part 1. PART 1

concordance between cancer in humans and in experimental CHAPTER 1 animals

chapter 1. Electrophilic agents James A. Bond and Ronald L. Melnick

Introduction or mice and, except for ethylene chloride), the lung (sulfur mustard), oxide, sufficient evidence of carci- the lymphohaematopoietic system In this chapter, electrophilic agents nogenicity from studies of exposed (benzene, 1,3-butadiene, and eth- include direct-acting electrophilic humans. For ethylene oxide, there ylene oxide), nasal tissue (formal- chemicals and chemicals that are was limited evidence of carcinogen- dehyde), and the kidney (TCE). For metabolized to reactive electro- icity in humans, but the classification bis(chloromethyl) (BCME), the philes. All of the chemicals discussed of this chemical was raised to carci- lung and the nasal cavity were iden- here are IARC Group 1 agents and nogenic to humans (Group 1) based tified as target organs in humans as such can be characterized as on strong mechanistic evidence and rats, respectively. In addition, carcinogenic to humans. Relevant of mutagenicity and clastogenici- angiosarcomas of the liver, which carcinogens discussed in this chap- ty, including the induction of sister are rare tumours, were identified in ter do not include pharmaceutical chromatid exchange (SCE), chro- humans, rats, and mice exposed to drugs classified in Group 1, which mosomal aberrations (CA), and mi- vinyl chloride. otherwise typically include alkylating cronuclei (MN) in workers exposed In several instances, tumour sites cytotoxic agents. to ethylene oxide. identified in animals were not de- Tumour sites identified in previous Among this group of chemicals, tected in epidemiological studies of IARC evaluations of the carcinogen- there is remarkable concordance in exposed workers. These apparent icity of several non-pharmaceutical tumour sites with sufficient evidence discrepancies may be due to dif- organic compounds in humans and or limited evidence of carcinogenicity ferences in susceptibility between laboratory animals are shown in in humans and sufficient evidence of humans and certain animal mod- Table 1.1. For each of these agents, carcinogenicity in rats and/or mice, els, differences in exposure con- there was sufficient evidence of car- for example for the liver (aflatoxins, ditions between studies in animals cinogenicity from studies in rats and/ trichloroethylene [TCE], and vinyl and in humans, or limitations in

Part 1 • Chapter 1. Electrophilic agents 1

Mice evidence Sufficient lymphoma tissue: Lymphoid granulocytic leukaemia tissue: Haematopoietic Mammary adenocarcinoma gland: bronchiolo-alveolarLung: carcinoma carcinoma gland: Zymbal cell squamous carcinoma gland: Preputial sarcomaSoft tissue: fibrosarcoma Skin: lymphoma tissue: Lymphoid haemangiosarcomaSoft tissue: hepatocellular carcinomaLiver: Mammary adenocarcinoma gland: bronchiolo-alveolarLung: carcinoma carcinoma cell squamous Forestomach: carcinomaHarderian gland: cell squamous carcinoma gland: Preputial Lung Lung Liver Lung extrahepatic: angiosarcoma and Liver bronchiolo-alveolarLung: carcinoma Mammary adenocarcinoma gland:

Rats evidence Sufficient hepatocellular carcinomaLiver: Oral cavity: carcinoma cell squamous Forestomach: carcinoma cell squamous carcinomaSkin: carcinoma gland: Zymbal Nasal cavity: olfactory neuroblastoma glioma Brain: lymphoma tissue: Lymphoid mesothelioma Peritoneum: Nasal cavity: cell squamous carcinoma Kidney extrahepatic: and Liver angiosarcoma hepatocellular carcinomaLiver: Mammary adenocarcinoma gland: carcinoma gland: Zymbal

Limited evidence Acute lymphoblasticAcute leukaemia lymphocyticChronic leukaemia myeloma Multiple Non-Hodgkin lymphoma Lymphohaematopoietic (non-Hodgkin lymphoma, chronic myeloma, multiple lymphocytic leukaemia) Breast sinuses Paranasal Larynx Non-Hodgkin lymphoma Liver Humans

Sufficient evidence Sufficient hepatocellularLiver: carcinoma myeloid Acute leukaemia Lung Lymphohaematopoietic Nasopharynx Leukaemia Lung Kidney angiosarcomaLiver: hepatocellularLiver: carcinoma Tumour sites in humans, Tumour rats, and mice for electrophilic agents Agent Aflatoxins Benzene Bis(chloromethyl)ether (BCME) 1,3-Butadiene oxide Ethylene Formaldehyde Sulfur mustard (TCE) Trichloroethylene chlorideVinyl

Table 1.1.

2 epidemiological studies that reduce Table 1.2. Common among these 10 interactions of organic compounds, their power to detect excess cancer agents is the electrophilic nature of or their metabolites, with DNA and risk at particular sites. For example, the parent chemical or a metabolite other critical macromolecules or re- the finding that mammary gland tu- thereof. All of these agents either ceptors are also important, because PART 1

mours were induced in female mice exist as direct-acting electrophilic these interactions can initiate the car- CHAPTER 1 exposed to benzene, 1,3-butadiene, species or can be metabolized to cinogenic process or affect its pro- or vinyl chloride, whereas breast can- reactive electrophilic species. It is gression. Determinants for metabol- cer risk was not elevated in exposed generally accepted that the abili- ism or molecular interactions are workers may be due to the fact that ty of these electrophiles, whether dependent on the exposure history women were not included in many alkylating agents, epoxides, or qui- (including the intensity, duration, occupational cohort or case–control nones, to react with nucleophiles, frequency, and route or routes of studies of these agents, sometimes such as DNA, is key to the carci- exposure, and the life stage of the because there were very few or no nogenicity of this group of agents exposed individual) and may differ women in relevant workforces, or (Table 1.1 and Table 1.2). according to the specific genotype of because they were exposed to much Because of the diversity in the the individual (i.e. genetic polymor- lower concentrations. In contrast, for biochemical and physical properties phisms in metabolic enzymes). hospital-based sterilization workers of organic electrophilic compounds, exposed to ethylene oxide, among it is useful to first examine, in a gen- Absorption whom there is a high proportion of eral way, factors that are important Organic compounds can be ab- women, increases in breast cancer for their absorption, distribution, sorbed after inhalation, dermal ex- incidence were observed. Exposure metabolism, and elimination. These posure, or ingestion. The sites and to ethylene oxide increased the inci- factors include, but are not limited extent of absorption depend on the dence of mammary gland tumours to, (i) physiological, (ii) chemical, physicochemical characteristics of in female mice but not in male mice. and (iii) metabolic determinants. the compound. Highly reactive or- Thus, limitations in human cancer Examples of physiological factors ganic chemicals typically interact databases and sex-specific tumours are alveolar ventilation rate, cardi- with tissues at the portal of entry, in animal studies need to be consid- ac output, blood flow to organs, or- and toxicity and carcinogenicity are ered in evaluations of site concor- gan volumes, and body mass and often most evident at these sites. dance for tumour induction between composition (e.g. percentage body Formaldehyde, for example, is a wa- humans and animals. fat). Examples of chemical factors ter-soluble, reactive volatile organic The carcinogenicity of organic include the stability and reactivity compound. After inhalation, form- compounds and their organ specifici- of the parent compound and its me- aldehyde interacts with the highly ty in animal models and in humans tabolites, partition coefficients that aqueous nasal mucosa, the first are influenced by numerous factors. control the distribution of organic respiratory tract tissue that is en- This chapter focuses on factors compounds between blood and air countered upon inspiration. In rats that affect tissue dosimetry, factors or blood and tissues, rates of uptake chronically exposed to formaldehyde that contribute to the multistep car- from the gastrointestinal tract, and vapours, the anterior portion of the cinogenic process for each agent, absorption through the dermis. For nasal cavity was the site of tumour and factors that might account for some organic chemicals, metabol- induction. interspecies and inter-individual ic determinants such as the cellular Sulfur mustard (also known as differences in susceptibility. capacity for metabolism and the af- finity of metabolic enzymes for the ) is another example of Chemical disposition compound are critical, both in acti- a reactive volatile vating the parent compound to the that can be absorbed after inhalation The role of metabolism in the forma- putative carcinogenic electrophilic or through dermal exposure. It is a tion of the putative carcinogenic inter- metabolite and in transforming the lipophilic substance that easily pene- mediates of the non-pharmaceutical parent compound or the electrophilic trates into the skin and mucosal sur- organic compounds that are carcino- intermediate into a metabolite that faces (Drasch et al., 1987; Somani genic to humans is summarized in can be readily eliminated. Molecular and Babu, 1989), resulting in a high

Part 1 • Chapter 1. Electrophilic agents 3 Table 1.2. Mechanisms for formation of electrophilic species

Agent Mechanism Electrophilic species

Bis(chloromethyl)ether (BCME) Direct-acting Chloroalkyl ether Chloromethyl methyl ether (CMME) Direct-acting Chloroalkyl ether Ethylene oxide Direct-acting Epoxide Formaldehyde Direct-acting Aldehyde Sulfur mustard Direct-acting Sulfonium ion Aflatoxins Metabolic activation Epoxide Benzene Metabolic activation Quinone, epoxide, aldehyde 1,3-Butadiene Metabolic activation Epoxides Trichloroethylene (TCE) Metabolic activation Epoxide, thioketene Vinyl chloride Metabolic activation Epoxide

degree of bioavailability. Sulfur mus- among the most potent animal and large blood–tissue interface of the tard is a bifunctional alkylating agent human carcinogens known. The fact alveoli in that region. The blood–air (IARC, 1987). Like for formaldehyde, that BCME and CMME are powerful partition coefficient is a key factor in there is evidence that DNA alkylation alkylating agents provides moderate determining the maximum levels of by sulfur mustard leads to forma- to strong evidence that they oper- the organic compound that can be tion of cross-links, inhibition of DNA ate by a genotoxic mechanism. This attained in the blood at any given synthesis and repair, and induction mechanism is likely to be similar to concentration of the compound in air. of point mutations and chromo- that of other strong alkylating agents, For example, the blood–air partition some-type and chromatid-type ab- involving modification of DNA and coefficients for the carcinogens vinyl errations (ATSDR, 2003). Some of resultant mutations. BCME can chloride, 1,3-butadiene, benzene, these changes are observed in nasal also be absorbed through the skin, and TCE are 1.2, 1.5, 7.8, and 10 tissue, consistent with the nose be- and studies in which mice were ex- respectively. At equivalent air con- ing a target organ for sulfur mustard. posed to BCME by dermal applica- centrations, higher levels of benzene BCME and chloromethyl methyl tion demonstrated that this agent is and TCE will be present in the blood ether (CMME) are highly reactive or- a potent complete skin carcinogen, at steady state, compared with vinyl ganic compounds that belong to the producing both papillomas and squa- chloride and 1,3-butadiene. group of chloroalkyl , which mous cell carcinomas (Van Duuren The organic compounds dis- are flammable, volatile, colourless et al., 1969). cussed here can also be absorbed liquids with highly irritating odours. Ethylene oxide is a water-soluble after oral exposure. Ingestion and In water and aqueous biological volatile organic compound that is rel- subsequent oral absorption repre- fluids, these substances are rapid- atively stable in aqueous solutions at sent the greatest potential route of ly hydrolysed to form hydrochloric neutral pH (half-life, approximately exposure to non-volatile organic acid, , and formaldehyde 72 hours). Because it is completely compounds. Organic chemicals may (Nichols and Merritt, 1973; National miscible with water, inhaled ethylene enter the body via food or in liquids. Toxicology Program, 2004). The car- oxide will dissolve in the aqueous lin- Aflatoxin is a compound for which cinogenic effects of BCME are re- ing of the respiratory tract and diffuse ingestion is considered the most stricted to the epithelial tissue where into the blood. Thus, uptake of this important route of exposure. For ex- exposure occurs, namely the lung organic compound will be substantial ample, human uptake of aflatoxins for humans and respiratory tract tis- throughout the respiratory tract. in quantities of nanograms to micro- sues for laboratory animals exposed Volatile organic compounds that grams per day occurs mainly through to BCME by inhalation. This por- are not reactive or water-soluble are consumption of contaminated maize tal-of-entry effect is consistent with generally absorbed into the blood, and peanuts, which are dietary sta- the short half-life of BCME in aque- primarily in the pulmonary region of ples in some tropical countries. ous media (ATSDR, 1989). BCME is the respiratory tract because of the Uptake of aflatoxin M1 in quantities

