Expression of a 32 kDa protein in rat mammary tumors induced by anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide

Racemic anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide (BcPDE) is a powerful rat mammary carcinogen and a metabolite of benzo[c]phenanthrene, a polynuclear aromatic hydrocarbon found in the environment. In elucidating potential molecular mechanisms that may play a role in the development of BcPDE-induced rat mammary tumors, we have identified a 32 kDa protein in 16 of 26 tumors analyzed but in only 1 of the 15 normal mammary tissues that were examined. The 32 kDa protein was identified with antibodies to Ets, which also recognized the 55 kDa Ets-1 protein that was expressed at similar levels in normal mammary tissues. The expression of the 32 kDa protein was also observed in mammary tumor-derived cell lines of both rat and human origin and in human melanoma, but not in normal human keratinocytes or rat fibroblast cell lines. Further characterization via 2D gels revealed that the protein exhibits a PI of 5.5. Southwestern analysis using Ets-1 target sequence revealed binding of the 55 kDa Ets-1 but not of the newly identified 32 kDa protein. Overall, the preferential expression of the 32 kDa protein in mammary tumor tissues may serve as a biomarker to follow the development of this tumor type.

Activation of chemically diverse procarcinogens by human cytochrome P-450 1B1

A human cytochrome P-450 (P450) 1B1 cDNA was expressed in Saccharomyces cerevisiae and the microsomes containing P450 1B1 were used to examine the selectivity of this enzyme in the activation of a variety of environmental carcinogens and mutagens in Salmonella typhimurium TA1535/pSK1002 or NM2009 tester strains, using the SOS response as an end point of DNA damage. We also determined and compared these activities of P450 1B1 with those catalyzed by recombinant human P450s 1A1 and 1A2, which were purified from membranes of Escherichia coli. The carcinogenic chemicals tested included 27 polycyclic aromatic hydrocarbons and their dihydrodiol derivatives, 17 heterocyclic and aryl amines and aminoazo dyes, three mycotoxins, two nitroaromatic hydrocarbons, N-nitrosodimethylamine, vinyl carbamate, and acrylonitrile. Among the three P450 enzymes examined here, P450 lB1 was found to have the highest catalytic activities for the activation of 11,12-dihydroxy-11,12-dihydrodibenzo[a,l]pyrene, 1,2-dihydroxy-1,2-dihydro-5-methylchrysene, (+)-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene, 11,12-dihydroxy-11,12-dihydrobenzo[g]chrysene, 3,4-dihydroxy-3,4-dihydrobenzo[c]phenanthrene, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, 2-aminoanthracene, 3-methoxy-4-aminoazobenzene, and 2-nitropyrene. P450 1B1 also catalyzed the activation of 2-amino-3,5-dimethylimidazo[4,5-f]quinoline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3-methylimidazo[4,5-f]quinoline, 2-aminofluorene, 6-aminochrysene and its 1,2-dihydrodiol, (-)-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene, 1,2-dihydroxy-1,2-dihydrochrysene, 1,2-dihydroxy-1,2-dihydro-5,6-dimethylchrysene, 2,3-dihydroxy-2,3-dihydrofluoranthene, 3,4-dihydroxy-3,4-dihydro-7,12-dimethylbenz[a]anthracene, and 6-nitrochrysene to appreciable extents. However, P450 1B1 did not produce genotoxic products from benzo[a]pyrene, trans- 3,4-dihydroxy-3,4-dihydrobenzo[a]anthracene, trans-8,9-dihydroxy-8,9-dihydrobenzo[a]anthracene, 7,12-dimethylbenz[a]anthracene and its cis-5,6-dihydrodiol, 5-methylchrysene, 11,12-dihydroxy-11,12-dihydro-3-methylcholanthrene, 1,2-dihydroxy-1,2-dihydro-6-methylchrysene, benzo[c]phenanthrene, 2-amino-6-methyldipyridol[1,2-a:3',2'-d]imidazole, 2-acetylaminofluorene, benzidine, 2-naphthylamine, aflatoxin B1, aflatoxin G1, sterigmatocystin, N-nitrosodimethylamine, vinyl carbamate, or acrylonitrile in this assay system. P450 1B1 is expressed constitutively in extrahepatic organs, including fetal tissue samples, and is highly inducible in various organs by 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds in experimental animal models. Thus, activation of procarcinogens by P450 lB1 may contribute to human tumors of extrahepatic origin.

Lack of tumorigenicity of cholesterol epoxides and estrone-3,4-quinone in the rat mammary gland

The purpose of this study is to test the long-standing hypothesis that endogenous agents found in human breast fluid and in plasma are potential initiators of breast cancer. Therefore, we evaluated the tumorigenicity in the mammary glands of female CD rats of cholestan-5 alpha,6 alpha-epoxy-3 beta-ol (cholesterol-alpha-epoxide), cholestan-5 beta,6 beta-epoxy-3 beta-ol (cholesterol-beta-epoxide), and 1,5(10)estradiene-3,14,17-trione (estrone-3,4-quinone). As a positive control, trans-3,4-dihydroxy-anti-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthren e (BcPDE) was used. Rats were fed a high-fat AIN-76A diet (23.5% corn oil) to mimic the Western dietary composition. Because literature data suggest that the endogenous agents tested in this study are weak electrophiles, the total doses of cholesterol epoxides (12.3 mumol/rat) and of estrone-3,4-quinone (30 mumol/rat)were 10- and 25- fold higher, respectively, than that of BcPDE (1.2 mumol/rat). Each agent was dissolved in DMSO, and one-sixth of the total dose was injected under each of six nipples on the right side. The thoracic glands of the rat were treated at 30 days of age, and those located in the inguinal area were treated on the following day. The experiment was terminated at 44 weeks after treatment. Consistent with our previous study, BcPDE was a strong mammary carcinogen. However, there were no differences between rats treated with DMSO alone or those receiving DMSO containing cholesterol-alpha-epoxide, cholesterol-beta-epoxide, or estrone-3,4-quinone. The results of this study clearly indicate, for the first time, that metabolites derived from cholesterol and estrone lack tumorigenic activity in the rat mammary gland, at least under the conditions of the present protocol.

The essential role of the functional group in alkyl isothiocyanates for inhibition of tobacco nitrosamine-induced lung tumorigenesis

The importance of the isothiocyanate group in alkyl isothiocyanate for inhibition of tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanone (NNK)-induce lung tumorigenesis was examined in A/J mice. Our previous structure-activity relationship study of isothiocyanates showed that 1-dodecyl isothiocyanate [CH3(CH2)11NCS], a simple alkyl isothiocyanate, is a potent inhibitor of NNK-induced lung tumorigenesis. It was chosen for this study due to its structural features and potency. A single dose of 1-dodecyl isothiocyanate given by gavage at 1 micromol/mouse 2 h prior to NNK administration completely inhibited lung tumorigenesis, while removal of the isothiocyanate group or replacing it with a hydroxyl group abolished the inhibitory activity. These results demonstrate that the isothiocyanate functional group is critical for the inhibitory activity of isothiocyanates in NNK-induced lung tumorigenesis. To gain more insights into the relationship of in vivo inhibition of tumorigenesis with the cytochrome P-450 enzyme inhibitory activity, the effects of these compounds on metabolism of NNK in mouse lung microsomes were studied. 1-Dodecyl isothiocyanate inhibited all three known oxidative pathways of NNK metabolism, with a stronger inhibitory activity toward NNK N-oxidation (IC50 430 nM) and keto alcohol formation (IC50 500 nM) than keto aldehyde formation (IC50 13,000 nM). 1-Dodecanol had a similar selectivity in inhibition of these metabolic pathways, but was less potent than 1-dodecyl isothiocyanate. Dodecane showed little or no inhibitory activity in the same concentration range. These results indicate that the isothiocyanate group of 1-dodecyl isothiocyanate is important for inhibition of NNK-induced lung tumorigenesis and also for effective inhibition of cytochrome P-450 enzymes involved in NNK oxidation.

Effects of dietary 1,4-phenylenebis(methylene)selenocyanate on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced DNA adduct formation in lung and liver of A/J mice and F344 rats

1,4-Phenylenebis(methylene)selenocyanate (p-XSC) was tested for its ability to inhibit DNA adduct formation induced by the tobacco-specific N-nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in the liver and lung of A/J mice and F344 rats. Dietary p-XSC, providing a dose of 5 p.p.m. selenium, significantly inhibited the formation of 7-methylguanine (7-mGua) induced by a single i.p. injection of 10 mumol of NNK(12.8% inhibition at 4 h and 19.9% at 96 h) and O6-methylguanine (O6-mGua) (16.5% at 4 h and 34.8% at 96 h) in the liver of A/J mice. Dietary supplements of p-XSC providing 15 p.p.m. of selenium reduced the levels of 7-mGua by 17.3% (4 h) and 33.6% (96 h). The formation of O6-mGua was inhibited by 69.5% (4th) and 73.8 (96h). In A/J mouse lung DNA the most significant reduction was observed in levels of O6-mGua. Dietary p-XSC at 5 p.p.m. as selenium inhibited the formation of this adduct by 73.1% (4 h). Ninety-six hours after NNK injection, and at both time points with p-XSC providing 15 p.p.m. selenium, O6-mGua was not detected. Although levels of 7- mGua in mouse lung DNA were also reduced, this was significant only 4 h after carcinogen administration. In general, selenite at a5 p.p.m. as selenium had no significant effect on the levels of these lesions; however, it inhibited O6-mGua in the liver only 4 h after NNK administration. These effects may explain why there is chemopreventive activity for p-XSC, but not for selenite, in NNK-induced lung carcinogenesis in A/J mice. Moreover, these findings raised our interest in determining the potential chemopreventive activity of p-XSC against NNK-induced lung adenocarcinomas in male F344 rats by first determining its effects on NNK-induced DNA methylation in the lungs of rats. Diet supplemented with 10 p.p.m. selenium as p-XSC did indeed inhibit the formation of adducts in pulmonary DNA of F344 rats treated with four consecutive injections of 81 mg/kg of NNK. Statistically significant inhibition of O6-mGua formation was observed 4 h after carcinogen treatment in both pulmonary (49.1% inhibition) and hepatic (39.8%) DNA. Statistically significant inhibition of 7-mGua formation was also measured in lung DNA isolated 24 h after the last NNK injection (45.0%) and in liver DNA 4 h after carcinogen treatment (31.8%). These results suggest that p-XSC would also inhibit induction of lung adenocarcinoma in male F344 rats by NNK.

