Association between the cytotoxicity of thymidine and tumorigenicity of clones derived from C3H10T12 mouse embryo fibroblasts

We have measured the cytotoxicity of thymidine to $\text{C3H}\text{10T}\text{1}\text{2}$ mouse embryo fibroblasts derived from morphologically transformed foci of cells from cultures exposed to chemical carcinogens. Four of these cell lines have previously been shown to be tumorigenic in irradiated syngeneic hosts and were all more sensitive to the lethal effects of thymidine than were the non-transformed cells. Strikingly, the most tumorigenic of the cell lines were most sensitive to thymidine. Differences in plating efficiencies or growth rates of the various cell lines were not associated with differences in thymidine sensitivity.     

Separation of multiple forms of protein-bound metabolites of the carcinogenic hydrocarbons 3-methylcholanthrene and 7,12-dimethylbenz[a]anthracene from several rodent species

Our findings demonstrate that the carcinogenic hydrocarbons 7,12-dimethylbenz[a] anthracene (DMBA) and 3-methylcholanthrene (3-MCA) bind in multiple forms to the proteins of skin and lung tissue. These metabolites are freed from the proteins by treatment with Raney nickel, thus, the metabolites are most likely bound through cysteine or homocysteine. The numbers and the relative quantities of the bound metabolites vary greatly among the Fischer rat, the Syrian golden hamster, and 3 mouse strains. It is possible that the metabolites (which indicate a particular pathway of metabolic activation) correlate with species susceptibility to hydrocarbon carcinogenesis.     

Protection against 3-methylcholanthrene-induced skin tumorigenesis in Balb/C mice by ellagic acid

Topical application of ellagic acid, a naturally occurring dietary plant phenol, to Balb/C mice resulted in significant protection against 3-methylcholanthrene (MCA)-induced skin tumorigenesis. Ellagic acid was found to be an effective inhibitor of tumor formation whether the tumor data are considered as percent mice with tumors, cumulative number of tumors, tumors per mouse or tumors per tumor bearing animal as a function of the number of weeks on test. By 8, 10, 12, 14, and 16 weeks of testing, the number of tumors per mouse in the group receiving MCA alone was 2.0, 3.4, 4.0, 4.9 and 5.3, respectively, whereas the corresponding numbers in the group receiving MCA plus 2 mumol ellagic acid were 0, 0.3, 0.4, 0.6 and 1.2, respectively. At the termination of the experiment (16 weeks) aryl hydrocarbon hydroxylase (AHH) activity in skin and liver and the extent of 3H-BP-binding to skin, liver and lung DNA were determined and both of these parameters were found to be significantly inhibited in the animals treated with ellagic acid. These results indicate that ellagic acid can inhibit the metabolism of polyaromatic hydrocarbons and modulate skin carcinogenesis induced by these chemicals.     

Conversion of environmental pollutant to mutagens by visible light.

Illumination of DMBA, 3-methylcholanthrene, 2-aminoanthracene and chrysene with visible light resulted in the formation of direct-acting chemicals endowed with genotoxic and frameshift mutagenic activities. These findings may be of relevance in assessing the potential health hazards inherent in the planned conversion to diesel fuels which is expected to result in increased atmospheric levels of polycyclic aromatic hydrocarbons.     

Covalent binding of benzo[a]pyrene to dna in fish liver

Benzo[a]pyrene became bound to the hepatic DNA in juvenile English sole ($\text{Parophrys vetulus}$) force fed tritiated benzo[a]pyrene. No statistically signïficant change was observed in the level of the binding from 16 h to 2 wk after the single exposure. Specific activities of binding were similar for both DNA and protein. Moreover, a binding index was calculated to represent the number of benzo[a]pyrene molecules bound per 10⁶ nucleotides after administration of a theoretical dose of 1 mmole of hydrocarbon per kg body weight. The value for English sole liver DNA was of the same order of magnitude as the values reported for mouse skin and mammary gland in which benzo[a]pyrene is carcinogenic.     