4 of nanograms per day occurs main- reactive exo-epoxide; binding of the to be metabolized via two CYP450 ly via consumption of aflatoxin-con- exo-epoxide to DNA, resulting in enzymes, rather than just one, taminated milk, including breast milk the formation of DNA adducts; and and that the putative, high-affinity (IARC, 2002). Once absorbed from miscoding during DNA replication, enzyme is active primarily at ben- PART 1 which leads to development of mu- zene concentrations below 1 ppm the gastrointestinal tract, aflatoxins CHAPTER 1 are transported via the hepatic por- tations, with eventual progression to (Rappaport et al., 2009). Whereas tal blood to the liver, where they are tumours. Aflatoxin B1, the most com- CYP2E1 is the primary enzyme re- metabolized. As discussed below, mon and potent of the aflatoxins, is sponsible for mammalian metabol- metabolism is key to understanding metabolized predominantly in the ism of benzene at higher levels of the carcinogenicity of aflatoxins. liver. In humans, CYP1A2, CYP2B6, exposure (Valentine et al., 1996; CYP3A4, CYP3A5, and CYP3A7, Nedelcheva et al., 1999), CYP2F1 Metabolic activation or as well as the phase II enzyme glu- and CYP2A13 have been proposed detoxification and elimination tathione-S-transferase M1 (GSTM1; as enzymes that metabolize ben- see below) are hepatic enzymes zene at environmental levels of expo- Metabolism plays a key role in both that mediate aflatoxin metabolism. sure, i.e. below 1 ppm (Powley and the activation and the detoxification In humans, the relative contribution Carlson, 2000; Sheets et al., 2004; of many organic compounds. The of these enzymes in vivo depends Rappaport et al., 2009). first step, generally called phase I not only on their affinity but also A large proportion of benzene metabolism, is oxidation to a meta- on their expression level in the liv- oxide spontaneously rearranges to bolic intermediate. This intermediate er, where CYP3A4 is predominant, phenol, which is either eliminated via becomes the substrate for the sec- mediating the formation of the afla- phase II conjugation or further metab- ond step, phase II, in which it is en- toxin B1 exo-epoxide and aflatoxin olized to hydroquinone and 1,4-ben- zymatically hydrolysed or conjugated Q1. In humans, as in other species, zoquinone. The remaining benzene with one of a variety of biological sub- the DNA binding and carcinogenicity oxide is either hydrolysed to produce strates, such as sulfate, glucuronic of aflatoxin B1 result from its con- benzene-1,2-dihydrodiol (catechol), acid, or glutathione (GSH). Phase II version to the exo-8,9-epoxide by which is further oxidized to 1,2-ben- reactions increase the water solubil- CYP3A4 (Essigmann et al., 1982). zoquinone, or conjugated with GSH ity of the chemical, which facilitates This epoxide is highly reactive and to produce S-phenylmercapturic its excretion in urine, or increase the is the main mediator of cellular injury acid. Metabolism of the oxepin tau- molecular weight, so that the agent (McLean and Dutton, 1995). In con- tomer of benzene oxide is thought to is more readily eliminated in bile. trast, CYP1A2 can generate some open the aromatic ring; this yields the Phase I metabolism of organic com- exo-epoxide but also a high propor- reactive muconaldehydes and mu- pounds can also result in formation tion of endo-epoxide and aflatoxin conic acid. Benzene oxide, the ben- of reactive intermediates that can M1. Aflatoxins M1 and Q1, produced zoquinones, the muconaldehydes, spontaneously interact with critical from aflatoxin B1 by CYP1A2 and and the benzene dihydrodiol epox- macromolecules. For many organic CYP3A4, respectively, are present ides (formed from CYP450-mediated chemicals, this is the first key step in in the urine of individuals exposed oxidation of benzene dihydrodiol) the carcinogenic process. to aflatoxins (Ross et al., 1992; Qian are electrophiles that react readily Cytochrome P450 (CYP450) is et al., 1994). with peptides, proteins, and DNA the collective name of the family of Benzene is also a substrate for (Bechtold et al., 1992; McDonald enzymes responsible for the initial CYP450 enzymes. In common with et al., 1993; Bodell et al., 1996; phase I metabolism of many organ- other compounds discussed in this Gaskell et al., 2005; Henderson et al., ic compounds. Metabolic activation section, benzene must be metabo- 2005; Waidyanatha and Rappaport, by various CYP450 isozymes is lized to become carcinogenic (Ross, 2005), thereby interfering with cellu- a key first step in the carcinogen- 2000; Snyder, 2004). The initial lar function (Smith, 1996). The role of ic process for aflatoxin, benzene, metabolic step involves CYP450- these different metabolites in the car- 1,3-butadiene, TCE, and vinyl chlo- dependent oxidation to benzene ox- cinogenicity of benzene remains un- ride. For example, in the mechanism ide, which exists in equilibrium with clear, but formation of benzoquinone of carcinogenicity of aflatoxins, the its tautomer oxepin. It has been re- from hydroquinone via myeloperoxi- key steps involve: metabolism to a ported that benzene is most likely dase in the bone marrow has been

Part 1 • Chapter 1. Electrophilic agents 5 suggested to be a key step (Smith, competition between 1,3-butadiene by dehydrogenase (ADH) 1996). Indeed, there is consider- and butenediol or epoxybutene for and ALDH, and glucuronidation. able evidence for an important role CYP450-mediated metabolism may The initial step in TCE oxidation in of the metabolic pathway that leads limit the extent to which the second both humans and laboratory ani- to formation of benzoquinone, be- oxidation reaction may occur. mals is catalysed by one of several cause the benzoquinone-detoxifying Vinyl chloride is another volatile CYP450 enzymes and results in enzyme NAD(P)H:quinone oxidore- organic compound that is primarily ductase 1 (NQO1) protects mice and rapidly metabolized in the liv- the formation of an enzyme-bound against benzene-induced myelodys- er (Reynolds et al., 1975; Ivanetich intermediate (an oxygenated TCE- plasia (Long et al., 2002; Iskander et al., 1977; Barbin and Bartsch, CYP450 transition state, TCE-O- and Jaiswal, 2005) and protects 1989; Lilly et al., 1998; Bolt, 2005) by CYP), which is chemically unstable. humans against the haematotoxicity CYP2E1 (WHO, 1999). The prima- This intermediate can be converted of benzene (Rothman et al., 1997). ry metabolites of vinyl chloride are to (i) the electrophile TCE epoxide, However, this does not rule out ad- the highly reactive chloroethylene (ii) N-hydroxy-acetyl-aminoethanol, verse effects from other metabolites. oxide, which is formed in a dose-de- or (iii) chloral, which is in equilibrium Similarly to the metabolism of pendent process and has a half-life with chloral hydrate. The majority of benzene, the first step in 1,3-buta- of 1.6 minutes in aqueous solution diene metabolism involves CYP450- at neutral pH (Barbin et al., 1975; the conversion is directed towards mediated oxidation to epoxybutene Dogliotti, 2006), and its rearrange- chloral/chloral hydrate. TCE epoxide (Himmelstein et al., 1997). At low ment product chloroacetaldehyde spontaneously generates dichloro- concentrations of 1,3-butadiene, (Bonse et al., 1975). Both can bind , another chemically metabolism via the CYP2E1 isozyme to proteins, RNA, and DNA and form unstable and reactive species, or predominates (IARC, 1999, 2008). etheno adducts in RNA and DNA. oxalic acid, which is readily excreted Epoxybutene may be metabolized Chloroethylene oxide is more reac- in urine. Dichloroacetyl chloride un- by conjugation with GSH mediated tive with nucleotides than is chlo- dergoes spontaneous dechlorination by glutathione S-transferase (GST) roacetaldehyde (Guengerich and to produce dichloroacetate. Chloral/ or by hydrolysis catalysed by epox- Watanabe, 1979). ide hydrolase (EH) (Csanády et al., Conjugation of chloroethylene chloral hydrate undergoes either re- 1992; Himmelstein et al., 1997). It oxide and chloroacetaldehyde with duction by ALDH or CYP450 to gen- may also be oxidized to multiple GSH eventually leads to the major erate trichloroethanol, or oxidation diastereomers of diepoxybutane urinary metabolites N-acetyl-S-(2- by ALDH to form trichloroacetate. (Seaton et al., 1995; Krause and hydroxyethyl)cysteine and thiodigly- Trichloroacetate is typically the major Elfarra, 1997), and dihydroxybutene colic acid (Plugge and Safe, 1977). urinary metabolite of TCE that is re- formed by hydrolysis of epoxybutene Chloroethylene oxide can also be de- covered, although trichloroethanol is may be oxidized to epoxybutanediol. toxified to glycolaldehyde by microso- also an important metabolite in urine. Diepoxybutane and epoxybutane- mal EH, and chloroacetaldehyde can Trichloroethanol can be oxidized by diol are also detoxified by GST or be converted to chloroacetic acid by EH (Boogaard et al., 1996). Partial aldehyde dehydrogenase 2 (ALDH2) CYP450 enzymes to yield trichloro- hydrolysis of diepoxybutane also (Guengerich and Watanabe, 1979; acetate, or can undergo glucuronida- produces epoxybutanediol. Bone ATSDR, 2006; IARC, 2008). tion by uridine 5′-diphosphate (UDP)- marrow myeloperoxidase can also Two metabolic pathways of TCE glucuronosyltransferases to produce epoxidize 1,3-butadiene. Each of have been characterized in both trichloroethanol glucuronide. In all the epoxide intermediates may con- humans and laboratory animals: species investigated, trichloroace- tribute to the mutagenicity and car- oxidation and GSH conjugation tate and trichloroethanol/trichloro- cinogenicity of 1,3-butadiene. The (IARC, 2014). The major pathway ethanol glucuronide are formed in formation of epoxybutanediol or di- is CYP450-mediated oxidation, re- epoxybutane requires a second oxi- sulting in the formation of a variety much larger quantities than other dation of butenediol or epoxybutene, of short- and long-lived metabolites. oxidative metabolites. There are respectively. At increasing exposure Subsequent processing of oxida- quantitative differences in the extent concentrations of 1,3-butadiene, tive metabolites involves reduction of oxidative TCE metabolism among

6 species at higher exposures, but at dehyde dehydrogenase, and cat- is converted (i) by enzymatic and lower exposures oxidation is limited alase, as well as CYP2E1. One- non-enzymatic hydrolysis to ethyl- by the hepatic blood flow. metabolism not mediated by ene glycol, which is partly excreted Conjugation with GSH is another CYP450 is central to many biologi- as such and partly metabolized fur- PART 1 important metabolic pathway for TCE, cal processes. In aqueous solution, ther via glycolaldehyde, glycolic acid, CHAPTER 1 resulting in the formation of short- formaldehyde is rapidly converted and glyoxylic acid to oxalic acid, for- lived and reactive metabolites. The to its dihydroxy form, methanediol mic acid, and carbon dioxide; and initial conjugation reaction occurs (CH2(OH)2, also known as formalde- (ii) by conjugation with GSH. primarily in the liver to form (1,2-di- hyde hydrate or methylene glycol), Sulfur mustard, BCME, and chlorovinyl)glutathione (DCVG). which is in dynamic equilibrium with CMME can also react spontaneous- formaldehyde. Subsequent processing of DCVG ly with biological molecules without occurs primarily in the kidney, which the need for metabolic activation. is a tumour target site in rats and hu- Direct-acting compounds For example, the reactivity of sulfur mans. In the kidney, DCVG can be Some organic compounds discussed mustard with a wide variety of cel- hydrolysed by γ-glutamyltransferase lular macromolecules is well docu- and cysteinylglycine dipeptidase to here are sufficiently reactive that they mented (IARC, 1975, 1987; ATSDR, 1,2-dichlorovinyl-cysteine (DCVC), do not require metabolic activation 2003). The presence of two which may be N-acetylated to form as the first step in the carcinogenic atoms makes it a strong bifunctional a mercapturate or converted by process. Formaldehyde reacts read- alkylating agent with a high chemi- β-lyase to generate a reactive thi- ily and reversibly with amino groups cal reactivity (Dacre and Goldman, olate that rearranges to form either to form Schiff bases, and with sulf- 1996). The chlorine atom is typically chlorothioketene or chlorothioacetyl hydryl groups resulting in the forma- chloride (Dekant et al., 1988; Völkel tion of S-hydroxymethylglutathione, released under formation of a car- and Dekant, 1998). Chlorothioketene which is oxidized by ADH3 to bonium ion, which then undergoes and chlorothioacetyl chloride are S-formylglutathione. S-formylglu- intramolecular cyclization to create a highly reactive and chemically un- tathione is further metabolized by highly reactive compound. Formation stable, and are thought to be the S-formylglutathione hydrolase to of the carbonium ion is facilitated molecular forms responsible for ad- generate formate and GSH. Formate in aqueous solutions (Somani and duct formation with nucleic acids in can also be formed non-enzymati- Babu, 1989); this explains the sensi- the kidney (Müller et al., 1998a, b). cally (Hedberg et al., 2002). Because tivity of mucosal tissues, such as the For both humans and rodents, the formaldehyde reacts non-enzymat- eye, to its effect (Solberg et al., 1997). information on urinary excretion of ically with critical macromolecules Elevated concentrations of thiodigly- stable end-products is much more (DNA and others), many of these en- col, the major hydrolysis product of extensive for the oxidative pathway zymatic processes can be viewed as mustard gas, were detected in hu- than for the GSH conjugation path- detoxification steps, especially those man urine after exposure to mustard way. However, this is not an accurate that lead to incorporation of the com- gas vapour and aerosol (Jakubowski indication of the overall flux through pound into the one-carbon pool. et al., 2000). BCME and CMME are each pathway, because it does not Ethylene oxide is another di- rapidly hydrolysed in water and in account for the formation of reactive rect-acting alkylating agent that re- aqueous biological fluids to form hy- and chemically unstable metabolites acts with nucleophiles without the drochloric acid, methanol, and form- via the GSH conjugation pathway. need for metabolic transformation. aldehyde (Nichols and Merritt, 1973; As noted above, CYP450 en- The direct reaction of ethylene ox- National Toxicology Program, 2004). zymes are not the only enzymes ide with DNA is thought to initiate involved in the metabolism of organ- the cascade of genetic and related Molecular interactions (DNA ic compounds. Formaldehyde, an events that lead to cancer (Swenberg adducts, genetic alterations, important intermediate in one-car- et al., 1990). The pathways of ethyl- etc.) bon metabolism, is a substrate for ene oxide metabolism can thus be several enzymes, including cyto- considered detoxification pathways A common feature of the above-men- solic ADH, mitochondrial ALDH, that increase the elimination of the tioned agents is that they either are cytosolic GSH-dependent formal- parent chemical. Ethylene oxide direct-acting electrophiles or are

