Sex differences in risk of lung cancer: Expression of genes in the PAH bioactivation pathway in relation to smoking and bulky DNA adducts

Sexually-dimorphic targeting of functionally-related genes in COPD

BACKGROUND

There is growing evidence that many diseases develop, progress, and respond to therapy differently in men and women. This variability may manifest as a result of sex-specific structures in gene regulatory networks that influence how those networks operate. However, there are few methods to identify and characterize differences in network structure, slowing progress in understanding mechanisms driving sexual dimorphism.

RESULTS

Here we apply an integrative network inference method, PANDA (Passing Attributes between Networks for Data Assimilation), to model sex-specific networks in blood and sputum samples from subjects with Chronic Obstructive Pulmonary Disease (COPD). We used a jack-knifing approach to build an ensemble of likely networks for each sex. By adapting statistical methods to compare these network ensembles, we were able to identify strong differential-targeting patterns associated with functionally-related sets of genes, including those involved in mitochondrial function and energy metabolism. Network analysis also identified several potential sex- and disease-specific transcriptional regulators of these pathways.

CONCLUSIONS

Network analysis yielded insight into potential mechanisms driving sexual dimorphism in COPD that were not evident from gene expression analysis alone. We believe our ensemble approach to network analysis provides a principled way to capture sex-specific regulatory relationships and could be applied to identify differences in gene regulatory patterns in a wide variety of diseases and contexts.

Gender susceptibility for cigarette smoking-attributable lung cancer: a systematic review and meta-analysis

OBJECTIVES

As the primary cause of lung cancer, whether smoking confers the same risk of lung cancer for women as men is unclear. Therefore, we aimed to compare male and female susceptibility for cigarette smoking-attributable lung cancer.

METHODS

A systematic review and meta-analysis was conducted by searching articles published up to July 2013 in three online databases (MEDLINE, EMBASE, and Cochrane Database). All studies estimated the association of cigarette smoking with the risk of lung cancer between men and women, respectively. A random effects model with inverse variance weighting was used to pool data. Male to female ratio of relative risk (RRR) was calculated to compare male and female susceptibility for cigarette smoking-attributable lung cancer.

RESULTS

47 articles containing 404,874 individuals were included in the final analysis. Compared with non-smokers, male to female RRR was 1.61 (95%CI: 1.37, 1.89) among current smokers. Based on pathological type, adenocarcinoma had the highest RRR (1.42; 95%CI: 0.86, 2.35), followed by squamous cancer and small cell lung cancer. Furthermore, compared with non-smoking men, current smoking men had higher risk of lung cancer than women in spite of smoking quantity, smoking duration or years since quitting.

CONCLUSIONS

These findings indicated that males had higher susceptibility for cigarette smoking-attributable lung cancer than females. It is contradicted with traditional opinion that females would be more easily suffered from cigarette smoking-attributable health problems than males. Hence, tobacco control is very crucial in both males and females.

Women are more susceptible than men to oxidative stress and chromosome damage caused by polycyclic aromatic hydrocarbons exposure

Exposure to environmental polycyclic aromatic hydrocarbons (PAHs) has been associated with increased risk of cancer, but evidence for gender differences in this association is limited. The aim of this study was to examine the gender differences in PAHs caused early genotoxic effects such as oxidative stress and chromosome damage, which are potential carcinogenic etiology of PAHs. A total of 478 nonsmoking workers (272 men and 206 women) from a coke oven plant were recruited. We determined 16 environmental PAHs in their workplaces, and measured concentrations of 12 urinary PAH metabolites (OH-PAHs), plasma benzo[a]pyrene-r-7,t-8,t-9,c-10-tetrahydotetrol-albumin (BPDE-Alb) adducts, urinary 8-hydroxydeoxyguanosine (8-OHdG) and 8-iso-prostaglandin-F2α (8-iso-PGF2α), and micronucleus frequencies in lymphocytes in all subjects. It showed that, women working at the office, adjacent to the coke oven, and on the bottom or side of the coke oven displayed significantly higher levels of urinary 8-OHdG and 8-iso-PGF2α, and lymphocytic micronucleus frequencies compared with men working at above areas, respectively (all P < 0.05). These gender differences remain significant after adjusted for potential confounders and urinary ΣOH-PAHs or plasma BPDE-Alb adducts. A significant interaction existed between gender and BPDE-Alb adducts on increasing micronucleus frequencies (Pinteraction  < 0.001). We further stratified all workers by the tertiles of urinary ΣOH-PAHs or plasma BPDE-Alb adducts, and the above gender differences were more evident in the median- and high-exposure groups (all P < 0.05). In conclusion, women were more susceptible than men to oxidative stress and chromosome damage induced by PAHs, which may add potential evidence underlying gender differences in PAH exposure-related lung cacinogenesis.

Heavy smoking and lung cancer: are women at higher risk? Result of the ICARE study

Background:

Whether women are more or equally susceptible to the carcinogenic effects of cigarette smoke on the lungs compared with men is a matter of controversy. Using a large French population-based case–control study, we compared the lung cancer risk associated with cigarette smoking by gender.

Methods:

The study included 2276 male and 650 female cases and 2780 male and 775 female controls. Lifetime smoking exposure was represented by the comprehensive smoking index (CSI), which combines the duration, intensity and time since cessation of smoking habits. The analysis was conducted among the ever smokers. All of the models were adjusted for age, department (a regional administrative unit), education and occupational exposures.

Results:

Overall, we found that the lung cancer risk was similar among men and women. However, we found that women had a two-fold greater risk associated with a one-unit increase in CSI than men of developing either small cell carcinoma (OR=15.9, 95% confidence interval (95% CI) 7.6, 33.3 and 6.6, 95% CI 5.1, 8.5, respectively; P<0.05) or squamous cell carcinoma (OR=13.1, 95% CI 6.3, 27.3 and 6.1, 95% CI 5.0, 7.3, respectively; P<0.05). The association was similar between men and women for adenocarcinoma.

Conclusion:

Our findings suggest that heavy smoking might confer to women a higher risk of lung cancer as compared with men.

Polyaromatic hydrocarbon exposure: an ecological impact ambiguity

Polyaromatic hydrocarbons (PAHs) represent a fraction of petroleum hydrocarbons and are currently one of the foremost sources of generating energy in today's contemporary society. However, evidence highlighted in this review show that PAH pollution, as a result of oil spills, hazardous PAH-contaminated working environments and technologies which do not efficiently utilise fuels, as well as natural sources of emissions (e.g. forest fires) may have significant health implications for all taxa. The extent of damage to organisms from PAH exposure is dependent on numerous factors including degree and type of PAH exposure, nature of the environment contaminated (i.e. terrestrial or aquatic), the ability of an organism to relocate to pristine environments, type and sensitivity of organism to specific hydrocarbon fractions and ability of the organism to metabolise different PAH fractions. The review highlights the fact that studies on the potential damage of PAHs should be carried out using mixtures of hydrocarbons as opposed to individual hydrocarbon fractions due to the scarcity of individual fractions being a sole contaminant. Furthermore, potential damage of PAH-contaminated sites should be assessed using an entire ecological impact outlook of the affected area.

