phenanthrenes and Precancerous-Conditions

Forty-four novel tricycles containing nonenolizable cyano enones (TCEs) were designed and synthesized on the basis of a semisynthetic pentacyclic triterpenoid, bardoxolone methyl, which is currently being developed in phase II clinical trials for the treatment of severe chronic kidney disease in diabetic patients. Most of the TCEs having two different kinds of nonenolizable cyano enones in rings A and C are highly potent suppressors of induction of inducible nitric oxide synthase stimulated with interferon-γ and are highly potent inducers of the cytoprotective enzymes heme oxygenase-1 and NAD(P)H:quinone oxidoreductase-1. Among these compounds, (±)-(4bS,8aR,10aS)-10a-ethynyl-4b,8,8-trimethyl-3,7-dioxo-3,4b,7,8,8a,9,10,10a-octahydrophenanthrene-2,6-dicarbonitrile ((±)-31) is the most potent in these bioassays in our pool of drug candidates including semisynthetic triterpenoids and synthetic tricycles. These facts strongly suggest that an essential factor for potency is not a triterpenoid skeleton but the cyano enone functionality. Notably, TCE 31 reduces hepatic tumorigenesis induced with aflatoxin in rats. Further preclinical studies and detailed mechanism studies on 31 are in progress.

Topics: Aflatoxin B1; Animals; Anti-Inflammatory Agents, Non-Steroidal; Antineoplastic Agents; Cells, Cultured; Cytoprotection; Enzyme Induction; Heme Oxygenase-1; Interferon-gamma; Liver; Liver Neoplasms, Experimental; Macrophages; Male; Mice; NAD(P)H Dehydrogenase (Quinone); Nitric Oxide Synthase Type II; Nitriles; Pentacyclic Triterpenes; Phenanthrenes; Precancerous Conditions; Rats; Stereoisomerism; Stomach; Structure-Activity Relationship

Gastric adenocarcinoma develops as a consequence of chronic inflammation of the stomach lining that is caused by persistent infection with the bacterium Helicobacter pylori. Gastric carcinogenesis progresses through a sequence of preneoplastic lesions that manifest histologically as atrophic gastritis, intestinal metaplasia, and dysplasia. We show here in several preclinical models of Helicobacter-induced atrophic gastritis, epithelial hyperplasia, and metaplasia that the inhibition of ADP ribosylation by the small-molecule inhibitor PJ34 not only prevents the formation of gastric cancer precursor lesions, but also efficiently reverses preexisting lesions. PJ34 exerts its chemopreventive and therapeutic effects by impairing Helicobacter-specific T-cell priming and T(H)1 polarization in the gut-draining mesenteric lymph nodes. The subsequent infiltration of pathogenic T cells into the gastric mucosa and the ensuing gastric T cell-driven immunopathology are prevented efficiently by PJ34. Our data indicate that PJ34 directly suppresses T-cell effector functions by blocking the IFN-gamma production of mesenteric lymph node T cells ex vivo. Upon exposure to PJ34, purified T cells failed to synthesize ADP-ribose polymers and to activate the transcription of genes encoding IFN-gamma, interleukin 2, and the interleukin 2 receptor alpha chain in response to stimuli such as CD3/CD28 cross-linking or phorbol 12-myristate 13-acetate/ionomycin. The immunosuppressive and chemoprotective effects of PJ34 therefore result from impaired T-cell activation and T(H)1 polarization, and lead to the protection from preneoplastic gastric immunopathology. In conclusion, ADP-ribosylating enzymes constitute novel targets for the treatment of Helicobacter-associated gastric lesions predisposing infected individuals to gastric cancer and may also hold promise for the treatment of other T cell-driven chronic inflammatory conditions and autoimmune pathologies.

Topics: Adenosine Diphosphate; Animals; Gastritis, Atrophic; Helicobacter Infections; Helicobacter pylori; Interferon-gamma; Interleukin-2; Lymphocyte Activation; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Phenanthrenes; Poly(ADP-ribose) Polymerase Inhibitors; Precancerous Conditions; Stomach Neoplasms; T-Lymphocytes

