Apolipoprotein E genotype, serum lipids, and colorectal adenomas in Japanese men

We examined the relation of serum lipids and apolipoprotein E genotype to colorectal adenomas among 205 cases and 220 controls with normal colonoscopy in Japanese men. With adjustment for body mass index, cigarette smoking, alcohol use, and other covaiates, odds ratios of proximal and distal adenomas associated with the presence of an allele varepsilon4 were 0.59 (95% confidence interval 0.23-1.45) and 0.99 (0.50-1.98), respectively. While serum total and LDL cholesterol were unrelated to both proximal and distal adenomas, serum triglycerides were positively related to distal adenomas. The findings suggest that altered lipid metabolism may be differentially associated with tumorigenesis in the proximal and distal colorectum.

Glutathione S-transferase polymorphisms and risk of colorectal adenomas

Glutathione S-transferases (GSTs) are a superfamily of detoxification enzymes that may play an important role in human carcinogenesis. While the genetic polymorphisms GSTM1 and GSTT1 have drawn particular interest in relation to cancer susceptibility, previous studies of colorectal cancer are inconsistent regarding their role. We examined the relation between GSTM1 and GSTT1 genotypes combined and colorectal adenomas, and the interaction with cigarette smoking among 205 cases of colorectal adenomas and 220 controls with normal total colonoscopy in Japanese men. Neither GSTM1 nor GSTT1 was related to colorectal adenomas, nor were the null genotypes of GSTM1 and GSTT1 combined. The lack of an association with GSTM1 and GSTT1 genotypes combined persisted even when the analysis was done separately for proximal and distal colorectal adenomas. A three- to fivefold significant increase in the odds of colorectal adenomas was observed among men with a high exposure to cigarette smoking across the genotype groups, and a statistically significant increasing trend was noted within each genotype group. The present findings do not support the role for GSTM1 and GSTT1 genotypes in the development of colorectal adenomas.

Lymphocyte DNA adducts and polymorphism in the DNA repair enzyme XPD

The effect of genetic polymorphism of DNA repair enzyme on the DNA adduct levels was evaluated in this study. We explored the relationship between polymorphism in the nucleotide excision repair enzyme XPD and DNA adduct levels in lymphocytes. Lymphocyte DNA adducts were measured by a (32.)

Genetic polymorphism of enzymes involved in xenobiotic metabolism and the risk of colorectal cancer

Environmental factors such as smoking cigarette, diets and alcohol may interact with genetic factors, which put one individual at a greater or lesser risk of a particular cancer than another. Advances in molecular biology have allowed many allelic variants of several drug metabolizing enzymes so that individuals with the susceptible genotypes can be determined easily. Many pieces of research have focused on the relationship between the distribution of polymorphic variants of different forms of the metabolic enzymes and colorectal cancer susceptibility because of importance roles of the metabolic enzymes in the activation of many procarcinogens or chemicals. In this respect five groups of the metabolic enzymes, cytochrome P450 (CYP) 1A1/CYP1A2, glutathione S-transferases (GSTs), N-acetyltransferases (NATs), aldehyde dehydrogenase 2 (ALDH2) and methylenetetrahydrofolate reductase (MTHFR), have been discussed here. A positive association between development of colorectal cancer and the mutant homozygous genotype in Msp1 polymorphism of CYP1A1 gene has been reported in Japanese in Hawaii. The relation between genetic polymorphisms in GSTs and cancer risk has also taken an interest. At least nine studies have demonstrated the relation between the GST polymorphisms and colorectal cancer. Two of these studies suggested an increased risk of approximately 2-fold among those with the GSTM1 null genotype, while others found no risk increase. None of these studies examined the combined effect of CYP1A1 and GST polymorphisms. Either NAT2 or CYP1A2 alone have been slightly associated with colorectal cancer. When CYP1A2 and NAT2 phenotype were combined, a significant increased risk (odds ratio of 2.8) was seen among well done meat consumers with the rapid-rapid phenotype. Two published studies have found that the risk of colorectal cancer can be enhanced (2-3 fold) in alcohol drinkers with heterozygous genotype of ALDH2 in two Japanese populations recently. Findings from three published studies suggested that the mutant genotype of MTHFR inversely slightly associated with colorectal cancer. Although some of genetic polymorphisms discussed here have not shown statistically significant increase/decrease in risk, individuals with differing genotypes may have different susceptibilities to colorectal cancer, based on environmental factors. Further studies are needed to identify risk groups more specific and to determine factors of importance in colorectal cancer development.