Detection of DNA and globin adducts of polynuclear aromatic hydrocarbon diol epoxides by gas chromatography-mass spectrometry and -3H-CH3I postlabeling of released tetraols

Gas chromatography-negative ion chemical ionization mass spectrometry--selected ion monitoring (GC-NICI-MS-SIM) was employed to detect tetramethyl ether derivatives of tetraols formed upon hydrolysis of DNA and globin adducts derived from diol epoxides of benzo[a]-pyrene (BP) and other polynuclear aromatic hydrocarbons (PAH). The tetramethyl ether derivatives could also be detected by [3H]CH3I postlabeling. The methodology involves the following steps: (1) isolation of DNA or globin; (2) mild acid hydrolysis under vacuum; (3) isolation of the resulting tetraols and derivatization to the corresponding tetramethyl ethers using methyl sulfinyl carbanion and unlabeled or 3H-labeled CH3I; (4) analysis by GC-NICI-MS-SIM or HPLC with radioflow detection. The optimum conditions for hydrolysis of adducts and derivatization of the resulting tetraols as well as the feasibility of this approach for detecting PAH adducts in mice and humans were explored. Using the set of four BP-tetraols that can be formed upon hydrolysis of adducts formed from r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) or r-7,t-8-dihydroxy-c-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (syn-BPDE) as models, the stability of the tetraols under the hydrolysis conditions was investigated. Adducts derived from anti-BPDE yield predominantly the stable r-7,t-8,9-c-10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (trans-anti-BP-tetraol), while adducts derived from syn-BPDE released cis-syn-BP-tetraol as a major hydrolysis product. Hydrolysis under vacuum significantly increased the recovery of tetraols. Conditions for derivatization of the BP-tetraols as well as tetraols derived from several other PAH anti-diol epoxides were investigated. Tetramethyl ethers proved to be superior derivatives that were stable, easy to prepare in high yields, and detectable with high sensitivity by GC-NICI-MS-SIM (1-50 fmol per injection). Alternatively, these derivatives could be detected by HPLC with radioflow detection if [3H]CH3I were employed for derivatization. The methodology was tested by comparing levels of DNA and globin adducts in mice treated with either unlabeled or 3H-labeled BP. Good agreement was obtained among the GC-NICI-MS-SIM, [3H]CH3I postlabeling, and conventional radiometric methods. Moreover, analysis of human hemoglobin by GC-NICI-MS-SIM resulted in detection of adducts derived from anti-BPDE and r-1,t-2-dihydroxy-t-3,4-epoxy-1,2,3,4-tetrahydrochrysene. The results of this study demonstrate that GC-NICI-MS-SIM of tetramethyl ethers of tetraols formed by hydrolysis of PAH diol epoxide DNA and globin adducts is a promising approach for detection and quantitation of adducts derived from a broad range of PAH.

Tnk1: a novel intracellular tyrosine kinase gene isolated from human umbilical cord blood CD34+/Lin-/CD38- stem/progenitor cells

Degenerate PCR was employed to identify novel tyrosine kinase genes from an enriched population of human umbilical cord blood hematopoietic stem/progenitor cells. One novel tyrosine kinase gene, designated Tnk1, was cloned. The sequence of the complete Tnk1 coding region predicts a 72 kD protein. Comparison of Tnk1 to available sequences in protein databases reveals that it is most homologous to Ack, an intracellular tyrosine kinase which associates with the GTP-bound form of p21cdc42Hs. Like Ack, Tnk1 consists of an N-terminal kinase domain, a putative SH3 domain immediately C-terminal to the kinase domain, and a proline-rich C-terminal region. Analysis of Tnk1 mRNA expression demonstrates that Tnk1 is expressed in all cord blood, bone marrow and adult blood sub-populations, as well as in most of the leukemia cell lines examined (16 of 20). Hybridization to fetal multi-tissue Northern blots detected several different Tnk1 transcripts in all fetal tissues examined. In contrast, a single Tnk1 transcript was detected in only five of 16 adult tissues examined (prostate, testis, ovary, small intestine and colon). Fluorescence in situ hybridization (FISH) analysis of metaphase chromosomes localized the Tnk1 gene to the short arm of chromosome 17 (17p13.1), near the p53 locus. Thus, Tnk1 is a novel tyrosine kinase that may be involved in signalling pathways utilized broadly during fetal development, more selectively in adult tissues and in cell of the lymphohematopoietic system.

Expression of the hematopoietic growth factor receptor FLT3 (STK-1/Flk2) in human leukemias

Normal expression of the hematopoietic growth factor receptor FLT3 (STK-1@Flk2) is limited to CD34+ stem/progenitor cells. We have evaluated the expression of FLT3 by RNase protection assay and Western blotting in 161 primary bone marrow (BM) samples from patients with leukemia. FLT3 RNA was found to be expressed at a higher level than in normal BM controls in 33 of 33 B-lineage acute leukemias, 11 of 12 acute myeloid leukemias (AMLs), and 3 of 11 T-cell acute leukemias (T-ALLs). Expression of FLT3 RNA was also observed in some cases of blast crisis CML. The FLT3 signal resulted from expression on the leukemic blasts, and was not caused by increased FLT3 expression on normal CD34+ stem/progenitor cells in the leukemic samples. To determine if FLT3 protein was also overexpressed, proteins were extracted from leukemic BM samples and screened by Western blotting with anti-FLT3 antisera. FLT3 protein was not detected in normal BM controls, but was found in 14 of 14 B-lineage ALLs, 36 of 41 AMLs, and 1 of 4 T-ALLs. Stimulation of patient samples with FLT3 ligand resulted in autophosphorylation of the FLT3 receptor, suggesting the receptor is functional in these cells. These data show that FLT3 RNA and protein are aberrantly expressed by AML and ALL cells in that CD34 expression and FLT3 expression are no longer synchronous, and suggest the possibility that overexpression of FLT3 could play a role in the survival and/or proliferation of malignant clones in acute myeloid and lymphoid leukemias.

Metabolism of 5-methylchrysene and 6-methylchrysene by human hepatic and pulmonary cytochrome P450 enzymes

The metabolism of environmentally occurring methylated polynuclear aromatic hydrocarbons by human cytochrome P450 (P450) enzymes has not been examined previously. We compared the metabolism of the tobacco smoke constituents 5-methylchrysene (5-MeC), a strong carcinogen, and 6-MeC, a weak carcinogen, in 18 hepatic and 11 pulmonary human microsomes. Major metabolites of 5-MeC were its proximate carcinogen trans-1,2-dihydroxy-1,2-dihydro-5-methylchrysene (5-MeC-1,2-diol), as well as 5-MeC-7,8-diol, bay region dihydrodiols, and phenols. 5-MeC-1,2-diol and 5-MeC-7,8-diol were formed stereoselectively, with the R,R enantiomers predominating. Major metabolites of 6-MeC were 6-MeC-1,2-diol, bay region dihydrodiols, phenols, and 6-(hydroxymethyl)chrysene. 6-MeC-1,2-diol was also formed stereoselectively in the 1R,2R configuration. All human liver samples formed the proximate carcinogenic 1,2-diols (0.2-2.3 pmol/mg protein/min for 5-MeC and 0.3-3.1 pmol/mg protein/min for 6-MeC). Comparable results were obtained in pulmonary microsomes, but the extent of metabolism was less than in the hepatic samples, and only 4 of 11 samples showed activity. Catalytic activities known to be associated with specific P450s were analyzed in each hepatic sample and correlated with levels of 5-MeC and 6-MeC metabolites in the same samples. The results of the correlation analysis indicated that P450s 1A1 and 1A2 were active in the formation of 5-MeC-1,2-diol and 6-MeC-1,2-diol, as well as several other metabolites resulting from ring oxidation. The formation of the hydroxymethyl metabolites was catalyzed by P450 3A4 (for 5-MeC) or P450s 3A4 and 1A2 (for 6-MeC). Experiments with chemical inhibitors and antibodies supported these results. The metabolism of 5-MeC and 6-MeC was also investigated using purified recombinant human P450s 1A1, 1A2, 2C10, 2D6, 2E1, 3A4, and 3A5. P450s 1A1, 1A2, and 2C10 had higher activities than the other enzymes for ring oxidation of 5-MeC and 6-MeC, whereas P450s 1A2 and 3A4 were more active than the other enzymes for methyl hydroxylation of 6-MeC. Only P450 3A4 showed substantial catalytic activity for methyl hydroxylation of 5-MeC. Collectively, the results of these studies demonstrate that P450s 1A2 and 2C10 are important catalysts of the metabolic activation of 5-MeC and 6-MeC in human liver, whereas P450 1A1 plays a major role in the metabolic activation of these compounds in human lung.

Base sequence-dependent bends in site-specific benzo[a]pyrene diol epoxide-modified oligonucleotide duplexes

The site specifically modified oligonucleotides 5'-d(TCCTCCTG1G2CCTCTC) (I) and 5'-d(CTATG1G2G3TATC) (II) were synthesized with single modified guanine residues at positions G1, G2, or G3, derived from the covalent binding reaction of 7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene ((+)-anti-BPDE) with the exocyclic amino groups of the guanine residues. In denaturing 20% polyacrylamide gels, the electrophoretic mobilities of the (+)-anti-BPDE-modified oligonucleotides I and II are slower than the mobilities of the respective unmodified oligonucleotides and independent of the positions of the BPDE-modified guanines. However, in the double-stranded forms in native 8% polyacrylamide gels, the electrophoretic mobilities of the duplexes with lesions at G2 or G3 are remarkably slower (reductions in mobilities up to approximately 40%) than to duplexes with lesions at G1 and are attributed to physical bends or flexible hinge joints at the sites of the BPDE lesions. These sequence-dependent mobility effects occur whenever the BPDE-modified guanine residues with (+)-trans-stereochemistry are flanked by unmodified G's on the 5'-side. These retarded electrophoretic mobilities are attributed to bending induced by steric hindrance effects involving the bulky 5'-flanking guanines and the pyrenyl residues that are known to point into the 5'-direction relative to the modified G [Cosman, M., et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 1914-1918]. These anomalous electrophoretic mobility effects are not observed in the case of (-)-anti-BPDE-modified sequences I with trans-(-)-anti-BPDE-N2-dG adduct stereochemistry.

