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Ambient particulate air pollution assessed as outdoor concentrations of particulate matter < or = 2.5 microm in diameter (PM(2.5)) has been associated with an increased cancer risk. However, outdoor PM(2.5) concentrations may not be the best measure of the individual particle exposure that is a sum of many sources besides outdoor particle levels, e.g., environmental tobacco smoke and cooking. We measured personal PM(2.5) and black smoke exposure in 50 students four times over 1 year and analyzed for biomarkers of different types of DNA damages. Ambient PM(2.5) concentrations were also measured. Exposure was measured for 48 h, after which blood samples were collected and analyzed for DNA damage in lymphocytes in terms of 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG), strand breaks, endonuclease III- and fapyguanine glycosylase-sensitive sites, and polyaromatic hydrocarbon adducts. Twenty-four-h urine collections were analyzed for 8-oxodG and 1-hydroxypyrene. Personal PM(2.5) exposure was found to be a predictor of 8-oxodG in lymphocyte DNA with an 11% increase in 8-oxodG/10 microg/m(3) increase in personal PM(2.5) exposure (P = 0.007). No other associations between exposure markers and biomarkers could be distinguished. The genotype of glutathione S-transferase M1 (GSTM1), T1 (GSTT1), and P1 (GSTP1) and NADPH:quinone reductase was also determined, but there were no effects of genotype on DNA polyaromatic hydrocarbon adducts or oxidative damage. The results suggest that moderate exposure to concentrations of PM can induce oxidative DNA damage and that personal PM(2.5) exposure is more important in this aspect than is ambient PM(2.5) background concentration.

A sucrose-rich diet has repeatedly been observed to have cocarcinogenic actions in the colon and liver of rats and to increase the number of aberrant crypt foci in rat colon. To investigate whether sucrose-rich diets might directly increase the genotoxic response in the rat colon or liver, we have added sucrose to the diet of Big Blue rats, a strain of Fischer rats carrying 40 copies of the lambda-phage on chromosome 4. Dietary sucrose was provided to the rats for 3 weeks at four dose levels including the background level in the purified diet [3.4% (control), 6.9%, 13.8%, or 34.5%] without affecting the overall energy and carbohydrate intake. We observed a dose-dependent increase in the mutation frequency at the cII site in the colonic mucosa with increased sucrose levels, reaching a 129% increase at the highest dose level. This would indicate a direct or indirect genotoxic effect of a sucrose-rich diet. No significant increase in mutations was observed in the liver. To seek an explanation for this finding, a variety of parameters were examined representing different mechanisms, including increased oxidative stress, changes in oxidative defense, effects on DNA repair, or changes in the background levels of DNA adducts. Sucrose did not increase the number of DNA strand breaks or oxidized bases assessed as endonuclease III-sensitive sites or 8-oxodeoxyguanosine in colon or liver. DNA repair capacity as determined by expression of the rERCC1 or rOGG1 genes was not increased in colon or liver, but the background level of DNA adducts (I-compounds) as determined by (32)P postlabeling was significantly decreased in colon. This decrease in colon I-compounds correlated inversely with both mutation frequency and ERCC1 DNA repair gene expression. Dietary sucrose did not change liver apoptosis or cell turnover as determined by the terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end labeling assay and proliferating cell nuclear antigen. An increase in liver ascorbate was also observed, whereas oxidative damage was not observed in proteins or lipids in liver cytosol or in blood plasma. We conclude that a sucrose-rich diet directly or indirectly increases the mutation frequency in rat colon in a dose-dependent manner and concomitantly decreases the level of background DNA adducts, without a direct effect on the expression of major DNA repair enzyme systems. We also conclude that an oxidative mechanism for this effect of sucrose is unlikely. This is the first demonstration of a genotoxic action of increased dietary sucrose in vivo. Both sucrose intake and colon cancer rates are high in the Western world, and our present results call for an examination of a possible direct relationship between the two.

Within the last decade, the comet assay has been used with increasing popularity to investigate the level of DNA damage in terms of strand breaks and alkaline labile sites in biomonitoring studies. The assay is easily performed on WBCs and has been included in a wide range of biomonitoring studies of occupational exposures encompassing styrene, vinyl chloride, 1,3-butadiene, pesticides, hair dyes, antineoplastic agents, organic solvents, sewage and waste materials, wood dust, and ionizing radiation. Eleven of the occupational studies were positive, whereas seven were negative. Notably, the negative studies appeared to have less power than the positive studies. Also, there were poor dose-response relationships in many of the biomonitoring studies. Many factors have been reported to produce effects by the comet assay, e.g., age, air pollution exposure, diet, exercise, gender, infection, residential radon exposure, smoking, and season. Until now, the use of the comet assay has been hampered by the uncertainty of the influence of confounding factors. We argue that none of the confounding factors are unequivocally positive in the majority of the studies. We recommend that age, gender, and smoking status be used as criteria for the selection of populations and that data on exercise, diet, and recent infections be registered before blood sampling. Samples from exposed and unexposed populations should be collected at the same time to avoid seasonal variation. In general, the comet assay is considered a suitable and fast test for DNA-damaging potential in biomonitoring studies.