[Lung cancer risk and genetic polymorphism at the glutathione S-transferase P1 locus in male Japanese]

The glutathione S-transferases (GSTs) are widely expressed in mammalian tissues and involved in Phase II detoxification reactions. The GSTs form a supergene family consisting of four distinct families, named alpha (GSTA), mu (GSTM) theta (GSTT) and pi (GSTP). Several of the GST genes are polymorphic in humans and are currently being investigated as possible cancer-risk modifiers. Among the GST genes, we examined GSTP1 polymorphism in exon 5 among male lung cancer patients (n = 86, male Japanese) and male healthy controls (n = 80, male Japanese) by restriction fragment length polymorphism-polymerase chain reaction method. The cancer patients showed frequency of the GSTP1 mutated genotype (individuals having at least one mutant allele, 29.1%) very similar to that of the control subjects (28.8%). After adjusting for smoking status, no association was found between the GSTP1 mutated genotype and lung cancer risk (odds ratio: 0.95; 95% confidence interval: 0.48-1.90). When study subjects were divided into two subgroups based on smoking status, the GSTP1 mutated genotype was not associated with an increased risk of lung cancer among smokers and non-smokers. These results suggest that GSTP1 polymorphism in exon 5 alone may not increase the risk of lung cancer in male Japanese.

Cigarette smoking, CYP1A1 MspI and GSTM1 genotypes, and colorectal adenomas

Cigarette smoking has been related to increased risk of colorectal adenomas, but the underlying mechanisms are unknown. Genetic polymorphisms are known for enzymes involved in the activation of polycyclic aromatic hydrocarbons and other tobacco-related carcinogens. Polycyclic aromatic hydrocarbons are activated by cytochrome P4501A1 (CYP1A1) and detoxified by glutathione S-transferases. We investigated the relation of CYP1A1 MspI and GSTM1 genotypes to the risk of colorectal adenomas with special reference to interaction with cigarette smoking among 205 cases of colorectal adenomas and 220 controls with normal total colonoscopy in a male Japanese population. Cigarette smoking was strongly associated with increased risk of colorectal adenomas. Overall, neither the CYP1A1 MspI genotype nor the GSTM1 genotype was related to colorectal adenomas. A significant trend for increased risk of colorectal adenomas associated with smoking was observed for each of the CYP1A1 MspI genotypes, and the increasing trends did not differ by MspI genotype. The positive association between smoking and colorectal adenomas did not vary much with GSTM1 genotypes. Among former and current smokers, adenoma risk did not differ according to the combination of CYP1A1 MspI and GSTM1 genotypes. CYP1A1 MspI and GSTM1 genotypes do not seem to modify the risk of colorectal adenomas associated with cigarette smoking.

Methylenetetrahydrofolate reductase polymorphism and risk of colorectal adenomas

A homozygous mutation at bp 677 in the gene for the methylenetetrahydrofolate reductase (MTHFR) was previously shown to be associated with a decreased risk of colorectal cancer. We examined the relation between the MTHFR genetic polymorphism and risk of colorectal adenoma in Japanese men using 205 cases of colorectal adenomas and 220 controls of normal total colonoscopy. The homozygous mutation was not measurably associated with colorectal adenomas. The findings corroborate the lack of an association between the MTHFR genotype and colorectal adenomas, but do not deny the possibility that the genotype may be involved in the late stage of colorectal carcinogenesis.