Part 1 • Chapter 1. Electrophilic agents 7 metabolized to electrophiles. The cause mutations and cytogenetic and enzymes involved in mismatch carcinogenicity of these chemicals is alterations. Entries with weak ev- repair and excision repair (Bernucci considered to be initiated by reaction idence may reflect the availability et al., 1997). of the electrophile with nucleophilic of few or no published studies for Sulfur mustard sites in DNA, leading to the induction certain characteristics of particular of mutations, DNA strand breaks, agents in animal or human tissues, The elimination of a chloride ion from and/or CA. However, additional pro- rather than negative responses sulfur mustard creates a highly re- cesses may also be involved, for ex- (Table 1.3). active cyclic sulfonium ion that can ample free-radical-mediated oxida- alkylate cellular macromolecules tive stress, inhibition of DNA repair, BCME and CMME including DNA, RNA, and proteins. inhibition of topoisomerase II, and Because of the presence of two chlo- The chloroalkyl ethers BCME and immunosuppression. In addition to rine atoms, sulfur mustard can act as CMME are often referred to as pow- time-dependent variation in tissue a bifunctional alkylating agent, pro- concentrations of DNA-reactive me- erful alkylating agents. However, ducing DNA interstrand or intrastrand tabolites of the chemicals described because these compounds are cross-links, for example by binding to above, the likelihood that these short-lived in aqueous solution and guanines on opposite strands or to compounds or their metabolites will undergo rapid hydrolysis, genotoxic- neighbouring guanines on the same bind to DNA and induce site-spe- ity studies of BCME and CMME are strand (Roberts et al., 1971; Walker, cific genetic alterations that lead to sparse and have produced mixed re- 1971; Shahin et al., 2001; Saladi tumour development is a function sults (IARC, 1987). Both compounds et al., 2006). Such cross-links can in- of the physicochemical properties were mutagenic in bacteria (Mukai hibit DNA synthesis and cell division. of the reactive agent (e.g. binding and Hawryluk, 1973; Anderson Sulfur mustard-specific 2-hydroxy­ ethylthioethyl–DNA adducts have affinity for DNA or protein), sever- and Styles, 1978) and caused an been detected in in vitro systems al cellular features (including tissue increase in the frequency of CA in and in multiple tissues of exposed concentrations of alternative binding peripheral lymphocytes of exposed animals (Somani and Babu, 1989; biomolecules such as GSH, rates of workers (Srám et al., 1983). BCME Fidder et al., 1994; van der Schans cell division and cell death, and the binds to guanine and adenine res- et al., 1994; Niu et al., 1996). Similar activities and effectiveness of repair idues of calf thymus DNA in vitro to the binding pattern for other alkyl- enzymes for DNA adducts), other (Goldschmidt et al., 1975). Both com- ating agents, sulfur mustard-derived physiological characteristics (e.g. pounds induced unscheduled DNA DNA adducts have been identified age, sex, health status, and immu- synthesis in cultured human cells at N7 of guanine, N3 of adenine, nocompetence), and lifestyle factors (Agrelo and Severn, 1981; Perocco and O6 of guanine (Fidder et al., (e.g. other exposures). Thus, multiple et al., 1983) and cell transforma- 1994). O6-alkylguanine DNA alkyl- factors and mechanistic processes tion in Syrian hamster embryo cells transferase is ineffective in repairing affect the tissue and species speci- (Casto, 1983) and cultured human O6-ethylthioethylguanine adducts ficity for tumour development asso- fibroblasts (Kurian et al., 1990). The (Ludlum et al., 1986). Thus, sulfur ciated with exposures to each of the carcinogenicity of BCME is widely mustard can inhibit cell division by carcinogenic chemicals discussed in cross-linking of DNA strands and thought to involve mutagenesis re- this chapter. can produce mutations by inducing sulting from alkylation of DNA bases Table 1.3 presents 10 key char- errors in DNA replication or repair. (Bernucci et al., 1997). BCME and acteristics of carcinogens (see Sulfur mustard induced mutations CMME may act synergistically with Chapter 10, by Smith) that have been and CA in exposed animals and in identified in in vivo and/or in vitro formaldehyde, one of their hydrolysis a variety of in vitro systems (IARC, studies on the electrophilic agents products. The likelihood of BCME– 1987). Further, TP53 mutations (pre- reviewed in this chapter. What is DNA adducts leading to mutations dominantly G → A transitions) were most evident from Table 1.3 is that depends on the cellular content and detected in DNA extracted from all these compounds produce DNA activity of DNA repair enzymes such lung tumours of individuals exposed adducts in humans and animals, and as methylguanine methyltransferase, to sulfur mustard (Hosseini-khalili

8 2 2 0 0 0 0 0 2 2 0 0 0 0 1 Animals Animals PART 1 CHAPTER 1 2 2 1 0 0 0 0 2 2 0 0 0 0 1 Vinyl chloride Ethylene oxide Humans Humans 2 2 0 0 0 0 0 2 2 0 1 0 0 1 1 0 1 Animals Animals 2 2 0 0 0 0 1 2 2 0 0 0 0 1 0 0 0 1,3-Butadiene Trichloroethylene Humans Humans 2 2 1 0 1 0 2 1 0 1 2 2 1 0 1 0 0 1 Animals Animals Benzene 2 2 1 1 1 0 2 1 0 1 2 2 1 0 1 0 0 1 Sulfur mustardSulfur Humans Humans 2 2 1 0 0 0 0 1 2 2 1 1 0 0 0 2 Animals Animals Aflatoxins 2 2 1 0 0 0 0 0 2 2 2 1 0 0 0 2 Formaldehyde Humans Humans in humans and animals characteristics of key of carcinogens a Levels of evidence Levels 2 = strong evidence, 1 = moderate evidence, 0 = weak evidence. Characteristic electrophiles to activated metabolically be can or electrophilic Is genotoxic Is Alters DNA repair or causes genomic instability alterations epigenetic Induces stress oxidative Induces Induces chronic inflammation immunosuppressive Is effects receptor-mediated Modulates immortalization Causes Alters cell proliferation, cell death, or nutrient supply Characteristic electrophiles to activated metabolically be can or electrophilic Is genotoxic Is Alters DNA repair or causes genomic instability alterations epigenetic Induces stress oxidative Induces Induces chronic inflammation immunosuppressive Is effects receptor-mediated Modulates immortalization Causes Alters cell proliferation, cell death, or nutrient supply a Table 1.3. Table

Part 1 • Chapter 1. Electrophilic agents 9 et al., 2009). The base excision re- Hong et al., 2007). Evidence was be the major determinants of the na- pair and nucleotide excision repair also provided for the involvement of sal carcinogenicity of formaldehyde pathways were activated in human mutations in p53. in humans and laboratory animals. lymphoblastoid cell lines exposed to The carcinogenicity of ethylene A mechanism for formalde- hyde-induced myeloid leukae- the sulfur mustard analogue 2-chlo- oxide is thought to be due to the mogenesis might involve pancytope- roethyl-ethylsulphide (Jowsey et al., induction of gene mutations and/ nia caused by genotoxicity leading 2009). or chromosomal changes resulting to damage of primitive progenitor from the formation of ethylene ox- Ethylene oxide cells in the bone marrow; mutation ide-derived DNA adducts. Although of myeloid progenitor cells by form- Ethylene oxide is a direct-acting al- evidence for the carcinogenicity of aldehyde and subsequent growth of kylating agent that reacts with nu- ethylene oxide was sufficient in ex- a mutant phenotype may then lead cleophiles, resulting in the formation perimental animals and limited in to myeloid leukaemia. Evidence of a of a variety of adducts in DNA, RNA, humans, the observed increases in mild pancytopenic effect of formal- and protein. Numerous studies have the frequencies of CA, SCE, and MN dehyde or changes in ratios of lym- demonstrated that ethylene oxide in lymphocytes of exposed workers phocyte subsets has been reported induces gene mutations and chro- in exposed workers (Kuo et al., 1997; served as the basis for raising the mosomal changes in in vitro systems Ye et al., 2005; Tang et al., 2009; classification of this alkylating agent and in prokaryotic and eukaryotic Zhang et al., 2010). In addition, col- to carcinogenic to humans (Group 1) organisms. 2-Hydroxyethyl–DNA ony formation by cultured progenitor (IARC, 1994, 2008). adducts formed upon exposure to cells that give rise to myeloid cells ethylene oxide have been observed Formaldehyde is inhibited by low concentrations of in vivo at N7 of guanine, N3 of ad- formaldehyde (Zhang et al., 2010). enine, and O6 of guanine (Walker Formaldehyde can react directly with The observation of increased mon- et al., 1992) and in vitro at N1 and cellular macromolecules including osomy (loss) of chromosome 7 and N6 of adenine and at the N3 posi- proteins and nucleic acids. The for- trisomy (gain) of chromosome 8 in cultured myeloid progenitor cells tion of cytosine, uracil, and thymine maldehyde-specific DNA adduct N6- obtained from the blood of workers (Tates et al., 1999). Genotoxicity re- hydroxymethyl-deoxyadenosine has exposed to formaldehyde may be rel- sulting from ethylene oxide-induced been identified in lymphocytes of evant to the potential involvement of DNA adducts may involve mispairing smokers (Wang et al., 2009). The ge- formaldehyde in leukaemogenesis, of altered bases, formation of aba- notoxicity of formaldehyde is well es- because these types of cytogenetic sic sites upon depurination of the tablished: it induces mutations (point changes are frequently seen in my- adducts at N7 of guanine followed mutations, deletions, and insertions), eloid leukaemia and myelodysplastic by insertion of a different base dur- CA, SCE, MN, DNA strand breaks, syndromes (Zhang et al., 2010). ing DNA synthesis, or DNA strand and DNA–protein cross-links in sev- breaks and subsequent chromo- 1,3-Butadiene eral in vitro and in vivo systems, in- some breakage (Tates et al., 1999; cluding CA, SCE, and MN in nasal 1,3-Butadiene can be metabolized to Houle et al., 2006). In mice, ethylene mucosal cells and/or lymphocytes of three different DNA-reactive epoxide oxide induced large deletion muta- exposed humans (IARC, 2006). In intermediates, which are direct-act- tions, base-pair substitutions, and ing mutagens (IARC, 2008). The ma- animals exposed to formaldehyde, frameshift mutations (Walker and jor DNA adducts formed from these genotoxic effects were more con- Skopek, 1993; Walker et al., 1997a, epoxide intermediates in rats and sistently found in nasal tissues than b). In tumours obtained from mice mice exposed to 1,3-butadiene are in blood lymphocytes. In addition, exposed to ethylene oxide, increas- at the N7 position of guanine. These es in K-Ras mutations with frequent formaldehyde produces irritation of N7-guanine adducts can undergo G → T transversions at codon 12 the nose and pharynx in humans and spontaneous or glycosylase-medi- and G → C transversions at codon laboratory animals. Genotoxicity and ated depurination, which leaves an 13 were reported (Houle et al., 2006; increased cell proliferation appear to apurinic site in the DNA. Epoxide

10 metabolites of 1,3-butadiene can effects of 1,3-butadiene and its me- oxide and/or by the rearrangement also react at sites involved in base tabolites are induction of CA, SCE, product chloroacetaldehyde (Bonse pairing and form adducts at the N3 and MN. et al., 1975). Both intermediates can position of cytosine, at N1 and N6 of Genetic alterations in 1,3-butadi- bind to proteins, RNA, and DNA PART 1

adenine, and at N1 and N2 of guanine ene-induced tumours in mice are of (Guengerich and Watanabe, 1979). CHAPTER 1 (Selzer and Elfarra, 1996a, b, 1997; the same type as those frequently Vinyl chloride is mutagenic in bac- Zhao et al., 1998; Zhang and Elfarra, involved in the development of a va- teria and mammalian cells. It is also 2004). An increase in the number of riety of human cancers. The K-Ras, clastogenic in vivo and in vitro, caus- N1-trihydroxybutyladenine adducts H-Ras, p53, p16/p15, and β-cate- ing increases in the frequencies of was detected in lymphocytes of work- nin mutations detected in tumours CA, SCE, and MN (IARC, 2008). ers exposed to 1,3-butadiene (Zhao from exposed mice are probably The major DNA adduct formed from et al., 2000). Alkylation of N1-adenine the result of the DNA reactivity and chloroethylene oxide is at the N7 po- by epoxybutene followed by hydro- the genotoxic effects of 1,3-butadi- sition of guanine. In addition, etheno 6 lytic deamination forms the highly ene-derived epoxides. Other DNA- DNA adducts (1,N -ethenoadenine, alkylating metabolites of 1,3-butadi- 4 2 mutagenic deoxyinosine (Rodriguez 3,N -ethenocytosine, N ,3-etheno- ene (hydroxymethylvinylketone and 2 et al., 2001), which codes for incor- guanine, and 1,N -ethenoguanine) crotonaldehyde) may also contribute poration of cytosine during DNA rep- have been identified after in vitro in- to the mutagenicity and carcino- cubations with chloroethylene oxide, lication, leading to the generation of genicity of this compound. A con- and levels of these adducts are in- A → G mutations. Diepoxybutane is sistent pattern of K-Ras mutations creased in multiple organs of rats ex- a bifunctional alkylating agent that (G → C transversions at codon 13) posed to vinyl chloride by inhalation can form monoadducts in DNA simi- was observed at multiple organ sites (Ciroussel et al., 1990; Guengerich, lar to those formed by epoxybutane- of 1,3-butadiene-induced cancers 1992; Swenberg et al., 2000). The diol, or DNA–DNA cross-links by (Hong et al., 2000; Sills et al., 2001; etheno adducts, which may be in- binding at the N7 position of guanine Ton et al., 2007). Alterations in the volved in base-pair substitutions, are of one DNA strand and at another p53 gene in brain tumours in mice much more persistent than the N7- site elsewhere in the DNA, such as were mostly G → A transition muta- guanine adduct (Fedtke et al., 1990) the N7 of another guanine or the N1 tions (Kim et al., 2005) that probably and have demonstrated miscoding of an adenine (Goggin et al., 2009). arose from miscoding at apurinic potential in vitro and in vivo, causing Depurination of these interstrand sites resulting from depurination of A → G transitions, A → T transver- or intrastrand lesions can induce N7-guanine adducts. Inactivation of sions, C → A transversions, C → T point mutations and large deletions. the tumour suppressor genes p16 transitions, and G → A transitions However, if diepoxybutane alkylates and p15 may also be important in the (Singer et al., 1987; Cheng et al., an adenine at N6 in DNA, an exocy- development of 1,3-butadiene-in- 1991; Mroczkowska and Kuśmierek, clic adenine adduct is formed pref- duced lymphomas (Zhuang et al., 1991; Singer et al., 1991; Basu et al., erentially to DNA–DNA cross-linked 2000). Mammary gland adenocarci- 1993). The same types of mutation products (Antsypovich et al., 2007). nomas induced by 1,3-butadiene in have been observed in the TP53 1,3-Butadiene is genotoxic at mice frequently had mutations in the and RAS genes in vinyl chloride-in- multiple tissue sites in mice and rats, p53, H-Ras, and β-catenin genes duced tumours. TP53 mutations and its epoxide metabolites are mu- (Zhuang et al., 2002). Overall, these associated with exposure to vinyl tagenic in a variety of in vitro sys- observations point to a genotoxic chloride (frequently A → T transver- tems. Deletion mutations and base mechanism underlying the devel- sions) were found in angiosarcomas substitution mutations induced by opment of 1,3-butadiene-induced in both humans and rats, and muta- these alkylating agents are consis- cancers. tions in K-RAS were also associated tent with their DNA adduct profiles with vinyl chloride-induced angio- Vinyl chloride and include G → A transition muta- sarcomas in humans (IARC, 2008). tions, G → C transversions, A → T The carcinogenicity of vinyl chloride Polymorphisms in XRCC1, a gene transversions, and A → G transitions is probably caused by its highly re- that encodes an enzyme that repairs (Lee et al., 2002). Other genotoxic active metabolite chloroethylene etheno DNA adducts, may account