Recent advances in particulate matter and nanoparticle toxicology: a review of the in vivo and in vitro studies

Epidemiological and clinical studies have linked exposure to particulate matter (PM) to adverse health effects, which may be registered as increased mortality and morbidity from various cardiopulmonary diseases. Despite the evidence relating PM to health effects, the physiological, cellular, and molecular mechanisms causing such effects are still not fully characterized. Two main approaches are used to elucidate the mechanisms of toxicity. One is the use of in vivo experimental models, where various effects of PM on respiratory, cardiovascular, and nervous systems can be evaluated. To more closely examine the molecular and cellular mechanisms behind the different physiological effects, the use of various in vitro models has proven to be valuable. In the present review, we discuss the current advances on the toxicology of particulate matter and nanoparticles based on these techniques.

An in vitro investigation of endocrine disrupting effects of the mycotoxin alternariol

Alternariol (AOH) is a mycotoxin commonly produced by Alternaria alternata on a wide range of foods. Few studies to date have been performed to evaluate the effects of AOH on endocrine activity. The present study makes use of in vitro mammalian cellular based assays and gene expression to investigate the ability of AOH to act as an endocrine disruptor by various modes of action. Reporter gene assays (RGAs), incorporating natural steroid hormone receptors for oestrogens, androgens, progestagens and glucocorticoids were used to identify endocrine disruption at the level of nuclear receptor transcriptional activity, and the H295R steroidogenesis assay was used to assess endocrine disruption at the level of gene expression and steroid hormone production. AOH exhibited a weak oestrogenic response when tested in the oestrogen responsive RGA and binding of progesterone to the progestagen receptor was shown to be synergistically increased in the presence of AOH. H295R cells when exposed to 0.1-1000ng/ml AOH, did not cause a significant change in testosterone and cortisol hormones but exposure to 1000ng/ml (3.87μM) AOH resulted in a significant increase in estradiol and progesterone production. In the gene expression study following exposure to 1000ng/ml (3.87μM) AOH, only one gene NR0B1 was down-regulated, whereas expression of mRNA for CYP1A1, MC2R, HSD3B2, CYP17, CYP21, CYP11B2 and CYP19 was up-regulated. Expression of the other genes investigated did not change significantly. In conclusion AOH is a weak oestrogenic mycotoxin that also has the ability to interfere with the steroidogenesis pathway.

Association of carcinogenic polycyclic aromatic hydrocarbon emissions and smoking with lung cancer mortality rates on a global scale

The objective of this research was to investigate the relationship between lung cancer mortality rates, carcinogenic polycyclic aromatic hydrocarbon (PAH) emissions, and smoking on a global scale, as well as for different socioeconomic country groups. The estimated lung cancer deaths per 100,000 people (ED100000) and age standardized lung cancer death rate per 100,000 people (ASDR100000) in 2004 were regressed on PAH emissions in benzo[a]pyrene equivalence (BaPeq), smoking prevalence, cigarette price, gross domestic product per capita, percentage of people with diabetes, and average body mass index using simple and multiple linear regression for 136 countries. Using stepwise multiple linear regression, a statistically significant positive linear relationship was found between loge(ED100000) and loge(BaPeq) emissions for high (p-value <0.01) and for the combination of upper-middle and high (p-value <0.05) socioeconomic country groups. A similar relationship was found between loge(ASDR100000) and loge(BaPeq) emissions for the combination of upper-middle and high (p-value <0.01) socioeconomic country groups. Conversely, for loge(ED100000) and loge(ASDR100000), smoking prevalence was the only significant independent variable in the low socioeconomic country group (p-value <0.001). These results suggest that reducing BaPeq emissions in the U.S., Canada, Australia, France, Germany, Brazil, South Africa, Poland, Mexico, and Malaysia could reduce ED100000, while reducing smoking prevalence in Democratic People's Republic of Korea, Nepal, Mongolia, Cambodia, and Bangladesh could significantly reduce the ED100000 and ASDR100000.

Are women who smoke at higher risk for lung cancer than men who smoke?

Worldwide lung cancer incidence is decreasing or leveling off among men, but rising among women. Sex differences in associations of tobacco carcinogens with lung cancer risk have been hypothesized, but the epidemiologic evidence is conflicting. We tested sex-smoking interaction in association with lung cancer risk within a population-based case-control study, the Environment and Genetics in Lung Cancer Etiology (EAGLE) Study (Lombardy, Italy, 2002-2005). Detailed lifetime smoking histories were collected by personal interview in 2,100 cases with incident lung cancer and 2,120 controls. Odds ratios and 95% confidence intervals for pack-years of cigarette smoking were estimated by logistic regression, adjusted for age, residence area, and time since quitting smoking. To assess sex-smoking interaction, we compared the slopes of odds ratios for logarithm of pack-years in a model for men and women combined. Overall, the slope for pack-years was steeper in men (odds ratio for female-smoking interaction = 0.39, 95% confidence interval: 0.24, 0.62; P < 0.0001); after restriction to ever smokers, the difference in slopes was much smaller (odds ratio for interaction = 0.63, 95% confidence interval: 0.29, 1.37; P = 0.24). Similar results were found by histological type. Results were unchanged when additional confounders were evaluated (e.g., tobacco type, inhalation depth, Fagerström-assessed nicotine dependence). These findings do not support a higher female susceptibility to tobacco-related lung cancer.

Lung cancer in women

Recent biological advances in tumor research provide clear evidence that lung cancer in females is different from that in males. These differences appear to have a direct impact on the clinical presentation, histology, and outcomes of lung cancer. Women are more likely to present with lung adenocarcinoma, tend to receive a diagnosis at an earlier age, and are more likely to be diagnosed with localized disease. Women may also be more predisposed to molecular aberrations resulting from the carcinogenic effects of tobacco, but do not appear to be more susceptible than men to developing lung cancer. The gender differences found in female lung cancer make it mandatory that gender stratification is used in clinical trials in order to improve the survival rates of patients with lung cancer.

DNA and protein adducts in human tissues resulting from exposure to tobacco smoke

Tobacco smoke contains a variety of genotoxic carcinogens that form adducts with DNA and protein in the tissues of smokers. Not only are these biochemical events relevant to the carcinogenic process, but the detection of adducts provides a means of monitoring exposure to tobacco smoke. Characterization of smoking-related adducts has shed light on the mechanisms of smoking-related diseases and many different types of smoking-derived DNA and protein adducts have been identified. Such approaches also reveal the potential harm of environmental tobacco smoke (ETS) to nonsmokers, infants and children. Because the majority of tobacco-smoke carcinogens are not exclusive to this source of exposure, studies comparing smokers and nonsmokers may be confounded by other environmental sources. Nevertheless, certain DNA and protein adducts have been validated as biomarkers of exposure to tobacco smoke, with continuing applications in the study of ETS exposures, cancer prevention and tobacco product legislation. Our article is a review of the literature on smoking-related adducts in human tissues published since 2002.

Gender differences in chemical carcinogenesis in National Toxicology Program 2-year bioassays

Differences in cancer incidences between men and women are often explained by either differences in environmental exposures or by influences of sex hormones. However, there are few studies on intrinsic gender differences in susceptibility to chemical carcinogens. We have analyzed the National Toxicology Program (NTP) database for sex differences in rat responses to chemical carcinogens. We found that the odds that male rat bioassays were assigned a higher level of evidence than female rat bioassays was 1.69 (p < .001). Of 278 carcinogenic chemicals in the database, 201 (72%) exhibited statistical gender differences (p ≤ .05) in at least one nonreproductive organ. One hundred thirty of these 201 chemicals induced gender-specific tumors in male rats and 59 in female rats. Sixty-eight chemicals induced tumors in males but no tumors in females. Less than one third (i.e., 19 chemicals) induced tumors in females but not males. Male-specific tumors included pancreatic and skin tumors, and female-specific tumors included lung tumors. For some tumor sites, these differences in gender susceptibility can be associated with literature data on sex hormone receptor expression. In conclusion, gender-specific tumors were common. The male dominance is in line with recent human data, and the male susceptibility to carcinogens should be further studied.