Biochemical and biophysical study of chemopreventive and chemotherapeutic anti-tumor potential of some Egyptian plant extracts

the present study the was done to evaluate chemopreventive and chemotherapeutic anti-tumor potential of some Egyptian plant extract (moringa, graviola, ginger garden cress and artemisinin) against 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis in Swiss albino mice. chemopreventive and chemotherapeutic evaluation was assessed by monitoring the tumor incidence and tumor volume as well as by analyzing the status of (a) biochemical markers (maspin, survivin, livin, caveolin-1, osteopontin and Fucosyltransferase 4 gene expressions), oxidative stress related profile including; total antioxidant capacity (TAC), glutathione reductase (GR) activity, glutathione-s-transferase (GST) activity assay, superoxide dismutase (SOD) activity, catalase (CAT) activity and lipid peroxidation (MDA), renal and hepatic toxicity markers (urea, creatinine, alanine transaminase (alt) activity, aspartate aminotransferase (ast) activity, alkaline phosphatase (ALP) Activity and γ-Glutamyltransferase (GGT) activity also study of (b) biophysical markers (trace and heavy metals (lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni), iron (Fe), selenium (Se), copper (Cu) and zinc (Zn)), dielectric properties and body water distribution) finally (c) histopathological examination oral administration of increasing dose of moringa, graviola, ginger garden cress and artemisinin extracts, respectively significantly prevented the tumor incidence and tumor volume as well as brought back the status of the above mentioned biochemical and biophysical variables. Histopathological changes also confirmed the formation of tumor tubules and neovascularization after the treatment. Overall, these results suggest that treatment with moringa, graviola, ginger garden cress and artemisinin extracts provided antioxidant defense with strong chemopreventive and chemotherapeutic activity against DMBA-induced mammary tumors.     

Evidence for the involvement of a diol-epoxide in the binding of 7,12-dimethylbenz(a)anthracene to DNA in cells in culture.

1,1,1-Trichloropropene 2,3-oxide (TCPO), a known inhibitor of the enzyme epoxide hydrase, inhibits binding of the carcinogen, 7,12-dimethylbenz(a)anthracene (DMBA), to the DNA of secondary mouse embryo cell cultures under conditions which do not appreciably decrease the overall metabolism of this carcinogen. This suggests that the formation of a transdihydrodiol is a necessary step in the metabolic pathway leading to DNA binding and that binding probably occurs through the generation of a reactive diol-epoxide. In concert with this, the major DMBA-DNA product isolated by chromatography on Sephadex LH-20 eluted with a methanol-water gradient is resolved into two separate components in a methanol-sodium borate solution gradient suggesting that, as is known for benzo(a)pyrene, two stereoisomeric diol-epoxides are involved in the binding of DMBA to DNA.     

Lack of association between induction of dominant-lethal mutations and induction of heritable translocations with benzo[a]pyrene in postmeiotic germ cells of male mice

Benzo[a]pyrene was tested for induction of dominant-lethal mutations in germ cells of male mice. Clear-cut dominant-lethal effects were induced in middle and early spermatoza. In contrast to the dominant-lethal effects observed the study showed no detectable increase in hertiable translocations for these stages over the spontaneous level. Thus, the results provide another example of a chemical mutagen that is effective in inducing dominant-lethal mutations but relatively ineffective in inducing heritable translocations in male postmeiotic germ cells.     

Effect of a peri fluoro substituent on the conformation of dihydrodiol derivatives of polycyclic aromatic hydrocarbons

$\text{Trans}$-3,4-, 5,6-, 8,9-, and 10,11-dihydrodiols formed from the metabolism of 7-fluorobenz[a]anthracene by rat liver microsomes were isolated by reversed-phase high performance liquid chromatography. Ultraviolet absorption, mass, and NMR spectral analyses indicated that the 5,6- and 8,9-dihydrodiols were preferentially in quasi-diaxial conformations, whereas the 3,4- and 10,11-dihydrodiols were preferentially in quasi-diequatorial conformations. CPK space-filling models suggest that the quasi-diaxial conformation is primarily the result of electronic repulsion between the fluorine and the $\text{peri}$ hydroxyl oxygen. These findings provide a structural basis in the interpretation of the carcinogenic potencies of some fluorinated polycyclic aromatic hydrocarbons.     