Expression of p53 and glutathione S-transferase-pi relates to clinical drug resistance in non-small cell lung cancer

To determine the predictive value of the expression of p53 and glutathione S-transferase-pi (GST-pi) with respect to chemotherapy response, immunostaining was performed on transbronchial biopsy specimens from previously untreated patients with non-small cell lung cancer. Of the 54 patients, 34 patients (63%) and 37 patients (69%) were positive for p53 and GST-pi, respectively. The response rates in the p53-positive and p53-negative group were 15 and 45%, and those in GST-pi-positive and GST-pi-negative groups were 16 and 47%, respectively. A multiple logistic regression analysis revealed that positive immunostaining for GST-pi was a significant risk factor for clinical chemotherapy resistance. The combination of these two markers was the most important independent factor in predicting a response to chemotherapy in multiple logistic regression analysis. Immunohistochemical expression of p53 and GST-pi was independently related to clinical chemoresistance in patients with non-small cell lung cancer. Combined use of these two biomarkers may be a useful predictor of clinical chemoresistance.

Inverse association between coffee drinking and serum uric acid concentrations in middle-aged Japanese males

Consumption of caffeine-rich beverages, which have diuretic properties, may decrease serum uric acid concentrations. We examined cross-sectionally the relationship of coffee and green tea consumption to serum uric acid concentrations in 2240 male self-defence officials who received a pre-retirement health examination at four hospitals of the Self-Defence Forces between 1993 and 1994. The mean levels of coffee and green tea consumption were 2.3 and 3.1 cups/d respectively. There was a clear inverse relationship between coffee consumption and serum uric acid concentration. When adjusted for hospital only, those consuming less than one cup of coffee daily had a mean serum uric acid concentration of 60 mg/l, while that of those drinking five or more cups of coffee daily was 56 mg/l (P < 0.0001). No such relationship was observed for green tea, another major dietary source of caffeine in Japan. The relationship between coffee consumption and serum uric acid concentration was independent of age, rank in the Self-Defence Forces, BMI, systolic blood pressure, serum creatinine, serum total cholesterol and serum HDL-cholesterol concentrations, smoking status, alcohol use, beer consumption and intake of dairy products. These findings suggest that coffee drinking may be associated with lower concentrations of serum uric acid, and further studies are needed to confirm the association.

Obesity, weight gain and risk of colon adenomas in Japanese men

Obesity has been related to increased risk of colon cancer or adenomas, but the epidemiologic findings are not entirely consistent. We examined the relation of not only body mass index (BMI) but also waist-to-hip ratio (WHR) and weight gain to colon adenoma risk in men who received a preretirement health examination at the Japan Self Defense Forces (SDF) Fukuoka and Kumamoto Hospitals during the period from 1995 to 1996. In the series of 803 men at age 47-55 years, 189 cases of colon adenomas and 226 controls with normal total colonoscopy were identified. Weight at 10 years before was ascertained by referring to the recorded data. After allowance for hospital, rank in the SDF, smoking and alcohol use, weight gain over the past 10 years was significantly associated with increased risk of colon adenomas (odds ratio for > or = 6 kg versus < or =-2 kg = 2.2; 95% confidence interval 1.0-4.8). High BMI and high WHR were each associated with increased risk, but only WHR was related to the risk independently of weight gain. In particular, weight gain accompanied with a high WHR was associated with a significant increase in the risk. Men with high physical activity tended to have lower risk. Associations with obesity-related variables and physical activity were not materially differential as regards the location and size of adenoma. The findings indicate that weight gain in middle age leading to abdominal obesity increases the risk of colon adenomas, and consequently of colon cancer.

[Role of metabolic polymorphisms in lung carcinogenesis]