Effects of dietary fat content on the metabolism of NNK and on DNA methylation induced by NNK

The available data support the concept that high-fat diets increase cytochrome P-450 activities in the liver, leading to increased rates of carcinogen metabolism and, in some instances, DNA adduct formation. Therefore we investigated whether a high-fat diet can also influence DNA methylation by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in the lungs of rats. Male F344 rats were fed a regular AIN-76A low-fat (5% corn oil) or AIN-76A high-fat (23.5% corn oil) diet. After three weeks on this dietary regimen, the animals were injected subcutaneously once daily for four days with NNK at 0.39 mmol/kg body wt. Groups of rats were sacrificed 4 and 24 hours after the last NNK administration; livers and lungs were excised for DNA isolation. We found that the high-fat diet significantly enhanced the formation of O6-methylguanine (O6-mGua) in the rat lung four hours (p < 0.01) after the last carcinogen administration. This may, in part, account for our previous finding in regard to the enhancing effect of the high-fat diet on NNK-induced lung carcinogenesis. There was no effect on O6-mGua or 7-mGua in the rat liver at either time point. To further elucidate the enhancing effect of the high-fat diet on DNA methylation by NNK in the lung, we determined its effect on the in vitro and in vivo metabolism of NNK. The in vitro data indicated that dietary fat has no measurable effect on liver and lung microsomal mixed-function oxidase in catalyzing the metabolic activation of NNK. The results of the metabolism study of NNK in vivo appear to be consistent with the in vitro finding, in that fat had no effect on the excretion pattern of NNK or on the distribution pattern of its urinary metabolites. It is apparent that the enhancing effect of the high-fat diet on O6-mGua in the lung of rats that was measured four hours after NNK injection requires future investigations.

Synthesis of tobacco-specific N-nitrosamines and their metabolites and results of related bioassays

Tobacco-specific N-nitrosamines (TSNA) are the most abundant, strong carcinogens in tobacco smoke. Seven TSNA have been identified in tobacco products: N'-nitrosonornicotine (NNN), N'-nitrosoanabasine (NAB), N'-nitrosoanatabine (NAT), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol (iso-NNAL), and 4-(methylnitrosamino)-4-3-pyridyl)butyric acid (iso-NNAC). The syntheses of these compounds are reviewed. The syntheses of 14C- and 3H-labeled NNK as well as metabolites of NNK and NNN are also discussed. Comparative assays for lung tumorigenesis in female A/J mice were carried out for six of the TSNA and for two related compounds, N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR). They yielded the following ranking of potency: NDMA > NNK > NNAL > NPYR > NNN > NAB. Iso-NNAL and iso-NNAC were inactive. These results are also compared with previous assays of TSNA carcinogenicity in rats and hamsters.

Ipomeanol analogs as chemopreventive agents: effect on the in vitro metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a tobacco-specific, powerful, organospecific lung carcinogen. 4-Ipomeanol (IPO) is an investigational chemotherapeutic drug with specific toxicity towards the lung. We hypothesized that non-toxic analogs of IPO could be competitive inhibitors of the metabolic activation of NNK. We had shown previously that 4-hydroxy-1-phenyl-1-pentanone (HPP) and 7-hydroxy-1-phenyl-1-octanone (4-HPO) are effectively inhibiting the lung tumor activity of NNK in A/J mice. In these extended studies we have synthesized 11 new analogs of HPP and tested them for their in vitro activities as inhibitors of the metabolism of NNK. The present study demonstrated that the lipophilicity in the molecule is playing an important role for the inhibition of NNK metabolism with pulmonary and hepatic microsomes of A/J mice.

Tumorigenicity in newborn mice of fjord region and other sterically hindered diol epoxides of benzo[g]chrysene, dibenzo[a,l]pyrene (dibenzo[def,p]chrysene), 4H-cyclopenta[def]chrysene and fluoranthene

Diol epoxides of benzo[g]chrysene, dibenzo[a,l]pyrene (dibenzo[def,p]chrysene), 4H-cyclopenta[def]chrysene and fluoranthene were tested for tumorigenicity in newborn mice. The compounds tested were racemic trans-11,12-dihydroxy-anti-13,14-epoxy-11,12,13, 14-tetrahydrobenzo[g]-chrysene (BgCDE), trans-11, 12-dihydroxy-anti-13,14-epoxy-11,12,13,14-tetrahydrodibenzo [a,l]pyrene (DB[a,l]PDE), trans-1,2-dihydroxy-anti-3, 3a-epoxy,1,2,3,3a-tetrahydro-4H-cyclopenta[def]chrysene (C[def]C-1,3a-DE), trans-6,7-dihydroxy-anti-8,9-epoxy-10b,1, 2,3-tetrahydrofluoranthene (FDE). BgCDE and DB[a,l]PDE are fjord region diol epoxides and their tumorigenic activities were compared to those of trans-3,4-dihydroxy-anti-1, 2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (BcPDE), a fjord region diol epoxide with known high tumorigenicity and trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]-pyrene (BPDE), a highly tumorigenic bay region diol epoxide. The protocol called for testing of each compound at a total dose of 25 nmol per mouse, administered on days 1, 7 and 15 of life, with killing at age 35 weeks. BgCDE had similar activity as BcPDE for induction of lung tumors and was more active than BcPDE for induction of liver tumors in male mice. Both compounds were significantly more tumorigenic than BPDE. DB[a,l]PDE was highly toxic. All mice died within 1 week of the first dose. It was then tested in a second study using total doses of 5 and 1 nmol per mouse. Only the first dose of the intended 5 nmol total dose was given due to toxicity. The full course of doses with a total of 1 nmol per mouse was administered; DB[a,l]PDE induced a significant incidence and multiplicity of lung tumors and, in male mice, liver tumors at both doses. These results demonstrate that fjord diol epoxides are highly active tumorigens in newborn mice, with activity greater than that of the most active unsubstituted bay region diol epoxide, BPDE. C[def]C-1-3a-DE and C[def]-6-9-DE were compared to trans-1,2-dihydroxy-anti-3, 4-epoxy-1,2,3,4-tetrahydrochrysene (CDE), at a total dose of 500 nmol per mouse. FDE was also tested at this dose. The most active compound among the chrysene derivatives was C[def]C-1-3a-DE, followed by C[def]C-6-9-DE and CDE. C[def]C-1-3a-DE has a sterically constrained bay region, in which the benzylic carbon of the tri-substituted epoxide ring is part of a fused ring system. This feature is also present in FDE, which and considerable tumorigenic activity, greater than that of CDE in lung and greater than any of the chrysene derivatives in liver.(ABSTRACT TRUNCATED AT 400 WORDS)

Determination of stereospecificity of benzo[a]pyrene diolepoxide-DNA antisera with site-specifically modified oligonucleotides

Antisera developed against benzo[a]pyrene diolepoxide (BPDE)-DNA adducts are sensitive tools for detection of DNA adducts in human samples. All antisera currently used for biomonitoring studies were produced against DNA or guanosine modified with racemic anti-BPDE. Using a non-competitive enzyme-linked immunosorbent assay (ELISA), Venkatachalam and Wani (Carcinogenesis, 15, 565-572, 1994) recently tested polyclonal and monoclonal (5D2) antisera for cross-reactivity against oligonucleotides containing (+)-and (-)-trans-anti-BPDE-N2-guanine or N6-adenine adducts and showed different stereospecificity for the two antisera. Because of the importance of antiserum specificity in human biomonitoring studies, we have tested several monoclonal (Mab 5D11 and 5D2) and polyclonal (Pab #29) antisera developed against racemic anti-BPDE-DNA adducts, and Mab 8E11 developed against anti-BPDE-guanosine adducts. Stereoisomeric anti-BPDE-modified oligonucleotide adducts in the sequence 5'-d(CC-AT-CG*CTACC)-3' where G* = anti-BPDE-N2-dG with (+)-trans, (-)-trans, (+)-cis and (-)-cis adduct stereochemistry at the C10 position of anti-BPDE were tested by competitive ELISA. Two structurally related 5-methylchrysene diolepoxide adducts with G* = (+)- and (-)-trans-anti-5-MeCDE-N2-dG in the same oligonucleotide were also tested. While Mab5D2 had the highest affinity for the (-)-trans-anti-BPDE-modified oligomer, Mab 5D11 and 8E11 and Pab #29 recognized the (+)-trans-anti-BPDE-modified oligomer better than the (-)-trans-anti-BPDE modified oligomer. Mab 5D11 and Pab #29 recognized racemic anti-BPDE-modified DNA adducts better than trans-anti-BPDE-modified oligonucleotides; however, Mab 8E11 showed similar sensitivity to racemic anti-BPDE-DNA adducts and (+)- and (-)-trans-anti-BPDE-modified oligomers. All antisera exhibited lower reactivities with both 5-MeCDE modified oligomers. Because of their sensitive detection of (+)-trans-anti-BPDE-dG adducts, the primary adduct produced in vivo, Mab 8E11 and 5D11 and Pab #29 are appropriate for measurement of most adducts formed in humans.

Mammary carcinogenicity in female CD rats of fjord region diol epoxides of benzo[c]phenanthrene, benzo[g]chrysene and dibenzo[a,l]pyrene

We compared the mammary carcinogenicity in female CD rats of three fjord region diol epoxides to test our hypothesis that such sterically hindered molecules would be potent carcinogens. The diol epoxides tested were racemic anti-3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (BcPDE), anti-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrobenzo[g]chrysene (BgCDE) and anti-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrodibenzo[a,l ]pyrene (DB[a,l]PDE). Each diol epoxide was dissolved in dimethylsulfoxide (DMSO) and injected under the six nipples on the left side of the rat, with DMSO only being injected under the nipples on the right side. The total dose of each diol epoxide was 1.2 mumol/rat and there were 20 rats/group. The experiment was terminated 41 weeks after treatment. All three diol epoxides were potent mammary carcinogens, with activity greater than previously observed for a bay region diol epoxide, anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). DB[a,l]PDE induced tumors most rapidly, followed by BcPDE and BgCDE. However, different types of tumors were induced. For induction of adenomas and adenocarcinomas, BcPDE and BgCDE had comparable potency; both were more active than DB[a,l]PDE. In contrast, for induction of sarcomas, DB[a,l]PDE was significantly more active than BcPDE and BgCDE. The results of this study support our hypothesis that sterically hindered fjord region diol epoxides are potent mammary carcinogens in the rat.