Non-steroidal anti-inflammatory drugs and endometrial cancer risk in the VITamins And Lifestyle (VITAL) cohort

OBJECTIVE

Chronic inflammation may be an important factor in the initiation and promotion of endometrial cancer. Use of non-steroidal anti-inflammatory drugs (NSAIDs), however, has been inconsistently associated with endometrial cancer risk.

METHODS

22,268 female residents of western Washington State, ages 50-76, completed a baseline questionnaire in 2000-2002 and reported on their use of individual NSAIDs over the past 10years. Use was categorized as none, low (<4days/week or <4years), and high (≥4days/week and ≥4years). Over 9years of follow-up, 262 incident invasive endometrial cancers were identified. Multivariable proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Relative to non-use, high use of aspirin was inversely associated with endometrial cancer risk (HR 0.64, 95% CI: 0.41-1.01; P trend=0.03). Findings were stronger for regular-strength than low-dose aspirin. High use of non-aspirin NSAIDs (HR 1.15, 95% CI: 0.68-1.95), including ibuprofen (HR 1.29, 95% CI: 0.73-2.28), and naproxen (HR 1.08, 95% CI: 0.39-2.95) was not associated with risk. In subgroup analyses, findings for aspirin were strongest for cancers of endometrioid histology and were restricted to non-smokers.

CONCLUSIONS

This study provides additional evidence that use of aspirin, but not non-aspirin NSAIDs, may reduce the risk of endometrial cancer, especially in estrogen-mediated cases; however additional prospective studies with high-quality measurement of NSAID use are needed. Aspirin should continue to be examined as a potential agent for cancer chemoprevention.

Genetic polymorphisms involved in carcinogen metabolism and DNA repair and lung cancer risk in a Japanese population

BACKGROUND

Several components of overall lung carcinogenesis, carcinogen metabolic and DNA repair pathways may be involved in individual genetic susceptibility to lung cancer.

METHODS

We evaluated the role of cytochrome P450 (CYP) 1A1 rs4646903 and rs104894, glutathione S-transferase (GST) M1 and GSTT1 deletion polymorphisms, GSTP1 rs1695, x-ray repair, excision repair cross-complementing group 2 (ERCC2) rs13181, complementing defective in Chinese hamster 1 rs25487, and XRCC3 rs861539 in a case-control study comprising 462 lung cancer cases and 379 controls in a Japanese population. Unconditional logistic regression was used to assess the adjusted odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

CYP1A1 rs4646903 (OR = 1.72, 95% CI = 1.25-2.38), rs1048943 (OR = 1.40, 95% CI = 1.02-1.92), the GSTM1 deletion polymorphism (OR = 1.38, 95% CI = 1.01-1.89), GSTP1 rs1695 (OR =1.48, 95% CI = 1.04-2.11), ERCC2 rs13181 (OR = 1.89, 95% CI = 1.28-2.78), and Chinese hamster 1 rs25487 (OR = 1.54, 95% CI = 1.12-2.13) were associated with lung cancer risk whereas the GSTT1 deletion polymorphism and XRCC3 rs861539 were not. A pertinent combination of multiple "at-risk" genotypes of CYP1A1 rs4646903, the GSTM1 deletion polymorphism and ERCC2 rs13181 was at a 5.94-fold (95% CI = 2.77-12.7) increased risk of lung cancer.

CONCLUSIONS

A pertinent combination of multiple at-risk genotypes may detect a high-risk group. Further studies are warranted to verify our findings.

Non-steroidal anti-inflammatory drugs and small cell lung cancer risk in the VITAL study

Few studies have examined the association between non-steroidal anti-inflammatory drug (NSAID) use and risk of small cell lung cancer (SCLC); among them, findings are mixed. Recently, we found that use of NSAIDs was differentially associated with lung cancer risk by histology. Here, we examine, more comprehensively, the association between individual NSAIDs and SCLC risk. 75,546 residents of western Washington State, ages 50-76, completed a baseline questionnaire in 2000-2002 and reported on their use of individual NSAIDs over the past 10 years. NSAID use was categorized as non-users, low (<4 days/week or <4 years), and high (≥4 days/week and ≥4 years). 111 SCLC were identified through linkage to a population-based cancer registry. Multivariable-adjusted Cox proportional hazards models including strong adjustment for smoking were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI). Compared to non-use, high use of regular-strength aspirin was associated with an elevated risk of SCLC (HR 1.78, 95% CI: 1.05-3.02; P-trend=0.03). Findings for low-dose aspirin were elevated but did not reach statistical significance. Use of non-aspirin NSAIDs was not associated with SCLC risk. Our findings provide further indication of heterogeneity in the association between aspirin and lung cancer morphologies. Large, prospective studies with comprehensive assessments of NSAID use and smoking history and data on both men and women, are needed in order to better understand the association between use of aspirin and SCLC.

DNA methylation of the CYP1A1 enhancer is associated with smoking-induced genetic alterations in human lung

CYP1A1 (cytochrome P4501A1) catalyze the conversion of polycyclic aromatic hydrocarbons into reactive metabolites, which may induce DNA damage. We hypothesized that DNA methylation of the CYP1A1 enhancer could be involved in inter-individual differences in mRNA levels of CYP1A1 or affect the smoking-induced DNA damage in human lung. Using DNA bisulfite conversion and pyrosequencing, we show that DNA methylation of the CYP1A1 enhancer is affected by smoking. In adjacent histologically normal lung from lung cancer patients (n = 120), low levels of DNA methylation of the CYP1A1 enhancer were related to high levels of smoking-induced hydrophobic DNA adduct (p < 0.03), and to the presence of TP53 or K-ras mutations in the corresponding lung tumors (p < 0.03). We found an inverse correlation between DNA methylation of the CYP1A1 enhancer and mRNA levels in vivo (Spearman r = -0.54; p < 0.0001). Thus, in lung tumor tissues, the CYP1A1 enhancer hypermethylation was associated with lower mRNA levels compared to adjacent histologically normal tissue (p < 0.0001). In vitro, using a panel of cultured human lung cells, we found hypermethylation of the CYP1A1 enhancer in cancer cell lines and an inverse correlation between DNA methylation and mRNA levels (Spearman r = -0.53; p = 0.003). Altogether, our results indicated that low levels of DNA methylation of the CYP1A1 enhancer in histologically normal human lung were associated with high CYP1A1 mRNA levels and with smoking-induced genetic alterations; thus, it may play a role in the initiation of lung carcinogenesis.

