Analysis of single nucleotide polymorphisms in chronic beryllium disease

Sarcoidosis and chronic beryllium disease (CBD) are phenocopies, however the latter one has a clear trigger factor that is beryllium exposure. This study analyses single nucleotide polymorphisms (SNPs) in a large cohort for beryllium-exposed persons. SNPs were chosen for their relevance in sarcoidosis. Even though one of largest cohorts of beryllium-exposed persons was analysed, no statistically relevant association between any SNP and CBD could be verified. Notably, some SNPs exhibit inverse OR for beryllium sensitization and CBD with nominally statistical significance, which allows hypothesizing about pathophysiological role of genes for the disease triggering and development.

Malignant Mesothelioma Mortality - United States, 1999-2015

Malignant mesothelioma is a neoplasm associated with occupational and environmental inhalation exposure to asbestos* fibers and other elongate mineral particles (EMPs) (1-3). Patients have a median survival of approximately 1 year from the time of diagnosis (1). The latency period from first causative exposure to malignant mesothelioma development typically ranges from 20 to 40 years but can be as long as 71 years (2,3). Hazardous occupational exposures to asbestos fibers and other EMPs have occurred in a variety of industrial operations, including mining and milling, manufacturing, shipbuilding and repair, and construction (3). Current exposures to commercial asbestos in the United States occur predominantly during maintenance operations and remediation of older buildings containing asbestos (3,4). To update information on malignant mesothelioma mortality (5), CDC analyzed annual multiple cause-of-death records† for 1999-2015, the most recent years for which complete data are available. During 1999-2015, a total of 45,221 deaths with malignant mesothelioma mentioned on the death certificate as the underlying or contributing cause of death were reported in the United States, increasing from 2,479 deaths in 1999 to 2,597 in 2015 (in the same time period the age-adjusted death rates§ decreased from 13.96 per million in 1999 to 10.93 in 2015). Malignant mesothelioma deaths increased for persons aged ≥85 years, both sexes, persons of white, black, and Asian or Pacific Islander race, and all ethnic groups. Despite regulatory actions and the decline in use of asbestos the annual number of malignant mesothelioma deaths remains substantial. The continuing occurrence of malignant mesothelioma deaths underscores the need for maintaining measures to prevent exposure to asbestos fibers and other causative EMPs and for ongoing surveillance to monitor temporal trends.

Detection of Carcinogen–Macromolecular Adducts in Humans

A major concern of molecular epidemiology is the identification of individuals at increased risk of cancer by obtaining evidence of high exposure to carcinogens that may lead to pathobiological lesions in target cells. DNA is considered to be a target for modification by mutagens and carcinogens; therefore, damage to DNA can be used as an internal, molecular dosimeter of carcinogen exposure. The reactive species of these carcinogens may bind either directly to DNA to form adducts or indirectly to cause secondary DNA lesions through free radicals and aldehydes. Highly sensitive and specific methods have been developed to measure DNA lesions and DNA repair products that are found in biological specimens from humans exposed to carcinogens in the environment. For example, DNA adducts have been measured in cells and tissues from people exposed environmentally to carcinogenic polycyclic aromatic hydrocarbons or alkylating agents. Antibodies recognizing carcinogen-DNA adducts have also been detected in human sera. Carcinogen-protein adducts are also being used as molecular dosimeters of carcinogen exposure. The advantages and limitations of the various methods used to measure carcinogen-macromolecular adducts are discussed here. The use of two or more complementary assays to obtain confirmatory results is recommended.

Reversible lysine-specific demethylase 1 antagonist HCI-2509 inhibits growth and decreases c-MYC in castration- and docetaxel-resistant prostate cancer cells

Background:

Lysine-specific demethylase 1 (LSD1 or KDM1A) overexpression correlates with poor survival and castration resistance in prostate cancer. LSD1 is a coregulator of ligand-independent androgen receptor signaling promoting c-MYC expression. We examined the antitumor efficacy of LSD1 inhibition with HCI-2509 in advanced stages of prostate cancer.

Methods:

Cell survival, colony formation, histone methylation, c-MYC level, c-MYC expression, cell cycle changes and in vivo efficacy were studied in castration-resistant prostate cancer cells upon treatment with HCI-2509. In vitro combination studies, using HCI-2509 and docetaxel, were performed to assess the synergy. Cell survival, colony formation, histone methylation and c-myc levels were studied in docetaxel-resistant prostate cancer cells treated with HCI-2509.

Results:

HCI-2509 is cytotoxic and inhibits colony formation in castration-resistant prostate cancer cells. HCI-2509 treatment causes a dose-dependent increase in H3K9me2 (histone H3lysine 9) levels, a decrease in c-MYC protein, inhibition of c-MYC expression and accumulation in the G0/G1 phase of the cell cycle in these cells. PC3 xenografts in mice have a significant reduction in tumor burden upon treatment with HCI-2509 with no associated myelotoxicity or weight loss. More synergy is noted at sub-IC₅₀ (half-maximal inhibitory concentration) doses of docetaxel and HCI-2509 in PC3 cells than in DU145 cells. HCI-2509 has growth-inhibitory efficacy and decreases the c-myc level in docetaxel-resistant prostate cancer cells.

Conclusions:

LSD1 inhibition with HCI-2509 decreases the c-MYC level in poorly differentiated prostate cancer cell lines and has a therapeutic potential in castration- and docetaxel-resistant prostate cancer.

Notes from the Field: Update: Silicosis Mortality - United States, 1999-2013

Silicosis is a potentially fatal but preventable occupational lung disease caused by inhaling respirable crystalline silica (silica). Chronic silicosis, the most common form, occurs after exposure to relatively low silica concentrations for >10 years. Accelerated silicosis occurs after 5-10 years of exposure to higher silica levels, and acute silicosis can occur after only weeks or months of exposure to extremely high silica concentrations. New national mortality data for silicosis have become available since a previous report on silicosis surveillance was published earlier this year. CDC reviewed multiple cause-of-death mortality files from the National Center for Health Statistics to analyze deaths from silicosis (International Classification of Diseases, 10th Revision diagnosis code J62: a pneumoconiosis due to dust containing silica) reported during 1999-2013. Each record lists one underlying cause of death (the disease or injury that initiated the chain of events that led directly and inevitably to death), and up to 20 contributing causes of death (other significant conditions contributing to death but not resulting in underlying cause). Available death certificates from 35 states were reviewed for the period 2004-2006 to identify occupations associated with silicosis among decedents aged 15-44 years. Results indicate that despite substantial progress in eliminating silicosis, silicosis deaths continue to occur. Of particular concern are silicosis deaths in young adults (aged 15-44 years). These young deaths likely reflect higher exposures than those causing chronic silicosis mortality in older persons, some of sufficient magnitude to cause severe disease and death after relatively short periods of exposure. A total of 12 such deaths occurred during 2011-2013, with nine that had silicosis listed as the underlying cause of death.

Silicosis mortality trends and new exposures to respirable crystalline silica - United States, 2001-2010

Silicosis is a preventable occupational lung disease caused by the inhalation of respirable crystalline silica dust and can progress to respiratory failure and death. No effective specific treatment for silicosis is available; patients are provided supportive care, and some patients may be considered for lung transplantation. Chronic silicosis can develop or progress even after occupational exposure has ceased. The number of deaths from silicosis declined from 1,065 in 1968 to 165 in 2004. Hazardous occupational exposures to silica dust have long been known to occur in a variety of industrial operations, including mining, quarrying, sandblasting, rock drilling, road construction, pottery making, stone masonry, and tunneling operations. Recently, hazardous silica exposures have been newly documented during hydraulic fracturing of gas and oil wells and during fabrication and installation of engineered stone countertops. To describe temporal trends in silicosis mortality in the United States, CDC analyzed annual multiple cause-of-death data for 2001-2010 for decedents aged ≥15 years. During 2001-2010, a total of 1,437 decedents had silicosis coded as an underlying or contributing cause of death. The annual number of silicosis deaths declined from 164 (death rate† = 0.74 per 1 million population) in 2001 to 101 (0.39 per 1 million) in 2010 (p = 0.002). Because of new operations and tasks placing workers at risk for silicosis, efforts to limit workplace exposure to crystalline silica need to be maintained.