Chemoprevention of colon carcinogenesis by phenylethyl-3-methylcaffeate

Previous studies from this laboratory have established that caffeic acid esters present in propolis, a natural resin produced by honey bees, are potent inhibitors of human colon adenocarcinoma cell growth, carcinogen-induced biochemical changes, and preneoplastic lesions in the rat colon. The present study was designed to investigate the chemopreventive action of dietary phenylethyl-3-methylcaffeate (PEMC) on azoxymethane-induced colon carcinogenesis and to examine the modulating effect of PEMC on phosphatidylinositol-specific phospholipase C (PI-PLC), phospholipase A2, lipoxygenase (LOX), and cyclooxygenase activities in the colonic mucosa and tumor tissues in male F344 rats. At 5 weeks of age, groups of rats were fed the control (modified AIN-76A) diet, or a diet containing 750 ppm of PEMC. At 7 weeks of age, all animals except those in the vehicle (normal saline)-treated groups were given 2 weekly s.c. injections of azoxymethane at a dose rate of 15 mg/kg body weight/week. All groups were maintained on their respective dietary regimen until the termination of the experiment 52 weeks after the carcinogen treatment. Colonic tumors were evaluated histopathologically. Both colonic mucosa and tumors were analyzed for PI-PLC, phospholipase A2, cyclooxygenase, and LOX activities. The results indicate that dietary administration of PEMC significantly inhibited the incidence and multiplicity of invasive, noninvasive, and total (invasive plus noninvasive) adenocarcinomas of the colon (P < 0.05-0.004). Dietary PEMC also suppressed the colon tumor volume by 43% compared to the control diet. Animals fed the PEMC diet showed significantly decreased activities of colonic mucosal and tumor PI-PLC (about 50%), but PEMC diet had no effect on phospholipase A2. The production of 5(S)-, 8(S)-, 12(S)-, and 15(S)-hydroxyeicosatetraenoic acids via the LOX pathway from arachidonic acid was reduced in colonic mucosa and tumors (30-60%) of animals fed the PEMC diet as compared to control diet. PEMC had no effect on the formation of colonic mucosal cyclooxygenase metabolites but inhibited the formation in colonic tumors by 15-30%. The precise mechanism by which PEMC inhibits colon tumorigenesis remains to be elucidated. It is likely that the chemopreventive action may be related, at least in part, to the modulation of PI-PLC-dependent signal transduction and LOX-mediated arachidonic acid metabolism.

Mammary carcinogenicity in female CD rats of a diol epoxide metabolite of fluoranthene, a commonly occurring environmental pollutant

We examined the mammary carcinogenicity in CD rats of anti-2,3-dihydroxy-1,10b-epoxy-10b,1,2,3-tetrahydro-fluoranthene (FDE), a genotoxic metabolite of the environmental pollutant fluoranthene. FDE (2 mumol or 10 mumol) in 0.1 ml dimethyl sulfoxide (DMSO) was injected beneath each of the three left thoracic nipples of groups of 20 rats each, with 0.1 ml DMSO alone being injected under the right nipples. On the next day, the procedure was repeated for the three inguinal nipples on each side. anti-3,4-Dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]-phenanthrene (BcPDE, 2 mumol per nipple) was used as a positive control and DMSO alone as a negative control. Tumor development was assessed weekly by palpation and the experiment was terminated after 41 weeks. Eighty five percent of the rats in each of the FDE treated groups developed histologically confirmed mammary tumors, compared to 11% in the DMSO treated animals (P < 0.01). Most tumors were on the left side. The lower dose of FDE induced a significant number of adenomas while the higher dose induced significant incidences of both adenomas and adenocarcinomas compared to controls. BcPDE was a powerful mammary carcinogen, confirming our previous observation. The results of this study demonstrate the carcinogenicity of FDE to the CD rat mammary gland. Since FDE is a potentially transportable human metabolite of fluoranthene, its possible role as an etiologic factor in breast cancer deserves further study.

Red cell alloantibody development associated with heart and lung transplantation

The development and persistence of clinically significant red cell alloantibodies were studied in 1132 patients who underwent a heart and/or lung transplant at Harefield Hospital. Clinically significant antibodies were detected in 15 patients (1.3%) preoperatively and appeared in a further 15 (2.1%) of 704 patients followed up 1-404 weeks after surgery. Anti-D developed in only 1 of 52 D-negative recipients of a D-positive donor graft and in only 2 of 6 D-negative patients who were transfused with between 6 and 32 units of D-positive red cells. Most antibodies that appeared after transplantation remained detectable for only a few weeks. Antibodies detected preoperatively that reacted only with papain-treated cells became persistently undetectable in 4 patients who were transfused with red cells expressing the corresponding antigen specificity. By contrast, antibodies detected preoperatively by indirect antiglobulin test were still detectable after periods of up to 260 weeks in 4 patients who received only antigen-negative red cells. Immunosuppressive therapy appeared to profoundly affect the natural history of red cell alloantibody production in these patients. The underlying mechanisms warrant further study.

Solution conformation of the (-)-trans-anti-5-methylchrysene-dG adduct opposite dC in a DNA duplex: DNA bending associated with wedging of the methyl group of 5-methylchrysene to the 3'-side of the modification site

This paper reports on NMR-molecular mechanics structural studies of the (-)-trans-anti-[MC]dG adduct positioned opposite dC in the sequence context of the d(C1-C2-A3-T4-C5-[MC]G6-C7-T8-A9-C10-C11).d(G12-G13-T14++ +-A15-G16-C17-G18- A19-T20-G21-G22) duplex [designated (-)-trans-anti-[MC]dG.dC 11-mer duplex]. This adduct is derived from the trans addition at C4 of (-)-anti-1(S),2(R)-dihydroxy-3(R),4(S)-epoxy-1,2,3,4-tetrahydro-5-met hylchrysen e [(-)-anti-5-MeCDE] to the N2 position of dG6 in this duplex sequence. The 5-methyl group is located adjacent to the MC(C4) binding site, with these groups juxtaposed in a sterically crowded bay region in the adduct duplex. The 5-methylchrysenyl and the nucleic acid exchangeable and nonexchangeable protons were assigned following analysis of two-dimensional NMR data sets in H2O and D2O buffer solution. The solution structure of the (-)-trans-anti-[MC]dG.dC 11-mer duplex has been determined by incorporating DNA-DNA and carcinogen-DNA proton-proton distances defined by lower and upper bounds deduced from NOESY data sets as restraints in molecular mechanics computations in torsion angle space. The results establish that the [MC]dG6.dC17 base pair and flanking dC5.dG18 and dC7.dG16 base pairs retain Watson-Crick alignments upon adduct formation. The aromatic chrysenyl ring is positioned in the minor groove of a right-handed B-DNA helix and stacks predominantly over the sugar of the dC17 residue across from it on the unmodified complementary strand. The chrysenyl ring points toward the 3'-end of the modified strand with its 5-methyl group inserting between the modified [MC]dG6.dC17 and dC7.dG16 base pairs. The adduct duplex bends by approximately 47 degrees as a result of the wedged insertion of the 5-methyl group from the minor groove face of the duplex. The solution structure of the (-)-trans-anti-[MC] dG.dC 11-mer duplex is compared with that of the corresponding (-)-trans-anti-[BP]dG.dC 11-mer [De los Santos et al. (1992) Biochemistry 31, 5245-5252] in which the [BP]dG adduct is derived from the binding of (-)-anti-BPDE [7(S),8(R)-dihydroxy-9(R),10(S)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene] to the N2 position in the same DNA sequence context. Although the solution structures of the (-)-trans-anti-stereoisomers of 5-methylchrysenyl-dG and benzo[a]pyrenyl-dG adducts opposite dC exhibit many features in common with each other, the [MC]dG adduct which contains a bay region methyl group bends the DNA helix to a greater extent than in the corresponding [BP]dG adduct, which lacks a bay region methyl group.(ABSTRACT TRUNCATED AT 400 WORDS)

Steel factor supports the cycling of isolated human CD34+ cells in the absence of other growth factors

Steel factor (SF) acts synergistically with other hematopoietic growth factors to support the proliferation of progenitor cells in a variety of culture systems. To determine whether SF alone could directly stimulate proliferation of early hematopoietic progenitor cells, isolated CD34+ cells from adult bone marrow and umbilical cord blood were studied in a short-term suspension culture in serum-free medium. Numbers of CD34+ and proliferating cells were quantified by flow cytometry; proliferation was assessed by simultaneous measurement of expression of the nuclear antigen Ki67 and DNA content (propidium iodide [PI]). In the absence of growth factors, the numbers of CD34+ and cycling cells declined over 2 days. Cells cultured in the presence of SF alone maintained the number of CD34+ and cycling cells at levels equal to the starting population. Withdrawal of growth factors led to a dramatic decrease in the number of cells in G1. Compared to cells grown in the absence of growth factors, cells grown in the presence of SF had significantly higher numbers of CD34+ and cycling cells (mean fold increase = 1.3 and 2; p < 0.05 and 0.01, respectively). SF increased the numbers of cells in both G1 and later phases of the cell cycle. Addition of interleukin-3 (IL-3) to SF led to further significant increases in CD34+ and cycling cells. The effects of SF could not be attributed to inhibition of apoptosis. CD34+ cells isolated from peripheral blood (PB) from patients with chronic myelogenous leukemia (CML) displayed similar characteristics. As assessed by binding of phycoerythrin (PE)-labeled ligand and flow cytometry, c-kit was expressed on 65 +/- 6% of isolated CD34+ cells and was detected on HLA-DRlow, CD38low, and Thy1+ subsets, as well as on more mature progenitor cells. Thus, while the effects of SF are most marked in combination with other growth factors, SF appears to bind to and directly maintain the active cell-cycle characteristics of isolated CD34+ cells.

