Antitumour benzothiazoles. Part 32: DNA adducts and double strand breaks correlate with activity; synthesis of 5F203 hydrogels for local delivery.

Potent, selective antitumour AhR ligands 5F 203 and GW 610 are bioactivated by CYPs 1A1 and 2W1. Herein we reason that DNA adducts' generation resulting in lethal DNA double strand breaks (DSBs) underlies benzothiazoles' activity. Treatment of sensitive carcinoma cell lines with GW 610 generated co-eluting DNA adducts (R(2)>0.

Glutathione transferase pi plays a critical role in the development of lung carcinogenesis following exposure to tobacco-related carcinogens and urethane.

Human cancer is controlled by a complex interaction between genetic and environmental factors. Such environmental factors are well defined for smoking-induced lung cancer; however, the roles of specific genes have still to be elucidated. Glutathione transferase pi (GSTP) catalyzes the detoxification of electrophilic diol epoxides produced by the metabolism of polycyclic aromatic hydrocarbons such as benzo[a]pyrene (BaP), a common constituent of tobacco smoke.

Detection of phosphodiester adducts formed by the reaction of benzo[a]pyrene diol epoxide with 2'-deoxynucleotides using collision-induced dissociation electrospray ionization tandem mass spectrometry.

In this study, we investigated the products formed following the reaction of benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (B[a]PDE) with 2'-deoxynucleoside 3'-monophosphates. The B[a]PDE plus 2'-deoxynucleotide reaction mixtures were purified using solid phase extraction (SPE) and subjected to HPLC with fluorescence detection. Fractions corresponding to reaction product peaks were collected and desalted using SPE prior to analysis for the presence of molecular ions corresponding to m/z 648, 632, 608 and 623 [M-H]- consistent with B[a]PDE adducted (either on the base or phosphate group) 2'-deoxynucleotides of guanine, adenine, cytosine and thymine, respectively, using LC-ESI-MS/MS collision-induced dissociation (CID).

Detection and quantitation of benzo[a]pyrene-derived DNA adducts in mouse liver by liquid chromatography-tandem mass spectrometry: comparison with 32P-postlabeling.

The polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P) is a proven animal carcinogen that is potentially carcinogenic to humans. B[a]P is an ubiquitous environmental pollutant and is also present in tobacco smoke, coal tar, automobile exhaust emissions, and charred food. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using electrospray ionization and selected reaction monitoring (SRM) has been developed for the detection of 10-(deoxyguanosin-N(2)-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (B[a]PDE-N(2)dG) adducts formed in DNA following the metabolic activation of B[a]P to benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (B[a]PDE).

Genotoxicity of the benzene metabolites para-benzoquinone and hydroquinone.

Our interest in benzene-DNA adduct formation and their consequence has led us to develop a number of sensitive methods for their analysis. A HPLC method for the analysis of 32P-postlabelled benzene-DNA adducts was developed and used to detect adducts formed from the reaction of DNA or individual deoxynucleotides with the metabolites para-benzoquinone (p-BQ) and hydroquinone (HQ). Reaction of DNA with BQ yielded four adducts, the major product being a deoxycytidine adduct.

Mutation spectra induced by alpha-acetoxytamoxifen-DNA adducts in human DNA repair proficient and deficient (xeroderma pigmentosum complementation group A) cells.

Tamoxifen, a breast cancer drug, has recently been approved for the chemoprevention of this disease. However, tamoxifen causes hepatic carcinomas in rats through a genotoxic mechanism and increases the risk of endometrial tumors in women. DNA adducts have been detected at low levels in human endometrium, and there is much interest in determining whether DNA damage plays a role in tamoxifen-induced endometrial carcinogenesis.

Hepatic DNA adduct dosimetry in rats fed tamoxifen: a comparison of methods.

Liver homogenates from rats fed tamoxifen (TAM) in the diet were shared among four different laboratories. TAM-DNA adducts were assayed by high pressure liquid chromatography-electrospray tandem mass spectrometry (HPLC-ES-MS/MS), TAM-DNA chemiluminescence immunoassay (TAM-DNA CIA), and (32)P-postlabeling with either thin layer ((32)P-P-TLC) or liquid chromatography ((32)P-P-HPLC) separation. In the first study, rats were fed a diet containing 500 p.

