Promotion of mouse two-stage skin carcinogenesis by diacylglycerol-rich edible oil.

Tumor promotion potential of diacylglycerol (DAG)-rich edible oil was examined using a two-stage mouse skin carcinogenesis model initiated with 7,12-dimethylbenz[a]anthracene (DMBA). Topical treatment with 75 mg DAG oil once a day for 5 days/week for 35 weeks caused papillomas in 4 of 23 (17%) DMBA-treated female ICR mice, while DMBA initiation alone and DAG treatment without DMBA initiation did not induce any skin tumors. Doubling the daily treatment (twice a day x 5 days/week) at doses of 75 and 30 mg caused both papillomas and squamous cell carcinomas after DMBA initiation, the incidences of tumors being 48% (12/25) and 44% (11/25), respectively, significantly higher than the 4% (1/23) in the DMBA+ 85 mg triacylglycerol group and 0% (0/24) in the DMBA+ vehicle-treated group.

Enhancement of antiproliferative activity of interferons by RNA interference-mediated silencing of SOCS gene expression in tumor cells.

The suppressor of cytokine signaling (SOCS) proteins, negative regulators of interferon (IFN)-induced signaling pathways, is involved in IFN resistance of tumor cells. To improve the growth inhibitory effect of IFN-beta and IFN-gamma on a murine melanoma cell line, B16-BL6, and a murine colon carcinoma cell line, Colon26 cells, SOCS-1 and SOCS-3 gene expression in tumor cells was downregulated by transfection of plasmid DNA expressing short hairpin RNA targeting one of these genes (pshSOCS-1 and pshSOCS-3, respectively). Transfection of pshSOCS-1 significantly increased the antiproliferative effect of IFN-gamma on B16-BL6 cells.

Periodic analysis of urethane-induced pulmonary tumors in living A/J mice by respiration-gated X-ray microcomputed tomography.

X-ray microcomputed tomography (micro-CT) with a respiratory gating system is a useful non-invasive approach to evaluate lung tumor development in living animal models. Here micro-CT was applied for the detection of lung lesions induced by a single intraperitoneal injection (250 mg/kg) of urethane in male A/J mice, at 2-week intervals from 10 to 30 weeks after carcinogen exposure. In micro-CT cross sections, lung tumor images were easily distinguished from surrounding non-tumorous tissues, the smallest detected tumor being approximately 0.

Occurrence of mutations in the epidermal growth factor receptor gene in X-ray-induced rat lung tumors.

Epidermal growth factor receptor (EGFR) gene alterations have been found in human lung cancers. However, there is no information on the factors inducing EGFR mutations. In rodents, K-ras mutations are frequently found in many lung carcinogenesis models, but hitherto, Egfr mutations have not been reported.

Possible application of human c-Ha-ras proto-oncogene transgenic rats in a medium-term bioassay model for carcinogens.

With the aim of developing a medium-term assay for screening of environmental carcinogens, we exposed mammary carcinogen sensitive human c-Ha-ras proto-oncogene transgenic (Hras128) rats to various carcinogens, including compounds that do not normally induce mammary tumors. Seven-week-old Hras128 rats and wild-type littermates received administrations of 3-methylcholanthrene (3-MC), benzo[a]pyrene (B[a]P), anthracene, pyrene, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), dimethylarsinic acid (DMA), diethylnitrosamine (DEN) or azoxymethane (AOM) and were sacrificed at week 12 (females) (at week 10 for the 3-MC group) or week 20 (males). Female Hras128 rats receiving NNK, DEN, or DMA showed a significant increase in mammary tumor incidence and/or multiplicity compared to the respective values with olive oil or deionized distilled water (DDW) vehicles.

Possible enhancing activity of diacylglycerol on 4-nitroquinoline 1-oxide induced carcinogenesis of the tongue in human c-Ha-ras proto-oncogene transgenic rats.

1,2-diacylglycerol (1,2-DAG) is involved in cell proliferation as an activator of protein kinase C (PKC) and has been shown to stimulate growth of cancer cells, raising the possibility of a role in tumor promotion. Ingested DAG oil, containing 70% 1,3-DAG and 30% 1,2-DAG, is digested and considered to be safe as edible oil. However, DAG may directly contact with oral cavity mucosa in undigested form.

Prevention of carcinogenesis and cancer metastasis by bovine lactoferrin.

Increasing attention is being paid to chemopreventive agents for individuals at high risk of cancer. We have concentrated on bovine lactoferrin (bLF), an 80 kDa iron-binding glycoprotein known to have anti-microbial and immunoprotective effects. Lactoferrin is particularly abundant in colostrum, and is also present in tears, saliva and seminal and uterine secretions.

Ductal origin of pancreatic adenocarcinomas induced by conditional activation of a human Ha-ras oncogene in rat pancreas.

Pancreatic ductal adenocarcinoma is one of the most debilitating malignancies in humans. Currently, radiation and chemotherapy are ineffective, with median survival times after treatment of <12 months. Animal models that reflect the human condition and can be used to explore screening and therapeutic approaches are clearly desirable.