Correlation between CYP1A1 transcript, protein level, enzyme activity and DNA adduct formation in normal human mammary epithelial cell strains exposed to benzo[a]pyrene

The polycyclic aromatic hydrocarbon (PAH) benzo(a)pyrene (BP) is thought to bind covalently to DNA, through metabolism by cytochrome P450 1A1 (CYP1A1) and CYP1B1, and other enzymes, to form r7, t8, t9-trihydroxy-c-10-(N(2)-deoxyguanosyl)-7,8,9,10-tetrahydro-benzo[a]-pyrene (BPdG). Evaluation of RNA expression data, to understand the contribution of different metabolic enzymes to BPdG formation, is typically presented as fold-change observed upon BP exposure, leaving the actual number of RNA transcripts unknown. Here, we have quantified RNA copies/ng cDNA (RNA cpn) for CYP1A1 and CYP1B1, as well as

NAD(P)H

quinone oxidoreductase 1 (NQO1), which may reduce formation of BPdG adducts, using primary normal human mammary epithelial cell (NHMEC) strains, and the MCF-7 breast cancer cell line. In unexposed NHMECs, basal RNA cpn values were 58-836 for CYP1A1, 336-5587 for CYP1B1 and 5943-40112 for NQO1. In cells exposed to 4.0 µM BP for 12h, RNA cpn values were 251-13234 for CYP1A1, 4133-57078 for CYP1B1 and 4456-55887 for NQO1. There were 3.5 (mean, range 0.2-15.8) BPdG adducts/10(8) nucleotides in the NHMECs (n = 16), and 790 in the MCF-7s. In the NHMECs, BP-induced CYP1A1 RNA cpn was highly associated with BPdG (P = 0.002), but CYP1B1 and NQO1 were not. Western blots of four NHMEC strains, chosen for different levels of BPdG adducts, showed a linear correlation between BPdG and CYP1A1, but not CYP1B1 or NQO1. Ethoxyresorufin-O-deethylase (EROD) activity, which measures CYP1A1 and CYP1B1 together, correlated with BPdG, but NQO1 activity did not. Despite more numerous levels of CYP1B1 and NQO1 RNA cpn in unexposed and BP-exposed NHMECs and MCF-7cells, BPdG formation was only correlated with induction of CYP1A1 RNA cpn. The higher level of BPdG in MCF-7 cells, compared to NHMECs, may have been due to a much increased induction of CYP1A1 and EROD. Overall, BPdG correlation was observed with CYP1A1 protein and CYP1A1/1B1 enzyme activity, but not with CYP1B1 or NQO1 protein, or NQO1 enzyme activity.

Chronic beryllium disease, HLA-DPB1, and the DP peptide binding groove

Multiple epidemiologic studies demonstrate associations between chronic beryllium disease (CBD), beryllium sensitization (BeS), and HLA-DPB1 alleles with a glutamic acid residue at position 69 (E69). Results suggest that the less-frequent E69 variants (non-*0201/*0202 alleles) might be associated with greater risk of CBD. In this study, we sought to define specific E69-carrying alleles and their amino acid sequences in the DP peptide binding groove, as well as their relationship to CBD and BeS risk, using the largest case control study to date. We enrolled 502 BeS/CBD subjects and 653 beryllium-exposed controls from three beryllium industries who gave informed consent for participation. Non-Hispanic white cases and controls were frequency-matched by industry. HLA-DPB1 genotypes were determined using sequence-specific primer PCR. The E69 alleles were tested for association with disease individually and grouped by amino acid structure using logistic regression. The results show that CBD cases were more likely than controls to carry a non-*02 E69 allele than an *02 E69, with odds ratios (95% confidence interval) ranging from 3.1 (2.1-4.5) to 3.9 (2.6-5.9) (p < 0.0001). Polymorphic amino acids at positions 84 and 11 were associated with CBD: DD versus GG, 2.8 (1.8-4.6), p < 0.0001; GD versus GG, 2.1 (1.5-2.8), p < 0.0001; LL versus GG, 3.2 (1.8-5.6), p < 0.0001; GL versus GG, 2.8 (2.1-3.8), p < 0.0001. Similar results were found within the BeS group and CBD/BeS combined group. We conclude that the less frequent E69 alleles confer more risk for CBD than does *0201. Recent studies examining how the composition and structure of the binding pockets influence peptide binding in MHC genes, as well of studies showing the topology of the TCR to likely bind DPB1 preferentially, give plausible biological rationale for these findings.

Work-related lung diseases

Work-related respiratory diseases affect people in every industrial sector, constituting approximately 60% of all disease and injury mortality and 70% of all occupational disease mortality. There are two basic types: interstitial lung diseases, that is the pneumoconioses (asbestosis, byssinosis, chronic beryllium disease, coal workers' pneumoconiosis (CWP), silicosis, flock workers' lung, and farmers' lung disease), and airways diseases, such as work-related or exacerbated asthma, chronic obstructive pulmonary disease and bronchiolitis obliterans (a disease that was recognized in the production of certain foods only 10 years ago). Common factors in the development of these diseases are exposures to dusts, metals, allergens and other toxins, which frequently cause oxidative damage. In response, the body reacts by activating primary immune response genes (i.e. cytokines that often lead to further oxidative damage), growth factors and tissue remodelling proteins. Frequently, complex imbalances in these processes contribute to the development of disease. For example, tissue matrix metalloproteases can cause the degradation of tissue, as in the development of CWP small profusions, but usually overexpression of matrix metalloproteases is controlled by serum protein inhibitors. Thus, disruption of such a balance can lead to adverse tissue damage. Susceptibility to these types of lung disease has been investigated largely through candidate gene studies, which have been characteristically small, often providing findings that have been difficult to corroborate. An important exception to this has been the finding that the HLA-DPB11(E69) allele is closely associated with chronic beryllium disease and beryllium sensitivity. Although chronic beryllium disease is only caused by exposure to beryllium, inheritance of HLA-DPB1(E69) carries an increased risk of between two- and 30-fold in beryllium exposed workers. Most, if not all, of these occupationally related diseases are preventable; therefore, it is disturbing that rates of CWP, for example, are again increasing in the United States in the 21st century.

CYP1A1 and CYP1B1 gene expression and DNA adduct formation in normal human mammary epithelial cells exposed to benzo[a]pyrene in the absence or presence of chlorophyllin

Benzo[a]pyrene (BP) is a potent pro-carcinogen and ubiquitous environmental pollutant. Here, we examined the induction and modulation of CYP1A1 and CYP1B1 and 10-(deoxyguanosin-N(2)-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPdG) adduct formation in DNA from 20 primary normal human mammary epithelial cell (NHMEC) strains exposed to BP (4muM) in the absence or presence of chlorophyllin (5muM). Real-time polymerase chain reaction (RT-PCR) analysis revealed strong induction of both CYP1A1 and CYP1B1 by BP, with high levels of inter-individual variability. Variable BPdG formation was found in all strains by r7, t8-dihydroxy-t-9, 10 epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-DNA chemiluminescence assay (CIA). Chlorophyllin mitigated BP-induced CYP1A1 and CYP1B1 gene expression in all 20 strains when administered with BP. Chlorophyllin, administered prior to BP-exposure, mitigated CYP1A1 expression in 18/20 NHMEC strains (p<0.005) and CYP1B1 expression in 17/20 NHMEC strains (p<0.005). Maximum percent reductions of CYP1A1 and CYP1B1 gene expression and BPdG adduct formation were observed when cells were pre-dosed with chlorophyllin followed by administration of the carcinogen with chlorophyllin (p<0.005 for CYP1A1 and CYP1B1 expression and p<0.0005 for BPdG adducts). Therefore, chlorophyllin is likely to be a good chemoprotective agent for a large proportion of the human population.

