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CC-1065 is a unique antitumor antibiotic produced by Streptomyces zelensis. The potent cytotoxic effects of this drug are thought to be due to its ability to form a covalent adduct with DNA through N3 of adenine. Thermal treatment of CC-1065-DNA adducts leads to DNA strand breakage. We have shown that the CC-1065 structural modification of DNA that leads to DNA strand breakage is related to the primary alkylation site on DNA. The thermally induced DNA strand breakage occurs between the deoxyribose at the adenine covalent binding site and the phosphate on the 3' side. No residual modification of DNA is detected on the opposite strand around the CC-1065 lesion. Using the early promoter element of SV40 DNA as a target, we have examined the DNA sequence specificity of CC-1065. A consensus sequence analysis of CC-1065 binding sites on DNA reveals two distinct classes of sequences for which CC-1065 is highly specific, i.e., 5'PuNTTA and 5'AAAAA. The orientation of the DNA sequence specificity relative to the covalent binding site provides a basis for predicting the polarity of drug binding in the minor groove. Stereo drawings of the CC-1065-DNA adduct are proposed that are predictive of features of the CC-1065-DNA adduct elucidated in this investigation.

The alpha- and beta-anomers of the 17 beta-D-glucuronide conjugate of ethynylestradiol were synthesized by the SnCl4-promoted reaction between beta-acetoxy GAM and the t-17 beta-hydroxyl group of EE2-3-acetate. The conjugates were resolved by crystallization and HPLC. Positive identification was established by u.v. spectrophotometry, i.r. and mass spectrometry and 1H- and 13C-n.m.r. The structure of the beta-anomer was confirmed by X-ray crystallographic analysis. In addition, the alpha-anomer was refractory to hydrolysis by bovine beta-glucuronidase, establishing a biochemical difference between the conjugate pair.

Administration of[3H]aflatoxin B2 (2,3-dihydroaflatoxin B1)(AFB2) to male rats resulted in levels of hepatic DNA- and ribosomal(r)RNA-aflatoxin adducts that were about 1% of those for rats given [3H]aflatoxin B1(AFB1). The levels of hepatic protein-aflatoxin adducts were 35 to 70% as great for AFB2-treated as compared to AFB1-treated rats...

In this work, we report on the binding of the novel antitumor agent CC-1065 to poly(dA).poly(dT) and to mixtures of dA and dT oligomers as determined by electronic absorption and circular dichroism (CD) methods. In addition, the DNA binding properties of CC-1065 and its binding mechanism are compared to those of netropsin. CC-1065 binds to the polymer by at least three mechanisms to produce one irreversibly and two reversibly bound species. One reversibly bound species is moderately stable, but in time (days), it converts to the irreversibly bound species. Both of these species bind within the minor groove of the polymer and exhibit intense CC-1065 induced CD spectra. The other reversibly bound species does not acquire an induced CD. CC-1065 forces B-form duplex formation between mixtures of single strand dA and dT oligomers and binds irreversibly to the duplexes without showing the presence of an intermediate, reversibly bound species. The induced CD increases with increasing length of the oligomer, from the 5-mer (barely detectable CD) to the 14-mer (intense CD). The 7-, 10- and 14-mer mixtures bind about 1, between 1 and 2, and between 2 and 3 CC-1065 molecules, respectively. Computer graphic models of the CC-1065-DNA complex show that the covalent adduct of CC-1065 and unreacted CC-1065 can attain the same close van der Waals contacts between adenine C2 hydrogens and antibiotic CH groups that were observed in the crystal structure of the netropsin-DNA complex. These contacts may account for the dA-dT base pair binding specificity of CC-1065 and for the stability of the reversibly bound CC-1065 species.

Methods were developed for the efficient routine degradation and fractionation of ethylated and methylated DNA. Alkylated DNA was hydrolyzed by a neutral thermal method to yield 3- and 7- alkylpurines and O2-alkylcytosines. The partially apurinic DNA was separated from the bases by precipitation in 0.1 N HCl. Portions of the DNA precipitate were further hydrolyzed either by 0.1 N HCl to yield purine bases, or by enzymes to yield nucleosides and phosphotriesters. The chemical and enzymic digests were fractionated by a combination of high pressure liquid chromatography systems to yield quantitative estimates of the following products from methylated or ethylated DNA: 1-, 3-, and 7-alkyladenines, O2-alkylcytosines, 3-, O6-, and 7- alkylguanines and O2-, 3-, and O4-alkylthymines. N6-Alkyladenines, 1-alkylguanines and N2-alkylguanines were not detected and the 3- alkylcytosines were detected but not quantified. Phosphotriesters were estimated from the amounts of recovered alkyl phosphotriesters of thymidylyl (3'-5') thymidine. Using these methods, it was possible to account for 98, 81, 98, and 92% of the DNA bound alkyl groups obtained from DNA reacted with [14C]methyl methanesulfonate, [3H]ethyl methanesulfonate, N-[3H]-methyl-N-nitrosourea, and N-[14C]ethyl-N-nitrosourea, respectively. The methods described provide reproducible and quantitative methods of analysis for all the known methylated or ethylated products in a single DNA sample.