Metabolism of most chemical carcinogens in humans is thought to occur in two distinct phases. The carcinogens exert their effect only after being metabolically activated to intermediates (phase I), which are capable of binding to DNA and causing mutations. The most ubiquitous phase I catalysts are the cytochrome P450s (CYPs). There is convincing epidemiological evidence that lung cancer risk associated with polycyclic aromatic hydrocarbons (PAHs) is mediated in part by aryl hydrocarbon hydroxylase (AHH), which is used as an indicator of the phenotype of CYP1A1. Since AHH is responsible for the activation PAHs in cigarette smoke, it may be important in the causation of lung cancer. Kellermann et al. reported a significant positive correlation between AHH inducibility and susceptibility to lung cancer. The finding, however, has been both supported and refuted by subsequent investigators. Advances in molecular biology have allowed many allelic variants of several drug metabolizing enzymes so that individuals with the susceptible genotypes can be determined easily. A close association between development of lung cancer and homozygous rare genotypes in MspI and Ile-Val polymorphisms of CYP1A1 gene has been recently reported in some Japanese populations. The association between GSTM1 polymorphism and lung cancer risk is not so strong, however. Following the phase I reaction, phase II enzymes such as glutathione S-transferases (GSTs) are responsible for detoxification of activated forms PAH-epoxides. GSTs form a superfamily of genes consisting of four distinct families, named Alpha, Mu, Pi and Theta. The GSTM1, GSTT1 and GSTP1 genes are polymorphic in humans. The phenotypic absence of GSTM1 activity is due to a homozygous inherited deletion of the gene, the null genotype. The homozygous deletion of GSTM1 genes has been shown to occur in approximately 50% of the populations of various ethnic origins. The GSTM1 null genotype confrs a moderately increased risk of smoking-related lung cancer, however. Genetically determined susceptibility to lung cancer may depend on the metabolic balance between phase I and phase II enzymes. Risk of lung cancer, especially squamous cell carcinoma is shown to be remarkably increased in individuals with a combination of a homozygous rare allele of the CYP1A1 gene and the nulled GSTM1 gene, compared with those having other combinations of genotypes. Individuals with susceptible genotypes may become important for the prevention of lung cancer.

Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa isolation from pharyngeal swab cultures among the Japanese elderly at admission to a geriatric hospital

The isolation rate of Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa from pharyngeal swab cultures in the Japanese elderly was studied at admission to a geriatric hospital which had long-term care units. The subjects were 233 consecutive patients who were admitted to K Hospital in the time period April 1994 to March 1996. The isolation rate of MRSA and of Pseudomonas aeruginosa was 10.3% and 8.2% respectively. The proportions of the patients with severely to moderately limited Activities of Daily Living (ADL) (ADL score = 0-1) (P < 0.01), those with fever (P < 0.01), those with CRP positive (P = 0.04) and those with hypoalbuminemia (serum albumin < 3.5 g/dl) (P < 0.01) were higher in the MRSA positive patients than in the negative patients while the proportion of the patients with fever was higher in the Pseudomonas aeruginosa positive patients than in the negative patients (P < 0.02). In the multiple logistic regression analysis, the limitation of ADL (ADL score 0-1 vs 2-3, OR = 1.54, 95% CI = 1.02-2.33) and fever (with vs without, OR = 1.77, 95% CI = 1.18-2.66) remained as risk factors for the isolation of MRSA while only fever (with vs without, OR = 1.67, 95% CI = 1.11-2.53) remained as a risk factor for the isolation of Pseudomonas aeruginosa.

The relationship between CYP1A1 aryl hydrocarbon hydroxylase activity and lung cancer in a Japanese population

Because aryl hydrocarbon hydroxylase (AHH) is considered to be responsible for the activation of benzo(a)pyrene and other polyaromatic hydrocarbons in cigarette smoke to carcinogens, it is important to examine CYP1A1 (AHH) activity in the determination of susceptibility to lung cancer. We investigated AHH activity in peripheral mitogen-treated lymphocytes in 108 lung cancer patients and 95 healthy control individuals. Non-induced AHH activity was detectable in all the samples. AHH inducibility (3-methylcholanthrene-induced/non-induced AHH activity) showed a very wide interindividual variation as well as non-induced AHH activity. No significant associations were found between adjusted AHH activity and histologic type of tumor among lung cancer patients. Adjusted AHH inducibility of genotype C [geometric mean and 95% confidence interval (CI); 15.56 and 11.69-20.71] in MspI polymorphism was significantly higher than those of the other two genotypes (P = 0.0001), while no significant difference was observed between genotypes A (4.76 and 3.82-5.93) and B (5.60 and 4.57-6.86). On the other hand, non-induced AHH activity of genotype Val/Val (0.121 and 0.082-0.178 pmol/min/10(6) cells) in isoleucine-valine (Ile-Val) polymorphism was significantly higher than those of genotypes Ile/Ile (0.042 and 0.034-0.052 pmol/min/10(6) cells) and Ile/Val (0.040 and 0.030-0.053 pmol/min/10(6) cells) (P < 0.0001). Even after controlling for age, cigarettes smoked per day and season of the year, high AHH inducibility (7.0 < versus 0 < < or = 3.0: OR and 95 %CI, 12.4 and 2.88-53.4) was an independent risk factor for lung cancer. The data indicate that high AHH inducibility may strongly associate with the susceptibility to lung carcinogenesis.