Part 1 • Chapter 1. Electrophilic agents 11 for inter-individual differences human hepatocellular carcinomas is gene mutations, it has shown poten- among exposed workers in suscep- associated with exposure to aflatoxin tial to affect DNA and chromosomal tibility to genetic damage induced by B1 (Gomaa et al., 2008). G → T trans- structure. The formation of DNA ad- vinyl chloride (Li et al., 2003). version mutations are predominant ducts (Mazzullo et al., 1992; Cai and in cell culture systems and animal Guengerich, 2001) and the mutage- Aflatoxins models and are consistent with the nicity of TCE in vitro are dependent

formation of the major aflatoxin B1- on the presence of metabolic acti- Aflatoxin B1 is genotoxic in prokary- otic and eukaryotic systems in vitro, derived N7-guanine adduct. This is vation systems (IARC, 2014). There including cultured human cells, and because adenine is most commonly is strong evidence that the GSH- in vivo in humans and in a variety of inserted opposite the apurinic site. conjugated metabolites of TCE, par- animal species. Its metabolism to a However, other types of mutation ticularly DCVC, are genotoxic, and reactive exo-8,9-epoxide results in have also been observed with afla- some of the oxidative metabolites DNA binding and formation of DNA toxin B1, including G → C transver- (TCE epoxide, dichloroacetate, and adducts that lead to gene mutations, sions and G → A transitions in DNA chloral/chloral hydrate) may also be CA, SCE, MN, and mitotic recombi- repair-deficient xeroderma pigmen- genotoxic. Thus, biotransformation nation in a variety of in vivo and in tosum cells (Levy et al., 1992); this of TCE can produce genotoxic me- vitro systems (IARC, 2002). Adduct suggests that DNA repair deficien- tabolites, particularly in the kidney, formation in DNA at the N7 position cy may influence the frequency and where in situ metabolism occurs of guanine represents more than distribution of mutations within a (IARC, 2014). 98% of the total adducts formed by gene. Aflatoxin B1 may contribute to Both genotoxic and non-genotox- the exo-8,9-epoxide (Guengerich genomic instability in hepatocellular ic mechanisms may contribute to the et al., 1998). Depurination of this gua- carcinomas (Kaplanski et al., 1997) carcinogenicity and toxicity of TCE nine adduct creates an apurinic site. by inducing mitotic recombination at other sites, including the liver, the Alternatively, the N7-guanine adduct and loss of heterozygosity. The lung, and the haematopoietic sys- may convert to the more stable ring- concurrent presence of hepatitis B tem. In addition to genotoxicity, epi- virus, which causes chronic active opened aflatoxin B1–formamidopy- genetic alterations, oxidative stress, rimidine adduct (Groopman et al., hepatitis and cirrhosis, increases the cytotoxicity, and altered rates of 1981). Differences in the mutational incidence of hepatocellular carcino- cell division or apoptosis may be in- specificity of an apurinic site-con- mas caused by aflatoxins in humans volved in tumour induction in the liver taining genome (derived from depu- (IARC, 2002). or lung. The immunotoxicity of TCE rination of aflatoxin B –N7-guanine) may be involved in the development 1 Trichloroethylene compared with that of a genome with of haematopoietic cancers. However, the aflatoxin B1–N7-guanine adduct Data from human studies suggest the data are inadequate for reliable itself, where mutations also occurred that exposure to TCE increases the conclusions to be drawn about caus- at the base 5′-adjacent to the site of frequency of CA in peripheral lym- al relationships between non-geno- the adducted guanine, suggest that phocytes (Tabrez and Ahmad, 2009) toxic mechanisms and TCE-induced intercalation of the aflatoxin moiety and leads to mutations in the von tumours in humans or laboratory on the 5′ side of the modified guanine Hippel–Lindau tumour suppressor animals (IARC, 2014). From toxicity perturbs both the modified and the gene VHL in renal cell carcinoma and carcinogenicity studies in hu- complementary DNA strands, caus- (Brüning et al., 1997; Brauch et al., mans and laboratory animals, there ing interference with 5′ base pairing 1999), but these findings have been is strong evidence for the kidney as a (Gopalakrishnan et al., 1990; Bailey reported in only a limited number target tissue for TCE-induced tumour et al., 1996). Thus, mutations result- of studies. TCE exposure induced formation. The database supporting ing from aflatoxin B1–N7-guanine MN both in vitro (Wang et al., 2001; the non-genotoxic mechanism of adducts may not be due only to Robbiano et al., 2004; Hu et al., kidney carcinogenesis is moderate. depurination. 2008) and in vivo (Hrelia et al., 1994; However, the strong evidence of ge- A specific AGG → AGT transver- Kligerman et al., 1994; Robbiano notoxicity of DCVC, the kidney me- sion mutation at codon 249 of the et al., 2004). Although TCE itself tabolite of TCE, supports the over- TP53 tumour suppressor gene in appears to be incapable of inducing all conclusion that the evidence for

12 a genotoxic mechanism of kidney of various parts of the long arm of interaction between the parent elec- carcinogenesis is strong. The evi- chromosome 5 or 7, or complete trophile or one or more electrophilic dence for the liver as a target tissue loss of these chromosomes, gain of metabolites and nucleophilic DNA, for TCE, from cancer assays and tox- the entire chromosome 8, and an leading to point mutations and induc- PART 1

icity findings in laboratory animals, is increased frequency of transloca- tion of CA. These effects have been CHAPTER 1 strong. The evidence for non-geno- tions between chromosomes 8 and observed in humans, in animals, and toxic and/or genotoxic mechanisms 21 in peripheral lymphocytes of ex- in in vitro systems. In addition, pro- of liver carcinogenesis is moderate. posed workers (Smith et al., 1998; duction of reactive species, The available data suggest multiple Zhang et al., 1999, 2002). Benzene inhibition of DNA synthesis or repair, non-genotoxic mechanisms and the and its quinone metabolites are in- and cytotoxicity/cell proliferation potential for genotoxic mechanisms hibitors of topoisomerase II, leading could complement DNA modification from the TCE metabolites dichloro- to increased frequencies of DNA to enhance DNA damage. Tumour acetate and chloral hydrate. cleavage complexes and DNA dou- outcome can result from certain ble-strand breaks; this effect can re- DNA adducts leading to mutations Benzene sult in the formation of chromosome and dysregulation initially described Benzene induced CA, SCE, and MN translocations and inversions (Hutt with reference to proto-oncogenes in bone marrow cells of exposed and Kalf, 1996; Lindsey et al., 2004, and tumour suppressor genes. For mice, CA in bone marrow cells of 2005; Deweese and Osheroff, 2009). benzene, chromosomal transloca- exposed rats, and CA and mutations Other potential pathways involved in tions, in combination with haemato- in human cells in vitro. CA in human benzene-induced acute myeloid leu- toxicity or immunosuppression, are peripheral lymphocytes have long kaemia include mutagenesis (pos- associated with increased risk of been associated with occupational sibly through generation of reactive haematopoietic cancer in humans. exposure to benzene (Forni, 1979; oxygen species), epigenetic changes The extent to which other process- IARC, 1982; Eastmond, 1993; Zhang due to altered methylation status, de- es (inflammation, oxidative stress, et al., 2002; Holecková et al., 2004). creased immunosurveillance (Cho, immunosuppression, epigenetic al- As noted above, metabolism of ben- 2008; Li et al., 2009), haematotoxicity terations, and immortalization) might zene produces several electrophilic and alterations in stem cell pool size contribute to the carcinogenicity of agents (benzene oxide, in equilibrium (Rothman et al., 1997), and inhibition this class of chemicals in general is with its tautomer oxepin, muconalde- of gap-junction intercellular commu- limited by the availability of few or no hyde, benzoquinone, and benzene nication (Rivedal and Witz, 2005). published studies that address these dihydrodiol epoxide) that can react Thus, multiple mechanisms are likely effects. with DNA or proteins. DNA binding to be involved in benzene-induced Polymorphisms and leukaemogenesis. Benzene produc- and adduct formation may not be susceptibility the major steps in the development es multiple cytogenetic abnormalities of benzene-induced leukaemias in human lymphocytes (Tough and Susceptibility to the carcinogenic (Whysner et al., 2004). Although the Brown, 1965; Picciano, 1979; Smith effects of organic compounds may mechanisms of benzene-induced and Zhang, 1998; Zhang et al., 2002) derive from acquired characteristics, carcinogenesis and the potential and induces specific chromosomal such as altered expression of certain relative roles of each of these me- changes associated with non-Hodg- enzymes, or from genetic factors, tabolites are not fully known, there is kin lymphoma in human lympho- such as enzyme polymorphisms. strong support for the involvement of cytes (Zhang et al., 2007). Induction Polymorphisms of enzymes involved clastogenic and aneugenic effects, of DNA double-strand breaks and in the metabolism of organic com- such as formation of CA, MN, and chromosomal rearrangements in pounds are likely to be responsible DNA strand breaks. lymphoid cells in combination with for individual differences in activa- Exposure to benzene has been immunosuppression by benzene tion and detoxification reactions that associated with chromosomal might be the cause of lymphoma. control tissue levels of electrophilic changes that are commonly ob- The carcinogenicity of the group intermediates. The enzymes that served in acute myeloid leukaemia, of electrophilic chemicals dis- catalyse epoxide formation and elim- including those comprising loss cussed above is likely to be due to ination are polymorphic in human

Part 1 • Chapter 1. Electrophilic agents 13 populations, and some isozymes derived epoxides or the in vivo muta- 20% of Caucasians and almost 50% may be induced by a variety of en- genicity of 1,3-butadiene in occupa- of Asians) has a homozygous de- vironmental and pharmaceutical tionally exposed workers (Wiencke letion (GSTT1-null genotype) (Bolt agents. For example, factors that et al., 1995; Abdel-Rahman et al., and Thier, 2006). As expected, these explain differences in the response 2003). The extent to which these individuals show a significantly ele- to aflatoxin between human individ- enzyme polymorphisms influence vated level of hydroxyethyl valine in uals and between animal species the carcinogenicity of 1,3-butadiene their haemoglobin, due to the pres- and strains include the proportion is not known. The genotoxic effects ence of endogenous ethylene oxide of aflatoxin metabolized to the exo- of 1,3-butadiene can be modulated (Thier et al., 2001). Nevertheless, the 8,9-epoxide (mainly by CYP450 by alterations in key determinants influence of this genetic trait on the enzymes) relative to other, much of its metabolism; this suggests that formation of this type of adduct as a less toxic metabolites, and the prev- markers of individual susceptibility result of exposure to exogenous eth- alence of pathways that lead to the can be identified. For example, mice ylene oxide in the workplace is less formation of non-toxic conjugates that lack a functional microsomal clear. with reduced mutagenicity and cyto- EH (mEH) gene were more sus- In the cytoplasm of erythrocytes toxicity (Guengerich et al., 1998). ceptible than wild-type mice to the obtained from 36 individuals, ethyl- Similarly, the expression of en- mutagenic effects of 1,3-butadiene ene oxide was eliminated 3–6 times zymes involved in aflatoxin metabol- or diepoxybutane (Wickliffe et al., as fast in samples from so-called ism can be modulated with che- 2003). EH activity varies consider- conjugators (defined by a standard- mopreventive agents, resulting in ably among humans. 1,3-Butadiene- ized conjugation reaction of methyl inhibition of DNA adduct formation exposed workers with the genotype bromide and GSH; 75% of the popu- and hepatocarcinogenesis, as has for low-activity EH were reported to lation) as in samples from individuals been demonstrated in rats. Oltipraz be more susceptible to 1,3-butadi- who lack this GST-specific activity is a chemopreventive agent that in- ene-induced genotoxicity (assessed (the remaining 25%). In whole-blood creases GSH conjugation and inhib- by HPRT mutant frequency in lym- samples incubated with ethylene ox- its the activity of some CYP450 en- phocytes) than individuals with the ide, an increase in the frequency of zymes (e.g. CYP1A2). Results from more common EH genotype (Abdel- SCE was observed in lymphocytes clinical trials with oltipraz in China Rahman et al., 2001, 2003). No sig- from the non-conjugators but not in are consistent with experimental nificant effects were observed for lymphocytes from the conjugators data in showing that after dietary induction of HPRT mutations or SCE (Hallier et al., 1993). exposure to aflatoxins, modulation in individuals with GSTM1 or GSTT1 The carcinogenicity and toxic- of the metabolism of aflatoxins with polymorphisms (Abdel-Rahman ity of TCE, particularly in the liver oltipraz can lead to reduced levels of et al., 2001). MN frequencies were and kidney, are associated with its DNA adducts (IARC, 2002; Kensler higher among 1,3-butadiene-ex- metabolism. There are inter-individ- et al., 2005). posed workers in China with poly- ual differences, both in humans and Increased susceptibility to the morphisms in GSTM1 and/or GSTT1 in rodents, in the formation of TCE toxic effects of benzene has been compared with workers with the metabolites that are thought to be linked to genetic polymorphisms that wild-type genes (Cheng et al., 2013). responsible for the toxic and carcino- increase the rate of metabolism of These differences in response are genic effects of TCE in the kidney and benzene to active intermediates or consistent with the known important liver. The susceptibility to adverse decrease the rate of detoxification of roles of EH and GST in the detoxi- health effects of TCE may be influ- these active intermediates (Rothman fication of 1,3-butadiene epoxides in enced by genetics, sex, life stage, et al., 1997; Xu et al., 1998; Kim et al., tissues in which these intermediates and other conditions that influence 2004). are produced. the extent and nature of the metabol- Enzyme polymorphisms also af- Ethylene oxide is a substrate of ism of this chemical. Polymorphisms fect the metabolism of 1,3-butadi- the GST isozyme T1 (Hayes et al., in metabolism genes in both ox- ene. Genetic polymorphisms in GST 2005). This detoxifying enzyme is idative (e.g. CYP2E1, ADH, and and microsomal EH affect the in polymorphic, and a relatively large ALDH) and GSH conjugation (e.g. vitro mutagenicity of 1,3-butadiene- proportion of the population (about GSTs) pathways have been studied

