seen in rodent hepatomas. They may reflect, therefore, a common profile of gene expression relevant to cell proliferation.

Immunological detection of aflatoxin B1-DNA adducts formed in vivo.

Two monoclonal antibodies (6A10 and 12F5) were obtained after fusion of mouse P3X63-AG.8.653 myeloma cells with spleen cells isolated from BALB/c mice immunized with imidazole ring-opened aflatoxin B1 (AFB1)-DNA and characterized by competitive enzyme-linked immunosorbent assays. Both antibodies are highly specific for imidazole ring opened AFB1-DNA and show some cross-reactivity with AFB1-DNA and no cross-reactivity with 8,9-dihydro-8-(7-guanyl)-9-hydroxy-AFB1, AFB1 conjugated with bovine serum albumin, aflatoxin M1 conjugated with bovine serum albumin, AFB1, or aflatoxin G1. Antibody 6A10 was further characterized and showed no cross-reactivity with DNA modified by several other carcinogens. It could detect adducts with 4-fold higher sensitivity in highly modified DNA (2.5 adducts/100 nucleotides) than in low modified DNA (4 adducts/10(5) nucleotides). With low modified DNA the limit of sensitivity is 5 adducts/10(7) nucleotides. Antibody 6A10 reliably detected adducts formed in vivo in rats and mice treated with AFB1. In a pilot study, AFB1 adducts were detected in liver tissues from individuals living in areas with suspected exposure to AFB1. Monitoring adduct levels in human tissue may provide information not only on carcinogen exposure but also on the relationship among infection with hepatitis B virus, dietary exposure to aflatoxin B1, and liver cancer.

Isolation of a complementary DNA encoding the catalytic subunit of protein kinase A and studies on the expression of this sequence in rat hepatomas and regenerating liver.

A complementary DNA (cDNA) clone (B4) encoding the catalytic subunit of a cAMP-dependent protein kinase (PKAc) was isolated from a lambda gt10 rat brain cDNA library, using a synthetic oligonucleotide probe whose sequence was based on the known amino acid sequence of a bovine cardiac PKAc. Sequence analysis of this clone revealed a region of 1002 nucleotides which encodes a protein that is 92% homologous to amino acids 17-350 of the bovine cardiac PKAc protein. This clone lacks coding sequences for amino acids 1-16 of the latter protein. Nevertheless, it provided a useful probe to analyze expression of the related gene in a variety of systems. Northern blot analyses using a 32P-labeled probe prepared from a 0.6-kilobase PstI fragment of clone B4 revealed an abundant 4.6-kilobase band in rat brain RNA and lesser amounts of this 4.6-kilobase RNA in rat heart and liver. A 4.6-kilobase RNA was also detected in RNA samples obtained from mouse fibroblasts. This probe also detected homologous RNA in a variety of nonrodent species. In subsequent experiments, this cDNA was used as a probe to elucidate the role of PKAc in post-surgical hepatic regeneration and diethylnitrosamine-induced hepatomas in the rat. These experiments revealed that, following partial hepatectomy, PKAc mRNA is decreased 3-fold by 12 h, returning to normal by 72 h; hepatomas showed no consistent pattern of change in PKAc mRNA levels as compared to controls. Our results indicate that this cDNA encodes an isoform of PKAc which is distinct from PKAc-alpha isolated by Uhler et al. (Proc. Natl. Acad. Sci. USA, 83: 1300-1304, 1986) but highly homologous to PKAc-beta isolated by Showers and Maurer (J. Biol. Chem., 261: 16288-16291, 1986), that depression of cAMP-dependent protein phosphorylation may be an important mechanism in the regeneration of mature rat liver but is not a consistent alteration in chemically induced hepatoma, and that this cDNA is useful as a probe for the study of the role of PKAc gene expression in growth control, particularly in rodent species.

XRCC1 polymorphisms: effects on aflatoxin B1-DNA adducts and glycophorin A variant frequency.