Prostaglandin E receptor EP3 deficiency modifies tumor outcome in mouse two-stage skin carcinogenesis.

We have recently shown that the prostaglandin E(2) (PGE(2)) receptor EP(3) plays an important role in suppression of colon cancer cell proliferation and that its deficiency enhances late stage colon carcinogenesis. Here we examined the effects of EP(3)-deficiency on two-stage skin carcinogenesis. 7,12-Dimethylbenz[a]anthracene (50 microg/200 microl of acetone) was thus applied to the back skin of female EP(3)-knockout and wild-type mice at 8 weeks of age, followed by treatment with 12-O-tetradecanoylphorbol-13-acetate (5 microg/200 microl of acetone) twice a week for 25 weeks.

High susceptibility of human c-Ha-ras proto-oncogene transgenic rats to carcinogenesis: a cancer-prone animal model.

Transgenic animals carrying human c-Ha-ras proto-oncogene, v-Ha-ras transgenic mice, pim-1 transgenic mice and several knockout mice deficient of tumor suppressor genes, such as p53, have been shown to exhibit increased carcinogen susceptibility. As a result, studies into practical application and medium-term screening of environmental carcinogens are under way. Given the advantages of rat models characterized by larger organ size, abundant information regarding preneoplasias and virus-free constitution, we have concentrated on the generation of transgenic rats bearing copies of the human c-Ha-ras proto-oncogene and shown the Hras128 strain to be extremely sensitive to the induction of mammary carcinomas, and to a lesser extent, lesions in the urinary bladder, esophagus and skin.

Immunological detection of severe acute respiratory syndrome coronavirus by monoclonal antibodies.

In order to establish immunological detection methods for severe acute respiratory syndrome coronavirus (SARS-CoV), we established monoclonal antibodies directed against structural components of the virus. B cell hybridomas were generated from mice that were hyper-immunized with inactivated SARS-CoV virion. By screening 2,880 generated hybridomas, we established three hybridoma clones that secreted antibodies specific for nucleocapsid protein (N) and 27 clones that secreted antibodies specific for spike protein (S).

Cancer prevention by natural compounds.

Increasing attention is being paid to the possibility of applying cancer chemopreventive agents for individuals at high risk of neoplastic development. For this purpose by natural compounds have practical advantages with regard to availability, suitability for oral application, regulatory approval and mechanisms of action. Candidate substances such as phytochemicals present in foods and their derivatives have been identified by a combination of epidemiological and experimental studies.

A subcutaneously injected UV-inactivated SARS coronavirus vaccine elicits systemic humoral immunity in mice.

The recent emergence of severe acute respiratory syndrome (SARS) was caused by a novel coronavirus, SARS-CoV. It spread rapidly to many countries and developing a SARS vaccine is now urgently required. In order to study the immunogenicity of UV-inactivated purified SARS-CoV virion as a vaccine candidate, we subcutaneously immunized mice with UV-inactivated SARS-CoV with or without an adjuvant.

Isoliquiritigenin, a flavonoid from licorice, reduces prostaglandin E2 and nitric oxide, causes apoptosis, and suppresses aberrant crypt foci development.

Isoliquiritigenin (ILTG), a flavonoid group compound, exists in some foodstuffs and herbal medicines such as licorice (Glycyrrhiza uralensis Fisher). Previously, we showed that ILTG can suppress azoxymethane (AOM)-induced colon carcinogenesis in ddY mice. In the present report, we present evidence that ILTG markedly decreases both prostaglandin E2 (PGE2) and nitric oxide (NO) production in RAW264.

Possible enhancing effects of atrazine and nonylphenol on 7,12-dimethylbenz[a]anthracene-induced mammary tumor development in human c-Ha-ras proto-oncogene transgenic rats.

Our transgenic (Tg) strain carrying copies of the human c-Ha-ras proto-oncogene is highly susceptible to 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis, possibly due to activation of the transgene, and can be used in medium-term bioassay models to test for modifying effects of estrogenic environmental compounds on tumor development. The present study was conducted to assess the influence of dietary feeding of the endocrine disruptors atrazine and nonylphenol on DMBA-induced carcinogenesis in c-Ha-ras Tg rats. Animals of both sexes were given a single oral dose of DMBA (25 mg/kg body weight) at 50 days of age and thereafter received soybean-free diet containing 5, 50 or 500 ppm atrazine, or 10, 25, 100 or 250 ppm nonylphenol.

Rapid induction of skin and mammary tumors in human c-Ha-ras proto-oncogene transgenic rats by treatment with 7,12-dimethylbenz[a]anthracene followed by 12-O-tetradecanoylphorbol 13-acetate.

We have established a transgenic rat line carrying 3 copies of the human c-Ha-ras proto-oncogene with its own promoter region (Jcl/SD-TgN(HrasGen)128Ncc) (Hras128 rat), expression being detectable in almost all organs. We have already demonstrated that the rat is highly sensitive to mammary, esophagus and bladder carcinogenesis. In the present study, male and female transgenic and wild-type littermates were topically treated with 2.