Genetic determinants of sensitivity to beryllium in mice

Chronic beryllium disease (CBD), an irreversible, debilitating granulomatous lung disease is caused by exposure to beryllium. This occupational hazard occurs in primary production and machining of Be-metal, BeO, beryllium - containing alloys, and other beryllium products. CBD begins as an MHC Class II-restricted, T(H)1 hypersensitivity, and the Human Leukocyte Antigen, HLA-DPB1E(69), is associated with risk of developing CBD. Because inbred strains of mice have not provided good models of CBD to date, three strains of HLA-DPB1 transgenic mice in an FVB/N background were developed; each contains a single allele of HLA-DPB1 that confers a different magnitude of risk for chronic beryllium disease: HLA-DPB1*0401 (OR approximately 0.2), HLA-DPB1*0201 (OR approximately 3), and HLA-DPB1*1701 (OR approximately 46). The mouse ear swelling test (MEST) was employed to determine if these different alleles would support a hypersensitivity response to beryllium. Mice were first sensitized on the back and subsequently challenged on the ear. In separate experiments, mice were placed into one of three groups (sensitization/challenge): C/C, C/Be, and Be/Be. In the HLA-DPB1*1701 mice, the strain with the highest risk transgene, the Be/Be group was the only group that displayed significant maximum increased ear thickness of 19.6% +/- 3.0% over the baseline measurement (p < 0.05). No significant changes were observed in the other transgenic strains for any treatment condition. In addition, inter-strain differences in response to beryllium in seven inbred strains were investigated through use of the MEST, these included: FVB/N, AKR, Balb/c, C3H/HeJ, C57/BL6, DBA/2, and SJL/J. The FVB/N strain was least responsive, while the SJL/J and C57/BL6 strains were the highest responders. Our results suggest that the HLA-DPB1*1701 transgene product is an important risk factor for induction of the beryllium-sensitive phenotype. This model should be a useful tool for investigating beryllium sensitization.

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.

Tamoxifen induces expression of immune response-related genes in cultured normal human mammary epithelial cells

Use of tamoxifen is associated with a 50% reduction in breast cancer incidence and an increase in endometrial cancer incidence. Here, we documented tamoxifen-induced gene expression changes in cultured normal human mammary epithelial cells (strains 5, 16, and 40), established from tissue taken at reduction mammoplasty from three individuals. Cells exposed to 0, 10, or 50 micromol/L of tamoxifen for 48 hours were evaluated for (E)-alpha-(deoxyguanosine-N(2)-yl)-tamoxifen (dG-N(2)-TAM) adduct formation using TAM-DNA (DNA modified with dG-N(2)-TAM) chemiluminescence immunoassay, gene expression changes using National Cancer Institute DNA-oligonucleotide microarray, and real-time PCR. At 48 hours, cells exposed to 10 and 50 micromol/L of tamoxifen were 85.6% and 48.4% viable, respectively, and there were no measurable dG-N(2)-TAM adducts. For microarrays, cells were exposed to 10 micromol/L of tamoxifen and genes with expression changes of >3-fold were as follows: 13 genes up-regulated and 1 down-regulated for strain 16; 17 genes up-regulated for strain 5, and 11 genes up-regulated for strain 40. Interferon-inducible genes (IFITM1, IFIT1, MXI, and GIP3), and a potassium ion channel (KCNJ1) were up-regulated in all three strains. No significant expression changes were found for genes related to estrogen or xenobiotic metabolism. Real-time PCR revealed the up-regulation of IFNA1 and confirmed the tamoxifen-induced up-regulation of the five other genes identified by microarray, with the exception of GIP3 and MX1, which were not up-regulated in strain 40. Induction of IFN-related genes in the three normal human mammary epithelial cell strains suggests that, in addition to hormonal effects, tamoxifen exposure may enhance immune response in normal breast tissue.

Immune response signatures of benzo{alpha}pyrene exposure in normal human mammary epithelial cells in the absence or presence of chlorophyllin

Carcinogenic polycylic aromatic hydrocarbons can alter immune responses. Changes in immune response gene expression profiles in multiple human mammary cell strains exposed to benzo(alpha)pyrene (BP) (4 microM) in vitro, in the presence or absence of chlorophyllin (5 microM), were observed using Affymetrix gene arrays. Expressions of five immune response genes were altered ~3.0-fold by BP exposure and 24 genes by BP in the presence chlorophyllin. In silico pathway analysis revealed altered immune response genes form interactive gene networks with many cellular processes, suggesting their role in a complex multigenic response to toxins. Additionally, it was suggestive of the possible immunomodulatory potential of chlorophyllin apart from various other well-documented mechanisms of action. Gene expression matrices revealed consistent alteration patterns involving IL1B, SECTM1 and CXCL14 on exposure to BP, and IL1RN, CD86, IF144 and GIP2 in the presence of chlorophyllin and BP, suggesting some of these genes might constitute putative immune response biomarkers of PAH exposure. This study has therefore identified a battery of potential immune response biomarkers of PAH exposure, amidst several genes, for future validation studies.

Impact of negatively charged patches on the surface of MHC class II antigen-presenting proteins on risk of chronic beryllium disease

Chronic beryllium disease (CBD) is a granulomatous lung disease that occurs primarily in workers who are exposed to beryllium dust or fumes. Although exposure to beryllium is a necessary factor in the pathobiology of CBD, alleles that code for a glutamic acid residue at the 69th position of the HLA-DPbeta1 gene have previously been found to be associated with CBD. To date, 43 HLA-DPbeta1 alleles that code for glutamic acid 69 (E69) have been described. Whether all of these E69 coding alleles convey equal risk of CBD is unknown. The present study demonstrates that, on the one hand, E69 alleloforms of major histocompatibility complex class II antigen-presenting proteins with the greatest negative surface charge convey the highest risk of CBD, and on the other hand, irrespective of allele, they convey equal risk of beryllium sensitization (BeS). In addition, the data suggest that the same alleles that cause the greatest risk of CBD are also important for the progression from BeS to CBD. Alleles convey the highest risk code for E26 in a constant region and for E69, aspartic acid 55 (D55), E56, D84 and E85 in hypervariable regions of the HLA-DPbeta1 chain. Together with the calculated high binding affinities for beryllium, these results suggest that an adverse immune response, leading to CBD, is triggered by chemically specific metal-protein interactions.

Transcriptional profiles of benzo(a)pyrene exposure in normal human mammary epithelial cells in the absence or presence of chlorophyllin

Benzo(a)pyrene (BP) exposure causes alterations in gene expression in normal human mammary epithelial cells (NHMECs). This study used Affymetrix Hu-Gene133A arrays, with 14,500 genes represented, to evaluate modulation of BP-induced gene expression by chlorophyllin in six NHMEC strains derived from different donors. A major goal was to seek potential biomarkers of carcinogen exposure and how they behave in the presence of a chemopreventive agent. NHMECs (passage 6 and 70% confluence) were exposed for 24h to either vehicle control, or BP, or chlorophyllin followed by BP and chlorophyllin together. BP exposure resulted in approximately 3-fold altered expression of 49 genes in at least one of the six NHMEC strains. When cells were exposed to chlorophyllin pre-treatment followed by BP plus chlorophyllin, expression of 125 genes was similarly altered. Genes in the functional categories of xenobiotic metabolism, cell signaling, cell motility, cell proliferation, cellular transcription, metabolism, cell cycle control, apoptosis and DNA repair were identified. Only CYP1B1 and ALDH1A3 were consistently up-regulated by approximately 3-fold in most of the cell strains (at least 4) when exposed to BP. Cluster analysis identified a suite of 13 genes induced by BP where induction was mitigated in the presence of chlorophyllin. Additionally, cluster analysis identified a suite of 16 genes down-regulated by BP where induction was partially restored in the presence of chlorophyllin.