Hereditary genetic defects in DNA repair lead to increased risk of cancer. Polymorphisms in several DNA repair genes have been identified; however, the impact on repair phenotype has not been elucidated. We explored the relationship between polymorphisms in the DNA repair enzyme, XRCC1 (codons 194, 280, and 399), and genotoxic end points measured in two populations: (a) placental aflatoxin B1 DNA (AFB1-DNA) adducts in a group of Taiwanese maternity subjects (n = 120); and (b) somatic glycophorin A (GPA) variants in erythrocytes from a group of North Carolina smokers and nonsmokers (n = 59). AFB1-DNA adducts were measured by ELISA, and erythrocyte GPA variant frequency (NN and NO) was assessed in MN heterozygotes with a flow cytometric assay. XRCC1 genotypes were identified by PCR-RFLPs. The XRCC1 399Gln allele was significantly associated with higher levels of both AFB1-DNA adducts and GPA NN mutations. Individuals with the 399Gln allele were at risk for detectable adducts (odds ratio, 2.4; 95% confidence interval, 1.1-5.4; P = 0.03). GPA NN variant frequency was significantly higher in 399Gln homozygotes (19.6 x 10(-6)) than in Gln/Arg heterozygotes (11.4 x 10(-6); P < 0.05) or Arg/Arg homozygotes (10.1 x 10(-6); P = 0.01). No significant effects were observed for other XRCC1 polymorphisms. These results suggest that the Arg399Gln amino acid change may alter the phenotype of the XRCC1 protein, resulting in deficient DNA repair.

Expression of retroviral sequences and oncogenes in rat liver tumors induced by diethylnitrosamine.

The expression of three cellular oncogenes (c-myc, c-Ha-ras, and c-delta-raf), the epidermal growth factor receptor gene, and two endogenous retrovirus-like sequences [rat leukemia virus (RaLV) and 30S] was examined in control rat livers and in 16 liver tumors. The tumors were induced in Sprague-Dawley male and female rats by a single i.p. injection of diethylnitrosamine at 1 or 2 days after birth, followed by dietary exposure to phenobarbital beginning at weaning. Increased expression of c-myc was seen in most of the tumors, but there was no consistent increase or decrease in expression of c-Ha-ras or c-delta-raf. It is of interest that a number of the tumor samples showed a decrease in epidermal growth factor receptor RNA. In all of the tumors, including both hepatocellular adenomas and carcinomas, there was a marked increase in expression of the endogenous RaLV sequence, and over 90% of the tumors displayed increased expression of the 30S endogenous retroviral-like sequence. No or a very low level of expression of the RaLV and 30S sequences was found in the control livers. The extent of expression of the RaLV and 30S sequences in individual tumors did not correlate with the extent of expression of c-myc or c-Ha-ras. Although increased expression of certain endogenous retrovirus-related sequences appears to be a common finding during rat liver carcinogenesis, the significance of this finding remains to be determined.

Quantitation of aflatoxin B1-DNA adducts in woodchuck hepatocytes and rat liver tissue by indirect immunofluorescence analysis.

A quantitative indirect immunofluorescence technique was developed utilizing a monoclonal antibody (6A10) recognizing the imidazole ring-opened form of the major N-7 guanine adduct of aflatoxin B1 (AFB1). This method was used to investigate adduct formation in woodchuck hepatocytes treated in culture and in liver tissue of rats treated i.p. with AFB1. Fluorescein isothiocyanate-labeled secondary antiserum was used for adduct localization in conjunction with 4',6-diamidino-2-phenylindole dihydrochloride staining to localize nuclei. Quantitation of AFB1-DNA adducts was carried out by densitometric analysis of photographic slides. Specific nuclear staining was observed in both woodchuck hepatocytes and rat liver tissue. There was a dose-response relationship between fluorescence intensity and AFB1 dose in treated animals. Turnover of adducts could also be followed in animals over 48 h with this method. DNA was isolated from liver tissue of treated animals and adduct levels were quantitated by competitive enzyme-linked immunosorbent assay with antibody 6A10 and by fluorescence spectroscopy. There was a significant correlation of the quantitative immunofluorescence intensity with levels of AFB1 adducts detected by enzyme-linked immunosorbent assay (r = 0.61, P less than 0.05) and spectrofluorescence (r = 0.78, P less than 0.01). This immunohistochemical method should be applicable to the detection of adducts in liver tissues of humans exposed to high levels of dietary AFB1.

The association of human papillomavirus 16/18 infection with lung cancer among nonsmoking Taiwanese women.