Direct synthesis and characterization of site-specific adenosyl adducts derived from the binding of a 3,4-dihydroxy-1,2-epoxybenzo[c]phenanthrene stereoisomer to an 11-mer oligodeoxyribonucleotide

Site-specifically modified oligonucleotides were obtained in milligram quantities by reacting racemic 3t,4r-dihydroxy-1,2t-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (B[c]PhDE-2, or anti-B[c]PhDE) with the single deoxyadenosine (dA) residue in the oligodeoxynucleotide d(CTCTCACTTCC). Enzyme digestion of the covalently modified oligonucleotides with the exonuclease spleen phosphodiesterase yielded covalently linked B[ca]PhDE-N6-deoxyadenosyl monophosphate (dAMP) adducts. Comparisons of the reverse phase HPLC retention times and CD spectra of these B[c]PhDE-3'-dAMP mononucleotide adducts, with those of standards derived from the reaction of the enantiomers (+)- and (-)-anti-B[c]PhDE with 3'-dAMP, show that two major oligonucleotide adducts (I and II) were obtained upon reacting racemic anti-B[c]PhDE with d(CTCTCACTTCC). In oligonucleotide adduct I, the lesion is a (+)-trans-anti-B[c]PhDE-N6-dA residue, and in oligonucleotide adduct II it is a (-)-trans-anti-B[c]PhDE-N6-dA residue. These assignments were further confirmed using a standard 32P postlabeling assay of B[c]PhDE-3'-dAMP mononucleotide adducts obtained from the digestion of oligonucleotides I and II by spleen phosphodiesterase. The melting points (Tm) of duplexes of modified oligonucleotides I and II and their natural complementary strands are not affected significantly by the presence of the covalently bound benzo[c]phenanthrenyl residues. Opposite stereoselective resistance to enzyme digestion by the exonucleases snake venom phosphodiesterase and spleen phosphodiesterase is exhibited by the stereoisomeric (+)-trans- and (-)-trans-anti-B[c]PhDE-modified oligonucleotide adducts I and II; these results are consistent with the intercalative insertion of the benzo[c]phenanthrenyl residues on the 5'-side of the modified dA residue in adduct I, and its insertion on the 3'-side of the dA residue in adduct II, as observed in the duplexes by high resolution NMR techniques [Cosman et al. (1993) Biochemistry 32, 12488-12497, and Cosman et all, Biochemistry, in press.

Laser pulse-induced photochemical strand cleavage of site-specifically and covalently modified (+)-anti-benzo[a]pyrene diol epoxide-oligonucleotide adducts

The specificity of the laser pulse-induced photocleavage method [Boles, T. C., and Hogan, M. E. (1986) Biochemistry 25, 3039] for detecting the sites of covalent binding of benzo[a]pyrene diol epoxide in DNA was investigated using site-specifically modified oligonucleotide duplexes d(CTCACAT[G*]TACACTCT).d(GAGAGTGTACATGTGA), where [G*] is the adducted guanine residue (+)-trans-anti-BPDE-N2-dG (anti-BPDE = 7 beta,8 alpha- dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene). The appropriate oligonucleotide strands were 32P-end-labeled, and the duplexes were irradiated with a pulse train of 355 nm Nd:YAG laser pulses (approximately 300 mW/cm2). The products of the photocleavage reaction were analyzed by denaturing gel electrophoresis. The major observed products included the intact oligonucleotide strand that had lost the BPDE residue, and shorter oligonucleotide fragments arising from strand scission at the BPDE-modified guanine residue and at nearby flanking bases. Photocleavage at the BPDE-modified G is dominant (approximately 50 +/- 5% of the sum of all of the shorter oligonucleotide fragments), and cleavage extends to at least 4 bases on the 5'-side, and 7 bases on the 3'-side of the BPDE-modified G residue; the probability of cleavage diminishes with increasing distance from the modified G residue. On the unmodified complementary strand, nonspecific strand cleavage is also observed, but the probability of cleavage is > or = 20 times smaller than at the BPDE-modified G residue on the modified strand. The photocleavage method thus preferentially causes strand scission at the sites of BPDE modification, but the occurrence of strand cleavage with lower probabilities at neighboring sites is also significant.

Visceral leishmaniasis after cardiac surgery

An English child developed visceral leishmaniasis (kala-azar) after cardiac surgery. Neither he nor his mother had ever been out of the UK, and his disease was probably transmitted by blood transfusion. Kala-azar should be considered in patients with unexplained fever and hepatosplenomegaly, even if there is no history of foreign travel.

Solution conformation of the (-)-trans-anti-benzo[c]phenanthrene-dA ([BPh]dA) adduct opposite dT in a DNA duplex: intercalation of the covalently attached benzo[c]phenanthrenyl ring to the 3'-side of the adduct site and comparison with the (+)-trans-anti-[BPh]dA opposite dT stereoisomer

This paper reports on NMR-molecular mechanics structural studies of the (-)- trans-anti-benzo[c]phenanthrene-dA adduct positioned opposite dT in the sequence context of the d(C1-T2-C3-T4-C5-[BPh]A6-C7-T8-T9-C10-C11).d(G12- G13-A14-A15-G16-T17-G18-A19-G20-A21- G22) duplex (designated as the (-)-trans-anti-[BPh]dA.dT 11-mer duplex). This adduct is derived from the covalent binding of (-)-1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-benzo[c]phenanthrene [(-)-anti-BPhDE] to N6 of dA6 in this duplex sequence. The benzo[c]phenanthrenyl and nucleic acid exchangeable and nonexchangeable protons were assigned in the predominant conformation following analysis of two-dimensional NMR data sets in H2O and D2O buffer solution. The solution structure of the (-)-trans-anti-[BPh]dA.dT 11-mer duplex has been determined by incorporating intramolecular and carcinogen-DNA proton-proton distances defined by lower and upper bounds deduced from NOESY data sets as restraints in molecular mechanics computations in torsion angle space. The results show that the [BPh]dA6.dT17 base pair propeller twists and buckles slightly to permit the covalently attached benzo[c]phenanthrenyl ring to intercalate between the [BPh]dA6.dT17 and dC7.dG16 base pairs to the 3'-side of the [BPh]dA6 lesion site without disrupting the Watson-Crick hydrogen bond alignments in the modified duplex. The strain in the highly sterically hindered fjord region of the benzo[c]phenanthrenyl moiety is relieved by the propeller-like nonplanar geometry of the aromatic phenanthrenyl ring system, which stacks predominantly with the dG16 and dT17 bases on the unmodified strand. The benzylic ring adopts a distorted half-chair form, in which the H1 and H2 protons are pseudo-diequatorial and the H3 and H4 protons are pseudodiaxial. The current observation that the (-)-trans-anti-[BPh]dA positioned opposite dT intercalates to the 3'-side of the intact modified base pair contrasts with our previous demonstration that the stereoisomeric (+)-trans-anti-[BPh]dA adduct positioned opposite dT intercalates to the 5'-side of the intact modified base pair [Cosman, M., et al. (1993b) Biochemistry 32, 12488-12497]. These stereochemically induced structural differences between isomeric [BPh]dA lesions derived from the binding of chiral (+)- and (-)-anti-BPhDE enantiomers may in turn profoundly influence the interactions of the carcinogen-modified DNA with repair and replication enzymes in the cell.

Mutational spectra for 5,6-dimethylchrysene 1,2-dihydrodiol 3,4-epoxides in the supF gene of pSP189

Dihydrodiol epoxides from 5,6-dimethylchrysene exhibit properties similar to those of fjord region-containing hydrocarbon derivatives in that they react extensively with deoxyadenosine residues in DNA and consequently generate substantial numbers of mutations at AT pairs as well as GC pairs. The syn-dihydrodiol epoxide favors reaction with deoxyadenosine (68% of adducts) to a greater extent than does the anti-dihydrodiol epoxide (52% of adducts), and point mutations at AT pairs (72% for syn- and 45% for anti-dihydrodiol epoxide) follow the same trend. A novel feature of the mutagenicity of the 5,6-dimethylchrysene derivatives is that they exhibit a higher fraction of AT-->GC transitions (28% and 26% for syn and anti, respectively) than has been seen for other hydrocarbon derivatives to date.

Regulation of c-jun by lung carcinogens in Clara cells of hamsters

In vitro differentiated hamster Clara cells were used to study the effects of lung carcinogens on the regulation of the c-jun oncogene. Northern blot analysis revealed a decrease in the expression of jun transcripts 24 h following the exposure of Clara cells to the direct acting forms of benzo[a]pyrene (BPDE*) or 5-methylchrysene (5MeCDE). To determine whether this decrease was mediated at the transcriptional level, we have used CAT reporter constructs driven by nested deletions of the 5' non-coding regulatory region of the c-jun oncogene. While BPDE was capable of activating certain regulatory domains of the c-jun promoter, this activation was not observed with either 5MeCDE or the less active lung carcinogens BADE or 6MeCDE. Analysis of enhancer elements identified the SP1 target site as a strong silencer after BPDE treatment. While positive regulatory element(s) mediating activation of c-jun by BPDE were localized within the promoter region up to -1639, further upstream sequences reduced this transcriptional activation. Thus, when the complete promoter region, up to -4500, was tested, no transcriptional activation was noted following BPDE treatment. These observations suggest that the regulation of c-jun in Clara cells exposed to potent lung carcinogens is mediated at the post-transcriptional level, possibly by reducing the stability and, in turn, the half life of c-jun mRNA. Overall, in contrast to the response of c-jun to numerous carcinogens and stress inducing agents noted in various other cell systems, our findings suggest the existence of a tissue-specific regulatory response for c-jun.