Single nucleotide polymorphisms as susceptibility, prognostic, and therapeutic markers of nonsmall cell lung cancer

Lung cancer is a major public health problem throughout the world. Among the most frequent cancer types (prostate, breast, colorectal, stomach, lung), lung cancer is the leading cause of cancer-related deaths worldwide. Among the two major subtypes of small cell lung cancer and nonsmall cell lung cancer (NSCLC), 85% of tumors belong to the NSCLC histological types. Small cell lung cancer is associated with the shortest survival time. Although tobacco smoking has been recognized as the major risk factor for lung cancer, there is a great interindividual and interethnic difference in risk of developing lung cancer given exposure to similar environmental and lifestyle factors. This may indicate that in addition to chemical and environmental factors, genetic variations in the genome may contribute to risk modification. A common type of genetic variation in the genome, known as single nucleotide polymorphism, has been found to be associated with susceptibility to lung cancer. Interestingly, many of these polymorphisms are found in the genes that regulate major pathways of carcinogen metabolism (cytochrome P450 genes), detoxification (glutathione S-transferases), adduct removal (DNA repair genes), cell growth/apoptosis (TP53/MDM2), the immune system (cytokines/chemokines), and membrane receptors (nicotinic acetylcholine and dopaminergic receptors). Some of these polymorphisms have been shown to alter the level of mRNA, and protein structure and function. In addition to being susceptibility markers, several of these polymorphisms are emerging to be important for response to chemotherapy/radiotherapy and survival of patients. Therefore, it is hypothesized that single nucleotide polymorphisms will be valuable genetic markers in individual-based prognosis and therapy in future. Here we will review some of the most important single nucleotide polymorphisms in the metabolic pathways that may modulate susceptibility, prognosis, and therapy in NSCLC.

[Sex- and species-differences on xenobiotic-induced toxicity: differences in constitutive and xenobiotic-mediated expression of cytochrome P450 1A subfamily enzymes (CYP1As)]

Cytochrome P450 1A subfamily enzymes (CYP1As) are important molecules in the metabolic activation of carcinogens such as polycyclic aromatic hydrocarbons and heterocyclic amines and are induced by their substrate exposure. There are species, sex, and organ differences in the induction of CYP1As, and susceptibilities to carcinogens are closely related to the constitutive and carcinogen-induced levels of CYP1As in target organs of experimental rodents. In this study, we investigated the induction of CYP1As and their species or sex differences after treatment with various chemicals using experimental animals and cultured cell lines. We found that: 1) newly established reporter cell lines, HepG2-A10 and KanR2-XL8, can be used for determining of activation of the aryl hydrocarbon receptor (AhR), a key transcription factor in the expression of CYP1As; 2) monocyclic aromatic amine (2-methoxy-4-nitroaniline) induced hepatic CYP1As in rats but not in other rodents in an AhR-independent manner; 3) androgen suppressed the constitutive expression or heterocyclic aromatic amine (Trp-P-1)-dependent induction of these enzymes in pigs and mice; and 4) nicardipine, a dihydropyridine calcium channel blocker, increased hepatic CYP1A expression in rats and augmented 3-methylcholanthrene-mediated induction of CYP1As and DNA-adduct formation in HepG2 cells. These findings indicate that there are species or sex differences in the induction of hepatic CYP1As via AhR-independent and unexplained transcriptional mechanisms. The elucidation of these mechanisms will aid in finding new predictors or developing new prevention strategies for chemical-induced carcinogenesis.

Airborne urban particles (Milan winter-PM2.5) cause mitotic arrest and cell death: Effects on DNA, mitochondria, AhR binding and spindle organization

Airborne particulate matter (PM) is considered to be an important contributor to lung diseases. In the present study we report that Milan winter-PM2.5 inhibited proliferation in human bronchial epithelial cells (BEAS-2B) by inducing mitotic arrest. The cell cycle arrest was followed by an increase in mitotic-apoptotic cells, mitotic slippage and finally an increase in "classical" apoptotic cells. Exposure to winter-PM10 induced only a slight effect which may be due to the presence of PM2.5 in this fraction while pure combustion particles failed to disturb mitosis. Fewer cells expressing the mitosis marker phospho-histone H3 compared to cells with condensed chromosomes, suggest that PM2.5 induced premature mitosis. PM2.5 was internalized into the cells and often localized in laminar organelles, although particles without apparent plasma membrane covering were also seen. In PM-containing cells mitochondria and lysosomes were often damaged, and in mitotic cells fragmented chromosomes often appeared. PM2.5 induced DNA strands breaks and triggered a DNA-damage response characterized by increased phosphorylation of ATM, Chk2 and H2AX; as well as induced a marked increase in expression of the aryl hydrocarbon receptor (AhR)-regulated genes, CYP1A1, CYP1B1 and AhRR. Furthermore, some disturbance of the organization of microtubules was indicated. It is hypothesized that the induced mitotic arrest and following cell death was due to a premature chromosome condensation caused by a combination of DNA, mitochondrial and spindle damage.

CYP1A1*2A polymorphism as a predictor of clinical outcome in advanced lung cancer patients treated with EGFR-TKI and its combined effects with EGFR intron 1 (CA)n polymorphism

BACKGROUND

Mutations in the epidermal growth factor receptor (EGFR) have been confirmed as predictors of efficacy for EGFR-tyrosine kinase inhibitors (TKIs). We investigated whether polymorphisms of the EGFR and cytochrome P450, family 1, member A1 (CYP1A1) genes were associated with clinical outcome in NSCLC patients treated with EGFR-TKI.

METHODS

Genotypes for the intron 1 (CA)n repeat and R497K polymorphisms in the EGFR gene and the *2A (3801 T→C) and *2C (2455 A→G) polymorphisms in CYP1A1 gene were evaluated in 115 NSCLC patients by PCR-RFLP and DNA sequencing. Genetic polymorphisms were correlated with clinical outcomes of EGFR-TKIs. From a subgroup of patients whose tumour tissues were available, associations between somatic EGFR mutations, EGFR expression, and genomic polymorphisms were also analysed.

RESULTS

EGFR intron 1 (CA)n and CYP1A1*2A polymorphisms were independent predictive factors (p=0.046, p=0.011, respectively) and the latter was also a prognostic factor (p=0.001) for patients treated with EGFR-TKIs. We also observed a strong synergistic effect from two genotypes. Specifically, patients with both the T/T allele of the CYP1A1 gene and shorter intron 1 CA repeats (≤ 16 CA) of the EGFR gene showed an improved response (p=0.002) compared with patients with the T/C or C/C allele and longer intron 1 CA repeats (both alleles >16 CA). In contrast, for R497K and CYP1A1*2C, no relationship was observed with clinical outcome for patients treated with EGFR-TKIs (p=0.573; p=0.629, respectively). Both SNPs in the CYP1A1 gene showed a correlation with EGFR somatic mutations.

CONCLUSIONS

The findings of this study suggest that the CYP1A1*2A polymorphism is a predictor for clinical outcome in NSCLC patients treated with EGFR-TKI therapy, and combining analysis of both CYP1A1*2A and EGFR intron 1 (CA)n polymorphisms may be useful for predicting treatment outcome in NSCLC patients treated with EGFR-TKIs.

In vitro steroidogenic effects of mixtures of persistent organic pollutants (POPs) extracted from burbot (Lota lota) caught in two Norwegian lakes

This study investigated the effects of two mixtures of persistent organic pollutants (POPs) on steroidogenesis in the H295R cell line. The two mixtures were obtained from the livers of burbot (Lota lota) caught in two Norwegian lakes (Mjøsa and Losna) with different contaminant profiles. Steroid hormone levels in the cell culture medium and mRNA levels of 16 genes involved in steroidogenesis were investigated. The crude Lake Mjøsa extract had to be diluted ten times more than the Lake Losna extract in order to prevent cytotoxicity. The ten times diluted Lake Mjøsa mixture had higher levels of DDT and derivates (∑DDTs, 1.7 times) and brominated flame retardants (∑BDEs and HBCD, 15-25 times) than the Lake Losna mixture, which, on the other hand, had higher concentrations of ∑PCBs (1.5 times higher) and also of HCB, ∑HCH isomers and ∑chlordane isomers (5-20 times higher). In the cell culture media, only cortisol levels were increased at the highest exposure concentration to the Lake Mjøsa mixture, while both cortisol and estradiol levels were increased following exposure to the two highest Lake Losna mixture exposure concentrations. Testosterone levels decreased only at the highest exposure concentration of the Lake Losna mixture. Multivariate models suggested that ∑PCBs, and to a lesser extent ∑DDTs, were responsible for the cortisol responses, while estradiol and testosterone alterations were best explained by HCB and ∑PCBs, respectively. Exposure to the mixtures generally increased mRNA levels, with smaller effects exerted by the Lake Mjøsa mixture than the Lake Losna mixture. It was concluded that both mixtures affected steroidogenesis in the H295R cells. Small differences in mixture composition, rather than the high content of brominated flame retardants in the Lake Mjøsa mixture, were suggested to be the most probable reason for the apparent differences in potencies of the two mixtures.