The XPD protein has a dual function, both in nucleotide excision repair and in basal transcription. We have studied the role of two nucleotide substitutions in the XPD gene, one in exon 23 leading to an amino acid substitution (Lys751Gln) and one silent in exon 6 in relation to basal cell carcinoma (BCC). Both are two-allele polymorphisms, with the nucleobases A and C at the given positions. We genotyped psoriasis patients with and without BCC and nonpsoriatic persons with and without BCC (4 x 20 persons). The choice to study psoriasis patients was motivated by their high genotoxic exposure via treatment and their high relative rate of early BCC. Subjects carrying two A alleles (AA genotype) in exon 23 were at 4.3-fold higher risk of BCC than subjects with two C alleles (95% CI, 0.79-23.57). In addition, the mean age at first skin tumor for BCC cases with the AA genotype was significantly lower than the mean age for BCC cases with the AC or CC genotype (P = 0.012). Thus, the variant C-allele of exon 23 may be protective. The exon 6 genotype was associated with the risk of BCC among the psoriasis patients; psoriatics carrying two A alleles in exon 6 were at 5.3-fold higher risk of BCC than psoriatics with two C alleles (95% CI, 0.78-36.31). For the psoriatics, the mean age at onset of BCC for cases with the AA genotype was marginally lower than the mean age for cases with genotype AC or CC (P = 0.060). Our results raise the possibility that the polymorphisms in the XPD gene may be contributing factors in the risk of BCC development. They are, therefore, important candidates for future studies in susceptibility to cancer.

The fate of carcinogens differs among individuals who have different activities of drug-metabolizing enzymes that are important in activating and detoxifying carcinogens. A drug that profoundly alters the metabolism of the drugs and carcinogens is the anticonvulsive agent phenobarbital. To investigate why epileptic patients appear to have a low risk of cancer of the urinary bladder, and on the basis of the observation that levels of aromatic amine-hemoglobin adducts are strongly associated with various risk factors for cancer at that site, we determined aromatic amine-hemoglobin adducts in 62 epileptic patients as a surrogate measure of the reaction of carcinogenic metabolites with DNA in target tissue. Although adducts were detected in all subjects, the levels were proportional to daily tobacco consumption. When the subjects were stratified into groups smoking 20 g tobacco/day or more, smoking <20 g/day, and not smoking, an effect of medication was detected. Epileptic patients treated chronically with phenobarbital or primidone, which is effectively metabolized to phenobarbital, were found to have lower levels of 4-aminobiphenyl adducts than patients on the other treatment (P = 0.02; ANOVA). In nonsmokers, no effect of medication could be demonstrated above background variation; however, an increasing effect was seen with tobacco consumption with only one-half the increase in adducts per g of tobacco smoked as epileptic patients on other treatment. The difference in the increases (slopes of regression lines) was highly significant statistically. This reduction in the level of hemoglobin-aromatic amine adducts is probably due to induction of detoxification enzymes in the patients treated with phenobarbital.

The p53 tumor suppressor gene is mutated in varying fractions of almost all tumor types studied. The rate of mutations and the mutational spectrum in some tumors are specific for environmental mutagens assumed to be involved in the carcinogenic process. Thus, hepatocellular carcinomas supposedly induced by aflatoxin exposure often contain a specific point mutation in codon 249, and in lung cancers of miners with heavy radon exposure, another specific point mutation in codon 249 suggestive of an alpha-particle-specific mutation has been shown. The interpretation of studies linking the mutational spectrum with specific environmental exposures is complicated by the multifactorial or unknown genesis of most tumors. However, people given injections of the X-ray contrast medium Thorotrast (Th) in the past have experienced an enormous risk of liver tumors, and virtually all of these are supposedly induced by alpha-particles from the decay of 232Th. The examination of these tumors may provide evidence as to whether specific p53 point mutations are relevant in alpha-particle carcinogenesis. Therefore, we collected paraffin-embedded, formalin-fixed archival tissues from 18 hepatocellular carcinomas, 9 cholangiocarcinomas, and 9 hepatic angiosarcomas from Thorotrast-exposed patients. The tissues were analyzed for p53 protein expression by immunohistochemical staining by using the mAb DO-7 and for mutations of exons 5-8 by PCR and constant denaturant gel electrophoresis. G --> T transversions of the third base of codon 249 of the p53 gene were specifically screened for by restriction enzymes. No high score for p53 protein expression (i.e., positive staining of >20% of examined cells) was observed; lower scores were seen in 5 of 18 (28%) hepatocellular carcinomas, 1 of 9 (11%) cholangiocarcinomas, and 0 of 8 (0%) hepatic angiosarcomas. Only one p53 mutation, a heterozygous T --> G transversion of the first base codon 176, occurred in a hepatocellular carcinoma. The rate of p53 point mutations in alpha-particle-induced liver tumors seems to be lower than in European hepatocellular carcinomas in general. The study does not exclude the possibility that alpha-particle carcinogenesis may involve inactivation of p53 by gross deletions of the gene, but it speaks against the proposed specificity of point mutations of codon 249 in cancer supposedly induced by alpha-particles from radon progeny.

To investigate the possible influence of anticonvulsant treatment on cancer risk, a nested case-control study of 104 lung cancers, 18 bladder cancers, and 322 cancer-free controls was conducted. The background for the study was previous observations among 8004 epileptics in Denmark with a significantly high risk for lung cancer and a significantly low risk for bladder cancer. Cigarette smoking appears to explain the lung cancer excess but not the low risk for bladder cancer, another tobacco-related disease. Information was abstracted on 94 and 95% of the cases and controls, respectively. Lung cancer was not associated with any anticonvulsant drug, but bladder cancer was inversely related to use of phenobarbital (PB). The apparent protective effect of PB was further evaluated in a study of rats given 4-aminobiphenyl (ABP), a bladder carcinogen. The levels of 4-aminobiphenyl adducts in hemoglobin and in bladder and liver DNA were significantly lower in rats given PB prior to 4-aminobiphenyl, compared to controls. These studies suggest that PB may induce drug-metabolizing enzymes of the liver that deactivate bladder carcinogens found in cigarette smoke and provide clues to the role of activation and detoxification of carcinogens in humans.