Comparison of the repair of DNA damage induced by the benzene metabolites hydroquinone and p-benzoquinone: a role for hydroquinone in benzene genotoxicity.

The human population is continually exposed to benzene due to its presence in complex environmental mixtures and exposure has been linked to a range of haematotoxic effects, including an increased risk of leukaemia. Several hypotheses have been postulated on how benzene exerts its toxic and carcinogenic effects, one idea being that following metabolism to more reactive species it can react with DNA to form adducts which subsequently give rise to mutations. Previously, we have demonstrated the formation of four major DNA adducts from the reaction of DNA with the benzene metabolites hydroquinone (HQ) and p-benzoquinone (p-BQ) and the mutagenicity of these adducts when analysed using the supF forward mutation assay after replication in a human kidney cell line.

Further development of 32P-postlabeling for the detection of alkylphosphotriesters: evidence for the long-term nonrandom persistence of ethyl-phosphotriester adducts in vivo.

DNA phosphate oxygens are sites for alkylation leading to phosphotriester adducts (PTEs). PTEs are reported to be both abundant and persistent and so may serve as long-term markers of genotoxicity. Previously, we reported a 32P-postlabeling assay for the specific detection of PTEs plus identification of nucleosides located 5' to PTEs.

Comparison of the mutagenic activity of the benzene metabolites, hydroquinone and para-benzoquinone in the supF forward mutation assay: a role for minor DNA adducts formed from hydroquinone in benzene mutagenicity.

Benzene, a ubiquitous environmental pollutant and occupational hazardous chemical, is a recognised human leukaemogen and rodent carcinogen. The mechanism by which benzene exerts its carcinogenic effects is to date unknown but it is considered that mutations induced by benzene-DNA adducts may play a role. The benzene metabolite, para-benzoquinone (p-BQ) following reaction in vitro with DNA, forms four major adducts, which include two adducts on 2'-deoxyguanosine 3'-monophosphate (dGp).

Effects of the order of exposure to a binary mixture of mutagens on the induced mutation spectra in the supF gene.

We have shown previously that UVC irradiation of benzo[a]pyrene diol epoxide (BPDE)-adducted DNA (BPDE/UVC) induces an increase in mutation frequency in the supF gene greater than the calculated additive value derived from either treatment alone, with a greater absolute increase in the level of BPDE signature transversions. Possible explanations were that (i) the BPDE adducts are photoactivated to a more mutagenic lesion or (ii) the presence of UV-induced DNA damage enhanced the mutagenicity of BPDE adducts elsewhere on the DNA. In the present study, to determine which of these mechanisms is responsible for the enhanced mutagenicity of the combined treatment, plasmid pSP189 containing supF was treated with UVC radiation before BPDE treatment (UVC/BPDE).

Tamoxifen DNA damage detected in human endometrium using accelerator mass spectrometry.

This study was aimed to establish whether tamoxifen binds irreversibly to uterine DNA when given to women. Patients were given a single therapeutic dose of [(14)C]tamoxifen citrate orally (20 mg, 0.37 or 1.

Identification and characterization of (3",4"-dihydroxy)-1,N(2)-benzetheno-2'-deoxyguanosine 3'-monophosphate, a novel DNA adduct formed by benzene metabolites.

Reaction of 2'-deoxyguanosine 3'-monophosphate with mixtures of the benzene metabolites p-benzoquinone (p-BQ) and hydroquinone (HQ) in an aqueous solution at pH 6.0 gave two main products which were isolated from the reaction mixture using reversed-phase HPLC and characterized using UV spectroscopy, negative ion electrospray mass spectrometry, and (1)H NMR. Variation of the ratio of p-BQ to HQ in the reaction mixture caused an increase in yield of one of the products.

DNA adducts formed from 4-hydroxytamoxifen are more mutagenic than those formed by alpha-acetoxytamoxifen in a shuttle vector target gene replicated in human Ad293 cells.

The drug tamoxifen, used to treat breast cancer, causes liver cancer in rats and endometrial cancer in women. Tamoxifen forms liver DNA adducts in both short- and long-term dosing of rodents, and DNA adducts have also been reported in tissues of women undergoing tamoxifen therapy. It is not known if the induction of endometrial cancer in women is through these DNA adducts or through the estrogenic nature of the drug.