In previous work we established the rat liver oval cell line OC/CDE 22 in order to study in vitro mechanisms of liver cell transformation. We have now exposed OC/CDE 22 cells to each of the four optically active fjord region dihydrodiol epoxides of benzo[c]phenanthrene to investigate their capacity for malignant transformation of liver cells. All four configurational isomers, which are among the most potent carcinogenic metabolites of polycyclic aromatic hydrocarbons tested in murine tumour models, malignantly transform OC/CDE 22 cells at a 2 microM dose level, resulting in a similar colony-forming efficiency in soft agar. Inoculation of the transformed cells into newborn syngeneic rats produced an extremely high incidence of carcinomas with a short latency period. The induced carcinomas displayed cholangiocellular, adenoid and solid growing structures. Neither cell growth in soft agar nor induction of tumor formation in newborn rats were achieved if confluent OC/CDE 22 cell cultures were exposed to each of the four stereoisomers and left in the confluent state for 4 weeks. In contrast, if confluent cells were exposed to the four stereoisomers, immediately split and then subcultured as usual, full transformation was accomplished. Our results indicate that the fjord region dihydrodiol epoxides of benzo[c]phenanthrene are highly efficient transforming agents for rat liver cells and that proliferation plays a pivotal role in the liver cell transformation process induced by polycylic aromatic hydrocarbons.

Topics: Animals; Carcinogens; Cell Division; Cell Transformation, Neoplastic; Liver; Liver Neoplasms, Experimental; Phenanthrenes; Precancerous Conditions; Rats; Rats, Sprague-Dawley; Stereoisomerism; Tumor Cells, Cultured

Our earlier studies demonstrated that the beta-hydroxy-beta-methylglutaryl coenzyme A (HMG CoA) reductase gene is hypomethylated and overexpressed in hepatic nodules initiated by 1,2-dimethylhydrazine (1,2-DMH). The study presented here examined whether the pattern of DNA methylation of the HMG CoA reductase gene in hepatic nodules reflected carcinogen-DNA interaction during initiation. Accordingly, hepatic nodules were generated in male Fischer 344 rats with either 1,2-DMH or aristolochic acid (AA), which interact predominantly with the guanine and adenine bases in DNA, respectively. DNA from individual nodules was restricted with HpaII, MspI, and HhaI, and the fragments obtained were hybridized to a cDNA probe for HMG CoA reductase. The results indicated that the hypomethylation pattern in the reductase gene in the nodules initiated with these two carcinogens was similar, although they interacted with different bases in the DNA. The question still remained whether the DNA fragments obtained by digesting the two sets of nodules with the restriction endonucleases were from the same domains in the genome of HMG CoA reductase. To examine this, probes for the different domains of the HMG CoA reductase gene were generated from the cDNA using the restriction enzyme Accl. Three probes were obtained: (i) a 5'-end fragment corresponding to the membrane-spanning region, (ii) a second fragment corresponding to the 3'-end of the protein, and (iii) a third fragment spanning the region between (i) and (ii). Each of these probes was radiolabeled and hybridized to the HpaII- and HhaI-generated fragments from the DNA of hepatic nodules initiated with 1,2-DMH and AA. Irrespective of the carcinogen used for initiation, hypomethylation occurred in all three domains of the gene. More important, the pattern of hypomethylation was similar in the nodules initiated by the two carcinogens. Furthermore, an overall similarity was seen in the hypomethylation patterns in the c-myc and c-Ha-ras genes in the DNA of nodules initiated with either 1,2-DMH or AA. These results raise the possibility that the pattern of hypomethylation established in the hepatic nodules may not directly reflect the interaction between the initiating carcinogen and DNA but may represent a unique phenotype of hepatic nodules.

Topics: 1,2-Dimethylhydrazine; Animals; Aristolochic Acids; Carcinogens; Cell Cycle; Dimethylhydrazines; DNA, Neoplasm; Gene Expression Regulation, Neoplastic; Genes; Genes, myc; Genes, ras; Hydroxymethylglutaryl CoA Reductases; Liver Neoplasms; Male; Methylation; Phenanthrenes; Polymorphism, Restriction Fragment Length; Precancerous Conditions; Rats; Rats, Inbred F344

Four N-Acetoxy-N-arylacetamides previously found to be local sarcomagens in the rat have been found to be initiators of tumorigenesis in mouse skin. The order of activity was: N-acetoxy-2-acetamidophenanthrene greater than N-acetoxy-4-acetamino-stilbene similar to N-acetoxy-2-acetamido-fluorene greater than N-acetoxy-4-acetamidobiphenyl. Two substituted N-benzoyloxypiperidines previously shown to yield nitrenium ions on solvolysis in methanol also had initiating activity in mouse skin.

Topics: Acetamides; Animals; Benzene Derivatives; Biphenyl Compounds; Female; Fluorobenzenes; Mice; Phenanthrenes; Piperidines; Precancerous Conditions; Skin Neoplasms; Stilbenes; Time Factors