Immunohistochemically detected p53 and P-glycoprotein predict the response to chemotherapy in lung cancer

While resistance to chemotherapy is a major problem in lung cancer treatment, there is no useful predictor of treatment response. We thus designed this study to determine the utility of p53 and P-glycoprotein expression in predicting the response to chemotherapy in patients with primary lung cancer, retrospectively. We evaluated transbronchial biopsy (TBB) specimens from 60 patients with lung cancer, who were previously untreated. Formalin-fixed, paraffin-embedded TBB specimens were immunostained using anti-p53 antibody (DO-1) and anti-P-glycoprotein antibody (JSB-1). The positivity of p53 was 63%, and that of P-glycoprotein was 17%. No correlation was observed between p53 and P-glycoprotein immunostaining. Positivity of p53 correlated significantly (P = 0.004) with a lack of response to chemotherapy in non-small cell lung cancer (NSCLC), but not in small cell lung cancer (SCLC). In contrast, positivity of P-glycoprotein was correlated with chemotherapy resistance in SCLC (P = 0.003), but not in NSCLC. Multiple logistic regression analysis revealed that positive immunostaining for p53 was a significant risk factor for chemotherapy resistance in NSCLC. These results suggest that immunostaining of p53 and P-glycoprotein for TBB specimens may help to predict response to chemotherapy in NSCLC and SCLC, although the results should be confirmed in a larger, more homogeneous series.

Environmental factors and aryl hydrocarbon hydroxylase activity (CYP1A1 phenotype) in human lymphocytes

Since aryl hydrocarbon hydroxylase (AHH) is considered to be responsible for the activation of benzo(a)pyrene (BP) and other polyaromatic hydrocarbons in cigarette smoke to carcinogens, it is important to examine AHH activity in the determination of susceptibility to lung cancer. Lymphocytes from healthy male adults (239) of non-smokers and smokers were cultured in vitro and assayed for non-induced and 3-methylcholanthrene (MC)-induced AHH activity and AHH inducibility (MC-induced AHH activity/non-induced AHH activity). A day-to-day variation in AHH activity was not observed while a seasonal variation was apparent. Very wide differences in non-induced AHH and MC-induced AHH activities were observed. The association of some selected environmental factors and AHH activity was studied. Age was related to non-induced AHH activity (Spearman's rank correlation coefficients (r), r = 0.185, p < 0.005) and AHH inducibility (r = -0.329, p < 0.001). Coffee consumption was associated with non-induced (age-adjusted r = 0.138, p < 0.05) and MC-induced AHH activity (age-adjusted r = 0.173, p < 0.01). Cigarette smoking was correlated with non-induced AHH activity (age-adjusted r = 0.191, p < 0.005) and AHH inducibility (age-adjusted r = -0.191, p < 0.005). No significant association was observed for any other selected factors, including alcohol intake or broiled food consumption. In conclusion, AHH activity might be affected by cigarette smoking and coffee consumption, and was dependent on the age of the donor. Day-to-day and seasonal variation analyses showed that this assay method was reproducible and reliable and AHH inducibility might be a useful biomarker in cancer epidemiology. As those factors may affect the AHH activity, a careful control of those factors to AHH activity is necessary in epidemiological studies on the association between AHH inducibility in human lymphocytes and lung cancer.