Tumor multiplicity, DNA adducts and K-ras mutation pattern of 5-methylchrysene in strain A/J mouse lung

This study was undertaken to evaluate the carcinogenic potential of 5-methylchrysene (5-MeC) in strain A/J mouse lung and to correlate the 5-MeC-DNA adduct profile in lung tissue with the mutation spectrum in the K-ras gene of lung tumors. Strain A/J mice received a single i.p. injection of 5-MeC at doses of 10, 50, 100 and 200 mg/kg and after 24, 48 and 72 h their lungs were collected for DNA adduct analysis. Eight months later, lungs from the remaining mice were harvested and the lung tumors counted and collected for subsequent mutational analysis of the K-ras gene. 5-MeC was found to be a potent lung carcinogen in strain A/J mice, inducing more than 100 tumors/mouse at a concentration of 200 mg/kg. Six 5-MeC-DNA adducts were observed; one adduct comigrated with the standard N2-deoxyguanosine adduct of 5-MeC-diol-epoxide I [1R,2S,3S-trihydroxy-4R-(N2-deoxy-guanosyl-3'-phosphate)- 1,2,3,4-tetrahydro-5-methyl-chrysene], derived from the bay-region diol-epoxide of 5-MeC. DNAs isolated from 5-MeC-induced lung tumors were evaluated for activating mutations in the K-ras gene by polymerase chain reaction-single strand conformation polymorphism and direct DNA sequencing analysis. Mutations were detected in 44 of 49 (90%) 5-MeC-induced tumors and the mutations were GGT-->TGT (50%), GGT-->GTT (23%) and GGT-->CGT (27%) in codon 12 of the gene. These results suggest that the N2-deoxyguanosine adduct of 5-MeC-diol-epoxide I may be one of the promutagenic adducts of 5-MeC in strain A/J mouse lung.

Convenient synthesis of 3-methoxybenz[a]anthracene-7,12-dione

The regioselective synthesis of 3-methoxybenz[a]anthracene-7,12-dione by oxidative photocyclization is described. The synthesis involved preparation of 1-(1-bromo-2-naphthyl)-2-(3- methoxyphenyl)ethylene by Wittig reaction, followed by photocyclization for 4 h. This gave 7-bromo-3-methoxybenz[a]anthracene. Extended photocyclization over 16 h under similar conditions gave 3-methoxybenz[a]anthracene-7,12-dione, an important intermediate in the synthesis of 7,12-dimethylbenz[a]anthracene-3,4-diol 1,2-epoxide.

Contrasting incidence of ras mutations in rat mammary and mouse skin tumors induced by anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide

Racemic anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide (anti-B[c]PhDE) is a powerful rat mammary carcinogen and is one of the most potent diol-epoxide tumorigens in mouse skin. Activation of ras genes has been proposed to be involved in tumorigenesis by this and related polynuclear aromatic hydrocarbon metabolites. Therefore, we analyzed rat mammary tumors and mouse skin tumors induced by anti-B[c]PhDE for mutations at codons 12, 13 and 61 of the Ki-ras and Ha-ras genes. No Ki-ras mutations were detected in either tumor type. In the rat mammary tumors, no Ha-ras mutations in codons 12 or 13 were observed in 25 tumors analyzed. Only one, a CAA-->CTA mutation, was detected in codon 61, of 42 tumors analyzed. These results indicate that Ki-ras and Ha-ras mutations are not involved in the induction of rat mammary tumors by anti-B[c]PhDE. Mutations in codon 61 of the Ha-ras gene were common, however, in mouse skin tumors induced by this diol-epoxide, being detected in 63% of the tumors analyzed; 90% of these mutations were CAA-->CTA. A dose-dependent difference in the occurrence of the CAA-->CTA mutations was observed; they were present in 75% of the tumors induced by a 100 nmol initiating dose of the diol-epoxide, but in only 34.5% of the tumors induced by a 400 nmol initiating dose. A CAA-->CTA mutation in codon 61 of Ha-ras was also detected in one of four acetone control tumors. In comparison with previous studies of other polynuclear aromatic hydrocarbons and their metabolites, the results suggest that the reactivity with DNA of anti-B[c]PhDE is one factor involved in the induction of A mutations in Ha-ras genes in mouse skin, but further studies are required to evaluate the significance of these mutations in mouse skin tumorigenesis.

Solution conformation of the (+)-trans-anti-[BP]dG adduct opposite a deletion site in a DNA duplex: intercalation of the covalently attached benzo[a]pyrene into the helix with base displacement of the modified deoxyguanosine into the major groove

This paper reports on the solution structure of the (+)-trans-anti-[BP]dG adduct positioned opposite a deletion site in a DNA oligomer duplex which defines the alignment of this covalent benzo[a]pyrene-N2-deoxyguanosine stereosiomer relative to the deletion site. The combined NMR-molecular mechanics computation studies were undertaken on the (+)-trans-anti-[BP]dG adduct embedded in the d(C5-[BP]G6-C7).d(G16-G17) sequence context in a duplex containing 11 residues on the modified strand and 10 on the partner, with no base opposite the modification. The exchangeable and nonexchangeable protons of the benzo[a]pyrenyl moiety and the nucleic acid were assigned following analysis of two-dimensional NMR data sets in H2O and D2O solution. The solution conformation of the (+)-trans-anti-[BP]dG.del 11-mer duplex has been determined by incorporating intramolecular and intermolecular proton-proton distances defined by lower and upper bounds deduced from NOESY spectra as restraints in molecular mechanics computations in torsion angle space. The benzo[a]pyrene ring of [BP]dG6 is intercalated between intact Watson-Crick dC5.dG17 and dC7.dG16 base pairs with the deoxyguanosine base of [BP]dG6 displaced into the major groove. The intercalation site is wedge shaped, being narrower toward the dG16-dG17 step on the deletion-containing strand. The deoxyguanosine base of [BP]dG6 which is positioned in the major groove is inclined relative to the helix axis and stacks over the 5'-flanking dC5 residue in the solution structure. The intercalative-base displacement structure of the (+)-trans-anti-[BP]dG.del 11-mer duplex exhibits several unusually shifted proton resonances which can be readily accounted for by the ring current contribution of the deoxyguanosyl and pyrenyl rings of the [BP]dG6 adduct. This solution structure of the (+)-trans-anti-[BP]dG.del 11-mer duplex where the pyrene ring intercalates into the helix with displacement of the modified deoxyguanosine into the major groove strikingly contrasts with our previous study on the (+)-trans-anti-[BP]dG.dC 11-mer duplex [Cosman, M., et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 1914-1918] where the benzo[a]pyrene ring is positioned in the minor groove without disruption of the Watson-Crick pairing at the [BP]dG.dC modification site. Thus, generation of the deletion site following removal of the dC opposite the (+)-trans-anti-[BP]dG results in a displacement of the entire [BP]dG residue toward the major groove and intercalation of the benzo[a]pyrene ring into the helix.

Solution conformation of the (+)-cis-anti-[BP]dG adduct opposite a deletion site in a DNA duplex: intercalation of the covalently attached benzo[a]pyrene into the helix with base displacement of the modified deoxyguanosine into the minor groove

We have applied a combined NMR-molecular mechanics approach to determine the solution structure of the (+)-cis-anti-[BP]dG adduct positioned opposite a deletion site in the sequence d(C5-[BP]G6-C7).d(G16-G17) at the DNA oligomer duplex level. Our structural studies establish that the benzo[a]pyrene ring intercalates into the helix opposite the deletion site while the modified deoxyguanosine is displaced into the minor groove with its plane parallel to the helix axis. The intercalation site is wedge-shaped with the benzo[a]pyrene ring stacked over intact flanking Watson-Crick dG.dC base pairs. The modified deoxyguanosine stacks over the minor groove face of the sugar ring of the 5'-flanking dC5 residue. The structure at the lesion site is consistent with the observed intermolecular NOEs which served as input restraints to guide the molecular mechanics calculations, and, in addition, the various stacking interactions explain the observed large ring current shifts associated with adduct formation. The solution structure of the (+)-cis-anti-[BP]dG adduct positioned opposite a deletion site reported in this study is similar to the corresponding structure of the same adduct positioned opposite dC reported previously [Cosman, M., de los Santos, C., Fiala, R., Hingerty, B. E., Luna, E., Harvey, R. G., Geacintov, N. E., Broyde, S., & Patel, D. J. (1993) Biochemistry 32, 4145-4155]. This is not surprising since the dC opposite the lesion site was looped out of the helix and it can be readily replaced by a deletion site through minor changes associated with buckling of the intercalation site. By contrast, the solution structures of the (+)-trans-anti-[BP]dG and (+)-cis-anti-[BP]dG adducts positioned opposite deletion sites in the same sequence context exhibit distinct surface topologies in the grooves of the DNA helix. Thus, even though the benzo[a]pyrene intercalates into the helix opposite the deletion site in both cases, the modified deoxyguanosine is displaced into the major groove for the (+)-trans-anti-[BP]dG adduct while it is displaced into the minor groove for the (+)-cis-anti-[BP]dG stereoisomer. The orientational differences reflect the chiral characteristics of the two [BP]-dG stereoisomeric adducts with the different alignments of the bulky DNA lesion opposite the deletion site likely to influence interactions with the cellular repair machinery.

Levels and correlates of maternal nutritional status in urban Bangladesh

OBJECTIVE

To determine the levels and correlates of maternal nutritional status.

DESIGN

Cross-sectional maternal weight, height, and mid-upper arm circumference (MUAC) data were correlated with sociodemographic data.

SETTING

Slums of Dhaka, Bangladesh.

SUBJECTS

Weight, height and MUAC were collected from a representative sample of 2417 nonpregnant mothers. Socioeconomic data such as age, education, religion and household economic status was collected from 2048 mothers; data on reproductive experiences such as number of pregnancies and number of children born alive now dead was available from 1314 mothers; and both sets of data from 1185 mothers.

METHODS

Using weight, height, MUAC and body mass index (BMI) data, the levels of maternal nutritional status were estimated. Bivariate and multivariate relationships of maternal nutritional status with socioeconomic and reproductive experiences variables were examined.

RESULTS

Mothers' mean weight, height, MUAC and BMI were 41.8 kg, 148.8 cm, 232.5 mm, and 18.8 respectively. In multivariate regression analyses, mothers' weight, BMI and MUAC were significantly positively correlated with mothers' years of schooling (P < 0.05) and household economic status (P < 0.01). Mothers' height was significantly positively correlated with years of schooling (P < 0.05), but not with household economic status. Maternal height and weight were significantly negatively correlated with number of child deaths (P < 0.05).

