The cytogenetic effects of cigarette smoke has been evaluated as one of many potential confounders in a large number of biomonitoring studies of occupationally or environmentally exposed populations and control subjects. Despite the well-known presence of carcinogens in the cigarette smoke, the results in the scientific literature linking smoking habits to micronuclei (MN) frequency, one of the cytogenetic markers, are rather controversial. Here, we investigated the relationships among MN frequency, smoking habits and five folate metabolic enzyme gene polymorphisms (MTHFR C677T and A1298C, MTR A2756G, MTRR A66G and TYMS 3'UTR) in 132 healthy Japanese men who were non-habitual drinkers. In never- and former-smokers, no statistically significant differences in the mean MN frequencies were observed according to the five folate metabolic enzyme gene polymorphisms. In current-smokers, however, subjects with the AA genotype for MTRR had a significantly higher mean MN frequency than the AG genotypes for MTRR (p<0.05). Furthermore, among subjects with the AA genotype for MTRR, current-smokers were found to have a significantly higher mean MN frequency than never- and former-smokers (p<0.05). To further characterize this association, we stratified the smoking status into five groups: non-smokers (never-smokers and former-smokers), 1-10 cigarettes/day, 11-20 cigarettes/day, 21-30 cigarettes/day and >or=31 cigarettes/day. There was an overall trend for the mean MN frequency in subjects with the MTRR AA genotype to increase as the number of cigarettes smoked per day increased (p<0.01, Jonckheere-Terpstra test). The results of our preliminary study suggest that the MTRR AA genotype acts to increase the MN frequency resulting from cigarette smoking. Therefore, studies on human genotoxicity based on cytogenetic markers of MN should take into account both the MTRR polymorphism and the potential confounding effect of smoking, although these preliminary findings need to be validated in larger populations because of the relatively small sample size.

BACKGROUND: Multiple risk factors possibly associated with lung cancer were examined as part of a large-scale residential radon case-control study conducted in Iowa between 1994 and 1997. We were particularly interested in stratifying risk factors by smoking status. Relatively little risk factor information is available for Midwestern rural women. METHODS: Four hundred thirteen female lung cancer cases and 614 controls aged 40-84, who were residents of their current home for at least 20 years, were included. Risk factors examined included cigarette smoking, passive smoking, occupation, chemical exposure, previous lung disease, family history of cancer, and urban residence. Multiple logistic regression analysis was conducted after adjusting for age, education, and cumulative radon exposure. RESULTS: As expected, active cigarette smoking was the major risk factor for lung cancer. While cessation of smoking was significantly associated with a reduced risk for lung cancer, the risk remained significantly elevated for 25 years. Among all cases, asbestos exposure was a significant risk. Among ex-smokers, pack-year history predominated as the major risk. Among never smokers, a family history of kidney or bladder cancer were significant risk factors (OR=7.34, 95% CI=1.91-28.18; and OR=5.02, 95% CI=1.64-15.39, respectively), as was a history of previous lung disease (OR=2.28, 95% CI=1.24-4.18) and asbestos exposure. No statistically significant increase in lung cancer risk was found for occupation or urban residence. CONCLUSIONS: Smoking prevention activities are urgently needed in rural areas of the United States. Relatives of individuals with smoking-related cancers are potentially at increased risk. Genetic risk factors should be more fully investigated in never smokers.

Prospective phytoestrogen exposure was assessed using both biomarkers and estimates of intake in 89 British men recruited into the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition study, men who subsequently developed prostate cancer. Results were compared with those from 178 healthy men matched by age and date of recruitment. Levels of seven phytoestrogens (daidzein, genistein, glycitein, O-desmethylangolensin, equol, enterodiol, and enterolactone) were measured in spot urine and serum samples. Five single-nucleotide polymorphisms in COMT, CYP19, ESR1, and SHBG genes were genotyped. Urinary levels of all phytoestrogens correlated strongly with serum levels. Correlation coefficients ranged from 0.63 (glycitein) to 0.88 (daidzein) (P < 0.001). Urinary and serum levels correlated significantly with isoflavone intake assessed from food diaries (R = 0.15-0.20; P < 0.05) but not with that from a food-frequency questionnaire. Odds ratios for phytoestrogen exposure, as assessed using the four methods, were not significantly associated with prostate cancer risk (P = 0.15-0.94). Men with the CC genotype for the ESRI PvuII polymorphism had significantly higher risk for prostate cancer compared with men with the TT genotype [adjusted odds ratio = 4.65 (1.60-13.49); P = 0.005]. Our results utilizing a combined prospective exposure provide no evidence that phytoestrogens alter prostate cancer risk in British men, whereas the C allele for the PvuII polymorphism may be associated with increased risk.

