Local and systemic delivery of siRNAs for oligonucleotide therapy.

RNA interference (RNAi) is a relatively new found phenomenon of posttranscriptional gene silencing to regulate the expression of multiple genes involved in a wide range of biological processes. The gene-silencing technology via RNAi has also been developed into a commonly anti-gene method. Furthermore, in vivo data indicate that small interfering RNAs (siRNAs) may be used to treat human diseases.

Glutathione S-transferase Pi mediates proliferation of androgen-independent prostate cancer cells.

Prostate cancers generally acquire an androgen-independent growth capacity with progression, resulting in resistance to antiandrogen therapy. Therefore, identification of the genes regulated through this process may be important for understanding the mechanisms of prostate carcinogenesis. We here utilized androgen-dependent/independent transplantable tumors, newly established with the 'transgenic rat adenocarcinoma in prostate' (TRAP) model, to analyze their gene expression using microarrays.

RNAi-based drug discovery and its application to therapeutics.

The discovery of RNA interference (RNAi) for target-specific gene silencing via short interfering RNA (siRNA) has rapidly created a powerful tool for the exploration of pathogenesis of disease. The identification of this remarkable molecular pathway has manifested in the new field of RNAi therapy. In efforts to establish the therapeutic application of RNAi therapy, a major focus has been on target gene-specific siRNA-delivery technology in vivo.

Gpx2 is an overexpressed gene in rat breast cancers induced by three different chemical carcinogens.

Gene expression alterations are essential for the process of carcinogenesis. A carcinogen may have specific mechanisms for inducing tumors, which may involve inducing characteristic gene expression alterations. In this study, we attempted to identify genes crucial for mammary carcinogenesis.

Both early and late stages of hepatocarcinogenesis are enhanced in Cx32 dominant negative mutant transgenic rats with disrupted gap junctional intercellular communication.

Connexins are a family of transmembrane proteins essential for the gap junctions, which mediate cell-to-cell communication. Several connexins are reported to be tumor suppressors, and we have established transgenic (Tg) rats with a connexin 32 (Cx32) dominant negative mutant showing high sensitivity to early-stage diethylnitrosamine (DEN)-induced liver carcinogenesis. In this study, we carried out two independent experiments using Tg rats to further investigate the roles of disrupted Cx32 in late-stage carcinogenesis (carcinoma induction and metastasis) in the liver.

Protective effects of citrus nobiletin and auraptene in transgenic rats developing adenocarcinoma of the prostate (TRAP) and human prostate carcinoma cells.

Dietary phytochemicals, including nobiletin and auraptene, have been shown to exert inhibiting effects in several chemically induced carcinogenesis models. We here investigated the influence of nobiletin and auraptene on prostate carcinogenesis using transgenic rats developing adenocarcinoma of the prostate (TRAP) bearing the SV40 T antigen transgene under control of the probasin promoter and human prostate cancer cells. Starting at 5 weeks of age, male TRAP rats received powder diet containing 500 p.

Prediction of carcinogenic potential by a toxicogenomic approach using rat hepatoma cells.

The long-term rodent bioassay is the standard method to predict the carcinogenic hazard of chemicals for humans. However, this assay is costly, and the results take at least two years to produce. In the present study, we conducted gene expression profiling of cultured cells exposed to carcinogenic chemicals with the aim of providing a basis for rapid and reliable prediction of carcinogenicity using microarray technology.

Inhibition of prostate carcinogenesis in probasin/SV40 T antigen transgenic rats by leuprorelin, a luteinizing hormone-releasing hormone agonist.

The effects of leuprorelin acetate, a luteinizing hormone-releasing hormone agonist (LHRH-A), on prostate carcinogenesis in probasin/SV40 Tag transgenic rat was investigated. Fifteen weeks after administration of 0.28 and 2.

Lack of modification of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) rat hepatocarcinogenesis by caffeine, a CYP1A2 inducer, points to complex counteracting influences.

2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), one of the most abundant carcinogenic heterocyclic amines in cooked foods, is speculated to be a human liver carcinogen. To test the hypothesis that it is metabolically activated by CYP1A2, we here investigated the effects of caffeine as a CYP1A2 inducer on MeIQx induced rat hepatocarcinogenesis in a medium-term liver bioassay system. Unexpectedly, no modifying effects of caffeine on MeIQx-induced hepatocarcinogenesis were evident, although up-regulation of CYP1A2 and NAT2 were detected.

Transgenic disruption of gap junctional intercellular communication enhances early but not late stage hepatocarcinogenesis in the rat.

Much experimental evidence supports the conclusion that loss of gap junctional intercellular communication (GJIC) contributes to carcinogenesis. Transgenic rats featuring a dominant negative mutant of the connexin 32 gene under albumin promoter control (Cx32Delta Tg-High and Cx32Delta Tg-Low lines, respectively with high and low copy numbers of the transgene) have disrupted GJIC, as demonstrated by scrape dye-transfer assay in vivo as previous report by Asamoto et al. (2004).

Tbx3 expression is related to apoptosis and cell proliferation in rat bladder both hyperplastic epithelial cells and carcinoma cells.