The case fatality rate of methicillin-resistant Staphylococcus aureus (MRSA) infection among the elderly in a geriatric hospital and their risk factors

From April 1991 to March 1993, there were 49 elderly patients with methicillin-resistant Staphylococcus aureus (MRSA) infection in a geriatric hospital in Fukuoka, Japan. The retrospective study was carried out in order to evaluate the various factors which may influence the case fatality rate of MRSA infection among the elderly. Among them, 33 patients (67.3%) died while only 16 patients became culture-negative for MRSA and discharged after recovering from MRSA infection. A univariate analysis revealed that male sex (odds ratio [OR] = 12.25, 95% confidence interval [CI] = 2.80-53.55), hypoalbuminemia (OR = 3.83, 95% CI = 1.11-13.21) and an excessive usage of antibiotics (OR = 6.67, 95% CI = 1.70-26.09) were risk factors for death among the patients with MRSA infection. In a multivariate analysis, male sex and an excessive usage of antibiotics were still risk factors while hypoalbuminemia was not. However, hypoalbuminemina was more common in male patients than female patients (78.3% vs. 42.3%, p < 0.05). These findings suggest that the case fatality rate of MRSA infection may be high and also suggest that the elderly with MRSA infection who had hypoalbuminemia and/or received many antibiotics may have a poor prognosis.

Methicillin-resistant Staphylococcus aureus (MRSA) isolation from pharyngeal swab cultures of Japanese elderly at admission to a geriatric hospital

The isolation rate of the methicillin-resistant Staphylococcus aureus(MRSA) from pharyngeal swab cultures in Japanese elderly was studied at admission to a geriatric hospital. The subjects were 233 consecutive patients admitted to Kitakyushu Tsuyazaki Hospital from April 1994 to March 1996. The isolation rate of MRSA was 3.0% in the patients admitted from their own homes, 9.7% in those transferred from nursing homes and 14.0% in those transferred from other hospitals. The patients from their own homes were younger than those from nursing homes, the latter being older than those transferring from other hospitals. The patients from their own homes had better activities of daily living(ADL), higher levels of hemoglobin and serum albumin than those from nursing homes or other hospitals. The white blood cell counts, and the proportion of patients with positive c-reactive protein or with fever did not differ among the three groups. Multiple logistic regression analysis revealed that fever and ADL disability were independent risk factors for the isolation of MRSA, and hypoalbuminemia was a risk factor for MRSA isolation in the model using serum albumin instead of ADL score. These results suggest that the lower isolation rate MRSA among patients from their own homes may be partly due to better ADL and nutritional status compared with those from nursing homes or other hospitals.

Risk factors for left ventricular hypertrophy in chronic hemodialysis patients

Left ventricular hypertrophy is reported to be common in chronic hemodialysis patients, and also to increase the risk for mortality in chronic hemodialysis patients. An echocardiographical and clinical study was carried out to investigate the risk factors for left ventricular hypertrophy in 151 non-diabetic chronic hemodialysis patients without valvular diseases or myocardial infarction in two hemodialysis units in Fukuoka, Japan. The left ventricular mass index (LVMI) correlated positively to age, systolic blood pressure and interdialysis weight gain while it correlated negatively to the duration of hemodialysis therapy and hematocrit. Resorting to a multivariate analysis, the LVMI was found to positively correlate to age and the systolic blood pressure while it correlated negatively with the duration of hemodialysis therapy and the hematocrit level. These findings suggest that hypertension and anemia may thus be independent risk factors for left ventricular hypertrophy.

Relationship of alcohol use, physical activity and dietary habits with serum carotenoids, retinol and alpha-tocopherol among male Japanese smokers

BACKGROUND

Despite considerable interest in the anticarcinogenic and anti-atherosclerotic effects of carotenoids and alpha-tocopherol, little is known about determinants of these serum micronutrients.

METHODS

The association of lifestyle factors including alcohol use, physical activity and dietary habits with serum levels of carotenoids (lycopene, lutein, cryptoxanthin and beta-carotene), retinol and alpha-tocopherol were studied in 194 healthy men aged 24-60 years who smoked > 15 cigarettes/day. A self-administered questionnaire ascertained consumption frequency of 12 food items, alcohol consumption, levels of physical activity and the number of cigarettes smoked per day.

RESULTS

Of the dietary items studied, total vegetable intake was significantly, positively associated with beta-carotene levels, as was fruit intake with serum levels of each carotenoid. Tofu intake was unexpectedly, but strongly related to decreased levels of cryptoxanthin and beta-carotene. None of the food items was materially related to serum levels of retinol and alpha-tocopherol. Alcohol consumption was most strongly and inversely associated with levels of all the carotenoids except lutein, whereas was positively associated with retinol level but not with alpha-tocopherol level. Frequency of participation in sports was significantly and positively associated with both retinol and alpha-tocopherol levels. The amount of cigarettes smoked per day was unrelated to each micronutrient level in this study of moderate or heavy smokers.