CONCLUSIONS

The findings suggest a possible inter-generational effect; thus, improvement of the nutritional status of girls of this generation would improve child survival in the next generation. This, however, will require complex and long-term planning. As an interim measure, shorter mothers should be targeted for appropriate antenatal and obstetric services.

Synthesis of Fjord region diol epoxides as potential ultimate carcinogens of dibenzo[a,l]pyrene

Dibenzo[a,l]pyrene (DB[a,l]P) is one of the strongest polynuclear aromatic hydrocarbon carcinogens known. This paper describes the synthesis of potential ultimate carcinogens of DB[a,l]P: anti- and syn-11,12-dihydroxy-13,14-epoxy-11,12,13,14- tetrahydroDB[a,l]P (DB-[a,l]P-11,12-diol-13,14-epoxides). The method employed is also useful for the preparation of key intermediates for the synthesis of 11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrobenzo-[g]chrysene (BgC-11,12-diol-13,14-epoxide). Photochemical cyclization of the appropriately substituted phenanthrylphenylethylenes provided 9-carbomethoxy-11-methoxyBgC (4) and 11-methoxyBgC (3). The former was converted by reduction, oxidation, one-carbon chain extension, and cyclization to 11-methoxy DB[a,l]P (7). Compounds 3 and 7 were converted by hydrolysis and oxidation to BgC-11,12-dione (10) and DB[a,l]P-11,12-dione (11), respectively. The diones are the precursors for the synthesis of the corresponding diol epoxides. anti- and syn-DB-[a,l]P-11,12-diol-13,14-epoxides 13 and 14 were prepared in 38% and 55% yields, respectively, from 11. Both diol epoxides had predominantly pseudodiequatorial hydroxyl groups, as seen in other sterically hindered diol epoxides.

STK-1, the human homolog of Flk-2/Flt-3, is selectively expressed in CD34+ human bone marrow cells and is involved in the proliferation of early progenitor/stem cells

We cloned the cDNA for stem cell tyrosine kinase 1 (STK-1), the human homolog of murine Flk-2/Flt-3, from a CD34+ hematopoietic stem cell-enriched library and investigated its expression in subsets of normal human bone marrow. The cDNA encodes a protein of 993 aa with 85% identity and 92% similarity to Flk-2/Flt-3. STK-1 is a member of the type III receptor tyrosine kinase family that includes KIT (steel factor receptor), FMS (colony-stimulating factor 1R), and platelet-derived growth factor receptor. STK-1 expression in human blood and marrow is restricted to CD34+ cells, a population greatly enriched for stem/progenitor cells. Anti-STK-1 antiserum recognizes polypeptides of 160 and 130 kDa in several STK-1-expressing cell lines and in 3T3 cells transfected with a STK-1 expression vector. Antisense oligonucleotides directed against STK-1 sequences inhibited hematopoietic colony formation, most strongly in long-term bone marrow cultures. These data suggest that STK-1 may function as a growth factor receptor on hematopoietic stem and/or progenitor cells.

Potent mammary carcinogenicity in female CD rats of a fjord region diol-epoxide of benzo[c]phenanthrene compared to a bay region diol-epoxide of benzo[a]pyrene

Two diol-epoxide metabolites of benzo[c]phenanthrene and benzo[a]pyrene, polynuclear aromatic hydrocarbons which occur in the environment, were tested for carcinogenicity by direct injection into the mammary fat pads of female CD rats. The compounds anti-3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (BcPDE), a fjord region diol-epoxide, and anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, a bay region diol-epoxide, were applied at total doses of 12.2 mumol. 6-Nitrochrysene was applied at the same dose as a positive control (K. El-Bayoumy, A. Rivenson, P. Upadhyaya, Y-H. Chae, and S. S. Hecht, Cancer Res. 53: 3719-3722, 1993). The sterically hindered fjord region diol-epoxide BcPDE was a powerful mammary tumorigen and carcinogen, rapidly inducing significantly more fibroadenoma and adenocarcinoma than either of the other compounds. Anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene was a weaker mammary tumorigen than BcPDE and 6-nitrochrysene. The results of this study provide the first evidence for mammary tumorigenicity of polynuclear aromatic hydrocarbon diol-epoxides and demonstrate the potent mammary carcinogenicity of BcPDE.

Solution conformation of the (+)-trans-anti-[BPh]dA adduct opposite dT in a DNA duplex: intercalation of the covalently attached benzo[c]phenanthrene to the 5'-side of the adduct site without disruption of the modified base pair

Benzo[c]phenanthrene diol epoxide can covalently bind to the exocyclic amino group of deoxyadenosine to generate [BPh]dA adducts where the polycyclic aromatic hydrocarbon is attached to the major groove edge of DNA. This paper reports on NMR-energy minimization structural studies of the (+)-trans-anti-[BPh]dA adduct positioned opposite dT in the sequence context d(C5-[BPh]A6-C7).d-(G16-T17-G18) at the 11-mer duplex level. The exchangeable and nonexchangeable protons of the benzo[c]phenanthrenyl moiety and the nucleic acid were assigned following analysis of two-dimensional NMR data sets in H2O and D2O solution. The solution structure of the (+)-trans-anti-[BPh]dA.dT 11-mer duplex has been determined by incorporating intramolecular and intermolecular proton-proton distances defined by upper and lower bounds deduced from NOESY data sets as restraints in energy minimization computations. The covalently attached benzo[c]phenanthrene ring intercalates to the 5'-side of the [BPh]-dA6 lesion site without disruption of the flanking Watson-Crick dC5.dG18 and [BPh]dA6.dT17 base pairs. The observed buckling of the intercalation cavity reflects the selective overlap of the intercalated phenanthrenyl ring with dT17 and dG18 bases on the unmodified strand. The structure provides new insights into how a polycyclic aromatic hydrocarbon covalently attached to the major groove edge of deoxyadenosine can still unidirectionally intercalate into the helix without disruption of the modified base pair. Our study establishes that among the contributing factors are a propeller-twisted [BPh]dA6.dT17 base pair, displacement of the carcinogen-DNA linkage bond from the plane of the dA6 base, the specific pucker adopted by the benzylic ring, and the propeller-like nonplanar geometry for the aromatic phenanthrenyl ring system. Our combined experimental-computational studies to date have now identified three structural motifs adopted by covalent polycyclic aromatic hydrocarbon-DNA adducts with their distribution determined by the chiral characteristics of individual stereoisomers and by whether the covalent adducts are generated at the minor or the major groove edge of the helix.

Opposite stereoselective resistance to digestion by phosphodiesterases I and II of benzo[a]pyrene diol epoxide-modified oligonucleotide adducts

The deoxyribooligonucleotide 5'-d(CTCACATGTACACTCT) was reacted separately with the chiral diol epoxide isomers 7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha- epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE)] and 7 alpha, 8 beta-dihydroxy-9 beta, 10 beta-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene [(-)-anti-BPDE)], to produce the modified oligonucleotides 5'-d(CTCACATGBPDETACACTCT). Adducts in which either (+)-anti-BPDE or (-)-anti-BPDE are covalently bound via their C10 positions by trans addition to the exocyclic amino group of the single G residues were isolated and purified by HPLC methods. Snake venom phosphodiesterase (SVPD, phosphodiesterase I), which hydrolyzes DNA from the 3'-OH terminus to the 5'-end, digests the (+)-trans-anti-BPDE-oligonucleotide adducts at a significantly faster rate than that of the sterically different (-)-trans-anti-BPDE-oligonucleotide adducts. However, using spleen phosphodiesterase (SPD, phosphodiesterase II), which hydrolyzes DNA in the 5'-->3' direction, the opposite stereoselective resistance to digestion is observed. Using shorter BPDE-modified oligonucleotides as standards, the enzyme stall sites have been defined by gel electrophoresis methods; the most digestion-resistant phosphodiester linkage is the 5'-d(...T-G*...)-3' bond in the case of (+)-trans-BPDE-modified oligonucleotide adducts for both enzymes, SVPD and SPD (the starred G denotes the site of BPDE modification). In the case of the (-)-trans-BPDE-modified oligonucleotide adducts, the phosphodiester bond on the 3'-side of the modified G [5'-d(...G*-T...)-3'] is most resistant to digestion by both enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of 4-(methylnitrosamino)-1-[3-(6-hydroxypyridyl)]-1-butanone as a urinary metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in rodents

A previously unknown urinary metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was identified as 4-(methylnitrosamino)-1-[3-(6-hydroxypyridyl)]-1-butanone (6-hydroxyNNK). The metabolite was initially isolated from rat urine. On the basis of its MS and NMR, it was either a 4- or 6-hydroxypyridyl derivative of NNK. Model compounds were synthesized to distinguish between these possibilities; the results indicated that the metabolite was 6-hydroxyNNK. This was confirmed by independent synthesis; the spectral and chromatographic properties of 6-hydroxyNNK were the same as those of the metabolite. F-344 rats and A/J mice treated with 100 mg/kg NNK excreted approximately 1% of urinary metabolites as 6-hydroxyNNK; it was not detected as a sulfate or glucuronide conjugate. This is the first example of a pyridyl-hydroxylated metabolite of a tobacco-specific nitrosamine. On the basis of comparison to published data on other pyridine derivatives, 6-hydroxyNNK may be formed by bacterial metabolism. The potential utility of 6-hydroxyNNK as a dosimeter of human uptake of NNK is discussed.

