N-acetylcysteine conjugate of phenethyl isothiocyanate enhances apoptosis in growth-stimulated human lung cells.

We previously showed that dietary treatment with the N-acetylcysteine conjugate of phenethyl isothiocyanate (PEITC-NAC) inhibited benzo(a)pyrene-induced lung tumorigenesis in A/J mice, and that tumor inhibition was associated with induction of activator protein-1 (AP-1) activity and stimulation of apoptosis in the lungs of mice. In the present study, we show that PEITC-NAC also induces apoptosis and AP-1 activity in human lung adenocarcinoma A549 cells, and that activation of AP-1 is important in PEITC-NAC induced apoptosis in these cells. PEITC-NAC induced AP-1 binding activity in A549 cells in a dose- and time-dependent manner; peak activity appeared at 10 micromol/L after 24 hours.

Fidelity of mispair formation and mispair extension is dependent on the interaction between the minor groove of the primer terminus and Arg668 of DNA polymerase I of Escherichia coli.

The hydrogen bonding interactions between the Klenow fragment of Escherichia coli DNA polymerase I with the proofreading exonuclease inactivated (KF(-)) and the minor groove of DNA were examined with modified oligodeoxynucleotides in which 3-deazaguanine (3DG) replaced guanine. This substitution would prevent a hydrogen bond from forming between the polymerase and that one site on the DNA. If the hydrogen bonding interaction were important, then we should observe a decrease in the rate of reaction.

Glutathione depletion enhances the formation of endogenous cyclic DNA adducts derived from t-4-hydroxy-2-nonenal in rat liver.

Earlier, we detected the cyclic adducts of deoxyguanosine (dG) derived from t-4-hydroxy-2-nonenal (HNE), a long chain alpha,beta-unsaturated aldehyde (enal) product from oxidation of omega-6 polyunsaturated fatty acids, in tissue DNA of rats and humans as endogenous DNA damage. Recent evidence implicates the cyclic HNE adducts in human liver carcinogenesis. Because glutathione (GSH) protects against oxidative stress, we undertook a study to examine the effect of GSH depletion on the HNE-derived cyclic adducts in vivo.

Resveratrol-induced cell growth inhibition and apoptosis is associated with modulation of phosphoglycerate mutase B in human prostate cancer cells: two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry evaluation.

Several studies provide evidence for the anti-carcinogenic activity of resveratrol, a phytoalexin present in grapes and berries, but the precise mechanisms involved in the modulation of prostate carcinogenesis by resveratrol remain to be elucidated. The inhibitory effects induced by resveratrol in human prostate cancer cells impact diverse cellular mechanisms associated with tumor initiation, promotion, and progression. In our earlier studies with prostate cancer cells using cDNA microarray analysis, we indicated the importance of p53-mediated molecular targets of resveratrol.

Induction of preneoplastic lung lesions in guinea pigs by cigarette smoke inhalation and their exacerbation by high dietary levels of vitamins C and E.

The development of effective chemopreventive agents against cigarette smoke-induced lung cancer could be greatly facilitated by the availability of suitable laboratory animal models. Here we report that male Hartley guinea pigs treated with cigarette smoke by inhalation twice a day for 28 days developed preneoplastic lung lesions, including bronchial hyperplasia, dysplasia and squamous metaplasia, analogous to those found in human smokers. The lesions were accompanied by increased expression of proliferating cell nuclear antigen and activation of the serine/threonine kinase Akt in the bronchial epithelium.

Treatment of canine haemangiosarcoma with suberoylanilide hydroxamic acid, a histone deacetylase inhibitor.

A case report is presented by describing the treatment of a 12-year-old dog - diagnosed with haemangiosarcoma (HSA) - with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor. The drug was administered orally, on a daily basis, approximately 2 weeks post-splenectomy at a dose of 3 mg kg(-1). HSA is a lethal malignancy of the endothelium, which is usually disseminated by the time it is diagnosed.

Regression of mouse prostatic intraepithelial neoplasia by nonsteroidal anti-inflammatory drugs in the transgenic adenocarcinoma mouse prostate model.

Purpose: Epidemiologic studies have revealed a decreased risk of colon cancer among people who have regularly taken cyclooxygenase (COX)-2 inhibitors such as aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs). Whereas the selective COX-2 inhibitor celecoxib and exisulind, a metabolic product of sulindac, have gained increasing attention as efficacious chemopreventive agents against colon and prostate cancer, not much is known about the underlying molecular targets and mechanisms. Moreover, the side effects of NSAIDs are a major obstacle for large-scale application to the prevention of cancer in humans; for example, in the United States in 1998, there were 16,550 deaths from NSAID-induced gastrointestinal complications.

Low doses of beta-carotene and lutein inhibit AOM-induced rat colonic ACF formation but high doses augment ACF incidence.

Epidemiological studies suggest that carotenoids such as beta-carotene and lutein play an important role in reducing the risk for several cancers. However, in colon cancer there is ambiguity with regard to the role of these compounds in that both preventive effects and tumor promotion have been observed. In the present study we observed that male F344 rats were able to tolerate up to 2,500 ppm of beta-carotene as well as of lutein.