In the present study, Tbx3, a member of the T-box family of transcription factors, was identified as an up-regulated gene by mRNA differential display in the regression (apoptosis) stage after uracil-induction of papillomatosis in the rat urinary bladder. Immunohistochemical analysis revealed that apoptosis cells are negative and apoptosis resistant cells are positive for Tbx3 expression. That suggests that Tbx3 is an apoptosis resistant gene rather than an apoptosis induced gene.

Inhibition of cell proliferation by nobiletin, a dietary phytochemical, associated with apoptosis and characteristic gene expression, but lack of effect on early rat hepatocarcinogenesis in vivo.

Dietary phytochemicals can inhibit the development of certain types of tumors. We here investigated the effects of nobiletin (Nob), garcinol (Gar), auraptene (Aur), beta-cryptoxanthin- and hesperidine-rich pulp (CHRP) and 1,1'-acetoxychavicol acetate (ACA) on hepatocarcinogenesis in a rat medium-term liver bioassay, and also examined their influence on cell proliferation, cell cycle kinetics, apoptosis and cell invasion of rat and human hepatocellular carcinoma (HCC) cells, MH1C1 and HepG2, respectively. While there were no obvious suppressive effects on the development of putative preneoplastic liver lesions, inhibition of hepatocarcinoma cell proliferation was evident in the Nob group.

Connexin 32 dominant-negative mutant transgenic rats are resistant to hepatic damage by chemicals.

Connexins are subunits of gap junction channels, which allow direct transfer of ions, secondary messenger molecules, and other metabolites between contacting cells. Gap junctions are believed to be involved in tissue homeostasis, embryonic development, and control of cell proliferation. Several studies have shown that cell damage signals are transmitted through gap junctions when cells are irradiated or when cells bearing the herpes simplex virus-thymidine kinase (HSV-TK) gene are treated with ganciclovir.

Rapid analysis of gene expression changes caused by liver carcinogens and chemopreventive agents using a newly developed three-dimensional microarray system.

We investigated changes of gene expression in livers of rats treated with carcinogens and tumor promoters using a novel three-dimensional microarray system developed by Olympus Optical Co., Ltd., to assess the feasibility of predicting modifying effects on hepatocarcinogenesis on the basis of changes in the patterns.

Lack of effect of human c-Ha-ras proto-oncogene overexpression on prostate carcinogenesis in probasin/SV40 T antigen transgenic rats.

We have previously reported that transgenic (Tg) rats bearing the SV40 T antigen under probasin promoter control (PB/SV40T) develop prostate carcinomas at 100% incidence, showing their prostate carcinoma growth to be completely androgen-dependent. Transgenic rats carrying three copies of the human c-Ha-ras proto-oncogene (Hras128) are also highly susceptible to carcinogen induction of multiple mammary carcinomas, in this case estrogen-independent, since ovariectomy does not affect mammary tumor formation. A relationship between ras/mitogen-activated protein kinase signaling and androgen responsiveness of prostate cancer cells has been reported.

Inhibitory effects of soy isoflavones on rat prostate carcinogenesis induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP).

Intake of isoflavones derived from soybean products may impact on prostate cancer risk. Here we evaluated the effects of Fujiflavone, a commercial isoflavone supplement, on rat prostate carcinogenesis induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most abundant heterocyclic amine in cooked meat. F344 male rats were given intragastric administrations of PhIP at the dose of 200 mg/kg twice weekly for 10 weeks.

Age-dependent histopathological findings in the prostate of probasin/SV40 T antigen transgenic rats: lack of influence of carcinogen or testosterone treatment.

Sequential changes in the phenotype of prostatic lesions and the impact of additional carcinogen treatment or castration on development and progression of prostate cancers were examined in probasin/simian virus 40 (SV40) T antigen transgenic (TG) rats. Non-invasive prostate adenocarcinomas were evident in all lobes at 15 weeks of age. Invasive tumors were limited to the anterior lobe at this time point and were found in all lobes in an age-dependent manner thereafter.

Regulation of cell proliferation by induction of p21/WAF1 in rat bladder carcinoma cells using the Cre--loxP system.

p21/WAF1, a cyclin-dependent kinase inhibitory protein, functions as a tumor suppressor. Loss of p21/WAF1 expression has been reported to be an important prognostic predictor in several human malignancies, including bladder carcinomas. In this study, we induced p21/WAF1 using a Cre-loxP gene expression switching vector system in BC31 rat bladder carcinoma cells that feature p53 gene mutations.

Effects of genetic background on prostate and taste bud carcinogenesis due to SV40 T antigen expression under probasin gene promoter control.

The incidence of prostate carcinomas in African-American men is greater than in white men, indicating genetic factors are involved in risk of this neoplasia. Recently, we have developed a transgenic rat model of prostate cancer, featuring development of malignancies within 15 weeks of age at very high incidence. Male transgenic rats with a Sprague-Dawley genetic background were mated with wild-type females of F344, Wistar and ACI strains.

Mammary carcinomas induced in human c-Ha-ras proto-oncogene transgenic rats are estrogen-independent, but responsive to d-limonene treatment.

We have previously shown that transgenic rats carrying three copies of the human c-Ha-ras proto-oncogene (Hras128) are highly susceptible to N-methyl-N-nitrosourea (MNU) mammary carcinogenesis. All transgenic rats treated with 50 mg / kg MNU, i.v.