CC-1065, a novel antibiotic produced by Streptomyces zelensis, was active against several experimental tumors in vivo and a broad spectrum of human tumor cells in vitro. This report describes its biological and biochemical effects of L1210 leukemia cells. CC-1065 is one of the most cytotoxic agents known. The concentrations required for a 50 and 90% inhibition of cell growth are 0.02 and 0.05 ng/ml, respectively. It is about 400 times more cytotoxic than was Adriamycin. The action of CC-1065 is rapid and is dose and time dependent. CC-1065 inhibits DNA synthesis much more than it inhibits RNA and protein synthesis. The concentrations required for a 50% inhibition of DNA synthesis and RNA synthesis are 4 to 6 and 45 to 60 ng/ml, respectively. Although the drug inhibition of DNA synthesis cannot completely account for its cytotoxic effects on L1210 cells, these results, along with those generated by other investigators, suggest that the inhibition of DNA synthesis represents a major mode of action of CC-1065. CC-1065 inhibited both thymidine kinase and DNA polymerase alpha activities, but the effect on highly purified DNA polymerase alpha was more pronounced. At 1 microgram/ml, CC-1065 inhibited more than 70% of the enzyme activity. In order to elucidate the mechanism of inhibition of DNA polymerase alpha, the interaction between CC-1065 and DNA was investigated. The studies with thermal melting of DNA and difference circular dichroism measurement indicate that CC-1065 is one of the strongest DNA-binding agents. It induced an increase in thermal melting temperature of calf thymus DNA by at least 31 degrees. The circular dichroism studies also reveal that CC-1065 binds only to double-stranded DNA but not to heat-denatured DNA or yeast RNA. These observations were supported by those obtained with two other experimental approaches. CC-1065 also appeared to interact with proteins, but the interaction was weak and reversible.

The factors influencing the binding of CC-1065 to DNA were examined using racemic analogs with varying chain lengths. The ability of these agents to bind DNA appeared to be related to cytotoxic potency, however this did not appear to be a direct quantitative correlation. Two enantiomers of a bis-indole analog of CC-1065 were studied for DNA binding and cytotoxic activity. The agent with the same stereochemical configuration as CC-1065 was a potent cytotoxin, but its enantiomer was essentially inactive. Both enantiomers showed significant binding to DNA, but the biologically less active isomer showed less overall binding. In all cases, the agents preferred AT-rich DNA, and all bound to similar regions in DNA as evidenced by positions of drug-initiated thermal breaks in single end-labelled fragments of phi X 174RF DNA. The overall similarity in site specificity for binding of the structurally diverse agents suggests that much of the specificity observed in binding of the agent to DNA lies in the DNA itself. Thus, it may be difficult to change minor groove specificity for agents of this type simply by designing structures that can encompass guanine or cytosine residues. Other modifications, such as changing the specificity of the alkylating moiety, may be required to achieve this goal.

Alkylating agents have proved useful as models, especially for low molecular weight mutagens and carcinogens, to probe molecular mechanisms of genotoxicity. Results of many studies have indicated that not all DNA substitutions cause mutagenic or carcinogenic responses. Often, quantitatively minor alkylation products are responsible for initiating these biological processes. The factors that influence the distribution of DNA substitution products include: the SN1 reactivity of the electrophilic species; the nucleophilicity and steric accessability of the DNA site; van der Waals or electrostatic interactions that attract the agent to specific DNA sites; and post-alkylation rearrangements. With low molecular weight alkylating agents, a primary determinant of product distribution in DNA, and of genotoxic potential, is the electrophilic reactivity. Agents with high SN1 reactivity (low Swain -Scott s factors) generally have high mutagenic and carcinogenic activity, at equal levels of total DNA alkylkation . This appears to be due to the ability of such agents to cause relatively more alkylation at oxygen sites in DNA, especially at O6 of guanine and at O4 of thymine. Alkylation of DNA alone is insufficient to induce cancer or mutations. Post-alkylation factors such as DNA repair, rate of cell turnover, or presence of tumor promoters can have a profound effect on the biological response to DNA damage (1,5,6,24,42). In this sense, the persistence of a specific miscoding of altered DNA base is significant in carcinogenesis or mutagenesis only to the extent that it remains in DNA long enough to be fixed into the code. This concept necessarily assumes that the altered base has promutagenic potential. Persistence of an alkylated DNA constituent does not, by itself, indicate that the alkylated constituent has biological significance.

The Salmonella mutagenicity test (Ames assay) is part of the routine screening battery applied to all new drugs at The Upjohn Company. The purpose of this paper is to report results for 29 compounds. These compounds are very diverse in chemical structure and represent classes of compounds selected because of known biological activity and other reasons. None of the compounds reported here produced an increase in revertant colonies in the Salmonella strains employed (TA98, TA100, TA1535, TA1537 and TA1538) and therefore the Salmonella mutagenicity results with these materials do not suggest potential for mutagenesis or carcinogenesis.

The association of restriction fragment length polymorphism genetic markers at the apolipoprotein AI-CIII-AIV gene locus with lipid and lipoprotein levels was evaluated in subsets of the 666 Caucasian students from the junior high school (11-14 years old) population of Muscatine, Iowa. Male students whose leukocyte DNA had an uncommon haplotype consisting of the minor allele of a SacI restriction site polymorphism (S2) in combination with the more common allele of an MspI site variation (M1) had significantly lower levels of high density lipoprotein (HDL)-cholesterol (P less than 0.05) when compared to a random sample of males; these levels were stable over a 2-year follow-up. The minor allele of an XmnI restriction site polymorphism (X2) was more frequent in females with triglyceride levels in the upper decile of the age and gender-specific triglyceride distribution than in normotriglyceridemic females (0.10 less than P less than 0.15) and triglyceride levels were higher in random sample females with an X2 allele than in X1 homozygotes (P less than 0.10). These results suggest that alleles of the known apolipoprotein genes (AI, CIII, AIV) at this locus or closely linked gene sequences may have major effects on lipid levels in members of the general population.