Application of oligonucleotide microarray technology to toxic occupational exposures

Microarray technology has advanced toward analysis of toxic occupational exposures in biological systems. Microarray analysis is an ideal way to search for biomarkers of exposure, even if no specific gene or pathway has been identified. Analysis may now be performed on thousands of genes simultaneously, as opposed to small numbers of genes as in the past. This ability has been put to use to analyze gene expression profiles of a variety of occupational toxins in animal models to classify toxins into specific categories based on response. Analysis of normal human cell strains allows an extension of this analysis to investigate the role of interindividual variation in response to various toxins. This methodology was used to analyze four occupationally related toxins in our lab: oxythioquinox (OTQ), a quinoxaline pesticide; malathion, an organophosphate pesticide; di-n-butyl phthalate (DBP), a chemical commonly found in personal care and cosmetic items; and benzo[a]pyrene (BaP), an environmental and occupational carcinogen. The results for each exposure highlighted signaling pathways involved in response to these occupational exposures. Both pesticides showed increase in metabolic enzymes, while DBP showed alterations in genes related to fertility. BaP exposure showed alterations in two cytochrome P450s related to carcinogenicity. When used with occupational exposure information, these data may be used to augment risk assessment to make the workplace safer for a greater proportion of the workforce, including individuals susceptible to disease related to exposures.

Human inter-individual variability in metabolism and genotoxic response to zidovudine

A mainstay of the antiretroviral drugs used for therapy of HIV-1, zidovudine (AZT) is genotoxic and becomes incorporated into DNA. Here we explored host inter-individual variability in AZT-DNA incorporation, by AZT radioimmunoassay (RIA), using 19 different strains of normal human mammary epithelial cells (NHMECs) exposed for 24 h to 200 microM AZT. Twelve of the 19 NHMEC strains showed detectable AZT-DNA incorporation levels (16 to 259 molecules of AZT/10(6) nucleotides), while 7 NHMEC strains did not show detectable AZT-DNA incorporation. In order to explore the basis for this variability, we compared the 2 NHMEC strains that showed the highest levels of AZT-DNA incorporation (H1 and H2) with 2 strains showing no detectable AZT-DNA incorporation (L1 and L2). All 4 strains had similar (> or =80%) cell survival, low levels of accumulation of cells in S-phase, and no relevant differences in response to the direct-acting mutagen bleomycin (BLM). Finally, when levels of thymidine kinase 1 (TK1), the first enzyme in the pathway for incorporation of AZT into DNA, were determined by Western blot analysis in all 19 NHMEC strains at 24 h of AZT exposure, higher TK1 protein levels were found in the 12 strains showing AZT-DNA incorporation, compared to the 7 showing no incorporation (p=0.0005, Mann-Whitney test). Furthermore, strains L1 and L2, which did not show AZT-DNA incorporation at 24 h, did have measurable incorporation by 48 and 72 h. These data suggest that variability in AZT-DNA incorporation may be modulated by inter-individual differences in the rate of induction of TK1 in response to AZT exposure.

TNF-alpha polymorphisms in chronic beryllium disease and beryllium sensitization

OBJECTIVE

Tumor necrosis factor-alpha (TNF-alpha) is a potent cytokine involved in normal immune functions. The aim of this study was to investigate if there is an association between chronic beryllium disease or beryllium sensitization and two variants of the TNF-alpha gene located at -308 and -238 called TNF-alpha-308*02 and TNF-alpha-238*02.

METHODS

TNF-alpha-308 and TNF-alpha-238 genotyping was conducted in a large, population-based cohort consisting of 886 beryllium workers (92 individuals with chronic beryllium disease, 64 who were beryllium sensitized, and 730 individuals without sensitization or disease).

RESULTS

The odds of chronic beryllium disease in the presence of at least one TNF-alpha-308*02 or TNF-alpha-238*02 allele was not significant (OR=1.0; 95% CI=0.7, 1.7 and OR=0.8; 95% CI=0.4, 1.6). This was true regardless of whether a worker was homozygous or heterozygous for TNF-alpha-308*02 or TNF-alpha-238*02. Similarly, neither allele was associated with sensitization (P>0.05).

CONCLUSIONS

Unlike an earlier report, there was no association between these specific TNF-alpha alleles and either chronic beryllium disease or sensitization to beryllium.

A statistical model for assessing genetic susceptibility as a risk factor in multifactorial diseases: lessons from occupational asthma

BACKGROUND

Incorporating the influence of genetic variation in the risk assessment process is often considered, but no generalized approach exists. Many common human diseases such as asthma, cancer, and cardiovascular disease are complex in nature, as they are influenced variably by environmental, physiologic, and genetic factors. The genetic components most responsible for differences in individual disease risk are thought to be DNA variants (polymorphisms) that influence the expression or function of mediators involved in the pathological processes.

OBJECTIVE

The purpose of this study was to estimate the combinatorial contribution of multiple genetic variants to disease risk.

METHODS

We used a logistic regression model to help estimate the joint contribution that multiple genetic variants would have on disease risk. This model was developed using data collected from molecular epidemiology studies of allergic asthma that examined variants in 16 susceptibility genes.

RESULTS

Based on the product of single gene variant odds ratios, the risk of developing asthma was assigned to genotype profiles, and the frequency of each profile was estimated for the general population. Our model predicts that multiple disease variants broaden the risk distribution, facilitating the identification of susceptible populations. This model also allows for incorporation of exposure information as an independent variable, which will be important for risk variants associated with specific exposures.

CONCLUSION

The present model provided an opportunity to estimate the relative change in risk associated with multiple genetic variants. This will facilitate identification of susceptible populations and help provide a framework to model the genetic contribution in probabilistic risk assessment.

Gene Expression Profiling of Di-n-Butyl Phthalate in Normal Human Mammary Epithelial Cells

Studies show that female workers in the personal-care industry have an increased risk of developing cancer believed to be the result of increased exposure to toxic and/or carcinogenic chemicals found in cosmetics, hair dyes, and nail polish. One chemical found in multiple personal-care products, di-n-butyl phthalate (DBP), is a known endocrine disruptor and has been found in increased levels in women of childbearing age. The goal of this study was to elucidate mechanisms of phthalate toxicity in normal human cells to provide information concerning interindividual variation and gene-environment interactions. Normal human mammary epithelial cell strains were obtained from discarded tissues following reduction mammoplasty [Cooperative Human Tissue Network (sponsors: NCI/NDRI)]. Gene transcription in each cell strain was analyzed using high-density oligonucleotide DNA microarrays (U133A, Affymetrix) and changes in the expression of selected genes were verified by real-time polymerase chain reaction (PCR) (ABI). DNA microarrays were hybridized with total RNA that was collected after DBP treatment for 5 hr and 10 hr. RNA was harvested from the vehicle control (acetone) at 10 hr. Data Mining Tool software (Affymetrix) was used to separate genes in clusters based on their expression patterns over time. Only 57 genes were found to be altered in all four cell strains following exposure to DBP. These included genes involved in fertility (inhibin, placental growth factor), immune response (tumor necrosis factor induced protein), and antioxidant status (glutathione peroxidase). Data from this study will help clarify the role of DBP in reproductive toxicity, and yield biomarkers of exposure for future epidemiology studies.