CONCLUSIONS

The consumption of vegetables and fruits is an important determinant of serum carotenoid levels even in smokers. Alcohol consumption is inversely associated with carotenoid levels, although the mechanism for this is not clear. Tofu and physical activity influence serum levels of antioxidative micronutrients, and these relationships need further studies.

The relationship between aryl hydrocarbon hydroxylase and polymorphisms of the CYP1A1 gene

We examined the relationship between aryl hydrocarbon hydroxylase (AHH) and the frequency of a MspI mutation in the 3'-flanking region of cytochrome P450 (CYP) 1A1 (MspI polymorphism) and another mutation in exon 7 (Ile-Val polymorphism) in 84 healthy male subjects in Fukuoka, Japan. AHH inducibility (3-methylcholanthrene (MC)-induced AHH activity/non-induced AHH activity) was correlated with the MspI polymorphism (P < 0.0001) and age class (P = 0.015), whereas no correlation was found for the Ile-Val polymorphism (P = 0.509). Age-adjusted AHH inducibility (mean +/- SE) of the predominant homozygote (genotype A), the heterozygote (genotype B) and a homozygote rare allele (genotype C) genotypes was 4.89 +/- 0.36, 4.82 +/- 0.29 and 13.61 +/- 1.44, respectively. The genotype C showed much higher AHH inducibility than genotypes A and B (P < 0.001), while no significant difference was observed between genotypes A and B. Non-induced AHH activity was also correlated with these polymorphisms. The AHH activity of a homozygous mutant Val/Val genotype (0.076 +/- 0.010 pmol/min/10(6) cells) was significantly higher (P < 0.05) than that of the wild-type homozygous Ile/Ile (0.044 +/- 0.004 pmol/min/10(6) cells) and heterozygous Ile/Val (0.047 +/- 0.007 pmol/min/10(6) cells) genotypes. Our study suggests that the genotypes C and Val/Val, which are more frequent in smoking-related lung cancer, are closely related with high AHH inducibility and high non-induced AHH activity, respectively. Thus, the positive relationship between AHH inducibility and lung cancer is supported by our study. If our results are confirmed and the assessment of genotype becomes feasible on a population basis, identification of smokers who have genetically high susceptibility to lung cancer (genotype C or Val/Val) may become important for the prevention of lung cancer.

Effects of polychlorinated dibenzo-p-dioxin and dibenzofuran congeners in human lymphoblastoid cells on aryl hydrocarbon hydroxylase activity

The separate and concurrent effects of polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners on aryl hydrocarbon hydroxylase (AHH) activity in human lymphoblastoid cells were examined. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-tetraCDD) induced AHH activity about 9-fold acetone-treated AHH activity, while octachlorodibenzo-p-dioxin (octaCDD) did not affect the AHH activity and 2,4,6,8-tetrachlorodibenzofuran (2,4,6,8-tetraCDF) reduced the AHH activity by 34%. The concurrent effect of 2,3,7,8-tetraCDD with 1,3,6,8-tetraCDD on AHH inducibility was much smaller than expected. The concurrent effect of 2,3,7,8-tetraCDD with 2,4,6,8-tetraCDF, octaCDD or 3,3',4,4',5,5'-hexaCB was as much as the effect of 2,3,7,8-tetraCDD alone. There was a difference between 3-methylcholanthrene (MC) and 2,3,7,8-tetraCDD in the concurrent effects of 3-methylsulfone-3',4,4',5-tetraCB (3-MSF-3',4,4',5-tetraCB) on AHH activity. The concurrent effect of MC with 3-MSF-3',4,4',5-tetraCB on AHH activity was equal to the effect of MC alone while that of 2,3,7,8-tetraCDD and 3-MSF-3',4,4',5-tetraCB on AHH activity was inhibitory. These results imply that congeners of PCDD and PCDF are considered to be more or less effective and isozymes of cytochrome P450, key enzymes for the AHH, induced by them are differently inhibited.