Nitric oxide signaling in colon cancer chemoprevention.

Nitric oxide (NO) is a pleiotrophic regulator, pivotal to numerous biological processes, including vasodilation, neurotransmission, and macrophage-mediated immunity. The highly reactive free radicals, produced by NO synthases (NOS) have been implicated in the modulation of carcinogenesis. Over-expression of inducible NOS (iNOS), a common phenomenon during chronic inflammatory conditions, generates sustainable amounts of NO, that its reactive intermediates are mutagenic, causing DNA damage or impairment of DNA repair, has been well established in carcinogenesis.

Effect of melatonin on the induction of foci of aberrant crypts in the colon by azoxymethane in rats.

Objective: A program of research was established on the question whether melatonin played a chemopreventive role in the development of foci of aberrant crypts in the intestinal tract of male rats. Male F344 rats were injected i.p.

Tissue glutathione and cysteine levels in methionine-restricted rats.

Objective: Previously, we demonstrated that lifelong methionine (Met) restriction (MR) increases lifespan, decreases the incidence of aging-related diseases, increases blood glutathione (GSH) levels, and prevents loss of GSH during aging in rats. Our present objective was to elucidate the effects of MR on GSH metabolism and transport by determining the time course and nature of GSH and cysteine changes in blood and other tissues in young and mature rats.

Methods: Male F-344 rats were placed on control (0.

Human cytochromes P450 1A1 and 1B1 catalyze ring oxidation but not nitroreduction of environmental pollutant mononitropyrene isomers in primary cultures of human breast cells and cultured MCF-10A and MCF-7 cell lines.

The position of the nitro group determines the relative carcinogenic activities of mono-nitropyrene isomers (mono-NPs) in the rat mammary gland. To determine whether the results obtained in rodents treated with these environmental pollutants can be applicable to humans, we examined their metabolic activation in primary cultures of human breast cells derived from reduction mammoplasty, as well as in the cultured human breast cancer cell line MCF-7 and the immortalized human mammary epithelial cell line MCF-10A. Primary cultures as well as cell lines were competent in metabolizing all three isomers via both ring oxidation and nitro reduction pathways.

Diosgenin, a steroid saponin of Trigonella foenum graecum (Fenugreek), inhibits azoxymethane-induced aberrant crypt foci formation in F344 rats and induces apoptosis in HT-29 human colon cancer cells.

Trigonella foenum graecum (fenugreek) is traditionally used to treat disorders such as diabetes, high cholesterol, wounds, inflammation, and gastrointestinal ailments. Recent studies suggest that fenugreek and its active constituents may possess anticarcinogenic potential. We evaluated the preventive efficacy of dietary fenugreek seed and its major steroidal saponin constituent, diosgenin, on azoxymethane-induced rat colon carcinogenesis during initiation and promotion stages.

Effects of a combination of docosahexaenoic acid and 1,4-phenylene bis(methylene) selenocyanate on cyclooxygenase 2, inducible nitric oxide synthase and beta-catenin pathways in colon cancer cells.

Epidemiological and preclinical studies suggest that diets that are rich in n-3 polyunsaturated fatty acids (PUFAs) and selenium (Se) reduce the risk of colon cancer. Studies conducted in our laboratory have indicated that synthetic organoselenium 1,4-phenylene bis(methylene) selenocyanate (p-XSC) is less toxic and more effective than inorganic Se and selenomethionine, the major Se compound in natural selenium yeast. Through cDNA microarray analysis, we have demonstrated earlier that the n-3 PUFA docosahexaenoic acid (DHA), modulated more than one signaling pathway by altering several genes involved in colon cancer growth.

Obesity, adipocytokines, and insulin resistance in breast cancer.

The adipocytokines are biologically active polypeptides that are produced either exclusively or substantially by the adipocytes, and act by endocrine, paracrine, and autocrine mechanisms. Most have been associated with obesity, hyperinsulinaemia, type 2 diabetes, and chronic vascular disease; in addition, six adipocytokines--vascular endothelial growth factor, hepatocyte growth factor, leptin, tumour necrosis factor-alpha, heparin-binding epidermal growth factor-like growth factor, and interleukin-6--promote angiogenesis while one, adiponectin, is inhibitory. Obesity and insulin resistance have both been identified as risk factors for breast cancer and are associated with late-stage disease and poor prognosis.

Mechanisms of mammary cancer chemoprevention by organoselenium compounds.

Searching for optimal diets and for naturally occurring agents in routinely consumed foods that may inhibit cancer development, although challenging, constitutes a valuable and plausible approach to finding ways to control and prevent cancer. To date, the use of the micronutrient selenium in human clinical trials is limited but the outcome of these investigations indicates that selenium is one of the most promising agents. Data presented in this mini-review indicate that the dose and the form (structure) in which selenium is used are the most critical determinants of success in future clinical trials.

Escherichia coli DNA polymerase I (Klenow fragment) uses a hydrogen-bonding fork from Arg668 to the primer terminus and incoming deoxynucleotide triphosphate to catalyze DNA replication.