Cytochrome P450-mediated pulmonary metabolism of carcinogens: regulation and cross-talk in lung carcinogenesis

Lung cancer is strongly associated with exogenous risk factors, in particular tobacco smoking and asbestos exposure. New research data are accumulating about the regulation of the metabolism of tobacco carcinogens and the metabolic response to oxidative stress. These data provide mechanistic details about why well known risk factors cause lung cancer. The purpose of this review is to evaluate the present knowledge of the role of cytochrome P450 (CYP) enzymes in the metabolism of tobacco carcinogens and associations with tobacco and asbestos carcinogenesis. Major emphasis is placed on human data and regulatory pathways involved in CYP regulation and lung carcinogenesis. The most exciting new research findings concern cross-talk of the CYP-regulating aryl hydrocarbon receptor with other transcription factors, such as nuclear factor-erythroid 2-related factor 2, involved in the regulation of xenobiotic metabolism and antioxidant enzymes. This cross-talk between transcription factors may provide mechanistic evidence for clinically relevant issues, such as differences in lung cancers between men and women and the synergism between tobacco and asbestos as lung carcinogens.

Tobacco use and cessation among women: research and treatment-related issues

The prevalence of tobacco use in women has increased over the past century. This has resulted in dramatic increases in smoking-related lung diseases, such as chronic obstructive pulmonary disease (COPD) and lung cancer. There is growing literature suggesting that women may be more susceptible than men to the effects of tobacco and to the development of COPD. Women may also have specific barriers that interfere with smoking cessation. This article addresses possible differences in lung function decline and nicotine metabolism in women compared to men. Differences in COPD between the sexes are discussed. Finally, barriers to smoking cessation in women are presented.

Sex differences in susceptibility to PAHs is an intrinsic property of human lung adenocarcinoma cells

Recent epidemiological studies have disputed whether females are at increased risk of lung cancer compared to males. However, several molecular studies are in support of an increased susceptibility to tobacco smoke carcinogens among females. Our earlier findings suggest that women display higher levels of smoking-induced bulky/hydrophobic DNA adducts which may be related to an increased expression of CYP1A1 in their lungs, compared to men. In this in vitro study, 11 lung adenocarcinoma cell lines, 6 of male and 5 of female origin, were exposed to benzo[a]pyrene, cigarette smoke condensate (CSC), or vehicle control. Subsequent expression analysis of genes in the polycyclic aromatic hydrocarbon bioactivation pathway was conducted with Real-Time RT-PCR. DNA adducts were measured in benzo[a]pyrene-exposed cells by ³²P-postlabelling analysis, and CYP1 activity was measured by EROD assay. Analysis of benzo[a]pyrene-DNA adducts showed higher levels of adducts in cell lines from women compared to cell lines from men (p=0.03). The results also revealed significant sex differences in CYP1A1 gene expression, both in untreated cells (p=0.03), and in cells exposed to benzo[a]pyrene (p=0.017) and cigarette smoke condensate (p=0.0043). In CSC-exposed cells, significantly higher levels of CYP1 activity was found in cell lines of female origin (p=0.049). These results are in support of the previously published in vivo data, providing evidence for a higher susceptibility to PAH of women's lungs.

The influence of gender, race, and marital status on survival in lung cancer patients: analysis of Radiation Therapy Oncology Group trials

OBJECTIVE

A meta-analysis was conducted to determine the influence of gender, race, and marital status on overall survival (OS) in Radiation Therapy Oncology Group nonoperative non-small cell lung cancer trials.

MATERIALS AND METHODS

Data from 1365 patients treated on nine prospective Radiation Therapy Oncology Group studies activated during the 1990s were analyzed. Impact of gender, marital status, and race was considered in the Cox proportional hazards models. Age, Karnofsky performance status, weight loss, stage, histology, location of primary tumor, biologic equivalent dose, deviation from protocol dose, and education level were adjusted in the model. A two-sided p value <0.05 was considered statistically significant.

RESULTS

Males had significantly higher mortality than females adjusted for other covariates (hazard ratio [HR] 1.22, 95% confidence interval 1.08 -1.38). Race and marital status were not independently predictive for OS. Single females had significantly better OS than single males (HR 0.72), and married males had lower OS than single females (HR 1.36).

CONCLUSIONS

These results suggest that although certain subgroups of gender, race, and/or marital status have better outcomes with respect to OS; gender seems to be the most significant factor influencing survival results among nonoperative non-small cell lung cancer patients.

[Comparative analysis of clinical epidemiology and pathological characteristics of 908 patients with primary lung cancer of Hunan Province in 1997 and 2007]

BACKGROUND AND OBJECTIVE

Epidemiology of lung cancer will be changed along with time and region. The aim of this study is to acknowledge the tendency of primary lung cancer in hunan province in recent years by comparing and analyzing the distribution of gender, age, area, smoking and pathology of patients who were initial diagnosed lung cancer and ancestral or permanent residence of hunan province in 1997 and 2007.

METHODS

Clinical data of 908 patients with primary lung cancer hospitalized in Xiangya hospital were collected and evaluated.

RESULTS

Compared patients in 2007 with those in 1997, ratio between male and female dropped from 3.8:1 to 2.98:1, while the proportion of young patients who were under 40 years old raised from 4.4% to 8.6% (chi2 = 4.465, P = 0.035), patients living in the county raised from 19.9% to 40.1% (chi2 = 30.670, P < 0.001), smoking rate of patients from county raised from 16.9% to 39.9% (chi2 = 24.939, P < 0.01). In addition, the proportion of rare histological types of lung cancer were also increased from 1.3% to 4.5% (chi2 = 5.142, P = 0.023).

CONCLUSION

Female patients, young patients, rural patients and rare histological types of lung cancer may have a tendency of increase in hunan province in recent years, whereas smoking cessation education should be strengthened.

Reduced DNA repair capacity for removing tobacco carcinogen-induced DNA adducts contributes to risk of head and neck cancer but not tumor characteristics

PURPOSE

Although cigarette smoking and alcohol use are known risk factors for squamous cell carcinoma of head and neck (SCCHN), only a few exposed individuals develop this disease, suggesting an individual susceptibility. In this study, we investigated the associations between genetically determined DNA repair capacity (DRC) for removing tobacco-induced DNA adducts and risk of SCCHN and tumor characteristics.

EXPERIMENTAL DESIGN

We measured DRC in cultured T lymphocytes using the host-cell reactivation assay in a hospital-based case-control study of 744 SCCHN patients and 753 age-, sex-, and ethnicity-matched cancer-free controls recruited from The University of Texas M.D. Anderson Cancer Center.