DNA-sequence determination of exon 2 of a novel HLA-DPB1 allele, HLA-DPB1*0403

Sequence determination using HLA-DPB1 allele-specific primers for a DNA sample donated by an African-American individual revealed the presence of a novel haplotype. This new allele was found as a heterozygote together with HLA-DPB1*0402. The new allele was similar to HLA-DPB1*1601, however, it varied in two single nucleotide polymorphisms resulting in alanine residues at positions 55 and 56 of the mature protein rather than aspartic acid and glutamic acid, respectively. Allele-specific DNA-sequence determination was verified by sequence determination in forward and reverse directions after cloning in pCR2.1. This cloning strategy resulted in DNA products representing 19 clones confirming the novel allele (GenBank accession number AY823995 and is now listed in the IMGT/HLA database as HLA-DPB1*0403) and 17 clones representing HLA-DPB1*0402.

The effects of esomeprazole combined with aspirin or rofecoxib on prostaglandin E2 production in patients with Barrett's oesophagus

BACKGROUND

Reducing mucosal cyclo-oxygenase-2 and prostaglandin E(2) production and suppressing intraoesophageal acid may be effective chemopreventive strategies in patients with Barrett's oesophagus.

AIM

To compare the effects of aspirin and rofecoxib when administered with esomeprazole on prostaglandin E(2) production, cyclo-oxygenase-2 expression and proliferating cell nuclear antigen expression in patients with Barrett's oesophagus.

METHODS

This exploratory, multicentre, randomized, open-label, four-way crossover study in 45 patients with Barrett's oesophagus evaluated prostaglandin E(2) content, proliferating cell nuclear antigen expression, and cyclo-oxygenase-2 expression after 10 days of sequential treatments with: esomeprazole 40 mg twice daily plus aspirin 325 mg once daily (E40 b.d. + A325); E40 b.d. plus rofecoxib 25 mg once daily (E40 b.d. + R25); E40 b.d.; and rofecoxib 25 mg once daily (R25).

RESULTS

Prostaglandin E(2) content reduction in Barrett's oesophagus tissue was significantly greater with E40 b.d. + A325 compared with E40 b.d. + R25, E40 b.d. or R25 (P < 0.05). All treatments containing E40 b.d. significantly decreased proliferating cell nuclear antigen expression from baseline (P < 0.05). None of the treatments significantly reduced cyclo-oxygenase-2 expression.

CONCLUSIONS

The combined treatment of esomeprazole 40 mg b.d. and aspirin 325 mg significantly decreased mucosal prostaglandin E(2) content and all treatments containing esomeprazole significantly reduced proliferating cell nuclear antigen expression in patients with Barrett's oesophagus.

Reduction in tamoxifen-induced CYP3A2 expression and DNA adducts using antisense technology

Tamoxifen (TAM) is widely used in the treatment and prevention of breast cancer. There is clear evidence that cytochrome P450 (CYP) 3A enzymes play an important role in TAM metabolism, resulting in metabolites that lead to formation of TAM-DNA adducts. We have investigated the effect of CYP3A2 antisense (AVI-4472) exposure on CYP3A2 transcription, enzyme activity, translation, and TAM-DNA adducts, in livers of rats administered TAM (50 mg/kg body weight [bw]/day) for 7 days. The study design included administration of 0, 0.5, 2.5, or 12.5 mg AVI-4472/kg bw/day for 8 days, beginning 1 day before TAM exposure. The specific activity of CYP3A2 was increased after TAM administration, and decreased significantly (approximately 70%) in the presence of 12.5 mg AVI-4472. CYP3A2 protein levels, determined by immunoblot analysis, showed a similar pattern. Hepatic TAM-DNA adduct levels were measurable in all TAM-exposed groups. However, when rats were co-treated with 2.5 and 12.5 mg AVI-4472/kg bw/day, statistically significant (approximately 50%) reductions in TAM-DNA adduct levels (2.0-2.8 adducts/10(8) nucleotides) were observed compared to rats treated with TAM alone (5.1 adducts/10(8) nucleotides). Rat toxicology U34 arrays (Affymetrix) were used to investigate the modulation of gene expression patterns on co-administration of TAM with AVI-4472. Results indicated that several CYP genes were down regulated although no significant induction of CYP3A2 was observed in the TAM-exposed rats co-treated with AVI-4472. Overall the data suggest the utility of antisense technology in the redirection of TAM metabolism thereby lowering TAM genotoxicity in rat liver.

Immunogenetic factors in beryllium sensitization and chronic beryllium disease

Exposure to beryllium in the workplace can cause beryllium sensitization and chronic beryllium disease. Sensitization to beryllium can be detected in the laboratory using the beryllium lymphocyte proliferation test. It was shown that anti-HLA antibodies could block the beryllium-specific response in the beryllium lymphocyte proliferation test, thereby implicating HLA genes in chronic beryllium disease. A supratypic genetic marker, HLA-DPB1*E69, was found to be strongly associated with immunologic sensitization to beryllium and chronic beryllium disease in beryllium workers. However, there are 40 HLA-DPB1 gene variants that have E69 but that also have other DNA sequence variations. The purpose of the study was to evaluate the evidence for potential differential susceptibility that may be associated with the physical characteristics of HLA protein molecules for which different HLA-DPB1*E69 variants code; that is, do some HLA-DPB1*E69 variants convey higher risk of beryllium sensitization and chronic beryllium disease than others. To do this, two approaches were pursued: first, detailed analysis of the findings from the published literature was performed, and second, computational chemistry was used to seek clues concerning the physical properties of the HLA protein molecules for which these alleles code. Among the 40 HLA-DPB1 gene variants that code for E69, molecular epidemiological studies have suggested a risk hierarchy, where some variants appear to convey low to moderate risk of chronic beryllium disease (e.g., HLA-DPB1*0201, approximately 3-fold increased risk), some convey an intermediate risk (e.g., HLA-DPB1*1901, approximately 5-fold) and others convey high risk (e.g., HLA-DPB1*1701, >10-fold). Molecular modeling has been used to further investigate a potential mechanistic basis for these observations. We found a strong correlation between the hierarchical order of risk of chronic beryllium disease associated with specific alleles and the predicted surface electrostatic potential and charge of the corresponding isotypes. Therefore, when alleles were grouped by the relative negative charge on the molecules for which they code, the data suggest that those alleles associated with the most negatively charged proteins carry the greatest risk of beryllium sensitization and disease.

High-performance liquid chromatography electrospray ionization tandem mass spectrometry for the detection and quantitation of benzo[a]pyrene-DNA adducts

A method, using HPLC combined with electrospray tandem mass spectrometry (ES-MS/MS), was developed and validated to detect and quantify the major DNA adduct resulting from exposure to the ultimate tumorigenic benzo[a]pyrene (BP) metabolite, trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). Calf thymus DNA was reacted with BPDE, digested enzymatically to nucleosides, and the major DNA adduct, 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (dG-BPDE), was purified by HPLC. Similar procedures were applied to prepare dG-BPDE-d8 from [1,2,3,4,5,6,11,12-(2)H8]BPDE for use as an internal standard. The HPLC-ES-MS/MS method was validated using a mixture of hydrolyzed salmon testis DNA (82 microg) and 10 pg dG-BPDE (analogous to 6.9 adducts/10(8) nucleotides). The results indicated an inter- and intraday accuracy of 99-100% and precision of 1.6-1.7% (relative standard deviation). When applied to a calf thymus DNA sample modified in vitro with [1,3-(3)H]BPDE, the method gave a value very similar to those obtained by radiolabeling, (32)P-postlabeling, and immunoassay. HPLC-ES-MS/MS analysis of hepatic DNA from mice treated intraperitoneally with 0.5 and 1.0 mg of [7,8-(3)H]BP gave values comparable to those determined by 32P-postlabeling and immunoassay. Lung DNA from mice fed a 0.3% coal tar diet (containing approximately 2 mg BP/g coal tar) for one month had 0.6 +/- 0.04 dG-BPDE adducts/10(8) nucleotides. This value is much lower than the 102 +/- 14 total DNA adducts/10(8) nucleotides determined by 32P-postlabeling, which suggests that dG-BPDE makes only a minor contribution to the DNA adducts formed in lung tissue of mice administered coal tar. The HPLC-ES-MS/MS method was used to assess human lung DNA samples for the presence of dG-BPDE. Based upon a limit of detection of 0.3 dG-BPDE adducts/10(8) nucleotides, when using 100 microg of DNA, dG-BPDE was detected in only 1 out of 26 samples. These observations indicate that HPLC-ES-MS/MS is suitable to assess the contribution of BP to DNA damage caused by exposures to polycyclic aromatic hydrocarbon (PAH) mixtures. The results further suggest that dG-BPDE may contribute only a small fraction of the total DNA adducts detected by other DNA adduct methodologies in individuals exposed to PAHs.