Effects of isothiocyanates on tumorigenesis by benzo[a]pyrene in murine tumor models

Previous studies have shown that benzyl isothiocyanate (BITC) inhibited lung tumorigenesis induced in A/J mice by benzo[a]pyrene (BaP), but other experiments using a somewhat different protocol demonstrated that phenethyl isothiocyanate (PEITC) had no effect on lung tumorigenesis induced by BaP in this strain. In contrast, PEITC but not BITC had been shown to inhibit lung tumorigenesis induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice. Therefore, one goal of this study was to directly compare the chemopreventive activities of BITC and PEITC on BaP-induced lung tumorigenesis in A/J mice. In the same experiment we also compared the tumorigenic activities of BaP and NNK. Either BITC or PEITC was administered by gavage 15 min before gavage of BaP. This regimen was carried out three times at 2-week intervals, and the mice were sacrificed 26 weeks after the first treatment. As assessed by tumor multiplicity, BITC but not PEITC significantly inhibited lung tumorigenesis by BaP, whereas PEITC but not BITC significantly inhibited forestomach tumorigenesis. Comparison of the tumorigenic activities of NNK and BaP demonstrated that NNK was about ten times more potent than BaP as a lung tumorigen, while BaP but not NNK induced forestomach tumors. In a second set of experiments we evaluated the effects of isothiocyanates on the mouse skin tumor-initiating activity of BaP. The isothiocyanates tested were BITC, PEITC, 6-phenylhexyl isothiocyanate (PHITC) and a series of isothiocyanates structurally related to polynuclear aromatic hydrocarbons: 9-phenanthryl isothiocyanate (9-PhenITC), 9-phenanthrylmethyl isothiocyanate (9-PhenMeITC), 6-chrysenyl isothiocyanate (6-ChrysITC) and 6-benzo[a]pyrenyl isothiocyanate (6-BaPITC). None of the isothiocyanates inhibited tumor development by BaP, and three of them--PHITC, 9-PhenITC and 9- PhenMeITC--enhanced skin tumor multiplicity. Taken together with available literature data, the results of this study suggest that different isothiocyanates selectively inhibit cytochrome P450 enzymes involved in the metabolic activation or detoxification of BaP and therefore have differing effects on BaP tumorigenesis.

Tumor-initiating activity on mouse skin of bay region diol-epoxides of 5,6-dimethylchrysene and benzo[c]phenanthrene

Previous metabolism and DNA-binding studies indicated that 5,6-dimethylchrysene (5,6-diMeC) is metabolically activated in mouse skin through formation of its 1,2-dihydrodiol (5,6-diMeC-1,2-diol) and bay region diol-epoxide (anti-5,6-diMeC-1,2-diol-3,4-epoxide). These metabolites were tested as tumor initiators on mouse skin. Included for comparison were syn-5,6-diMeC-1,2-diol-3,4-epoxide and anti-4,3-dihydroxy-2,1-epoxy- 4,3,2,1-tetrahydrobenzo[c]phenanthrene (anti-B[c]Ph-4,3-diol-2,1-epoxide). At an initiating dose of 100 nmol/mouse, 5,6-diMeC-1,2-diol and anti-5,6-diMeC-1,2-diol-3,4-epoxide were significantly more tumorigenic than 5,6-diMeC, inducing 7.1 and 3.9 skin tumors per mouse respectively compared to 1.1 induced by 5,6-diMeC. Similar results were obtained at an initiating dose of 33 nmol/mouse. This is the first example of a methylated polynuclear aromatic hydrocarbon bay region diol-epoxide which is more tumorigenic than its parent hydrocarbon on mouse skin. syn-5,6-diMeC-1,2-diol-3,4-epoxide was only weakly tumorigenic. Comparisons of anti-5,6-diMeC-1,2-diol-3,4-epoxide and anti-B[c]Ph-4,3-diol-2,1-epoxide demonstrated that the latter was a stronger tumor initiator. The results of this study confirm the bay region diol-epoxide metabolic activation pathway of 5,6-diMeC but do not provide an explanation for the relatively weak tumorigenicity of this hydrocarbon on mouse skin.

Inhibitory effect of caffeic acid esters on azoxymethane-induced biochemical changes and aberrant crypt foci formation in rat colon

Previous work from this laboratory established that caffeic acid esters, present in the propolis of honey bee hives, are potent inhibitors of human colon tumor cell growth, suggesting that these compounds may possess antitumor activity against colon carcinogenesis. The present study was designed to investigate (a) the inhibitory effects of methyl caffeate (MC) and phenylethyl caffeate (PEC) on azoxymethane (AOM)-induced ornithine decarboxylase (ODC), tyrosine protein kinase (TPK), and arachidonic acid metabolism in liver and colonic mucosa of male F344 rats, (b) the effects of caffeic acid, MC, PEC, phenylethyl-3-methylcaffeate (PEMC), and phenylethyl dimethylcaffeate (PEDMC) on in vitro arachidonic acid metabolism in liver and colonic mucosa, and (c) the effects of PEC, PEMC, and PEDMC on AOM-induced aberrant crypt foci (ACF) formation in the colon of F344 rats. At 5 weeks of age, groups of animals were fed diets containing 600 ppm MC or PEC (biochemical study) or 500 ppm PEC, PEMC, or PEDMC (ACF study). Two weeks later, all animals except the vehicle-treated groups were given s.c. injections of AOM, once weekly for 2 weeks. The animals intended for the biochemical study were sacrificed 5 days later and colonic mucosa and liver were analyzed for ODC, TPK, lipoxygenase, and cyclooxygenase metabolites. The animals intended for the ACF study were sacrificed 9 weeks later and analyzed for ACF in the colon. The results indicate that the PEC diet significantly inhibited AOM-induced ODC (P < 0.05) and TPK (P < 0.001) activities in liver and colon. The PEC diet significantly (P < 0.001) suppressed the AOM-induced lipoxygenase metabolites 8(S)- and 12(S)-hydroxyeicosatetraenoic acid (HETE). The animals fed the MC diet exhibited a moderate inhibitory effect on ODC and 5(S)-, 8(S)-, 12(S)-, and 15(S)-HETEs and a significant (P < 0.001) effect on colonic TPK activity. However, the MC and PEC diets showed no significant inhibitory effects on cyclooxygenase metabolism. In an in vitro study, caffeic acid and MC showed inhibitory effects on HETE formation only at a 100 microM concentration, whereas PEC, PEMC, and PEDMC suppressed in vitro HETE formation in a dose-dependent manner. AOM-induced colonic ACF were significantly inhibited in the animals fed PEC (55%), PEMC (82%), or PEDMC (81%). The results of the present study indicate that PEC, PEMC, and PEDMC, present in honey, inhibit AOM-induced colonic preneoplastic lesions, ODC, TPK, and lipoxygenase activity, which are relevant to colon carcinogenesis.

Unwinding and hydrodynamic flow linear dichroism characteristics of supercoiled DNA covalently modified with two isomeric methylchrysene diol epoxides of different biological activities

Adducts derived from the covalent binding of two positional monomethyl-substituted isomers of a bay region chrysene diol epoxide to supercoiled pIBI30 DNA (2926 base pairs/genome) were prepared, and their characteristics were investigated by a combination of gel electrophoresis and flow linear dichroism techniques. The 5- and 6-methyl derivatives of trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydrochrysene [(+)-5- and (+)-6-MeCDE, respectively], both with 1R,2S,3S,4R stereochemistry, are characterized by significant differences in their biological activities [Melikian et al. (1988) Cancer Res. 48, 1781-1787]. When covalently bound to plasmid DNA, these two molecules give rise to striking differences in the gel electrophoretic and flow hydrodynamic characteristics of the modified supercoiled DNA. The hydrodynamic flow linear dichroism of linearized DNA molecules (obtained by EcoRI enzyme digestion of covalently closed supercoiled pIBI30 DNA), modified covalently with the highly tumorigenic and mutagenic (+)-5-MeCDE derivative, indicates that flexible joints, bends, or kinks are formed at the site of binding of (+)-5-MeCDE. Slab gel data, as well as ethidium bromide-titration tube agarose gel electrophoresis data, indicate that the formation of (+)-5-MeCDE-DNA lesions causes the removal of superhelical turns with an unwinding angle of 13 +/- 3 degrees per covalently bound polycyclic aromatic residue. In contrast, the biological inactive (+)-6-MeCDE does not significantly alter the characteristics of supercoiled DNA, the unwinding angle is only 2.7 +/- 1 degrees, and the changes in persistence lengths detected by the flow linear dichroism technique are significantly smaller than in the case of (+)-5-MeCDE-DNA adducts.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of transplacental and neonatal initiation of mouse lung and liver tumors by N-nitrosodimethylamine (NDMA) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and promotability by a polychlorinated biphenyls mixture (Aroclor 1254)

We have previously shown a positive tumor-promoting effect of a single dose of Aroclor 1254 on lung and liver tumors initiated neonatally in the mouse by N-nitrosodimethylamine (NDMA). In this study, we have confirmed and extended this observation with NDMA and the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) given either transplacentally or postnatally, followed by a single dose of Aroclor 1254 on day 56. This polychlorinated biphenyl (PCB) mixture was an effective promoter of both lung and liver tumors; however, there were specific initiator and sex-related differences in this response. Aroclor administration significantly increased the incidence of lung tumors initiated transplacentally by NDMA or NNK in male mice. Neither nitrosamine initiated tumors transplacentally in females, but lung tumors initiated with NNK and liver tumors caused by NDMA in neonatal females were promoted by PCBs. Both liver and lung tumors initiated neonatally by NDMA in male animals, but not NNK-initiated tumors, were promoted by PCBs. These data confirm that PCBs are able to promote both NDMA- and NNK-initiated tumors, but with chemical-, sex- and age-dependent difference; this suggests influences of both quantitative and qualitative factors in susceptibility to tumor promotion.

A study of tobacco carcinogenesis. LI. Relative potencies of tobacco-specific N-nitrosamines as inducers of lung tumours in A/J mice

Tobacco-specific N-nitrosamines (TSNA) are formed from nicotine and the minor Nicotiana tabacum alkaloids during tobacco processing and tobacco smoking. The TSNA are the most abundant strong carcinogens in smokeless tobacco and in smoke. In this comparative study six TSNA and two major volatile N-nitrosamines of cigarette smoke are assayed for their relative tumorigenicities in strain A/J female mice and for their potential to induce lung tumors. N-nitrosodimethylamine was the most potent inducer of lung adenoma in the A/J mouse model followed in order of decreasing potencies by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, N-nitrosopyrrolidine, N'-nitrosonornicotine and N'-nitrosoanabasine. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol and 4-(methylnitrosamino)-4-(3-pyridyl)butyric acid were inactive. The relative tumorigenic activities of the tobacco-specific nitrosamines in strain A/J mice compare well with the available data for their relative tumorigenic activities in F344 rats and Syrian golden hamsters.