Biomedical subjects

Tomoyuki Shirai

Publications and source records attributed to Tomoyuki Shirai.

At least 19 recordsLinked to original sources

PubMed2006

Differences in gene expression profiles in the liver between carcinogenic and non-carcinogenic isomers of compounds given to rats in a 28-day repeat-dose toxicity study.

Some compounds have structural isomers of which one is apparently carcinogenic, and the other not. Because of the similarity of their chemical structures, comparisons of their effects can allow gene expression elicited in response to the basic skeletons of the isomers to be disregarded. We compared the gene expression profiles of male Fischer 344 rats administered by daily oral gavage up to 28 days using an in-house oligo microarray. 2-Acetylaminofluorene (2-AAF), 2,4-diaminotoluene (2,4-DAT), 2-nitropropane (2-NP), and 2-nitro-p-phenylenediamine (2-NpP) are hepatocarcinogenic. However, their isomers, 4-acetylaminofluorene (4-AAF), 2,6-diaminotoluene (2,6-DAT), 1-nitropropane (1-NP), and 4-nitro-o-phenylenediamine (4-NoP), are non-hepatocarcinogenic. Because of the limited carcinogenicity of 2-NpP, we attempted to perform two-parametric comparison analyses with (1) a set of 4 isomers: 2-AAF, 2,4-DAT, 2-NP, and 2-NpP as "carcinogenic", and 4-AAF, 2,6-DAT, 1-NP, and 4-NoP as "non-carcinogenic"; and (2) a set of 3 isomers: 2-AAF, 2,4-DAT, and 2-NP, as "carcinogenic", and 4-AAF, 2,6-DAT, and 1-NP as "non-carcinogenic". After ratio filtering and Welch's approximate t-test analysis, 54 and 28 genes were selected from comparisons between the sets of 3 and 4 isomers, respectively, for day 28 data. Using hierarchical clustering analysis with the 54 or 28 genes, 2-AAF, 2,4-DAT, and 2-NP clustered into a "carcinogenic" branch. 2-NpP was in the same cluster as 4-NoP and 4-AAF. This clustering corresponded to the previous finding that 2-NpP is not carcinogenic in male Fischer 344 rats, which indicates that comparing the differences in gene expression elicited by different isomers is an effective method of developing a prediction system for carcinogenicity.

Animals↗

PubMed2006

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. We selected 39 chemicals, including 17 rat hepatocarcinogens and eight compounds demonstrating carcinogenicity in organs other than the liver. The remaining 14 were non-carcinogens. When rat hepatoma cells (MH1C1) were treated with the chemicals for 3 days at a non-toxic dose, analysis of gene expression changes with our in-house microarray allowed a set of genes to be identified differentiating hepatocarcinogens from non-carcinogens, and all carcinogens from non-carcinogens, by statistical methods. Moreover, optimization of the two gene sets for classification with an SVM and LOO-CV resulted in selection of 39 genes. The highest predictivity was achieved with 207 genes for differentiation between non-hepatocarcinogens and non-carcinogens. The overlap between the two selected gene sets encompassed 26 genes. This gene set contained significant genes for prediction of carcinogenicity, with a concordance of 84.6% by LOO-CV SVM. Using nine external samples, correct prediction of carcinogenicity by SVM was 88.9%. These results indicate that short-term bioassay systems for carcinogenicity using gene expression profiling in hepatoma cells have great promise.

Animals↗

PubMed2006

Toxicity of di(2-ethylhexyl)phthalate (DEHP) and di(2-ethylhexyl)adipate (DEHA) under conditions of renal dysfunction induced with folic acid in rats: enhancement of male reproductive toxicity of DEHP is associated with an increase of the mono-derivative.