Lung cancer is the leading cause of cancer death in Taiwanese women since 1982. High lung cancer mortality ratio of male:female in Taiwan (2:1) was observed, although less than 10% of female lung cancer patients are smokers. Until now, the etiological factor remains unknown. We hypothesize that high-risk human papillomavirus (HPV) 16/18 may be associated with lung cancer development based on high prevalence of p53 negative immunostainings in female lung tumors compared with that of male lung tumors. In this study, 141 lung cancer patients and 60 noncancer control subjects were enrolled to examine whether HPV 16/18 DNA existed in lung tumor and normal tissues by nested PCR and in situ hybridization (ISH), respectively. The concordant detection of HPV 16 and 18 DNA between nested PCR and ISH method was 73 and 85.5%, respectively. Our data showed that 77 (54.6%) of 141 lung tumors had HPV 16/18 DNA compared with 16 (26.7%; P = 0.0005) of 60 noncancer control subjects. In addition, ISH data showed that HPV 16/18 DNA was uniformly located in lung tumor cells, but not in the adjacent nontumor cells. When study subjects were stratified by gender, age, and smoking status, nonsmoking female lung cancer patients who were older than 60 years old had significantly high prevalence of HPV 16/18 infection. The odds ratio of HPV 16/18 infection of nonsmoking female lung cancer patients is much higher at 10.12 (95% confidence interval, 3.88-26.38) compared with 1.98 (95% confidence interval, 0.84-4.76) of nonsmoking male lung cancer patients. This result strongly suggests that HPV infection is associated with lung cancer development of nonsmoking female lung cancer patients. The high prevalence of HPV 16/18 infection may explain to a certain extent why Taiwanese women nonsmokers had a higher lung cancer mortality rate.

Increased chromosome-type chromosome aberration frequencies as biomarkers of cancer risk in a blackfoot endemic area.

To examine whether biomarkers such as sister chromatid exchanges (SCEs) and chromosome aberrations (CAs) can predict cancer development, a nested case-control study was performed in a blackfoot endemic area with a known high cancer risk. A cohort of 686 residents was recruited from three villages in the blackfoot endemic area. Personal characteristics were collected, and venous blood was drawn for lymphocyte culture and stored in a refrigerator. The vital status and cancer development were followed using the National Death Registry, Cancer Registry, and Blackfoot Disease Registry. The follow-up period was from August 1991 to July 1995. During this 4-year period, 31 residents developed various types of cancer. Blood culture samples from nine of these subjects were unsuitable for experiments due to improper storage. Finally, a total of 22 cancer cases had cytogenetic samples that could be analyzed. Twenty-two control subjects were selected from those who did not develop cancer in the study period, and these subjects were matched to cases by sex, age, smoking habits, and residential area. The results showed that there was no significant difference in the frequencies of SCE and chromatid-type CAs between the case and control groups. However, the frequencies of chromosome-type CAs, e.g., chromosome-type gaps, chromosome-type breaks, chromosome-type breaks plus exchanges, total chromosome-type aberrations, and total frequencies of CAs in the case group, were significantly higher than those in the control group (P < 0.05). The odds ratio of cancer risk in subjects with more than zero chromosome-type breaks was 5.0 (95% confidence interval = 1.09-22.82) compared to those with zero chromosomal breaks. The odds ratios for more than zero chromosome-type breaks plus exchanges and a frequency of total chromosome-type aberrations of >1.007% were 11.0 and 12.0, respectively (P < 0.05). Subjects with a total CA frequency of >4.023% had a 9-fold increase for cancer risk. These results indicate that chromosome-type CAs are good biomarkers for the prediction of cancer development, whereas SCEs and chromatid-type CAs cannot predict cancer risk.

Changes in expression of oncogenes and endogenous retroviral-like sequences during colon carcinogenesis.