RESULTS

Patients with SCCHN had significantly lower mean DRC (8.84% +/- 2.68%) than controls (9.97% +/- 2.61%; P < 0.0001), and the difference accounted for approximately 2-fold increased risk of SCCHN [adjusted odds ratio (OR), 1.91; 95% confidence interval (CI), 1.52-2.40] after adjustment for other covariates. Compared with the highest DRC quartile of controls, this increased risk was dose dependent (second highest quartile: OR, 1.40; 95% CI, 0.99-1.98; third quartile: OR, 1.87; 95% CI, 1.34-2.62; and fourth quartile: OR, 2.76; 95% CI, 1.98-3.84, respectively; P(trend) < 0.0001). We also assessed the performance of DRC in risk prediction models by calculating the area of under the receiver operating characteristic curve. The addition of DRC to the model significantly improved the sensitivity of the expanded model. However, we did not find the association between DRC and tumor sites and stages.

CONCLUSION

DRC is an independent susceptibility biomarker for SCCHN risk but not a tumor marker.

Differential expression of biomarkers in men and women

Lung cancer is one of the most common cancers in the world. While historically, more men than women have died from lung cancer as a result of higher numbers of male smokers, the sex mortality ratio is now showing signs of narrowing. Tumors in women with lung cancer may be slightly different to those in men with lung cancer. This review focuses on biomarkers differentially expressed between female and male patients with lung cancer. There is variation in gene expression between men and women in some genes that encode carcinogen-metabolizing enzymes (CYP1A1, GSTM). Gastrin-releasing peptide (GRP), a bombesin-like peptide, is present in two actively transcribed alleles in women compared with men. Higher prevalence of infection with oncogenic variants human papilloma viruses (HPVs) HPV16 and HPV18 has been suggested in women. A higher frequency of G to T transversion was found in the p53 gene in lung tumors of women. KRAS mutation was found to be more frequent in women with resected non-small cell lung cancer (NSCLC) than in men with resected NSCLC. Epidermal growth factor receptor (EGFR) mutation is more frequently found in lung tumors from women, but the confounding effect of tobacco exposure may explain this difference. Lower levels of ERCC1 and BRCA1 have been reported in women with NSCLC. Lung tumors from women are more likely to express estrogen receptors than those from men. An in silico analysis of transcriptome datasets from lung cancer patients demonstrated that only seven genes (in at least two studies) had significantly different expression patterns in male versus female patients. All of these genes are localized on the sex chromosomes: one on chromosome X and six on chromosome Y. Many areas remain under debate and there are still significant gaps in our understanding, particularly how sex-linked factors relate to lung cancer risk, and to biological and clinical behaviors. Future research into lung cancer needs to address these gender differences more specifically.

A comparison of exposure to carcinogens among roll-your-own and factory-made cigarette smokers

Consumption of roll-your-own (RYO) tobacco is rising, but little is known about its in vivo delivery of toxins relative to factory-made (FM) cigarettes. To start to address this issue, this study compared the concentrations of metabolites of recognized human carcinogens in smokers of RYO tobacco and FM cigarettes. We opportunistically recruited 127 FM and 28 RYO cigarette smokers in central London and collected saliva and urine samples. Saliva samples were assayed for cotinine while urinary samples were assayed for 1-hydroxypyrene (1-HOP) and total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), metabolic markers of polycyclic aromatic hydrocarbons and tobacco-specific N-nitrosamines, respectively. Data on socio-demographic, anthropometric and puffing characteristics were also obtained. Both unadjusted and adjusted analyses (controlling for age, sex, body mass index, puff flow, puff duration and cotinine) showed no difference in metabolic markers between RYO and FM cigarette smokers. However, significant main effects for cotinine levels and sex were observed in adjusted analyses. Greater levels of cotinine were associated with a greater concentration of both 1-HOP (B = 0.002, P = 0.037) and NNAL (B = 0.002, P < 0.001). In addition, women had significantly greater concentrations of urinary 1-HOP (B = 0.679, P = 0.004) and total NNAL metabolites (B = 0.117, P = 0.024) than men, irrespective of the type of cigarettes smoked. More research is now needed to confirm these findings and gender-specific effects in a larger, representative sample. However, results do not support the common belief that RYO cigarettes are less harmful than manufactured cigarettes.

Chlorophyllin significantly reduces benzo[a]pyrene-DNA adduct formation and alters cytochrome P450 1A1 and 1B1 expression and EROD activity in normal human mammary epithelial cells

We hypothesized that chlorophyllin (CHLN) would reduce benzo[a]pyrene-DNA (BP-DNA) adduct levels. Using normal human mammary epithelial cells (NHMECs) exposed to 4 microM BP for 24 hr in the presence or absence of 5 microM CHLN, we measured BP-DNA adducts by chemiluminescence immunoassay (CIA). The protocol included the following experimental groups: BP alone, BP given simultaneously with CHLN (BP+CHLN) for 24 hr, CHLN given for 24 hr followed by BP for 24 hr (preCHLN, postBP), and CHLN given for 48 hr with BP added for the last 24 hr (preCHLN, postBP+CHLN). Incubation with CHLN decreased BPdG levels in all groups, with 87% inhibition in the preCHLN, postBP+CHLN group. To examine metabolic mechanisms, we monitored expression by Affymetrix microarray (U133A), and found BP-induced up-regulation of CYP1A1 and CYP1B1 expression, as well as up-regulation of groups of interferon-inducible, inflammation and signal transduction genes. Incubation of cells with CHLN and BP in any combination decreased expression of many of these genes. Using reverse transcription real time PCR (RT-PCR) the maximal inhibition of BP-induced gene expression, >85% for CYP1A1 and >70% for CYP1B1, was observed in the preCHLN, postBP+CHLN group. To explore the relationship between transcription and enzyme activity, the ethoxyresorufin-O-deethylase (EROD) assay was used to measure the combined CYP1A1 and CYP1B1 activities. BP exposure caused the EROD levels to double, when compared with the unexposed controls. The CHLN-exposed groups all showed EROD levels similar to the unexposed controls. Therefore, the addition of CHLN to BP-exposed cells reduced BPdG formation and CYP1A1 and CYP1B1 expression, but EROD activity was not significantly reduced.

Biomarkers of induced active and passive smoking damage

In addition to the well-known link between smoking and lung cancer, large epidemiological studies have shown a relationship between smoking and cancers of the nose, oral cavity, oropharynx, larynx, esophagus, pancreas, bladder, kidney, stomach, liver, colon and cervix, as well as myeloid leukemia. Epidemiological evidence has reported a direct link between exposure of non-smokers to environmental tobacco smoke and disease, most notably, lung cancer. Much evidence demonstrates that carcinogenic-DNA adducts are useful markers of tobacco smoke exposure, providing an integrated measurement of carcinogen intake, metabolic activation, and delivery to the DNA in target tissues. Monitoring accessible surrogate tissues, such as white blood cells or bronchoalveolar lavage (BAL) cells, also provides a means of investigating passive and active tobacco exposure in healthy individuals and cancer patients. Levels of DNA adducts measured in many tissues of smokers are significantly higher than in non-smokers. While some studies have demonstrated an association between carcinogenic DNA adducts and cancer in current smokers, no association has been observed in ex or never smokers. The role of genetic susceptibility in the development of smoking related-cancer is essential. In order to establish whether smoking-related DNA adducts are biomarkers of tobacco smoke exposure and/or its carcinogenic activity we summarized all data that associated tobacco smoke exposure and smoking-related DNA adducts both in controls and/or in cancer cases and studies where the effect of genetic polymorphisms involved in the activation and deactivation of carcinogens were also evaluated. In the future we hope we will be able to screen for lung cancer susceptibility by using specific biomarkers and that subjects of compared groups can be stratified for multiple potential modulators of biomarkers, taking into account various confounding factors.