14 in connection with susceptibility to pigmentosum cells (human fibro- pancytopenia) may have increased TCE toxicity and carcinogenicity. blasts) compared with repair-profi- susceptibility to leukaemia from Polymorphisms in genes for organic cient cells; the location of mutations formaldehyde. anion transporters (OAT1 and OAT3) was affected by repair proficiency A common polymorphism in PART 1 in the kidney may also influence the (Levy et al., 1992). the DNA repair gene XRCC1 is CHAPTER 1 rates of uptake and the extent of cellu- Polymorphisms in genes involved a biomarker of susceptibility to lar accumulation of DCVG or DCVC. in repair of DNA double-strand TP53-induced mutations in work- With respect to life-stage susceptibil- breaks (WRN [Werner syndrome], ers exposed to vinyl chloride (Li ity, data are available to support the TP53, BLM [Bloom syndrome], et al., 2003). In workers exposed to influence of differences in exposure RAD51, and BRCA1) can modify 1,3-butadiene, MN frequencies were (e.g. transplacental transfer or ex- susceptibility to benzene-induced higher in peripheral lymphocytes of posure through breast milk in early individuals with polymorphisms in life stages) or life stage-specific dif- haematotoxicity in exposed workers XRCC1 compared with individuals ferences in toxicokinetics. Lifestyle (Shen et al., 2006; Lan et al., 2009; carrying the wild-type repair gene factors (e.g. consumption of alcohol- Ren et al., 2009). (Wang et al., 2010). ic beverages) may also affect TCE Mice deficient in nucleotide exci- In summary, genetic polymor- metabolism, and nutrition or obesity sion repair were more susceptible phisms and variability in expression may affect internal concentrations of than wild-type mice to the mutagenic of enzymes due to induction or inhi- TCE and its metabolites. effects of 1,3-butadiene or its reac- bition of constitutive enzyme levels Genes involved in DNA repair act tive metabolites epoxybutene and di- can have considerable impact on the to maintain the integrity of the ge- epoxybutane (Wickliffe et al., 2007). carcinogenic process. Determining nome by removing lesions (i.e. ad- Chicken cells deficient in the the existence and functional role of ducts) that – if left unrepaired – could Fanconi anaemia complemen- genetic polymorphisms in cancer eti- result in mutations or chromosomal tation groups/breast cancer A damage. Individuals with defects in ology is an active area of research in (FANC/BRCA) pathway are hyper- genes that encode DNA repair en- molecular epidemiology. sensitive (with reduced survival) to zymes are at elevated risk for cer- formaldehyde at levels measured in tain cancers (Poulsen et al., 1993). human plasma (Ridpath et al., 2007). Heterozygous carriers may also This observation is consistent with have increased susceptibility, be- cause of suboptimal levels of repair. an essential role for this pathway in the repair of DNA–protein cross- The reactive aflatoxin B1 me- tabolite exo-8,9-epoxide induced links caused by formaldehyde, and a higher mutation frequency in a suggests that patients with Fanconi shuttle vector plasmid transfected anaemia (a genetic disorder that into DNA repair-deficient xeroderma is characterized by progressive

Part 1 • Chapter 1. Electrophilic agents 15 References

Abdel-Rahman SZ, Ammenheuser MM, Barbin A, Brésil H, Croisy A, Jacquignon P, Brauch H, Weirich G, Hornauer MA, Störkel Ward JB Jr (2001). Human sensitivity to Malaveille C, Montesano R, et al. (1975). Liver- S, Wöhl T, Brüning T (1999). Trichloroethylene 1,3-butadiene: role of microsomal epoxide microsome-mediated formation of alkylating exposure and specific somatic mutations hydrolase polymorphisms. Carcinogenesis. agents from vinyl bromide and vinyl chloride. in patients with renal cell carcinoma. J Natl 22(3):415–23. http://dx.doi.org/10.1093/ Biochem Biophys Res Commun. 67(2):596– Cancer Inst. 91(10):854–61. http://dx.doi. carcin/22.3.415 PMID:11238181 603. http://dx.doi.org/10.1016/0006- org/10.1006/taap.1996.0037 PMID:8619238 291X(75)90854-2 PMID:1201042 Abdel-Rahman SZ, El-Zein RA, Ammenheuser Brüning T, Weirich G, Hornauer MA, Höfler MM, Yang Z, Stock TH, Morandi M, et al. Basu AK, Wood ML, Niedernhofer LJ, Ramos H, Brauch H (1997). Renal cell carcinomas (2003). Variability in human sensitivity to LA, Essigmann JM (1993). Mutagenic and in trichloroethene (TRI) exposed persons 1,3-butadiene: influence of the allelic variants genotoxic effects of three vinyl chloride- are associated with somatic mutations in the of the microsomal epoxide hydrolase gene. induced DNA lesions: 1,N6 -ethenoadenine, von Hippel-Lindau (VHL) tumour suppressor Environ Mol Mutagen. 41(2):140–6. http:// 3,N4-ethenocytosine, and 4-amino-5- gene. Arch Toxicol. 71(5):332–5. http://dx.doi. dx.doi.org/10.1002/em.10142 PMID:12605384 (imidazol-2-yl)imidazole. Biochemistry. org/10.1007/s002040050394 PMID:9137812 32(47):12793–801. http://dx.doi.org/10.1021/ Agrelo CE, Severn BJ (1981). A simplified bi00210a031 PMID:8251500 Cai H, Guengerich FP (2001). Reaction of method for measuring scheduled and trichloroethylene oxide with proteins and unscheduled DNA synthesis in human Bechtold WE, Willis JK, Sun JD, Griffith DNA: instability of adducts and modulation fibroblasts. Toxicology. 21(2):151–8. http:// WC, Reddy TV (1992). Biological markers of functions. Chem Res Toxicol. 14(1):54– dx.doi.org/10.1016/0300-483X(81)90125-6 of exposure to benzene: S-phenylcysteine 61. http://dx.doi.org/10.1021/tx000185n PMID:7281203 in albumin. Carcinogenesis. 13(7):1217–20. PMID:11170508 http://dx.doi.org/10.1093/carcin/13.7.1217 Anderson D, Styles JA (1978). The bacterial PMID:1638689 Casto BC (1983). Comparison of the sensitivity mutation test. Six tests for carcinogenicity. of rodent and human cells to chemical Br J Cancer. 37(6):924–30. http://dx.doi. Bernucci I, Turrini D, Landi MT (1997). Bis- carcinogens using viral transformation, DNA org/0.1038/bjc.1978.134 PMID:354673 chloromethyl ether and carcinogenesis damage, and cytotoxicity assays. Basic Life of alkylating agents [in Italian]. Med Lav. Sci. 24:429–49. PMID:6305332 Antsypovich S, Quirk-Dorr D, Pitts C, 88(5):347–55. PMID:9489299 Tretyakova N (2007). Site specific N6 - Cheng KC, Preston BD, Cahill DS, Dosanjh (2-hydroxy-3,4-epoxybut-1-yl)adenine Bodell WJ, Pathak DN, Lévay G, Ye Q, MK, Singer B, Loeb LA (1991). The vinyl oligodeoxynucleotide adducts of 1,2,3,4- Pongracz K (1996). Investigation of the DNA chloride DNA derivative N2,3-ethenoguanine diepooxybutane: synthesis and stability adducts formed in B6C3F1 mice treated with produces G → A transitions in Escherichia at physiological pH. Chem Res Toxicol. benzene: implications for molecular dosimetry. coli. Proc Natl Acad Sci U S A. 88(22):9974– 20(4):641–9. http://dx.doi.org/10.1021/ Environ Health Perspect. 104(Suppl 6):1189– 8. http://dx.doi.org/10.1073/pnas.88.22.9974 tx060178k PMID:17355152 93. http://dx.doi.org/10.1289/ehp.961041189 PMID:1946466 PMID:9118892 ATSDR (1989). Toxicological profile for Cheng X, Zhang T, Zhao J, Zhou J, Shao bis(chloromethyl) ether. Atlanta (GA), USA: Bolt HM (2005). Vinyl chloride – a classical H, Zhou Z, et al. (2013). The association Agency for Toxic Substances and Disease industrial toxicant of new interest. Crit between genetic damage in peripheral Registry. Available from: https://www.atsdr. Rev Toxicol. 35(4):307–23. http://dx.doi. blood lymphocytes and polymorphisms of cdc.gov/toxprofiles/tp128.pdf. org/10.1080/10408440490915975 three glutathione S-transferases in Chinese PMID:15989139 workers exposed to 1,3-butadiene. Mutat Res. ATSDR (2003). Toxicological profile for 750(1–2):139–46. http://dx.doi.org/10.1016/j. mustard gas. Draft for public comment. Bolt HM, Thier R (2006). Relevance mrgentox.2012.10.008 PMID:23159492 Update. Atlanta (GA), USA: Agency for Toxic of the deletion polymorphisms of the Substances and Disease Registry. glutathione S-transferases GSTT1 and Cho JY (2008). Suppressive effect of GSTM1 in pharmacology and toxicology. hydroquinone, a benzene metabolite, on in ATSDR (2006). Toxicological profile for vinyl Curr Drug Metab. 7(6):613–28. http:// vitro inflammatory responses mediated by chloride. Atlanta (GA), USA: Agency for Toxic dx.doi.org/10.2174/138920006778017786 macrophages, monocytes, and lymphocytes. Substances and Disease Registry. Available PMID:16918316 Mediators Inflamm. 2008:298010. from: http://www.atsdr.cdc.gov/toxprofiles/ http://dx.doi.org/10.1155/2008/298010 tp20.pdf. Bonse G, Urban T, Reichert D, Henschler PMID:19148301 D (1975). Chemical reactivity, metabolic Bailey EA, Iyer RS, Stone MP, Harris TM, oxirane formation and biological reactivity Ciroussel F, Barbin A, Eberle G, Bartsch H Essigmann JM (1996). Mutational properties of chlorinated ethylenes in the isolated (1990). Investigations on the relationship of the primary aflatoxin B1-DNA adduct. perfused rat liver preparation. Biochem between DNA ethenobase adduct levels in Proc Natl Acad Sci U S A. 93(4):1535–9. Pharmacol. 24(19):1829–34. http://dx.doi. several organs of vinyl chloride-exposed http://dx.doi.org/10.1073/pnas.93.4.1535 org/10.1016/0006-2952(75)90468-2 rats and cancer susceptibility. Biochem PMID:8643667 PMID:1233985 Pharmacol. 39(6):1109–13. http://dx.doi. Barbin A, Bartsch H (1989). Nucleophilic org/10.1016/0006-2952(90)90291-R Boogaard PJ, Sumner SCJ, Bond JA PMID:2322297 selectivity as a determinant of carcinogenic (1996). Glutathione conjugation of potency (TD50) in rodents: a comparison 1,2:3,4-diepoxybutane in human liver and Csanády GA, Guengerich FP, Bond JA of mono- and bi-functional alkylating rat and mouse liver and lung in vitro. Toxicol (1992). Comparison of the biotransformation agents and vinyl chloride metabolites. Appl Pharmacol. 136(2):307–16. http://dx.doi. of 1,3-butadiene and its metabolite, butadiene Mutat Res. 215(1):95–106. http://dx.doi. org/10.1006/taap.1996.0037 PMID:8619238 monoepoxide, by hepatic and pulmonary org/10.1016/0027-5107(89)90222-4 tissues from humans, rats and mice. PMID:2811916 Carcinogenesis. 13(7):1143–53. http://dx.doi. org/10.1093/carcin/13.7.1143 PMID:1638680