Transcriptional Signatures of Normal Human Mammary Epithelial Cells in Response to Benzo[a]pyrene Exposure: A Comparison of Three Microarray Platforms

Microarrays are used to study gene expression in a variety of biological systems. A number of different platforms have been developed, but few studies exist that have directly compared the performance of one platform with another. The goal of this study was to determine array variation by analyzing the same RNA samples with three different array platforms. Using gene expression responses to benzo[a]pyrene exposure in normal human mammary epithelial cells (NHMECs), we compared the results of gene expression profiling using three microarray platforms: photolithographic oligonucleotide arrays (Affymetrix), spotted oligonucleotide arrays (Amersham), and spotted cDNA arrays (NCI). While most previous reports comparing microarrays have analyzed pre-existing data from different platforms, this comparison study used the same sample assayed on all three platforms, allowing for analysis of variation from each array platform. In general, poor correlation was found with corresponding measurements from each platform. Each platform yielded different gene expression profiles, suggesting that while microarray analysis is a useful discovery tool, further validation is needed to extrapolate results for broad use of the data. Also, microarray variability needs to be taken into consideration, not only in the data analysis but also in specific probe selection for each array type.

Beryllium exposure: dermal and immunological considerations

OBJECTIVE

People exposed to beryllium compounds are at increased risk of developing beryllium sensitization and chronic beryllium disease (CBD). The purpose of this short communication is to present information regarding the potential importance of skin exposure to beryllium, an exposure and alternate immune response pathway to the respiratory tract, which has been largely overlooked in epidemiologic and exposure assessment studies.

METHODS

We reviewed the published literature, including epidemiologic, immunologic, genetic, and laboratory-based studies of in vivo and in vitro models, to assess the state of knowledge concerning skin exposure to beryllium.

RESULTS

Reduction in inhalation exposure to beryllium has not resulted in a concomitant reduction in the occurrence of beryllium sensitization or CBD, suggesting that continued prevalence may be due, in part, to unchecked skin exposure to beryllium-containing particles.

CONCLUSIONS

Recent developments in our understanding of the multiple exposure pathways that may lead to beryllium sensitization and CBD suggest that a prudent approach to worker protection is to assess and minimize both skin and inhalation exposures to beryllium.

Genetic factors modify the risk of developing beryllium disease

Chronic beryllium disease (CBD) is a debilitating, granulomatous lung disease that occurs in 1 to 5% of exposed workers. Beryllium stimulates a major histocompatibility Class II-restricted, TH1, CD4+ T cell-mediated immune response. The immunological component of the illness, coupled with the small subset of beryllium workers who develop disease, led researchers to hypothesize that genetic factors modify risk of disease. Analysis of human leukocyte antigen (HLA) genes, the T cell receptor, and tumor necrosis factor (TNF)-alpha focused on three critical steps in the development of beryllium specific immunity. Molecular epidemiological analysis of the association of HLA-DP, -DR, and -DQ has implicated HLA-DPB1E69 allelic variants in disease; however, its role in sensitization is unclear. A single report suggested association between HLA-DQB1G86 and progression from sensitization to disease. A beryllium-specific binding motif was identified in CBD-derived T cell clones. Beryllium-stimulated proliferation using HLA-DPB1*0201 and TCRAV22S1/TCRBVb3 T cell receptors (TCRs) confirmed beryllium specificity of these molecules. The G/A transition at -308 in the TNF-alpha promoter was associated with high concentrations of TNF-alpha in bronchoalveolar lavage and to disease severity. Although these studies are continuing, the data confirm the role of genetic factors in the cellular response to beryllium.

Differential gene expression in normal human mammary epithelial cells treated with malathion monitored by DNA microarrays

Organophosphate pesticides are a major source of occupational exposure in the United States. Moreover, malathion has been sprayed over major urban populations in an effort to control mosquitoes carrying West Nile virus. Previous research, reviewed by the U.S. Environmental Protection Agency, on the genotoxicity and carcinogenicity of malathion has been inconclusive, although malathion is a known endocrine disruptor. Here, interindividual variations and commonality of gene expression signatures have been studied in normal human mammary epithelial cells from four women undergoing reduction mammoplasty. The cell strains were obtained from the discarded tissues through the Cooperative Human Tissue Network (sponsors: National Cancer Institute and National Disease Research Interchange). Interindividual variation of gene expression patterns in response to malathion was observed in various clustering patterns for the four cell strains. Further clustering identified three genes with increased expression after treatment in all four cell strains. These genes were two aldo-keto reductases (AKR1C1 and AKR1C2) and an estrogen-responsive gene (EBBP). Decreased expression of six RNA species was seen at various time points in all cell strains analyzed: plasminogen activator (PLAT), centromere protein F (CPF), replication factor C (RFC3), thymidylate synthetase (TYMS), a putative mitotic checkpoint kinase (BUB1), and a gene of unknown function (GenBank accession no. AI859865). Expression changes in all these genes, detected by DNA microarrays, have been verified by real-time polymerase chain reaction. Differential changes in expression of these genes may yield biomarkers that provide insight into interindividual variation in malathion toxicity.

Transcriptional signatures of environmentally relevant exposures in normal human mammary epithelial cells: benzo[a]pyrene

Changes in gene expression in a panel of primary normal human mammary epithelial cell strains, developed from healthy breast tissue obtained at reduction mammoplasty from different donors, in response to benzo[a]pyrene exposure have been investigated. It was expected that both gene expression changes common to cell strains derived from different donors as well as inter-individual variation would be observed. Therefore, the strategy that has been adopted is to identify potentially important changes, or useful changes from a biomonitoring perspective, using gene-array technology and a small number of donors; then investigate selected transcription responses using a large number of tissue donors and a cheaper method of transcript detection (real-time polymerase chain reaction). Here we report results from four primary normal human mammary epithelial cell strains that were treated with benzo[a]pyrene in vitro for either 6 or 24 h. Transcription was monitored using high-density oligonucleotide arrays (Affymetrix HuGeneFL). Total RNA was used for the preparation of labeled targets that were hybridized to microarrays containing probes representing more than 6800 human genes and expressed sequence tags. Gene expression data were analyzed using the GeneChip software (MAS 5.0). Altered gene expression patterns were observed in response to benzo[a]pyrene in human mammary epithelial cell strains from different donors. Specifically, the dioxin inducible cytochrome P450 CYP1B1 was consistently induced in response to 6 and 24 h exposure to benzo[a]pyrene in cell strains from all four donors. Two other genes that were relatively consistently induced were IL1beta and MMP1. Less consistent changes in other metabolism genes (CYP1A1, CYP11B2, and NQO1) and certain cell cycle control genes GOS2 and AF1Q were also induced, while EGR1 was suppressed. Although no change in p53 transcription was observed, an accumulation of p53 protein was detected using antibodies. A similar accumulation of Waf1 (p21) was also observed using immunohistochemistry, this was expected since p53 is p21's transcription factor. Significant inter-individual variations in both the levels and patterns of gene expression were observed, in response to benzo[a]pyrene exposure. These studies provide a complementary approach to molecular epidemiology for the investigation of differential susceptibility to chemical carcinogens, and specifically polycyclic aromatic hydrocarbons.