Terminal endbuds and acini as the respective major targets for chemical and sporadic carcinogenesis in the mammary glands of human c-Ha-ras protooncogene transgenic rats.

A rat strain carrying the human c-Ha-ras protooncogene, established by our laboratory, is highly susceptible to mammary chemical carcinogens. The transgenic rats exhibit increased number of terminal endbuds (TEBs) at the tips of developing ducts in the mammary gland compared to non-transgenic littermates. Confocal microscopy revealed the level of active mitogen-activated protein kinase to be elevated in these TEBs, and a close correlation between their numbers and tumorigenic response initiated by 7,12-dimethylbenz[a]anthracene was confirmed.

Promotion of Liver Lesion Development in the Syrian Hamster by Dietary Fat Following Multi-organ Initiation is Inhibited by DHEA-S Administration.

The influence of dietary supplementation with dehydroepiandrosterone-sulphate (DHEA-S) at 0.6% was investigated in male Syrian golden hamsters initiated by treatments with azoxymethane(AOM), and dihydroxy-di-n-propyl nitrosamine (DHPN), timed after transfer from a choline-deficient to a normal diet. These carcinogens respectively target the colon, and the respiratory tract, the liver and pancreas.

Lack of initiation activity in rat liver of low doses of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline.

It has been generally accepted that genotoxic carcinogens have no threshold in exerting their potential for cancer induction. However, the non-threshold theory can be challenged for cancer risk assessment in humans. Here we examined low dose carcinogenicity of a food-derived, genotoxic hepatocarcinogen, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), using an in vivo medium-term bioassay to detect initiating activity for rat hepatocarcinogenesis.

Inhibitory effects of 17beta-estradiol and 4-n-octylphenol on 7,12-dimethylbenz[a]anthracene-induced mammary tumor development in human c-Ha-ras proto-oncogene transgenic rats.

Experiments were conducted to determine whether the natural estrogen and an environmental compound with estrogenic action, 4-n-octylphenol (4nOP), could modify tumor development in human c-Ha-ras proto-oncogene transgenic (Tg) rats which are highly susceptible to mammary and skin carcinogens. Female and male Tg and non-transgenic (non-Tg) rats were given a single oral dose of 7,12-dimethylbenz[a]anthracene (DMBA) (25 mg/kg body weight) at 50 days of age and thereafter subcutaneously implanted with cholesterol pellets containing 0.01, 0.

Intranasal inoculation of a recombinant influenza virus containing exogenous nucleotides in the NS segment induces mucosal immune response against the exogenous gene product in mice.

To establish a mucosal vaccine system, we evaluated the immunogenicity of a recombinant influenza virus, designated NS2Acat, in which the chloramphenicol acetyltransferase (CAT) reporter gene is fused in frame to the NS1 gene in the NS gene segment. The NS2Acat replicated slightly within the lungs in BALB/c mice after intranasal administration, accompanying expression of the CAT and the viral HA mRNA. NS2Acat induced delayed-type hypersensitivity (DTH) and sensitized the CAT-specific T lymphocytes in the regional lymph nodes, which proliferated and synthesized several cytokines in vitro upon antigenic challenge.

Studies on cancer chemoprevention by traditional folk medicines XXIV. Inhibitory effect of a coumarin derivative, 7-isopentenyloxycoumarin, against tumor-promotion.

7-Isopentenyloxycoumarin (1) was isolated from Heracleum lanatum MICHX. (Umbelliferae). Compound 1 inhibited phospholipid metabolism and Epstein-Barr virus activation caused by a potent tumor promoter.

Organotropic chemopreventive effects of n-3 unsaturated fatty acids in a rat multi-organ carcinogenesis model.

Organotropic chemopreventive effects of n-3 unsaturated fatty acids were studied using a multi-organ carcinogenesis model in male rats. Rats were treated with diethylnitrosamine (DEN), N-methyl-N-nitrosourea (MNU), N-butyl-N-4-hydroxybutylnitrosamine (BBN), 1,2-dimethylhydrazine (DMH) and dihydroxy-di-n-propylnitrosamine (DHPN) during the first 7 weeks, and then given unsaturated fatty acid (UFAs), docosahexaenoic acid (n-3, C(22:6)) (DHA), eicosapentaenoic acid (n-3, C(20:5)) (EPA), linoleic acid (n-6, C(18:2)) (LA) or oleic acid (n-9, C(18:1)) (OA) at a dose of 1.0 ml/rat, 3 times a week by gavage for the consecutive 30 weeks.

Persistent synchronized oscillations in prolactin gene promoter activity in living pituitary cells.

PRL gene expression in the anterior pituitary gland responds rapidly to different hormonal signals. We have investigated the long-term timing of transcriptional activation from the PRL, GH, and cytomegalovirus promoters in response to different stimulus duration, using real-time imaging of luciferase expression in living stably transfected GH3 cells. Long-term stimulation of serum-starved cells with 50% serum induced a homogeneous rise in PRL promoter activity, with subsequent heterogeneous fluctuations in luciferase activity in individual cells.