16 Dacre JC, Goldman M (1996). Toxicology and Goggin M, Swenberg JA, Walker VE, Hedberg JJ, Hoog JO, Grafstrom RC (2002). pharmacology of the chemical warfare agent Tretyakova N (2009). Molecular dosimetry Assessment of formaldehyde metabolizing sulfur mustard. Pharmacol Rev. 48(2):289– of 1,2,3,4-diepoxybutane-induced DNA- enzymes in human oral mucosa and cultured 326. PMID:8804107 DNA cross-links in B6C3F1 mice and F344 oral keratinocytes indicate high capacity for rats exposed to 1,3-butadiene by inhalation. detoxification of formaldehyde. In: Heinrich U, Dekant W, Berthold K, Vamvakas Cancer Res. 69(6):2479–86. http://dx.doi. Mohr U, editors. Crucial issues in inhalation S, Henschler D, Anders MW (1988). org/10.1158/0008-5472.CAN-08-4152 research — mechanistic, clinical and PART 1 Thioacylating intermediates as metabolites PMID:19276346 epidemiologic (INIS Monographs). Stuttgart, CHAPTER 1 of S-(1,2-dichlorovinyl)-l-cysteine and Germany: Fraunhofer IRB Verlag; pp. 103–15. S-(1,2,2-trichlorovinyl)-l-cysteine formed Goldschmidt BM, van Duuren BL, Frenkel by cysteine conjugate β-lyase. Chem Res K (1975). The reaction of 14C-labelled Henderson AP, Bleasdale C, Delaney K, Toxicol. 1(3):175–8. http://dx.doi.org/10.1021/ bis(chloromethyl) ether with DNA. Proc Am Lindstrom AB, Rappaport SM, Waidyanatha tx00003a008 PMID:2979728 Assoc Cancer Res. 16:66. S, et al. (2005). Evidence for the formation of Michael adducts from reactions of (E,E)- Deweese JE, Osheroff N (2009). The DNA Gomaa AI, Khan SA, Toledano MB, Waked I, muconaldehyde with glutathione and other cleavage reaction of topoisomerase II: wolf Taylor-Robinson SD (2008). Hepatocellular thiols. Bioorg Chem. 33(5):363–73. http:// in sheep’s clothing. Nucleic Acids Res. carcinoma: epidemiology, risk factors and dx.doi.org/10.1016/j.bioorg.2005.05.004 37(3):738–48. http://dx.doi.org/10.1093/nar/ pathogenesis. World J Gastroenterol. PMID:16005934 gkn937 PMID:19042970 14(27):4300–8. http://dx.doi.org/10.3748/ wjg.14.4300 PMID:18666317 Himmelstein MW, Acquavella JF, Recio L, Dogliotti E (2006). Molecular mechanisms Medinsky MA, Bond JA (1997). Toxicology of carcinogenesis by vinyl chloride. Ann Ist Gopalakrishnan S, Harris TM, Stone MP and epidemiology of 1,3-butadiene. Crit Super Sanita. 42(2):163–9. PMID:17033136 (1990). Intercalation of aflatoxin B1 in two Rev Toxicol. 27(1):1–108. http://dx.doi. oligodeoxynucleotide adducts: comparative org/10.3109/10408449709037482 Drasch G, Kretschmer E, Kauert G, von 1 AFB H NMR analysis of d(ATC GAT).d(ATCGAT) PMID:9115622 Meyer L (1987). Concentrations of mustard AFB and d(AT GCAT)2. Biochemistry. gas [bis(2-chloroethyl)sulfide] in the tissues 29(46):10438–48. http://dx.doi.org/10.1021/ Holecková B, Piesová E, Sivikova K, Dianovskỳ of a victim of a vesicant exposure. J Forensic bi00498a002 PMID:2125491 J (2004). Chromosomal aberrations in humans Sci. 32(6):1788–93. http://dx.doi.org/10.1520/ induced by benzene. Ann Agric Environ Med. JFS11235J PMID:3430139 Groopman JD, Croy RG, Wogan GN (1981). In 11:175 –9. PMID:15627321 vitro reactions of aflatoxin B1-adducted DNA. Eastmond DA (1993). Induction of micronuclei Proc Natl Acad Sci U S A. 78(9):5445–9. Hong HH, Devereux TR, Melnick RL, and aneuploidy by the quinone-forming http://dx.doi.org/10.1073/pnas.78.9.5445 Moomaw CR, Boorman GA, Sills RC agents benzene and o-phenylphenol. PMID:6795633 (2000). Mutations of ras protooncogenes Toxicol Lett. 67(1–3):105–18. http://dx.doi. and p53 tumor suppressor gene in cardiac org/10.1016/0378-4274(93)90049-4 Guengerich FP (1992). Roles of the vinyl hemangiosarcomas from B6C3F1 mice PMID:8451753 chloride oxidation products 1-chlorooxirane exposed to 1,3-butadiene for 2 years. and 2-chloroacetaldehyde in the in vitro Toxicol Pathol. 28(4):529–34. http:// Essigmann JM, Croy RG, Bennett RA, Wogan formation of etheno adducts of nucleic acid GN (1982). Metabolic activation of aflatoxin B : dx.doi.org/10.1177/019262330002800404 1 bases [corrected]. Chem Res Toxicol. 5(1):2– PMID:10930038 patterns of DNA adduct formation, removal, 5. http://dx.doi.org/10.1021/tx00025a001 and excretion in relation to carcinogenesis. PMID:1581532 Hong H-HL, Houle CD, Ton T-VT, Sills RC Drug Metab Rev. 13(4):581–602. http:// (2007). K-ras mutations in lung tumors and dx.doi.org/10.3109/03602538209011088 Guengerich FP, Johnson WW, Shimada T, tumors from other organs are consistent PMID:6813091 Ueng Y-F, Yamazaki H, Langouët S (1998). with a common mechanism of ethylene Activation and detoxication of aflatoxin B1. oxide tumorigenesis in the B6C3F1 Fedtke N, Boucheron JA, Walker VE, Mutat Res. 402(1–2):121–8. http://dx.doi. Swenberg JA (1990). Vinyl chloride- mouse. Toxicol Pathol. 35(1):81–5. http:// org/10.1016/S0027-5107(97)00289-3 dx.doi.org/10.1080/01926230601063839 induced DNA adducts. II: Formation and PMID:9675258 persistence of 7-(2′-oxoethyl)guanine and PMID:17325976 2 N ,3-ethenoguanine in rat tissue DNA. Guengerich FP, Watanabe PG (1979). Hosseini-khalili A, Haines DD, Modirian E, 14 36 Carcinogenesis. 11(8):1287–92. http://dx.doi. Metabolism of [ C]- and [ C]-labeled Soroush M, Khateri S, Joshi R, et al. (2009). org/10.1093/carcin/11.8.1287 PMID:2387014 vinyl chloride in vivo and in vitro. Biochem Mustard gas exposure and carcinogenesis Pharmacol. 28(5):589–96. http://dx.doi. Fidder A, Moes GWH, Scheffer AG, van der of lung. Mutat Res. 678(1):1–6. http:// org/10.1016/0006-2952(79)90140-0 dx.doi.org/10.1016/j.mrgentox.2009.05.022 Schans GP, Baan RA, de Jong LPA, et al. PMID:444246 (1994). Synthesis, characterization, and PMID:19559099 quantitation of the major adducts formed Hallier E, Langhof T, Dannappel D, Houle CD, Ton T-VT, Clayton N, Huff J, between sulfur mustard and DNA of calf Leutbecher M, Schröder K, Goergens HW, Hong H-H, Sills RC (2006). Frequent thymus and human blood. Chem Res Toxicol. et al. (1993). Polymorphism of glutathione p53 and H-ras mutations in benzene- 7(2):199–204. http://dx.doi.org/10.1021/ conjugation of methyl bromide, ethylene and ethylene oxide-induced mammary tx00038a013 PMID:8199309 oxide and in human gland carcinomas from B6C3F1 mice. blood: influence on the induction of sister Toxicol Pathol. 34(6):752–62. http:// Forni A (1979). Chromosome changes and chromatid exchanges (SCE) in lymphocytes. benzene exposure. A review. Rev Environ dx.doi.org/10.1080/01926230600935912 Arch Toxicol. 67(3):173–8. http://dx.doi. PMID:17162533 Health. 3(1):5–17. PMID:395589 org/10.1007/BF01973304 PMID:8494496 Hrelia P, Maffei F, Vigagni F, Fimognari C, Flori Gaskell M, McLuckie KI, Farmer PB (2005). Hayes JD, Flanagan JU, Jowsey IR Genotoxicity of the benzene metabolites P, Stanzani R, et al. (1994). Interactive effects (2005). Glutathione transferases. Annu between trichloroethylene and pesticides para-benzoquinone and hydroquinone. Rev Pharmacol Toxicol. 45(1):51–88. Chem Biol Interact. 153-154:267–70. at metabolic and genetic level in mice. http://dx.doi.org/10.1146/annurev. Environ Health Perspect. 102(Suppl 9):31–4. http://dx.doi.org/10.1016/j.cbi.2005.03.034 pharmtox.45.120403.095857 PMID:15822171 PMID:15935826 http://dx.doi.org/10.1289/ehp.94102s931 PMID:7698080

Part 1 • Chapter 1. Electrophilic agents 17 Hu C, Jiang L, Geng C, Zhang X, Cao J, Jakubowski EM, Sidell FR, Evans RA, et al. Lan Q, Zhang L, Shen M, Jo WJ, Vermeulen Zhong L (2008). Possible involvement of (2000). Quantification of thiodiglycol in human R, Li G, et al. (2009). Large-scale evaluation oxidative stress in trichloroethylene-induced urine after an accidental sulfur mustard of candidate genes identifies associations genotoxicity in human HepG2 cells. Mutat exposure. Toxicol Methods. 10:143–50. http:// between DNA repair and genomic Res. 652(1):88–94. http://dx.doi.org/10.1016/j. dx.doi.org/10.1080/10517230050083375 maintenance and development of benzene mrgentox.2008.01.002 PMID:18289923 hematotoxicity. Carcinogenesis. 30(1):50–8. Jowsey PA, Williams FM, Blain PG (2009). DNA http://dx.doi.org/10.1093/carcin/bgn249 Hutt AM, Kalf GF (1996). Inhibition of human damage, signalling and repair after exposure PMID:18978339 DNA topoisomerase II by hydroquinone and of cells to the sulphur mustard analogue p-benzoquinone, reactive metabolites of 2-chloroethyl ethyl sulphide. Toxicology. Lee DH, Kim TH, Lee SY, Kim HJ, Rhee SK, benzene. Environ Health Perspect. 104(Suppl 257(3):105–12. http://dx.doi.org/10.1016/j. Yoon B, et al. (2002). Mutations induced 6):1265–9. http://dx.doi.org/10.1289/ tox.2008.12.001 PMID:19111594 by 1,3-butadiene metabolites, butadiene ehp.961041265 PMID:9118903 diolepoxide. and 1,2,3,4-diepoxybutane at Kaplanski C, Chisari FV, Wild CP (1997). the Hprt locus in CHO-K1 cells. Mol Cells. IARC (1975). Some aziridines, N-, S- & Minisatellite rearrangements are increased 14(3):411–9. PMID:12521305 O-mustards and selenium. IARC Monogr in liver tumours induced by transplacental

Eval Carcinog Risk Chem Man. 9:1–268. aflatoxin B1 treatment of hepatitis B virus Levy DD, Groopman JD, Lim SE, Seidman Available from: http://publications.iarc.fr/27 transgenic mice, but not in spontaneously MM, Kraemer KH (1992). Sequence specificity

PMID:1234596 arising tumours. Carcinogenesis. 18(4):633– of aflatoxin B1-induced mutations in a plasmid 9. http://dx.doi.org/10.1093/carcin/18.4.633 replicated in xeroderma pigmentosum and IARC (1982). Some industrial chemicals and PMID:9111192 DNA repair proficient human cells. Cancer dyestuffs. IARC Monogr Eval Carcinog Risk Res. 52(20):5668–73. PMID:1394191 Chem Hum. 29:1–398. Available from: http:// Kensler TW, Chen JG, Egner PA, Fahey JW, publications.iarc.fr/47 PMID:6957379 Jacobson LP, Stephenson KK, et al. (2005). Li B, Li YQ, Yang LJ, Chen SH, Yu W, Effects of glucosinolate-rich broccoli sprouts Chen JY, et al. (2009). Decreased T-cell IARC (1987). Genetic and related effects: an on urinary levels of aflatoxin-DNA adducts receptor excision DNA circles in peripheral updating of selected IARC Monographs from and phenanthrene tetraols in a randomized blood mononuclear cells among benzene- Volumes 1 to 42. IARC Monogr Eval Carcinog clinical trial in He Zuo township, Qidong, exposed workers. Int J Immunogenet. Risks Hum Suppl. 6:1–729. PMID:3504843 People’s Republic of China. Cancer Epidemiol 36(2):107–11. http://dx.doi.org/10.1111/j.1744- IARC (1994). Some industrial chemicals. Biomarkers Prev. 14(11 Pt 1):2605–13. http:// 313X.2009.00832.x PMID:19228219 IARC Monogr Eval Carcinog Risks Hum. dx.doi.org/10.1158/1055-9965.EPI-05-0368 PMID:16284385 Li Y, Marion MJ, Ho R, Cheng TJ, Coulibaly D, 60:1–560. Available from: http://publications. Rosal R, et al. (2003). Polymorphisms for vinyl iarc.fr/78 PMID:7869568 Kim SY, Choi JK, Cho YH, Chung EJ, chloride metabolism in French vinyl chloride IARC (1999). Re-evaluation of some organic Paek D, Chung HW (2004). Chromosomal workers. Int J Occup Med Environ Health. chemicals, hydrazine and peroxide. aberrations in workers exposed to low 16(1):55–9. PMID:12705718 IARC Monogr Eval Carcinog Risks Hum. levels of benzene: association with genetic polymorphisms. Pharmacogenetics. Lilly PD, Thornton-Manning JR, Gargas 71:1–315. Available from: http://publications. ML, Clewell HJ, Andersen ME, Manning iarc.fr/89 PMID:10507919 14(7):453–63. http://dx.doi.org/10.1097/01. fpc.0000114751.08559.7b PMID:15226677 JRT (1998). Kinetic characterization of IARC (2002). Some traditional herbal CYP2E1 inhibition in vivo and in vitro by the medicines, some mycotoxins, naphthalene Kim Y, Hong HH, Lachat Y, Clayton NP, chloroethylenes. Arch Toxicol. 72(10):609–21. and styrene. IARC Monogr Eval Carcinog Devereux TR, Melnick RL, et al. (2005). http://dx.doi.org/10.1007/s002040050551 Risks Hum. 82:1–556. Available from: http:// Genetic alterations in brain tumors following PMID:9851676 publications.iarc.fr/100 PMID:12687954 1,3-butadiene exposure in B6C3F1 mice. Toxicol Pathol. 33(3):307–12. http:// Lindsey RH Jr, Bender RP, Osheroff N (2005). IARC (2006). Formaldehyde, 2-butoxyethanol dx.doi.org/10.1080/01926230590922848 Effects of benzene metabolites on DNA and 1-tert-butoxypropan-2-ol. IARC Monogr PMID:15814359 cleavage mediated by human topoisomerase Eval Carcinog Risks Hum. 88:1–478. II alpha: 1,4-hydroquinone is a topoisomerase Available from: http://publications.iarc.fr/106 Kligerman AD, Bryant MF, Doerr CL, Erexson II poison. Chem Res Toxicol. 18(4):761– PMID:17366697 GL, Evansky PA, Kwanyuen P, et al. (1994). 70. http://dx.doi.org/10.1021/tx049659z Inhalation studies of the genotoxicity of PMID:15833037 IARC (2008). 1,3-butadiene, ethylene trichloroethylene to rodents. Mutat Res. oxide and vinyl halides (vinyl fluoride, vinyl 322(2):87–96. http://dx.doi.org/10.1016/0165- Lindsey RH Jr, Bromberg KD, Felix CA, chloride and vinyl bromide). IARC Monogr 1218(94)00013-1 PMID:7519326 Osheroff N (2004). 1,4-Benzoquinone is Eval Carcinog Risks Hum. 97:1–510. a topoisomerase II poison. Biochemistry. Available from: http://publications.iarc.fr/115 Krause RJ, Elfarra AA (1997). Oxidation 43(23):7563–74. http://dx.doi.org/10.1021/ PMID:20232717 of butadiene monoxide to meso- and bi049756r PMID:15182198 (±)-diepoxybutane by cDNA-expressed IARC (2014). Trichloroethylene, human cytochrome P450s and by mouse, rat, Long DJ 2nd, Gaikwad A, Multani A, Pathak tetrachloroethylene, and some other and human liver microsomes: evidence for S, Montgomery CA, Gonzalez FJ, et al. chlorinated agents. IARC Monogr Eval preferential hydration of meso-diepoxybutane (2002). Disruption of the NAD(P)H:quinone Carcinog Risks Hum. 106:1–514. Available in rat and human liver microsomes. Arch oxidoreductase 1 (NQO1) gene in mice from: http://publications.iarc.fr/130 Biochem Biophys. 337(2):176–84. http:// causes myelogenous hyperplasia. Cancer PMID:26214861 dx.doi.org/10.1006/abbi.1996.9781 Res. 62(11):3030–6. PMID:12036909 PMID:9016811 Iskander K, Jaiswal AK (2005). Quinone Ludlum DB, Kent S, Mehta JR (1986). 6 oxidoreductases in protection against Kuo H, Jian G, Chen C, Liu C, Lai J (1997). Formation of O -ethylthioethylguanine in DNA myelogenous hyperplasia and benzene White blood cell count as an indicator of by reaction with the sulfur mustard, chloroethyl toxicity. Chem Biol Interact. 153–154:147–57. formaldehyde exposure. Bull Environ Contam sulfide, and its apparent lack of repair by 6 http://dx.doi.org/10.1016/j.cbi.2005.03.019 Toxicol. 59(2):261–7. http://dx.doi.org/10.1007/ O -alkylguanine-DNA alkyltransferase. PMID:15935811 s001289900473 PMID:9211697 Carcinogenesis. 7(7):1203–6. http://dx.doi. org/10.1093/carcin/7.7.1203 PMID:3719912 Ivanetich KM, Aronson I, Katz ID (1977). Kurian P, Nesnow S, Milo GE (1990). The interaction of vinyl chloride with rat Quantitative evaluation of the effects of hepatic microsomal cytochrome P-450 human carcinogens and related chemicals on in vitro. Biochem Biophys Res Commun. human foreskin fibroblasts. Cell Biol Toxicol. 74(4):1411–8. http://dx.doi.org/10.1016/0006- 6(2):171–84. http://dx.doi.org/10.1007/ 291X(77)90599-X PMID:14640 BF00249592 PMID:2361190