F344 male rats were given five consecutive weekly subcutaneous injections of folic acid for induction of chronic renal dysfunction and then di(2-ethylhexyl)phthalate (DEHP) or di(2-ethylhexyl)adipate (DEHA) in the diet at a concentration of 0, 6000 or 25,000 ppm for 4 weeks in order to investigate whether male reproductive toxicity of the two chemicals might be enhanced under conditions of renal disease. Control animals also received DEHP or DEHA in the same manner but without folic acid pretreatment. Decreased testicular weights, seminiferous atrophy with vacuolization of sertoli cells and diminished sperm counts were more prominent in rats given folic acid and then 25,000 ppm DEHP as compared to those exposed to DEHP alone. No such reproductive toxicity was evident in rats given 6000 ppm DEHP or either dose of DEHA. An increased concentration of the mono-derivative of DEHP (mono(2-ethylhexyl)phthalate, MEHP) in the blood, testis and urine was considered relevant to the enhanced reproductive toxicity observed with DEHP.

Adipates↗

PubMed2006

Complete regression of experimental prostate cancer in nude mice by repeated hyperthermia using magnetite cationic liposomes and a newly developed solenoid containing a ferrite core.

BACKGROUND: Magnetite cationic liposomes (MCLs) can be used to induce hyperthermia because they generate heat in an alternating magnetic field (AMF). This study aimed at developing more practical method for MCL hyperthermia examining the effect of MCL-induced hyperthermia on human prostate cancer in vivo. MATERIALS AND METHODS: A newly developed AMF generator incorporating a solenoid with a ferrite core (FC) was used. Human prostate cancer cells (PC-3 and LNCap) were injected subcutaneously into nude mice. MCLs were injected into tumor nodule and the mice were exposed into AMF three times at 24-hr intervals (repeated hyperthermia; RH) until complete tumor regression was observed. RESULTS: Irradiation with an AMF generated by newly developed device can adequately increase the temperature of tumor tissue. Frequent RH resulted in complete tumor regression in all nude mice. CONCLUSION: RH using MCLs may be a promising new therapy for hormone-refractory human prostate cancer in the future.

Animals↗

PubMed2006

Expression of prothymosin alpha is correlated with development and progression in human prostate cancers.

BACKGROUND: Our previous study clearly demonstrated that decreased expression of prothymosin alpha (PTMA) was associated with inhibition of rat prostate carcinogenesis by isoflavones. The purpose of the present investigation was to provide a better understanding of the role of PTMA in human prostate cancers. METHODS AND RESULTS: PTMA expression in 68 prostate cancer cases and in prostate cancer cell lines was examined by immunohistochemistry and immunoblotting, and its levels were increased with progression from normal epithelium, through prostatic intraepithelial neoplasia (PIN) to carcinomas, correlating with the Gleason's pattern. All cell lines studied (LNCaP, 22Rv1, DU145, and PC3) showed high PTMA expression compared with prostate epithelial cells (PrEC). Knockdown of PTMA expression in PC3 cells by RNAi resulted in the inhibition of both cell growth and invasion in vitro. CONCLUSIONS: The present study clearly demonstrated that PTMA expression is intimately involved in the differentiation and progression of human prostate cancers, and could be a target for therapy and diagnostic purposes.

Autopsy↗

PubMed2006

Differences between latent and clinical prostate carcinomas: lower cell proliferation activity in latent cases.

BACKGROUND: Biological significance of prostate latent cancers as early phase of clinical cancers has been controversial. The characterization of the latent cancer may be important to investigate differences between latent and clinical prostate cancers. METHODS: Latent cancers of the prostate, discovered at autopsy in men with no prior treatment for prostate disease and clinical prostate cancers, were compared for cell proliferation activities with parameters such as markers Ag-nucleolar organizer regions (AgNOR), topoisomerase II-alpha, and Ki-67. We also immunohistochemically studied alpha-methylacyl-CoA racemase (AMACR) expression that was recently identified as a possible positive marker of the prostate cancers. We analyzed 50 latent cancers and 50 clinical cancers, and samples were analyzed with Gleason grades or tumor volume. RESULTS: In the latent cancers, Gleason grades 1-4 were observed, but in the clinical cancers Gleason grades 2-5 were recognized. Cell proliferation activities were significantly lower in the latent cancers in Gleason grade 3, and similar results were obtained but without statistical significance in Gleason grades 2 and 4. When analysis was performed according to the tumor size, it was shown that the growth activities of the tumor of the clinical cancer were higher than the latent cancer. CONCLUSIONS: These results indicate that proliferation activities of the latent cancers were lower than the clinical cancers at the same Gleason grades. The data also suggest that latent cancers are just of preclinical stage and there is a possibility to progress to clinical ones by changing life style and longer life expectancy.