Induction of CYP1A1 and CYP1B1 and formation of carcinogen-DNA adducts in normal human mammary epithelial cells treated with benzo[a]pyrene

Inter-individual variation in formation of carcinogen-DNA adducts and induction of cytochrome P450 genes was measured in 23 cultured normal human mammary epithelial cell (NHMEC) strains established from reduction mammoplasty tissue. Semi-confluent cells were exposed to 4 microM benzo[a]pyrene (BP) for 12 h and BP-DNA adduct levels were measured by chemiluminescence immunoassay using antiserum elicited against DNA modified with r7, t8-dihydroxy-t-9, 10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). BP-DNA adduct levels for 22 of 23 different cell strains ranged from non-detectable (three samples) to about 15 adducts/10(8) nucleotides. Increases in levels of CYP1A1 and CYP1B1 were detected using both oligonucleotide arrays and reverse transcription/quantitative real-time polymerase chain reactions (RT-PCRs). For CYP1A1 and CYP1B1, the oligonucleotide array data and RT-PCR data were highly correlated (r=0.73 and 0.70, respectively), suggesting that oligonucleotide arrays are a suitable gene discovery tool, and demonstrating that the complementary and efficient RT-PCR may be used to confirm microarray data for a specific gene in a large number of samples. As measured by RT-PCR, inter-individual variation in CYP1A1 induction was 100-fold, while the variation in CYP1B1 induction was almost 40-fold. On a per-person basis, CYP1A1 and CYP1B1 induction were well-correlated (r=0.88, P<0.001), which is to be expected as they are under the control of a common transcriptional regulation mechanism in response to BP exposure. Inter-individual variation in carcinogen-DNA adduct formation could not be explained only by variation in levels of CYP1A1 or CYP1B1 induction, as neither was well-correlated with BPDE-DNA adduct level (r=0.40 and 0.50 for CYP1A1 and CYP1B1, respectively). Evaluation of glutathione-S-transferase M1 genotype (GSTM1 positive or null) revealed an apparent correlation between positive GSTM1 genotype and BPDE-DNA adduct levels (r=0.84 and 0.77 for CYP1A1 and CYP1B1, respectively); however, after removal of the single outlier this relationship was not significant. Overall the data suggest that BPDE-DNA adduct levels in normal human breast tissue may be modulated by multiple factors that include, but are not exclusive to, CYP1A1 and CYP1B1 inducibility and the presence or absence of GSTM1.

Altered gene expression patterns in MCF-7 cells induced by the urban dust particulate complex mixture standard reference material 1649a

Human exposures to polycyclic aromatic hydrocarbon (PAH) occur in complex mixtures. Here, gene expression patterns were investigated using standard reference material (SRM) 1649a (urban dust). MCF-7 cells were exposed to SRM 1649a alone or SRM 1649a with either benzo[a]pyrene (BP) or dibenzo[a,l]pyrene (DBP) for 24 hours. Global analyses of the gene expression data revealed alterations of 41 RNA transcripts with at least 2-fold change (signal log ratio </= -1 or >/= 1) in response to SRM 1649a exposure. Increase in expression of cytochrome P450 (CYP) genes was observed in response to BP exposure (CYP1A1 and CYP1B1; signal log ratio of 4.7 and 2.5, respectively). An additive induction of CYP1A1 and CYP1B1 was observed with cotreatment of SRM 1649a and BP. On the contrary, no change in gene expression of CYP1A1 and CYP1B1 was observed when the cells were exposed to DBP. Furthermore, to study the effect of complex PAH mixtures on the metabolic activation of carcinogenic PAH to DNA-binding derivatives and to relate this with gene expression studies, PAH-DNA adduct formation was determined. SRM 1649a decreased the total level of BP-DNA adducts in comparison with BP alone. No significant difference in adduct levels was observed in response to either DBP alone or in combination with SRM 1649a. These results provide a transcriptional signature for chemical carcinogen exposure; in addition, they suggest a major factor in carcinogenic activity of PAH within complex mixtures is their ability to promote or inhibit the activation of carcinogenic PAH by the induction of CYP enzymes.

Effects of suberoylanilide hydroxamic acid and trichostatin A on induction of cytochrome P450 enzymes and benzo[a]pyrene DNA adduct formation in human cells

In this study, we investigated the effects of histone deacetylase (HDAC) inhibitors suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA) on the metabolism of polycyclic aromatic hydrocarbons (PAH) in human mammary carcinoma derived MCF-7 cells in culture. Benzo[a]pyrene (B[a]P) induces cytochrome P450 (CYP) 1A1, CYP1B1 and other xenobiotic metabolizing enzymes. Results from our study indicated a significant increase in CYP activity in comparison to vehicle control in cells treated with SAHA or TSA as measured by ethoxyresorufin-O-deethylase assay. However, co-treatment with 1.0 microM SAHA and BP, reduced the mRNA levels of CYP1B1 relative to B[a]P alone. When co-treated with 1.0 microM TSA and BP, a reduction in the mRNA levels of both CYP1A1 and CYP1B1 was observed relative to BP alone. We further investigated to ascertain if the differential expression and activity of CYP1A1 and CYP1B1 influenced levels of B[a]P DNA adduct formation. MCF-7 cells co-treated with B[a]P and SAHA or TSA formed DNA adducts, although no significant differences in levels of DNA binding were revealed. These results suggest that while CYP enzyme activity and gene expression were affected by the HDAC inhibitors SAHA and TSA, they had no apparent influence on B[a]P DNA binding.

CYP3A4 polymorphisms--potential risk factors for breast and prostate cancer: a HuGE review

The steroid hydroxylase CYP3A4 is the most abundant P-450 enzyme in the human liver, and CYP3A enzymes metabolize more than 50% of prescription drugs. The CYP3A4 gene is expressed in the liver, gut, colon, prostate, and breast. Individual variation in CYP3A4 may play a role in breast and prostate carcinogenesis through modulation of sex hormone metabolite levels. Alternatively, CYP3A4 can metabolically activate exogenous carcinogens. CYP3A4 activity varies widely in humans, and more than 78 DNA sequence polymorphisms are known. These observations prompted the hypothesis that variant CYP3A4 may be involved in breast and prostate cancer. Two epidemiologic studies of breast cancer and five of prostate cancer examined CYP3A4 genotypes. A US study showed that inheritance of CYP3A4*1B correlates with early menarche, a breast cancer risk factor. However, an Australian breast cancer case-control study found no association with CYP3A4*1B. Two Scottish prospective studies showed CYP3A4*1B to be a risk factor for prostate cancer among men with benign prostatic hyperplasia. Three other studies were undertaken in the United States: two were case-only studies and the other was a case-sibling control study. Although results for African Americans were inconsistent, these studies suggested that CYP3A4*1B was associated with markers of advanced disease. These observations support the notion that development of robust, conventional molecular epidemiologic case-control studies to address these questions, including gene-gene and gene-environment interactions, will be timely.

The effect of oxythioquinox exposure on normal human mammary epithelial cell gene expression: a microarray analysis study

BACKGROUND

Inter-individual variation in normal human mammary epithelial cells in response to oxythioquinox (OTQ) is reported. Gene expression signatures resulting from chemical exposures are generally created from analysis of exposures in rat, mouse or other genetically similar animal models, limiting information about inter-individual variations. This study focused on the effect of inter-individual variation in gene expression signatures.