Interactions between the minor groove of the DNA and DNA polymerases appear to play a major role in the catalysis and fidelity of DNA replication. In particular, Arg668 of Escherichia coli DNA polymerase I (Klenow fragment) makes a critical contact with the N-3-position of guanine at the primer terminus. We investigated the interaction between Arg668 and the ring oxygen of the incoming deoxynucleotide triphosphate (dNTP) using a combination of site-specific mutagenesis of the protein and atomic substitution of the DNA and dNTP.

Studies with the azoxymethane-rat preclinical model for assessing colon tumor development and chemoprevention.

During recent years, multidisciplinary studies in epidemiology and molecular biology have contributed to our understanding of the etiology of colorectal cancer; more importantly they have enabled us to approach its prevention. An impressive body of epidemiological data suggests an inverse relationship between colorectal cancer risk and consumption of diets rich in omega (omega)-3 fatty acids (n-3 PUFAs) or the regular use of nonsteroidal antiinflammatory drugs (NSAIDs), including aspirin. The development of strategies for the chemoprevention of colorectal cancer have been facilitated by the use of relevant animal models mimicking the neoplastic processes that occur in humans, including similarities in histopathology and molecular and genetic lesions during both the early and promotion/progression stages of carcinogenesis.

NO-donating nonsteroidal antiinflammatory drugs (NSAIDs) inhibit colon cancer cell growth more potently than traditional NSAIDs: a general pharmacological property?

The novel nitric oxide-donating nonsteroidal antiinflammatory drugs (NO-NSAIDs), consisting of a traditional NSAID to which a NO releasing moiety is covalently attached, may have an important role in colon cancer prevention and/or treatment. Preclinical studies have shown that NO-aspirin (NO-ASA) is more potent than traditional ASA in preventing colon cancer. Preclinical and clinical studies have also documented its superior safety, compared to traditional ASA.

A Highly Abbreviated Synthesis of Dibenzo[def,p]chrysene and Its 12-Methoxy Derivative, a Key Precursor for the Synthesis of the Proximate and Ultimate Carcinogens of Dibenzo[def,p]chrysene.

Dibenzo[def,p]chrysene (DBC) (1), is by far the most mutagenic and toxic polycyclic aromatic hydrocarbon identified. Its metabolic activation leads to trans-11,12-dihydroxy-11,12-dihydro-DBC (2), which is further metabolized to the ultimate metabolite, anti-trans-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydro-DBC (3), that binds to DNA causing mutations and ultimately tumor induction. We report a facile route for the syntheses of DBC (1) and its 12-methoxy derivative (12-methoxy-DBC) (13), a key intermediate for the synthesis of 2 and 3, using a Suzuki cross-coupling approach.

Overexpression of caveolin-1 in experimental colon adenocarcinomas and human colon cancer cell lines.

Caveolin-1, -2, and -3 are the principal proteins of caveolae, the vesicular invaginations of the plasma membrane. Recent studies suggest that caveolins play an important role in cellular signaling and, possibly, in tumorigenesis. We examined the expression of the three caveolins in azoxymethane-induced rat colon adenocarcinoma and normal-appearing colonic mucosa, and also in human colon cancer cells with inherently different proliferation rates.

Inhibition of experimental tobacco carcinogen induced head and neck carcinogenesis.

Oral cancer models have attempted to demonstrate inhibition of oral carcinogenesis. These models used synthetic carcinogens, lacked a specific mechanism of activity or used non-physiologic doses for carcinogen or inhibitor. To correct these problems the tobacco and environmental carcinogen, dibenzo[a,l]pyrene (DB[a,l]P) (0.

Detection of nitrated benzene metabolites in bone marrow of B6C3F1 mice treated with benzene.

Benzene, a constituent of cigarette smoke, is a human leukemogen and induces bone marrow toxicity. The mechanism of benzene-induced toxicity is not well-established. We hypothesized that relatively high levels of nitric oxide formed in bone marrow can react with oxygen and/or superoxide anion that is generated during redox cycling of ring-hydroxylated benzene metabolites to yield peroxynitrite as well as other NO-derived intermediates.

Modulation of cyclooxygenase-2 activities by the combined action of celecoxib and decosahexaenoic acid: novel strategies for colon cancer prevention and treatment.

To develop efficient synergistic or additive combinations of chemopreventive and nutritional agents to reduce the risk of colon cancer, experiments were designed to test the application of a selective cyclooxygenase-2 (COX-2) inhibitor together with dietary omega-3 polyunsaturated fatty acids (PUFAs), such as decosahexaenoic acid (DHA). Thus, individual application of celecoxib, a COX-2 inhibitor, DHA, a omega-3 PUFA, and combinations of both were tested for their effectiveness using cell proliferation, apoptosis, and COX-2 expression as markers in the human colon cancer HCA-7 cell line. HCA-7 cells exposed to various subtoxic doses of celecoxib, DHA, or combinations of both were analyzed for inhibition of cell proliferation by trypan blue exclusion and proliferating cell nuclear antigen methods, induction of apoptosis by 4',6-diamidino-2-phenylindole method, and COX-2 by reverse transcription-PCR and Western blot analysis.