Paternal smoking, genetic polymorphisms in CYP1A1 and childhood leukemia risk

We conducted a case-control study to evaluate the association between paternal smoking and childhood leukemia and to evaluate potential modification by polymorphisms in CYP1A1. Histologically confirmed childhood leukemia cases (n=164) and non-cancer controls (n=164) were recruited from three teaching hospitals in Seoul, Korea. Five single nucleotide polymorphisms in CYP1A1 (-17961T>C, -9893G>A, I462V, 1188C>T (*2A), and 11599C>G) were genotyped and haplotypes were estimated by the expectation-maximization method. We also conducted a meta-analysis of 12 studies that have reported the association between paternal smoking and childhood leukemia risk. Paternal smoking at home was associated with all leukemias (OR=1.8, 95% CI=1.1-2.8) and acute lymphoblastic leukemia (ALL) (2.0, 1.2-3.4). An increasing trend in risk was observed for pack-years smoked after birth (P(trend)=0.06 and 0.02, respectively) and the number of smokers in the home during the child's life (P(trend)=0.05 and 0.03, respectively). Among those without the CGACC haplotype, ALL risk was significantly increased by the father's smoking at home (2.8, 1.5-5.3) and the presence of at least one smoker in the home (2.3, 1.2-4.4), and the test for interaction was significant (P(interaction)=0.03 and 0.02, respectively). The meta-analysis showed that overall paternal smoking (1.13, 1.04-1.24) and smoking before the pregnancy of the child (1.12, 1.04-1.21) were significantly associated with childhood leukemia risk. Our results suggest that paternal smoking is a risk factor for childhood leukemia and the effect may be modified by CYP1A1 genotype.

The changing epidemiology of lung cancer

The 20th century witnessed the scourge of lung cancer as the disease rapidly rose the ranks to become the commonest cause of cancer mortality in the world. Epidemiological evidence conclusively associated cigarette smoking with the causation of lung cancer in the 1950s. Since then and the few decades after, lung cancer of the squamous cell or small cell histological subtypes was mainly diagnosed among male smokers in developed countries. As we move into the 21st century, the incidence of lung cancer is unlikely to abate but the burden will shift from the developed to the less-developed countries. Other epi-demiological changes of lung cancer include the narrowing of the gap between men and women affected by the disease, predominance of the adenocarcinoma histological subtypes as well as more never-smokers afflicted with the disease. Unless we eliminate tobacco smoking completely, lung cancer will continue its wrath into the 21st century.

Estrogenic status modulates the effect of soy on hepatic responses to 7,12-dimethylbenz(a)anthracene (DMBA)

We examined the influence of estradiol (E2) status and soy protein isolate (SPI) intake on the hepatic responses altered by 7,12-dimethylbenz(a)anthracene (DMBA, a polycyclic aromatic hydrocarbon [PAH]). Sprague-Dawley rats were ovariectomized (OVX) at PND50 and infused with E2 or vehicle for 14 d and gavaged with 50 mg/kg DMBA or vehicle 24 h before sacrifice at PND64. Rats were fed an AIN-93G diet made with SPI or casein as sole protein source throughout the study. Basal AhR protein levels were reduced (P<0.05) by SPI feeding irrespective of the E2 status. However, DMBA increased (P<0.05) AhR-induced CYP1A1 gene expression in OVX, SPI-fed rats, but reduced (P<0.05) CYP1A1 in OVX+E2, SPI-fed rats. Chromatin-immunoprecipitation demonstrated lower (P<0.05) DMBA-mediated recruitment of estrogen receptor alpha to the CYP1A1 promoter by SPI feeding in the presence of E2, suggesting an estrogen-like action of SPI on DMBA-mediated signaling in the absence of E2. Further, microarray analysis (Rat 230-2.0 Affymetrix-GeneChip) revealed 231 genes common to SPI+DMBA and SPI+E2+DMBA (normalized to E2) treatments. AhR-activated genes (CYP1A1, CYP1A2, and NQO1) were down-regulated by SPI+E2+DMBA compared to SPI+DMBA. Unique interactions among SPI, DMBA and E2 altered the expression profile of 316 genes, not observed by either treatment alone. Our data suggest that although E2 status does not effect soy-mediated AhR degradation, it modulates the effects of soy on many genes, including CYP1A1.

Molecular epidemiology to better predict lung cancer risk

Although it is clear that smoking causes lung cancer, it is not known why some smokers develop the disease while others do not. Little is also known regarding risk factors for lung cancer among never-smokers, particularly women, or why women with lung cancer are more likely to have a family history of cancer, to be diagnosed at a young age, or to have adenocarcinoma. The application of molecular epidemiology to the study of lung cancer risk might facilitate elucidation of these questions. In this review, the molecular epidemiology of lung cancer is discussed, with an emphasis on studies of genetic variability in metabolic pathways as a means for determining susceptibility. Work that has assessed intermediate markers of risk, such as DNA adducts, is also presented, as are studies of tumor tissue alterations, such as mutations and DNA methylation, in relation to risk of lung cancer. Finally, approaches to evaluating factors that might explain the differing epidemiology of lung cancer between men and women are also presented. It is likely that, by incorporating biomarkers of susceptibility, exposure, and effect, molecular epidemiologic approaches might better define factors that explain some of the variability in lung cancer risk.

CYP1A1, GSTM1, and GSTT1 polymorphisms, smoking, and lung cancer risk in a pooled analysis among Asian populations

To evaluate the roles of CYP1A1 polymorphisms [Ile 462Val and T 6235C (MspI)] and deletion of GSTM1 and GSTT1 in lung cancer development in Asian populations, a pooled analysis was conducted on 13 existing studies included in Genetic Susceptibility to Environmental Carcinogenesis database. This pooled analysis included 1,971 cases and 2,130 controls. Lung cancer risk was estimated as odds ratios (OR) and 95% confidence intervals (95% CI) using unconditional logistic regression model adjusting for age, sex, and pack-year. The CYP1A1 6235C variant was associated with squamous cell lung cancer (TC versus TT: OR, 1.42; 95% CI, 0.96-2.09; CC versus TT: OR, 1.97; 95% CI, 1.26-3.07; P trend = 0.003). In haplotype analysis, 462Val-6235T and Ile-C haplotypes were associated with lung cancer risk with reference to the Ile-T haplotype (OR, 3.41; 95% CI, 1.78-6.53 and OR, 1.39; 95% CI, 1.12-1.71, respectively). The GSTM1-null genotype increased squamous cell lung cancer risk (OR, 1.36; 95% CI, 1.05-1.77). When the interaction was evaluated with smoking, increasing trend of lung cancer risk as pack-year increased was stronger among those with the CYP1A1 6235 TC/CC genotype compared with those with TT genotype (P interaction = 0.001) and with the GSTM1-null genotype compared with the present type (Pinteraction = 0.08, when no genotype effect with no exposure was assumed). These results suggest that genetic polymorphisms in CYP1A1 and GSTM1 are associated with lung cancer risk in Asian populations. However, further investigation is warranted considering the relatively small sample size when subgroup analyses were done and the lack of environmental exposure data other than smoking.