METHODS

Gene expression was studied in primary normal human mammary epithelial cells (NHMECs) derived from four women undergoing reduction mammoplasty [Cooperative Human Tissue Network (National Cancer Institute and National Disease Research Interchange)]. Gene transcription in each cell strain was analyzed using high-density oligonucleotide DNA microarrays (HuGeneFL, Affymetrix) and changes in the expression of selected genes were verified by real-time polymerase chain reaction at extended time points (ABI). DNA microarrays were hybridized to materials prepared from total RNA that was collected after OTQ treatment for 15, 60 and 120 min. RNA was harvested from the vehicle control (DMSO) at 120 min. The gene expression profile included all genes altered by at least a signal log ratio (SLR) of +/- 0.6 and p value < or = 0.05 in three of four cell strains analyzed.

RESULTS

RNA species were clustered in various patterns of expression highlighting genes with altered expression in one or more of the cell strains, including metabolic enzymes and transcription factors. Of the clustered RNA species, only 36 were found to be altered at one time point in three or more of the cell strains analyzed (13 up-regulated, 23 down-regulated). Cluster analysis examined the effects of OTQ on the cells with specific p53 polymorphisms. The two strains expressing the major variant of p53 had 83 common genes altered (35 increased, 48 decreased) at one or more time point by at least a 0.6 signal log ratio (SLR). The intermediate variant strains showed 105 common genes altered (80 increased, 25 decreased) in both strains.

CONCLUSION

Differential changes in expression of these genes may yield biomarkers that provide insight into inter-individual variation in cancer risk. Further, specific individual patterns of gene expression may help to determine more susceptible populations.

The association between HLA-DPB1Glu69 and chronic beryllium disease and beryllium sensitization

BACKGROUND

Several case-control studies have found an association between chronic beryllium disease (CBD) and HLA-DPB1 gene variants. However, the relationship between HLA-DPB1 and beryllium sensitization, and whether the presence of one or two HLA-DPB1(Glu69) alleles is differentially associated with CBD and beryllium sensitization have not been completely resolved.

METHODS

Restriction fragment length polymorphism (RFLP) analysis was used to address these questions in a large population-based cohort consisting of 884 beryllium workers (90 with CBD, 64 beryllium sensitized).

RESULTS

HLA-DPB1(Glu69) was associated with both CBD (OR = 9.4; 95% CI = 5.4, 16.6) and sensitization (OR = 3.3, 95% CI = 1.9, 5.9). Further, workers with CBD and sensitization were more likely to be homozygous HLA-DPB1(Glu69) compared to workers without disease or sensitization (P < 0.001).

CONCLUSIONS

Follow-up of this cohort, scrutiny of HLA-DPB1 haplotypes, and evaluation of gene-environment and gene-gene interactions will be important for fully understanding the immunogenetic nature of this occupational disease.

Applying new biotechnologies to the study of occupational cancer--a workshop summary

As high-throughput technologies in genomics, transcriptomics, and proteomics evolve, questions arise about their use in the assessment of occupational cancers. To address these questions, the National Institute for Occupational Safety and Health, the National Cancer Institute, the National Institute of Environmental Health Sciences, and the American Chemistry Council sponsored a workshop 8-9 May 2002 in Washington, DC. The workshop brought together 80 international specialists whose objective was to identify the means for best exploiting new technologies to enhance methods for laboratory investigation, epidemiologic evaluation, risk assessment, and prevention of occupational cancer. The workshop focused on identifying and interpreting markers for early biologic effect and inherited modifiers of risk.

Electrostatic potential on human leukocyte antigen: implications for putative mechanism of chronic beryllium disease

The pathobiology of chronic beryllium disease (CBD) involves the major histocompatibility complex class II human leukocyte antigen (HLA). Although occupational exposure to beryllium is the cause of CBD, molecular epidemiologic studies suggest that specific (Italic)HLA-DPB1(/Italic) alleles may be genetic susceptibility factors. We have studied three-dimensional structural models of HLA-DP proteins encoded by these genes. The extracellular domains of HLA-DPA1*0103/B1*1701, *1901, *0201, and *0401, and HLA-DPA1*0201/B1*1701, *1901, *0201, and *0401 were modeled from the X-ray coordinates of an HLA-DR template. Using these models, the electrostatic potential at the molecular surface of each HLA-DP was calculated and compared. These comparisons identify specific characteristics in the vicinity of the antigen-binding pocket that distinguish the different HLA-DP allotypes. Differences in electrostatics originate from the shape, specific disposition, and variation in the negatively charged groups around the pocket. The more negative the pocket potential, the greater the odds of developing CBD estimated from reported epidemiologic studies. Adverse impact is caused by charged substitutions in positions 55, 56, 69, 84, and 85, namely, the exact same loci identified as genetic markers of CBD susceptibility as well as cobalt-lung hard metal disease. These findings suggest that certain substitutions may promote an involuntary cation-binding site within a putatively metal-free peptide-binding pocket and therefore change the innate specificity of antigen recognition.

HLA-DPB1 and chronic beryllium disease: a HuGE review

The human leukocyte antigen (HLA) complex is a series of genes located on chromosome 6 that are important in normal immune function. Susceptibility to chronic beryllium disease, a granulomatous lung disease that appears in workers exposed to beryllium, is modified by genetic variants of the HLA-DP subregion. Evaluation of HLA-DPB1 sequence motifs in current and former beryllium workers implicated a glutamic acid residue at position 69 (HLA-DPB1(Glu69)) in chronic beryllium disease. This finding has since been extended to specific HLA-DPB1(Glu69) alleles. Specific job tasks have also been implicated in degree of risk, and in this paper the authors explore gene-environment interaction. The utility of this genetic information for prospective, current, and former beryllium workers must be weighed against the potential for employment and insurance discrimination. Continued research in the beryllium-exposed population will be important for improving personal risk assessment and identifying high-risk genes associated with disease progression.

Priorities for development of research methods in occupational cancer

Occupational cancer research methods was identified in 1996 as 1 of 21 priority research areas in the National Occupational Research Agenda (NORA). To implement NORA, teams of experts from various sectors were formed and given the charge to further define research needs and develop strategies to enhance or augment research in each priority area. This article is a product of that process. Focus on occupational cancer research methods is important both because occupational factors play a significant role in a number of cancers, resulting in significant morbidity and mortality, and also because occupational cohorts (because of higher exposure levels) often provide unique opportunities to evaluate health effects of environmental toxicants and understand the carcinogenic process in humans. Despite an explosion of new methods for cancer research in general, these have not been widely applied to occupational cancer research. In this article we identify needs and gaps in occupational cancer research methods in four broad areas: identification of occupational carcinogens, design of epidemiologic studies, risk assessment, and primary and secondary prevention. Progress in occupational cancer will require interdisciplinary research involving epidemiologists, industrial hygienists, toxicologists, and molecular biologists.

Effects of electrical stimulation-induced leg training on skeletal muscle adaptability in spinal cord injury

Neuromuscular electrical stimulation has grown in popularity as a therapeutic device for training and an ambulation aid to human paralyzed muscle. Despite its current clinical use, few studies have attempted to concurrently investigate the functional and intramuscular adaptations which occur after electrical stimulation training. Six individuals with a spinal cord injury performed 10 weeks of electrical stimulation leg cycle training (30 min d(-1), 3 d week(-1)). The paralyzed vastus lateralis muscle showed significant alterations in skeletal muscle characteristics after the training, indicated by an improvement in total work output (52-112 kJ; P < 0.05), an increase in fiber cross-sectional area (18 to 41 x 10(2) microm(2); P < 0.05), a reduction in the percentage of type IIX fibers (75% to 12%; P < 0.05), a decrease in myosin heavy chain IIx (68% to 44%; P < 0.05), an increase in capillary density (2-3.5 capillaries around fiber; P < 0.05) and increases in activity levels of citrate synthase (7-16 mU mg(-1) protein) and hexokinase (1.2-2.4 mU mg(-1) protein). This study showed that 10 weeks of electrical stimulation training of human paralyzed muscle induces concurrent improvements in functional capacity and oxidative metabolism.