The modifying effects of dietary feeding with chrysin (5,7-dihydroxyflavone) on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were investigated in male F344 rats. We also assessed the effect of chrysin on mitosis and apoptosis in 'normal appearing' crypts. To induce ACF, rats were given two weekly subcutaneous injections of AOM (20 mg/kg body weight). They also received an experimental diet containing chrysin (0.001 or 0.01%) for 4 weeks, starting 1 week before the first dose of AOM. AOM exposure produced a substantial number of ACF (73+/-13/rat) at the end of the study (week 4). Dietary administration of chrysin caused significant reduction in the frequency of ACF: 0.001% chrysin, 37+/-17/rat (49% reduction, P<0.001); and 0.01% chrysin, 40+/-10/rat (45% reduction, P<0.001). In addition, chrysin administration significantly reduced the mitotic index and significantly increased the apoptotic index in 'normal appearing' crypts. These findings might suggest a possible chemopreventive activity of chrysin in the early step of colon tumorigenesis through modulation of cryptal cell proliferation activity and apoptosis.

Dietary chemoprevention has emerged as a cost-effective approach for cancer control. We evaluated the chemopreventive effects of black tea polyphenols (Polyphenon-B) administration during the preinitiation phase of 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. The expression of proliferating cell nuclear antigen (PCNA) in the buccal pouch and the concentration of lipid peroxides, protein carbonyl, and the antioxidant status in the buccal pouch, liver and erythrocytes were used as biomarkers of chemoprevention. All the hamsters painted with DMBA alone for 14 weeks developed buccal pouch carcinomas associated with increased expression of PCNA, diminished lipid and protein oxidation, and enhanced antioxidant status. In the liver and erythrocytes of tumor-bearing animals, enhanced oxidation of lipids and proteins was accompanied by compromised antioxidant defenses. Dietary administration of Polyphenon-B effectively suppressed DMBA-induced HBP carcinogenesis as revealed by decreased incidence of tumours and PCNA expression. In addition, Polyphenon-B modulated lipid and protein oxidation and enhanced the antioxidant status in the pouch, liver, and erythrocytes. We suggest that Polyphenon-B exerts its chemopreventive effects by inhibiting cell proliferation in the target tissue and modulating the oxidant-antioxidant status in the target as well as in host tissues.