The possible roles in experimental colon carcinogenesis of two protooncogenes (c-myc and c-H-ras), two endogenous retrovirus-related DNA sequences [rat leukemia virus (RaLV) and the 30S sequence], and two cell cycle related genes (beta-actin and ornithine decarboxylase) were studied by analyzing the levels of their corresponding RNAs during the course of azoxymethane induced and high fat promoted colon carcinogenesis. F-344 male rats received three s.c. injections of azoxymethane (15 mg/kg) or normal saline and were then subdivided into high or low fat diet groups. During subsequent serial sacrifices normal colon mucosa, adenomas, and carcinomas were harvested for histology and RNA extraction. Seventy-one RNA samples were analyzed by the Northern blot hybridization procedure using the appropriate 32P-labeled DNA probes. A marked increase in the abundance of c-myc, RaLV, and 30S RNAs were seen in all of the colon tumors, including adenomas and invasive carcinomas. No or a very low level of expression of RaLV and c-myc RNA was found in the flat grossly normal mucosa adjacent to the tumors and in the mucosa of the control rats. Some of the colon tumors also displayed increased levels of c-H-ras, ornithine decarboxylase and beta-actin RNAs but these findings were less striking and more variable than those seen with c-myc, RaLV, and 30S RNAs. These results suggest that increased expression of the c-myc protooncogene and of the endogenous retrovirus-like sequences (RaLV) and 30S are hallmarks of colon carcinogenesis in this model system.

Ethnic variation in the CYP2E1 gene: polymorphism analysis of 695 African-Americans, European-Americans and Taiwanese.

Human cytochrome P4502E1 (CYP2E1) is inducible by ethanol and is involved in metabolism of many known carcinogens including N-nitrosodimethylamine, butadiene, benzene, and carbon tetrachloride. A 50-fold variability in CYP2E1 enzyme activity in humans has been observed but it is unknown whether the basis for this variation is genetic or environmental. Recently, two restriction fragment length polymorphisms (RFLPs) within the CYP2E1 gene have been suggested as genetic markers of risk for cancer. The first was a Rsa I polymorphism in the 5' regulatory region that appeared to alter transcriptional activation of the gene and the second was a Dra I polymorphism located approximately 7000 bp downstream in an intron. Rare alleles at each of these loci have been associated with a reduced risk for lung cancer in Japanese and Swedish populations. We have used a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to determine the genotype frequency for each of these CYP2E1 RFLPs in 695 individuals of Taiwanese, African-American or European-American background. Genotype and allele frequencies for Taiwanese were significantly different from those of African-Americans and European-Americans at either Rsa I or Dra I sites (p < 0.0001). Allele frequencies for African-Americans and European-Americans were significantly different at the Rsa I site (p = 0.03). The rare alleles (c2 and C) occurred at frequencies of 0.28 and 0.24 in Taiwanese, 0.01 and 0.08 in African-Americans, and 0.04 and 0.11 in European-Americans. In addition, we describe three haplotypes common to all three population samples and a fourth haplotype that was only detected in the Taiwanese population sample. This fourth haplotype may have been caused by a recombination event between these markers.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of aflatoxin B(1)-albumin adduct levels with hepatitis B surface antigen status among adolescents in Taiwan.

Chronic hepatitis B virus (HBV) infection and aflatoxin B(1) (AFB(1)) exposure interact synergetically to induce hepatocellular carcinoma. One suggested mechanism for this interaction is the enhanced activation of AFB(1) in chronically HBV-infected individuals. Whereas no associations between chronic HBV infection and AFB(1)-albumin adducts were observed in several studies in adults, hepatitis B surface antigen (HbsAg)-positive children were found to have elevated adducts in Gambia. To assess the association between chronic HBV infection and AFB(1)-albumin adduct level in Taiwan, 200 junior high school adolescents from 20 townships were assayed for HBsAg and AFB(1)-albumin adducts. The mean AFB(1)-albumin adduct level was higher in HBsAg-positive compared with HBsAg-negative subjects. The association between HBsAg status and AFB(1)-albumin adducts remained after multivariate adjustment. This finding additionally supports the synergetic interaction between HBV and AFB(1), but the mechanism remains to be elucidated.

Metabolic gene polymorphism frequencies in control populations.

Using the International Project on Genetic Susceptibility to Environmental Carcinogens (GSEC) database containing information on over 15,000 control (noncancer) subjects, the allele and genotype frequencies for many of the more commonly studied metabolic genes (CYP1A1, CYP2E1, CYP2D6, GSTM1, GSTT1, NAT2, GSTP, and EPHX) in the human population were determined. Major and significant differences in these frequencies were observed between Caucasians (n = 12,525), Asians (n = 2,136), and Africans and African Americans (n = 996), and some, but much less, heterogeneity was observed within Caucasian populations from different countries. No differences in allele frequencies were seen by age, sex, or type of controls (hospital patients versus population controls). No examples of linkage disequilibrium between the different loci were detected based on comparison of observed and expected frequencies for combinations of specific alleles.