In vivo investigation of progressive alterations in rat mammary gland tumors by near-infrared spectroscopy

We have investigated mammary gland tissues of female rats treated with 7,12-dimethylbenz[a]anthracene in sesame oil by a near infrared (NIR) spectroscopy finding that the DNA and water contents in the cancerous tissues were larger than those in the normal tissues but that the lipid content in the former was less than that in the latter. With protein contents, however, little difference was observed between the two. Thus, we used a lipid band around 1725 nm (the first overtone of n-alkane) and a protein band around 2054 nm (a combination band of amide A and amide II of polypeptides) for a quantitative evaluation of malignant changes in the mammary gland tissues. The lipid/protein band intensity ratios were calculated from the spectra of the mammary glands in the control animals and those of the noncancerous and cancerous sites in the treated animals. The lipid/protein ratios in the control animals, in the noncancerous sites, and in the cancerous sites were 1.452 +/- 0.221 (n = 5), 0.728 +/- 0.069 (n = 5), and 0.362 +/- 0.060 (n = 5), respectively. These values were significantly different from each other (P < 0.001). The lipid changes observed by near-infrared (NIR) spectroscopy were confirmed by the results obtained from chemical methods for the evaluation of lipid levels in the same samples. Thus, our NIR spectroscopic method would be able not only to discriminate between cancerous and normal tissues but also to distinguish animals with cancers from normal animals. In addition, as the cancer grew, the lipid band intensity decreased, this band was shifted to higher wavelengths, and collagen peaks appeared in the tissues. These findings were supported by histological examinations of the cancerous and normal tissues. The present study indicates that NIR spectroscopy has high specificity and sensitivity in discriminating cancerous tissues from normal mammary glands in animals and it may offer potential for noninvasive, in vivo diagnosis of female breast cancer in the near future.     

Metabolite repression inhibits degradation of benzo[a]pyrene and dibenz[a,h]anthracene by Stenotrophomonas maltophilia VUN 10,003

Large inocula of Stenotrophomonas maltophilia VUN 10,003 were used to investigate bacterial degradation of benzo[a]pyrene and dibenz[a,h]anthracene. Although strain VUN 10,003 was capable of degrading 10–15 mg l⁻¹ of the five-ring compounds in the presence of pyrene after 63 days, further addition of pyrene after degradation of the five-ring polycyclic aromatic hydrocarbons (PAHs) ceased did not stimulate significant decreases in the concentration of benzo[a]pyrene or dibenz[a,h]anthracene. However, pyrene was degraded to undetectable levels 21 days after its addition. The amount of benzo[a]pyrene and dibenz[a,h]anthracene degraded by strain VUN 10,003 was not affected by the initial concentration of the compounds when tested at 25–100 mg l⁻¹, by the accumulation of by-products from pyrene catabolism or a loss of ability by the cells to catabolise benzo[a]pyrene or dibenz[a,h]anthracene. Metabolite or by-product repression was suspected to be responsible for the inhibition: By-products from the degradation of the five-ring compounds inhibited their further degradation. Journal of Industrial Microbiology & Biotechnology (2002) 28, 88–96 DOI: 10.1038/sj/jim/7000216 Received 30 January 2001/ Accepted in revised form 10 October 2001     

Leukotriene A: stereochemistry and enzymatic conversion to leukotriene B

Leukotriene A was assigned the structure 5(S)-$\text{trans}$-5,6-oxido-7,9-$\text{trans}\text{-11,14-}\text{cis}$-eicosatetraenoic acid by the enzymatic conversion of a synthetic product of known stereochemistry into the naturally occurring isomer of 5(S),12(R)-dihydroxy-6,8,10,14-eicosatetraenoic acid in human polymorphonuclear leukocytes.     

Differences in effects of norharman with various classes of chemical mutagens and amounts of S-9.

The mutagenicities of aniline, $\text{o}$-toluidine and yellow OB were demonstrated only in the presence of the β-carboline compound, norharman. The effect of norharman increased linearly with increase in the amount of S-9. The mutagenicity of 4-dimethylaminoazobenzene was greatly enhanced by the presence of norharman, and again dose-dependency on the amount of S-9 was observed. In the presence of a large amount of S-9, norharman caused several fold enhancement of the mutagenicities of $\text{N}$-2-fluorenylacetamide, benzo(a)-pyrene, and 1,4-dimethyl-3-amino-5$\text{H}$-pyrido(4,3$\text{b}$) indole, isolated from a tryptophan pyrolysate. However, norharman suppressed the mutagenicities of these compounds in the presence of a small amount of S-9. The mutagenicity of kaempferol, a flavonoid, was inhibited by norharman with either a large or small amount of S-9.