Applications of CYP-450 expression for biomonitoring in environmental health

Cytochrome P450s (CYPs) are one of the first steps in the metabolism of xenobiotics, such as polycyclic aromatic hydrocarbons (PAHs), which are bioactivated into carcinogens. As such, changes in CYP expression are potential biomarkers in human biomonitoring applications. For the proper biomonitoring of environmental toxicants, it is important to understand the biological relevance of each biomarker and the associations among the biomarkers for uses as exposure, effects, and susceptibility biomarkers. Here, we have reviewed various aspects of CYPs for biomonitoring environmental health in terms of the CYP substrates, such as PAHs, aromatic amines, benzene/toluene, and tobacco smoking-related nitrosamines. This review also includes association studies between CYP phenotypical alterations and other exposure, susceptibility, and effect biomarkers. The association studies were mainly performed in CYP gene-transfected cells and noninvasive human biospecies, such as urine and peripheral blood. In conclusion, we suggest that phenotypical alterations in CYPs with exposure to environmental toxicants are useful as susceptibility or effect biomarkers, particularly when the phenotype-related genotypes are unknown.

Crystalline silica is a negative modifier of pulmonary cytochrome P-4501A1 induction

Polycyclic aromatic hydrocarbons (PAHs) are products of incomplete combustion that are commonly inhaled by workers in the dusty trades. Many PAHs are metabolized by cytochrome P-4501A1 (CYP1A1), which may facilitate excretion but may activate pulmonary carcinogens. PAHs also stimulate their own metabolism by inducing CYP1A1. Recent studies suggest that respirable coal dust exposure inhibits induction of pulmonary CYP1A1 using the model PAH beta-naphthoflavone. The effect of the occupational particulate respirable crystalline silica was investigated on PAH-dependent pulmonary CYP1A1 induction. Male Sprague-Dawley rats were exposed to intratracheal silica or vehicle and then intraperitoneal beta-naphthoflavone, a CYP1A1 inducer, and/or phenobarbital, an inducer of hepatic CYP2B1, or vehicle. Beta-naphthoflavone induced pulmonary CYP1A1, but silica attenuated this beta-naphthoflavone-induced CYP1A1 activity and also suppressed the activity of CYP2B1, the major constitutive CYP in rat lung. The magnitude of CYP activity suppression was similar regardless of silica exposure dose within a range of 5 to 20 mg/rat. Phenobarbital and beta-naphthoflavone had no effect on pulmonary CYP2B1 activity. Both enzymatic immunohistochemistry and immunofluorescent staining for CYP1A1 indicated that sites of CYP1A1 induction were nonciliated airway epithelial cells, endothelial cells, and the alveolar septum. Using immunofluorescent colocalization of CYP1A1 with cytokeratin 8, a marker of alveolar type II cells, the proximal alveolar region was the site of both increased alveolar type II cells and decreased proportional CYP1A1 expression in alveolar type II cells. Our findings suggest that in PAH-exposed rat lung, silica is a negative modifier of CYP1A1 induction and CYP2B1 activity.

Basal gene expression in male and female Sprague-Dawley rat nasal respiratory and olfactory epithelium

The nasal epithelium is an important target site for chemically induced toxicity and carcinogenicity. Experimental studies show that site-specific lesions can arise within the nasal respiratory or olfactory epithelium following the inhalation of certain chemicals. Moreover, gender differences in epithelial response are also reported. To better understand and predict gender differences in response of the nasal epithelium to inhaled xenobiotics, gene expression profiles from naive male and female Sprague-Dawley rats were constructed. Epithelial cells were manually collected from the nasal septum, naso- and maxillo-turbinates, and ethmoid turbinates of nine male and nine female rats. Gene expression analysis was performed using the Affymetrix Rat Genome 430 2.0 microarray. Surprisingly, there were few gender differences in gene expression. Gene ontology enrichment analysis identified several functional categories, including xenobiotic metabolism, cell cycle, apoptosis, and ion channel/transport, with significantly different expression between tissue types. These baseline data will contribute to our understanding of the normal physiology and selectivity of the nasal epithelial cells' response to inhaled environmental toxicants.

Gender-related differences in oxidative stress levels among elderly patients with coronary artery disease

OBJECTIVE

To evaluate whether gender-related differences exist concerning oxidative stress levels in aged patients with coronary artery disease (CAD).

DESIGN

Case-control.

SETTING

Clinical and research center.

PATIENT(S)

Elderly subjects of both genders with or without CAD.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Serum hydroperoxides (HP) as index of oxidative stress levels.

RESULT(S)

The HP levels were comparable in aged control subjects of both genders (376 +/- 20 arbitrary units [AU] in women, 333 +/- 19 AU in men) but significantly increased in CAD (456 +/- 15 AU) compared with all control subjects (357 +/- 14 AU). Moreover, among CAD patients, the HP levels were higher in women than in men (536 +/- 33 AU and 428 +/- 15 AU, respectively). Multivariate analysis, in which CAD represented the dependent variable, indicated that dyslipidemia was independently associated with CAD in men (odds ratio [OR] 5.8), whereas HP >50th percentile represented the only strong independent risk factor for CAD in elderly women (OR 8.4).

CONCLUSION(S)

Differences in oxidative stress levels between elderly males and females might provide a biochemical basis for the epidemiologic differences in CAD, which might help to open new opportunities in the management of patients with cardiovascular disease from a gender point of view.

Differences between small-cell lung cancer and non-small-cell lung cancer among tobacco smokers

It is known that smoking increases the risk for all histological subtypes of lung cancer. To date, the factors that determine why some patients develop small-cell lung cancer (SCLC) while others develop non-small-cell lung cancer (NSCLC) remain unknown. We compared the characteristics of 774 smokers with SCLC and NSCLC diagnosed during the period January 1999 till December 2002. Multivariate logistic regression was used to estimate the odds ratio (OR) with 95% CI. Testing of linear trend across categories of pack-years was also conducted. Six hundred and sixty-five NSCLC were compared to 109 SCLC. Among SCLC, there were significantly more females (20.2% versus 12.8%), current-smokers (81.7% versus 71.9%) as well as smokers who had smoked more than 40 pack-years (75.6% versus 50.3%). Comparing SCLC with NSCLC among the men only, having smoked more than 40 pack-years was associated with a significantly elevated odds ratio (OR) of 3.71 of developing SCLC (95% CI, 1.05-13.1; p=0.041). There was a decreasing trend in OR with increasing smoking cessation period. When comparing SCLC with adenocarcinoma, the women had a higher OR of 2.37 of developing SCLC (95% CI, 1.05-5.31; p=0.037) compared to the men. Our findings suggest that cumulative smoking exposure in terms of pack-years smoked is an important determining factor for the preferred development of SCLC among smokers.

Women and lung cancer: Epidemiology, tumor biology, and emerging trends in clinical research

Lung cancer is the leading cause of cancer-related death in both men and women. Environmental carcinogens, particularly tobacco smoke, play a dominant role in the development of lung cancer, although 10-15% of all patients diagnosed are non-smokers. In addition, emerging data demonstrate sex-specific differences in lung cancer susceptibility and prognosis. This implies that the development of lung cancer is modulated by complex interactions between genetic, hormonal, behavioral, and environmental factors. A better understanding of the differences between men and women and their impact on the prevention, diagnosis, and treatment of lung cancer requires continued basic and clinical research. Recent data on the epidemiological aspects of lung cancer in women, lung tumor biology, and emerging trends in clinical research were presented at a thought leaders' roundtable hosted by the Society for Women's Health Research. The panel concluded that as the patient population in lung cancer is changing from mostly male smokers to include women and non-smokers, an urgent need exists to increase awareness and research funding to improve lung cancer care, particularly in women. To further improve survival in this disease, both clinical characteristics and tumor biology should be considered in the development of new treatment options.