Influence of CETP gene variation on plasma lipid levels and coronary heart disease: a survey in Taiwan.

Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester from high-density lipoprotein (HDL) to very low-density lipoprotein (VLDL), low-density lipoprotein (LDL) and chylomicron in exchange for triglycerides. Two CETP genetic variation and four polymorphisms are investigated by polymerase chain reaction (PCR) and restriction enzyme digestion in a population of Taiwan. The results show that a very rare variation frequency is found for CETP intron 14 splice site G-->A change. The population shows a predominant 405Ile allele (61%), 442Asp (97.7%), intron 1Taq1B(+) G allele (52%), intron 8 Msp1(-) A allele (89%) and intron 9 EcoN1(-) T allele (59.2%) in the control group. Patients with coronary heart disease (CHD) have more CETP EcoN1(+/+) GG genotype (25.3%) than the controls (13.6%) (P=0.049). The intron 1 Taq1B(-) A allele is associated with a high HDL cholesterol and apoA1 level, the EcoN1(+) G allele with a low apoA1 level and the 442Gly with both high total cholesterol and LDL cholesterol levels. Paradoxically, the 442Gly is also present with a higher frequency (5.2%) in HDL cholesterol > or =65 mg/dl group than that in the general population (2.3%) (P=0.04).

Loss of heterozygosity of APC/MCC gene in differentiated and undifferentiated gastric carcinomas in Taiwan.

Recently, two genes in 5q21 involved in colon carcinogenesis, APC and MCC, were identified, and also shown to be associated with the development of esophageal and lung cancers. To determine if these genes are also involved in the development of gastric cancer, 79 primary human gastric cancers were examined for loss of heterozygosity of APC or MCC or both. Loss of APC was detected in 20% of 15 informative differentiated cases, but not in 20 informative undifferentiated cases, while loss of MCC occurred in 23.5% of 17 informative undifferentiated cases, but not in 19 informative differentiated cases. These data suggest that loss of heterozygosity of APC/MCC gene is involved in the development of gastric carcinomas, and that distinctly different molecular mechanism(s) may be responsible for the development of differentiated and undifferentiated gastric carcinomas.

Absence of APC gene mutation in the mutation cluster region in hepatocellular carcinoma.

APC gene mutations have been demonstrated not only in colorectal carcinoma but also in a variety of human cancers. To define the possible role of mutations of the APC gene in hepatocarcinogenesis, we examined 46 pairs of hepatocellular carcinomas and corresponding non-tumorous liver tissue by polymerase chain reaction and single strand conformation polymorphism. All 46 hepatocellular carcinomas had no altered electrophoretic mobility to suggest the presence of APC gene mutation in the mutation cluster region. We also examined the possible loss of heterozygosity of APC and MCC gene loci by fragment length polymorphism analysis and by polymerase chain reaction. None of the cases showed a loss of heterozygosity at the APC and MCC gene loci. The results suggested that the possibility of APC and MCC as the gene defect in the genesis of human hepatocellular carcinoma may be very rare.

Frequency of Epstein-Barr virus-associated gastric adenocarcinoma in Taiwan.

Eighty-two gastric adenocarcinomas (32 intestinal and 50 diffuse type) were investigated for the presence of Epstein-Barr virus (EBV) DNA by amplifying the 78-bp fragment from the EBNA1 gene with polymerase chain reaction. EBV was detected in 17 (20.7%) of the 82 gastric tumorous specimens. Of these 17 EBV-positive cases, only one was EBV-positive in the adjacent non-tumorous tissue. EBV-positive gastric adenocarcinoma was present in 15.6 and 24.0% of the intestinal and diffuse type tumors, respectively, but within the two classes there was significant non-homogeneity by type. EBV was found more frequently in adenocarcinomas of the tubular (25%) and poorly differentiated (30.3%) types. EBV involvement was found more in male than in female patients. Eighty of the 82 tumors were also checked for the prevalence of p53 gene mutation. Of the 17 EBV-positive gastric adenocarcinomas, only two showed p53 gene mutations. The p53 mutation rate was lower in EBV-positive tumors (11.8%) than in EBV-negative tumors (25.4%).