18 Mazzullo M, Bartoli S, Bonora B, Colacci Perocco P, Bolognesi S, Alberghini W (1983). Robbiano L, Baroni D, Carrozzino R, Mereto A, Lattanzi G, Niero A, et al. (1992). In vivo Toxic activity of seventeen industrial E, Brambilla G (2004). DNA damage and and in vitro interaction of trichloroethylene and halogenated compounds on human micronuclei induced in rat and human kidney with macromolecules from various organs of lymphocytes cultured in vitro. Toxicol Lett. cells by six chemicals carcinogenic to the rat and mouse. Res Commun Chem Pathol 16:69–76. http://dx.doi.org/10.1016/0378- rat kidney. Toxicology. 204(2–3):187–95. Pharmacol. 76(2):192–208. PMID:1376481 4274(83)90012-7 PMID:6836616 http://dx.doi.org/10.1016/j.tox.2004.06.057 PMID:15388244 PART 1

McDonald TA, Waidyanatha S, Rappaport Picciano D (1979). Cytogenetic study of CHAPTER 1 SM (1993). Production of benzoquinone workers exposed to benzene. Environ Res. Roberts JJ, Brent TP, Crathorn AR (1971). adducts with hemoglobin and bone-marrow 19(1):33–8. http://dx.doi.org/10.1016/0013- Evidence for the inactivation and repair proteins following administration of [13C6] 9351(79)90031-8 PMID:510268 of the mammalian DNA template after benzene to rats. Carcinogenesis. 14(9):1921– alkylation by mustard gas and half mustard 5. http://dx.doi.org/10.1093/carcin/14.9.1921 Plugge H, Safe S (1977). Vinyl chloride gas. Eur J Cancer. 7(6):515–24. http:// PMID:8403219 metabolism – a review. Chemosphere. dx.doi.org/10.1016/0014-2964(71)90056-9 6(6):309–25. http://dx.doi.org/10.1016/0045- PMID:5143809 McLean M, Dutton MF (1995). Cellular 6535(77)90095-9 interactions and metabolism of aflatoxin: an Rodriguez DA, Kowalczyk A, Ward JB Jr, update. Pharmacol Ther. 65(2):163–92. http:// Poulsen HE, Loft S, Wassermann K (1993). Harris CM, Harris TM, Lloyd RS (2001). Point dx.doi.org/10.1016/0163-7258(94)00054-7 Cancer risk related to genetic polymorphisms mutations induced by 1,2-epoxy-3-butene N1 PMID:7540767 in carcinogen metabolism and DNA repair. deoxyinosine adducts. Environ Mol Mutagen. Pharmacol Toxicol. 72(Suppl 1):93–103. 38(4):292–6. http://dx.doi.org/10.1002/ Mroczkowska MM, Kuśmierek JT (1991). http://dx.doi.org/10.1111/j.1600- 0773.1993. em.10026 PMID:11774359 Miscoding potential of N2,3-ethenoguanine tb01676.x PMID:8474997 studied in an Escherichia coli DNA-dependent Ross D (2000). The role of metabolism and RNA polymerase in vitro system and possible Powley MW, Carlson GP (2000). specific metabolites in benzene-induced role of this adduct in vinyl chloride-induced Cytochromes P450 involved with benzene toxicity: evidence and issues. J Toxicol mutagenesis. Mutagenesis. 6(5):385–90. metabolism in hepatic and pulmonary Environ Health A. 61(5–6):357–72. http:// http://dx.doi.org/10.1093/mutage/6.5.385 microsomes. J Biochem Mol Toxicol. dx.doi.org/10.1080/00984100050166361 PMID:1795643 14(6):303–9. http://dx.doi.org/10.1002/1099- PMID:11086940 0461(2000)14:6<303::AID-JBT2>3.0.CO;2-8 Mukai FH, Hawryluk I (1973). Mutagenicity PMID:11083083 Ross RK, Yuan J-M, Yu MC, Wogan GN, of some halo-ethers and halo-ketones. Qian GS, Tu JT, et al. (1992). Urinary aflatoxin Mutat Res. 21(4):228. http://dx.doi. Qian GS, Ross RK, Yu MC, Yuan JM, Gao biomarkers and risk of hepatocellular org/10.1016/0165-1161(73)90241-0 YT, Henderson BE, et al. (1994). A follow- carcinoma. Lancet. 339(8799):943–6. http:// up study of urinary markers of aflatoxin dx.doi.org/10.1016/0140-6736(92)91528-G Müller M, Birner G, Dekant W (1998a). exposure and liver cancer risk in Shanghai, PMID:1348796 Reactivity of haloketenes and halothioketenes People’s Republic of China. Cancer Epidemiol with nucleobases: chemical characterization Biomarkers Prev. 3(1):3–10. PMID:8118382 Rothman N, Smith MT, Hayes RB, Traver of reaction products. Chem Res Toxicol. RD, Hoener B, Campleman S, et al. (1997). 11(5):454–63. http://dx.doi.org/10.1021/ Rappaport SM, Kim S, Lan Q, Vermeulen Benzene poisoning, a risk factor for tx9701438 PMID:9585476 R, Waidyanatha S, Zhang L, et al. (2009). hematological malignancy, is associated Evidence that humans metabolize benzene with the NQO1 609C→T mutation and rapid Müller M, Birner G, Sander M, Dekant W via two pathways. Environ Health Perspect. fractional excretion of chlorzoxazone. Cancer (1998b). Reactivity of haloketenes and 117(6):946 –52. http://dx.doi.org/10.1289/ Res. 57(14):2839–42. PMID:9230185 halothioketenes with nucleobases: reactions ehp.0800510 PMID:19590688 in vitro with DNA. Chem Res Toxicol. Saladi RN, Smith E, Persaud AN (2006). 11(5):464–70. http://dx.doi.org/10.1021/ Ren X, Lim S, Smith MT, Zhang L (2009). Mustard: a potential agent of chemical tx9701440 PMID:9585477 Werner syndrome protein, WRN, protects warfare and terrorism. Clin Exp Dermatol. cells from DNA damage induced by the 31(1):1–5. http://dx.doi.org/10.1111/j.1365- National Toxicology Program (2004). NTP benzene metabolite hydroquinone. Toxicol 2230.2005.01945.x PMID:16309468 11th report on carcinogens. Rep Carcinog. Sci. 107(2):367–75. http://dx.doi.org/10.1093/ 11:1–A32. PMID:19826456 toxsci/kfn254 PMID:19064679 Seaton MJ, Follansbee MH, Bond JA (1995). Oxidation of 1,2-epoxy-3-butene to Nedelcheva V, Gut I, Soucek P, Tichavská B, Reynolds ES, Moslen MT, Szabo S, Jaeger 1,2:3,4-diepoxybutane by cDNA-expressed Týnkova L, Mráz J, et al. (1999). Metabolism RJ (1975). Vinyl chloride-induced deactivation human cytochromes P450 2E1 and 3A4 and of benzene in human liver microsomes: of cytochrome P-450 and other components human, mouse and rat liver microsomes. individual variations in relation to CYP2E1 of the liver mixed function oxidase system: Carcinogenesis 16(10):2287–93. http://dx.doi. expression. Arch Toxicol. 73(1):33–40. an in vivo study. Res Commun Chem Pathol org/10.1093/carcin/16.10.2287 PMID:7586124 http://dx.doi.org/10.1007/s002040050583 Pharmacol. 12(4):685–94. PMID:175418 PMID:10207612 Selzer RR, Elfarra AA (1996a). Ridpath JR, Nakamura A, Tano K, Luke Characterization of N1- and N6 -adenosine Nichols RW, Merritt RF (1973). Relative AM, Sonoda E, Arakawa H, et al. (2007). adducts and N1-inosine adducts formed by solvolytic reactivities of chloromethyl ether Cells deficient in the FANC/BRCA pathway the reaction of butadiene monoxide with and bis(chloromethyl)ether. J Natl Cancer are hypersensitive to plasma levels of adenosine: evidence for the N1-adenosine Inst. 50(5):1373–4. PMID:4712596 formaldehyde. Cancer Res. 67(23):11117–22. adducts as major initial products. Chem http://dx.doi.org/10.1158/0008-5472.CAN-07- Res Toxicol. 9(5):875–81. http://dx.doi. Niu T, Matijasevic Z, Austin-Ritchie P, Stering 3028 PMID:18056434 A, Ludlum DB (1996). A 32P-postlabeling org/10.1021/tx960039a PMID:8828924 method for the detection of adducts in the Rivedal E, Witz G (2005). Metabolites of Selzer RR, Elfarra AA (1996b). Synthesis and DNA of human fibroblasts exposed to sulfur benzene are potent inhibitors of gap-junction biochemical characterization of N1-, N2 -, and mustard. Chem Biol Interact. 100(1):77– intercellular communication. Arch Toxicol. N7-guanosine adducts of butadiene monoxide. 84. http://dx.doi.org/10.1016/S0009- 79(6):303–11. http://dx.doi.org/10.1007/ Chem Res Toxicol. 9(1):126–32. http://dx.doi. 2797(96)03690-3 PMID:8599857 s00204-004-0638-0 PMID:15690152 org/10.1021/tx950101o PMID:8924581