OBJECTIVES: Epidemiological and experimental studies indicate that non-steroidal anti-inflammatory drugs (NSAIDs) are chemopreventive agents of gastrointestinal cancers, but few studies on gastric cancer have been carried out. A decrease in folic acid supplement and subsequent DNA hypomethylation are related to gastrointestinal cancers, and it has been shown that high-dose folic acid may interfere with gastric carcinogenesis in dogs. The objective of this study was to investigate the effects of rofecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, and folic acid on the chemoprevention of gastric cancer induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Wistar rats, and to evaluate the cell proliferation of gastric mucosa in different experimental groups. METHODS: Eighty male Wistar rats were randomly divided into five groups (16 rats in each group). In the control group, the rats were given pure water and basal diet. In the MNNG group, the rats received MNNG in drinking water (100 mg/L) and basal diet. In the MNNG + low-dose rofecoxib group, the rats were given MNNG and rofecoxib 5 mg/kg per day with basal diet. In the MNNG + high-dose rofecoxib group, the rats were given MNNG and rofecoxib 15 mg/kg per day with basal diet. In the MNNG + folic acid group, the rats were given MNNG and folic acid 5 mg/kg per day with basal diet. The experiment was terminated at 50 weeks, and all rats were killed. Blood samples of 3 mL were obtained for measurement of serum folic acid concentrations in the control group, the MNNG group and the MNNG + folic acid group by using chemiluminescent method. The stomach was removed from all rats for histopathological examination and immunohistochemical study. Proliferating cell nuclear antigen (PCNA) expression in gastric epithelial cells was also determined. RESULTS: In the MNNG group, five of 11 rats (45.5%) developed gastric cancer, while in all other four groups no gastric cancer was found (P < 0.05). The positivity rate of PCNA expression in the cancerous tissues was significantly higher than that in the non-cancerous tissues (80.0%vs 14.1%, P < 0.05). The positivity rate of PCNA expression in the gastric mucosal cells of the MNNG group was significantly higher than that in the other four groups. The mean serum folic acid concentration of rats was significantly higher in the MNNG + folic acid group (193.70 +/- 60.73 ng/mL) than those in the control group (84.21 +/- 25.26 ng/mL) and the MNNG group (72.27 +/- 16.70 ng/mL, P < 0.05). It was shown that both low- and high-dose rofecoxib as well as folic acid interfered with the development of gastric cancer induced by MNNG in Wistar rats. CONCLUSIONS: The results indicate that rofecoxib as well as folic acid interferes with gastric carcinogenesis induced by MNNG in Wistar rats, and the suppression of gastric cell proliferation may play a crucial role in the chemoprevention of gastric cancer by rofecoxib and folic acid. The higher serum folic acid concentration of rats may play an important role in the prevention of gastric cancer.

After 1946, the WISMUT Company developed the third-largest uranium-mining province in the world in the German Democratic Republic. METHODS: A case-control study among former WISMUT miners was conducted to investigate the lung cancer risk in relation to attained age, time since exposure, exposure duration, and exposure rate. It consisted of 505 patients with lung cancer and 1,073 controls matched to cases according to the year of birth. The cumulative exposure to radon and radon decay products was calculated as the sum of yearly exposures and expressed in Working Level Months (WLM). Cases had a mean cumulative exposure of 552 WLM compared to 420 WLM in controls. RESULTS: There was a statistically significant increase in lung cancer risk for cumulative exposures above 800 WLM. Under the assumption of a linear risk model, there was a significant increase in the relative risk of 0.10 per 100 WLM after adjusting for smoking and asbestos exposure. For current smokers the increase in relative risk was lower (0.05 per 100 WLM), whereas it was higher (0.20 per 100 WLM) among nonsmokers and longtime ex-smokers. After correcting in a sensitivity analysis for the fact that the controls of this study had a higher average exposure than the population of WISMUT workers they were recruited from, the adjusted ERR increased to 0.24 per 100 WLM. Lung cancer risk declined with time since exposure, except for exposures received 45 or more years ago. No inverse dose rate effect was observed.

The cytochrome P4501A1 (CYP1A1) is involved in the metabolism of environmental carcinogens and estrogen. We hypothesized that CYP1A1 genetic polymorphism may be a susceptibility factor for endometrial hyperplasia (EH) and endometrial carcinoma (ECa). We therefore evaluated this hypothesis in patients with EH and ECa and control subjects using allele-specific polymerase chain reaction-based method in a Turkish population. The patients with CYP1A1 Ile/Val genotype had a fivefold higher risk of having EH than those with Ile/Ile. In contrast, a higher frequency of any Val genotype (Ile/Val and Val/Val) was found in patients with EH, indicating that persons carrying any Val allele are at increased risk for developing EH. In the ECa group, patients were also more likely to have CYP1A1 Ile/Val allele, with an adjusted odds ratio of 3.0. Moreover, there was a statistically significant increase in relative risk association with any Val genotype between patients and controls, suggesting that individuals carrying any Val genotype are at increased risk for developing ECa. We concluded that variant alleles of the CYP1A1 gene might be associated with EH and ECa susceptibility. Further studies with a large sample size should be considered to address issues of interactions between CYP1A1 and other risk factors.