Polymorphisms of human Ah receptor gene are not involved in lung cancer

The Ah receptor (Ahr) is a ligand-dependent transcription factor that positively regulates inducible expression of the CYP1A1 gene. Based on the sequence information of the human Ahr and the intron-exon junctions of the mouse counterpart, an analysis of single-strand conformational polymorphism (SSCP) was carried out to detect subtle base differences in the coding region of the gene among individuals. We found that the Ahr protein has at least two forms of variants in a Japanese gene pool, and that these variants can be ascribed to one amino acid replacement of Arg by Lys at codon 554. The frequencies of Arg-coded and Lys-coded alleles were 0.57 and 0.43, respectively. We found, however, that this germ line polymorphism of the Ahr gene did not show a significant association with aryl hydrocarbon hydroxylase (AHH) inducibility nor with lung cancer incidence.

[A role of aryl hydrocarbon hydroxylase inducibility in susceptibility to lung carcinogenesis]

Lung cancer mortality has been increasing rapidly in recent years in Japan and is expected to exceed that of stomach cancer in male Japanese in the near future. Although chronic inhalation of cigarette smoke is a major risk factor for the development of lung cancer, it seems important to examine genetic susceptibility to the disease as well. Aryl hydrocarbon hydroxylase (AHH), a drug-metabolism enzyme, is useful in determining the individual differences in genetic susceptibility to lung carcinogenesis. AHH is a microsomal membrane-bound monooxygenase system located in most tissues of the body. In mice, AHH inducibility is under the control of the Ah locus and certain inbred strains of mice are susceptible to AHH induction by 3-methylcholanthrene treatment (Ah responsive strains), while other strains are not (Ah non-responsive strains). A strong correlation was observed between AHH inducibility and tumor incidence in mice. Since AHH is also responsible for the activation to carcinogens of benzo (a)pyrene and other aromatic hydrocarbons in cigarette smoke, it may also be important in humans in the causation of lung cancer. Kellermann et al. investigated the genetics of AHH in a human population and reported that the inducibility of this enzyme was controlled by a single gene locus with 2 dominant alleles. They classified humans as having low, intermediate, or high inducibility of AHH. In addition, they reported a significant positive correlation between the extent of inducibility and susceptibility to lung cancer. Their claim, however, has been both supported and refuted by subsequent investigators. Recently, a close association between development of lung cancer and three polymorphisms of CYP1A1 caused by the presence or absence of one MspI site in the 3'-flanking region, namely, a predominant homozygote pattern (A), a heterozygote pattern (B) and a homozygous rare allele pattern (C), has been reported. The relationship between AHH inducibility and polymorphisms of CYP1A1 had not been investigated previously. Our study indicated that the genotype of C, very frequent in Kreyberg type I, was closely related to high AHH inducibility. Thus, the relationship between AHH inducibility and lung cancer, suggested by Kellermann et al., is supported by our study. Further studies will be needed to confirm the present results. Identification of smokers who have genetically high susceptibility to lung cancer (pattern C), may become important for the prevention of lung cancer.

In vivo effect of 7,8-benzoflavone on aryl hydrocarbon hydroxylase activity of mouse liver microsomes

In vivo administration of 3-methylcholanthrene (MC) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) produced much higher hepatic microsomal aryl hydrocarbon hydroxylase (AHH) induction than 7,8-benzoflavone (7,8-BF) in both aromatic hydrocarbon (Ah)-responsive and nonresponsive strains of mice. Simultaneous treatment or pre-treatment with 7,8-BF produced an inhibitory effect on AHH induction by MC or TCDD (i.e., the degrees of the inhibition, with TCDD, were 28% in the Ah-responsive strain C57BL/6N (C57) mice and 45% in the nonresponsive strain DDD;Qdj (DDD) mice). However, posttreatment with 7,8-BF was inclined to promote the induction of AHH by MC or TCDD (i.e., the degrees of the enhancement, with MC, were 15% in C57 mice and 45% in DDD mice). These results may suggest that the inhibitory effect of 7,8-BF in vivo is limited not to the combination of AHH inducer (MC or TCDD) but to its application of timing or Ah responsiveness.