Part 1 • Chapter 1. Electrophilic agents 19 Selzer RR, Elfarra AA (1997). Chemical Snyder R (2004). Xenobiotic metabolism Tough IM, Brown WM (1965). Chromosome modification of deoxycytidine at different and the mechanism(s) of benzene toxicity. aberrations and exposure to ambient sites yields adducts of different stabilities: Drug Metab Rev. 36(3–4):531–47. http:// benzene. Lancet. 1(7387):684. http://dx.doi. characterization of N3 - and O2 -deoxycytidine dx.doi.org/10.1081/DMR-200033445 org/10.1016/S0140-6736(65)91835-0 and N3 -deoxyuridine adducts of butadiene PMID:15554234 PMID:14258551 monoxide. Arch Biochem Biophys. 343(1):63– 72. http://dx.doi.org/10.1016/S0009- Solberg Y, Alcalay M, Belkin M (1997). Ocular Valentine JL, Lee SS, Seaton MJ, Asgharian 2797(01)00275-7 PMID:11714481 injury by mustard gas. Surv Ophthalmol. B, Farris G, Corton JC, et al. (1996). 41(6):461–6. http://dx.doi.org/10.1016/S0039- Reduction of benzene metabolism and Shahin S, Cullinane C, Gray PJ (2001). 6257(97)00021-0 PMID:9220568 toxicity in mice that lack CYP2E1 expression. Mitochondrial and nuclear DNA damage Toxicol Appl Pharmacol. 141(1):205–13. http:// induced by sulphur mustard in keratinocytes. Somani SM, Babu SR (1989). Toxicodynamics dx.doi.org/10.1016/S0041-008X(96)80026-3 Chem Biol Interact. 138(3):231–45. http:// of sulfur mustard. Int J Clin Pharmacol Ther PMID:8917693 dx.doi.org/10.1016/S0009-2797(01)00275-7 Toxicol. 27(9):419–35. PMID:2681003 PMID:11714481 van der Schans GP, Scheffer AG, Mars- Srám RJ, Samková I, Holá N (1983). High- Groenendijk RH, Fidder A, Benschop HP, Sheets PL, Yost GS, Carlson GP (2004). dose ascorbic acid prophylaxis in workers Baan RA (1994). Immunochemical detection Benzene metabolism in human lung cell lines occupationally exposed to halogenated of adducts of sulfur mustard to DNA of calf BEAS-2B and A549 and cells overexpressing ethers. J Hyg Epidemiol Microbiol Immunol. thymus and human white blood cells. Chem CYP2F1. J Biochem Mol Toxicol. 18(2):92– 27(3):305–18. PMID:6227657 Res Toxicol. 7(3):408–13. http://dx.doi. 9. http://dx.doi.org/10.1002/jbt.20010 Swenberg JA, Fedtke N, Fennell TR, Walker org/10.1021/tx00039a019 PMID:8075373 PMID:15122651 VE (1990). Relationships between carcinogen Van Duuren BL, Sivak A, Goldschmidt BM, Shen M, Lan Q, Zhang L, Chanock S, Li G, exposure, DNA adducts and carcinogenesis. Katz C, Melchionne S (1969). Carcinogenicity Vermeulen R, et al. (2006). Polymorphisms in In: Clayson DB, Munro IC, Shubik P, Swenberg of halo-ethers. J Natl Cancer Inst. 43(2):481– genes involved in DNA double-strand break JA, editors. Progress in predictive toxicology. 6. PMID:5805453 repair pathway and susceptibility to benzene- Amsterdam, Netherlands: Elsevier Scientific induced hematotoxicity. Carcinogenesis. Publications; pp. 161–84. Völkel W, Dekant W (1998). Chlorothioketene, the ultimate reactive intermediate formed 27(10):2083–9. http://dx.doi.org/10.1093/ Swenberg JA, Ham A, Koc H, Morinello E, carcin/bgl061 PMID:16728435 by cysteine conjugate β-lyase-mediated Ranasinghe A, Tretyakova N, et al. (2000). cleavage of the trichloroethene metabolite Sills RC, Hong HL, Boorman GA, Devereux DNA adducts: effects of low exposure to S-(1,2-Dichlorovinyl)-l-cysteine, forms TR, Melnick RL (2001). Point mutations ethylene oxide, vinyl chloride and butadiene. cytosine adducts in organic solvents, but of K-ras and H-ras genes in forestomach Mutat Res. 464(1):77–86. http://dx.doi. not in aqueous solution. Chem Res Toxicol. neoplasms from control B6C3F1 mice org/10.1016/S1383-5718(99)00168-0 11(9):1082–8. http://dx.doi.org/10.1021/ and following exposure to 1,3-butadiene, PMID:10633179 tx980084d PMID:9760283 isoprene or chloroprene for up to 2-years. Tabrez S, Ahmad M (2009). Toxicity, Chem Biol Interact. 135-136:373–86. http:// Waidyanatha S, Rappaport SM (2005). biomarkers, genotoxicity, and carcinogenicity Investigation of cysteinyl protein adducts of dx.doi.org/10.1016/S0009-2797(01)00179-X of trichloroethylene and its metabolites: PMID:11397402 benzene diolepoxide. Chem Biol Interact. a review. J Environ Sci Health C Environ 153-154:261–6. http://dx.doi.org/10.1016/j. Singer B, Kuśmierek JT, Folkman W, Carcinog Ecotoxicol Rev. 27(3):178–96. http:// cbi.2005.03.033 PMID:15935825 Chavez F, Dosanjh MK (1991). Evidence dx.doi.org/10.1080/10590500903091340 for the mutagenic potential of the vinyl PMID:19657920 Walker IG (1971). Intrastrand bifunctional chloride induced adduct, N2,3-etheno- alkylation of DNA in mammalian cells Tang X, Bai Y, Duong A, Smith MT, Li L, Zhang treated with mustard gas. Can J Biochem. deoxyguanosine, using a site-directed L (2009). Formaldehyde in China: production, kinetic assay. Carcinogenesis. 12(4):745–7. 49(3):332–6. http://dx.doi.org/10.1139/o71- consumption, exposure levels, and health 049 PMID:5549736 http://dx.doi.org/10.1093/carcin/12.4.745 effects. Environ Int. 35(8):1210–24. http:// PMID:2013138 dx.doi.org/10.1016/j.envint.2009.06.002 Walker VE, Fennell TR, Upton PB, Skopek TR, Singer B, Spengler SJ, Chavez F, Kuśmierek PMID:19589601 Prevost V, Shuker DE, et al. (1992). Molecular dosimetry of ethylene oxide: formation and JT (1987). The vinyl chloride-derived Tates AD, van Dam FJ, Natarajan AT, van nucleoside, N2,3-ethenoguanosine, is a persistence of 7-(2-hydroxyethyl)guanine in Teylingen CMM, de Zwart FA, Zwinderman DNA following repeated exposures of rats highly efficient mutagen in transcription. AH, et al. (1999). Measurement of HPRT Carcinogenesis. 8(5):745–7. http://dx.doi. and mice. Cancer Res. 52(16):4328–34. mutations in splenic lymphocytes and PMID:1643630 org/10.1093/carcin/8.5.745 PMID:3581434 haemoglobin adducts in erythrocytes of Lewis Smith MT (1996). The mechanism of rats exposed to ethylene oxide. Mutat Res. Walker VE, Meng Q, Clement NL (1997a). benzene-induced leukemia: a hypothesis 431(2):397–415. http://dx.doi.org/10.1016/ Spectra of mutations in hprt exon 3 of T-cells and speculations on the causes of leukemia. S0027-5107(99)00182-7 PMID:10636004 from F344 rats and lacI transgenic and nontransgenic B6C3F1 mice exposed by Environ Health Perspect. 104(Suppl 6):1219– Thier R, Balkenhol H, Lewalter J, Selinski S, 25. http://dx.doi.org/10.1289/ehp.961041219 inhalation to ethylene oxide. Environmental Dommermuth A, Bolt HM (2001). Influence and Molecular Mutagenesis. 29:2854. PMID:9118896 of polymorphisms of the human glutathione Smith MT, Zhang L (1998). Biomarkers of transferases and cytochrome P450 2E1 Walker VE, Sisk SC, Upton PB, Wong leukemia risk: benzene as a model. Environ enzyme on the metabolism and toxicity of BA, Recio L (1997b). In vivo mutagenicity Health Perspect. 106(Suppl 4):937–46. ethylene oxide and acrylonitrile. Mutat Res. of ethylene oxide at the hprt locus in http://dx.doi.org/10.1289/ehp.98106s4937 482(1–2):41–6. http://dx.doi.org/10.1016/ T-lymphocytes of B6C3F1 lacI transgenic PMID:9703476 S0027-5107(01)00208-1 PMID:11535247 mice following inhalation exposure. Mutat Res. 392(3):211–22. http://dx.doi.org/10.1016/ Smith MT, Zhang L, Wang Y, Hayes RB, Ton TV, Hong HH, Devereux TR, Melnick S1383-5718(97)00062-4 PMID:9294020 Li G, Wiemels J, et al. (1998). Increased RL, Sills RC, Kim Y (2007). Evaluation of translocations and aneusomy in chromosomes genetic alterations in cancer-related genes Walker VE, Skopek TR (1993). A mouse model 8 and 21 among workers exposed to benzene. in lung and brain tumors from B6C3F1 mice for the study of in vivo mutational spectra: Cancer Res. 58(10):2176–81. PMID:9605763 exposed to 1,3-butadiene or chloroprene. sequence specificity of ethylene oxide at the Chem Biol Interact. 166(1–3):112–20. hprt locus. Mutat Res. 288(1):151–62. http:// http://dx.doi.org/10.1016/j.cbi.2006.04.015 dx.doi.org/10.1016/0027-5107(93)90216-3 PMID:16860786 PMID:7686258

20 Wang J-L, Chen W-L, Tsai S-Y, Sung Wiencke JK, Pemble S, Ketterer B, Kelsey Zhang L, Tang X, Rothman N, Vermeulen P-Y, Huang R-N (2001). An in vitro model KT (1995). Gene deletion of glutathione R, Ji Z, Shen M, et al. (2010). Occupational for evaluation of vaporous toxicity of S-transferase theta: correlation with induced exposure to formaldehyde, hematotoxicity, trichloroethylene and tetrachloroethylene genetic damage and potential role in and leukemia-specific chromosome changes to CHO-K1 cells. Chem Biol Interact. endogenous mutagenesis. Cancer Epidemiol in cultured myeloid progenitor cells. Cancer 137(2):139–54. http://dx.doi.org/10.1016/ Biomarkers Prev. 4(3):253–9. PMID:7606200 Epidemiol Biomarkers Prev. 19(1):80–8. S0009-2797(01)00226-510.1016/S0009- http://dx.doi.org/10.1158/1055-9965.EPI-09- PART 1 2797(01)00226-5 PMID:11551530 Xu X, Wiencke JK, Niu M, et al. (1998). 0762 PMID:20056626 CHAPTER 1 Benzene exposure, glutathione S-transferase Wang M, Cheng G, Balbo S, Carmella theta homozygous deletion, and sister Zhang XY, Elfarra AA (2004). Characterization SG, Villalta PW, Hecht SS (2009). Clear chromatid exchanges. Am J Ind Med. of the reaction products of 2′-deoxyguanosine differences in levels of a formaldehyde- 33:157–63. http://dx.doi.org/10.1002/ and 1,2,3,4-diepoxybutane after acid DNA adduct in leukocytes of smokers and (SICI)1097-0274(199802)33:2<157::AID- hydrolysis: formation of novel guanine and nonsmokers. Cancer Res. 69(18):7170–4. AJIM7>3.0.CO;2-V PMID:9438048 pyrimidine adducts. Chem Res Toxicol. http://dx.doi.org/10.1158/0008-5472.CAN-09- 17(4):521–8. http://dx.doi.org/10.1021/ 1571 PMID:19738046 Ye X, Yan W, Xie H, Zhao M, Ying C (2005). tx034243r PMID:15089094 Cytogenetic analysis of nasal mucosa cells Wang Q, Ji F, Sun Y, Qiu Y-L, Wang W, Wu and lymphocytes from high-level long-term Zhao C, Koskinen M, Hemminki K (1998). F, et al. (2010). Genetic polymorphisms formaldehyde exposed workers and low- 32P-postlabelling of N6-adenine adducts of of XRCC1, HOGG1 and MGMT and level short-term exposed waiters. Mutat epoxybutanediol in vivo after 1,3-butadiene micronucleus occurrence in Chinese vinyl Res. 588(1):22–7. http://dx.doi.org/10.1016/j. exposure. Toxicol Lett. 102-103:591–4. http:// chloride-exposed workers. Carcinogenesis. mrgentox.2005.08.005 PMID:16257574 dx.doi.org/10.1016/S0378-4274(98)00253-7 31(6):1068–73. http://dx.doi.org/10.1093/ PMID:10022318 carcin/bgq075 PMID:20378691 Zhang L, Eastmond DA, Smith MT (2002). The nature of chromosomal aberrations Zhao C, Vodicka P, Srám RJ 1, Hemminki K WHO (1999). Vinyl chloride (Environmental detected in humans exposed to benzene. (2000). Human DNA adducts of 1,3-butadiene, Health Criteria 215). Geneva, Switzerland: Crit Rev Toxicol. 32(1):1–42. http:// an important environmental carcinogen. World Health Organization. Available from: dx.doi.org/10.1080/20024091064165 Carcinogenesis. 21(1):107–11. http://dx.doi. whqlibdoc.who.int/ehc/WHO_EHC_215.pdf. PMID:11846214 org/10.1093/carcin/21.1.107 PMID:10607741

Whysner J, Reddy MV, Ross PM, Mohan M, Zhang L, Rothman N, Li G, Guo W, Yang Zhuang SM, Wiseman RW, Söderkvist P Lax EA (2004). Genotoxicity of benzene and its W, Hubbard AE, et al. (2007). Aberrations (2000). Mutation analysis of the pRb pathway metabolites. Mutat Res. 566(2):99–130. http:// in chromosomes associated with lymphoma in 2′,3′-dideoxycytidine- and 1, 3-butadiene- dx.doi.org/10.1016/S1383-5742(03)00053-X and therapy-related leukemia in benzene- induced mouse lymphomas. Cancer Lett. PMID:15164977 exposed workers. Environ Mol Mutagen. 152(2):129–34. http://dx.doi.org/10.1016/ 48(6):467–74. http://dx.doi.org/10.1002/ S0304-3835(99)00447-4 PMID:10773403 Wickliffe JK, Ammenheuser MM, Salazar em.20306 PMID:17584886 JJ, Abdel-Rahman SZ, Hastings-Smith DA, Zhuang SM, Wiseman RW, Söderkvist P Postlethwait EM, et al. (2003). A model of Zhang L, Rothman N, Wang Y, Hayes RB, Yin (2002). Frequent mutations of the Trp53, sensitivity: 1,3-butadiene increases mutant S, Titenko-Holland N, et al. (1999). Benzene Hras1 and beta-catenin (Catnb) genes frequencies and genomic damage in mice increases aneuploidy in the lymphocytes in 1,3-butadiene-induced mammary lacking a functional microsomal epoxide of exposed workers: a comparison of adenocarcinomas in B6C3F1 mice. hydrolase gene. Environ Mol Mutagen. data obtained by fluorescence in situ Oncogene. 21(36):5643–8. http://dx.doi. 42(2):106–10. http://dx.doi.org/10.1002/ hybridization in interphase and metaphase org/10.1038/sj.onc.1205649 PMID:12165863 em.10181 PMID:12929123 cells. Environ Mol Mutagen. 34(4):260–8. http://dx.doi.org/10.1002/(SICI)1098- Wickliffe JK, Herring SM, Hallberg LM, 2280(1999)34:4<260::AID-EM6>3.0.CO;2-P Galbert LA, Masters OE 3rd, Ammenheuser PMID:10618174 MM, et al. (2007). Detoxification of olefinic epoxides and nucleotide excision repair of epoxide-mediated DNA damage: Insights from animal models examining human sensitivity to 1,3-butadiene. Chem Biol Interact. 166(1–3):226–31. http://dx.doi.org/10.1016/j. cbi.2006.04.017 PMID:16730686

Part 1 • Chapter 1. Electrophilic agents 21