Antigens, Neoplasm↗

PubMed2006

Persistence of prostatic intraepithelial neoplasia after effective chemoprevention of microscopic prostate cancer with antiandrogen in a rat model.

PURPOSE: We determined the chemopreventive effect of the antiandrogen bicalutamide (Zeneca Co., Ltd., Osaka, Japan) on Fisher 344 rat prostate carcinogenesis induced by DMAB (3,2'-dimethyl-4-aminobiphenyl) (Nard Co., Ltd., Osaka, Japan). We have previously reported that rat prostate microscopic carcinogenesis in this model was paradoxically enhanced when continuous treatment with bicalutamide was begun 20 weeks after the initiation of DMAB. In the current study we determined whether antiandrogen would promote or suppress the prostate carcinogenesis when administration was begun at a later period of carcinogenesis. MATERIALS AND METHODS: DMAB at a dose of 50 mg/kg was injected subcutaneously into all animals 10 times at 2-week intervals. To clarify the target lesions of bicalutamide we used 2 control groups (groups 1 and 2). Animals in groups 1 and 2 were autopsied at 60 and 74 weeks, respectively, after the initiation of DMAB. Treatment with bicalutamide began in the 60th week in group 3 rats and continued for 14 weeks. They were sacrificed in the 74th week. RESULTS: Microscopic cancer was revealed in 27% of group 1 rats and the incidence was increased to 42% in group 2 (statistically not significant). Delayed bicalutamide treatment significantly suppressed the cancer lesion. No cancerous lesion was detected in the ventral or other lobes of the prostate of the rats in group 3. In contrast, bicalutamide did not affect the incidence of PIN. The difference in the incidence of PIN in groups 2 and 3 (84% and 78%, respectively) was not significant. CONCLUSIONS: The current investigation indicates that, if bicalutamide is started in the later period, it can efficiently eradicate existing microscopic cancer. Despite this suppressive effect on microscopic cancer bicalutamide permits the persistence of PIN. The latter finding suggests that the sensitivity of PIN to antiandrogen might be more complicated than previously recognized.

Aminobiphenyl Compounds↗

PubMed2006

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 2.8 mg/kg leuprorelin, prostate weights and serum testosterone levels were significantly decreased compared to values for transgenic controls. Histopathological findings revealed that the incidence of prostatic adenocarcinomas was significantly reduced in ventral, dorsal and lateral lobes of the prostate, correlating with decreased expression of SV40 Tag oncoprotein as well as inhibition of DNA synthesis and proliferation of epithelial cells in neoplastic lesions of the ventral prostate. Microarray analysis further showed leuprorelin acetate to significantly inhibit testicular steroidogenesis, suppressing the expression of SV40 Tag oncoprotein and altering the expression of a large number of genes which might be involved in the inhibition of prostate cancer progression in this rat model.

Adenocarcinoma↗

PubMed2006

Pitfalls with MRI evaluation of prostate cancer detection: comparison of findings with histopathological assessment of retropubic radical prostatectomy specimens.

INTRODUCTION: To assess differences between MRI findings and histopathologically defined prostate cancer localization, we compared clinical results with mapping of radical prostatectomy specimens, and conducted a retrospective MRI cancer localization re-assessment by a urologist-technician after surgery. METHODS: We performed MRI for a total of 37 suspected prostate cancer patients. Subsequently, all underwent retropubic radical prostatectomy after prostate biopsy for confirmation of the diagnosis. All the specimens were studied histopathologically with serial sectioning using a whole organ approach. RESULTS: Of the 37 patients, 26 had positive MRI findings. All the surgical specimens contained cancerous lesions, and 23 had multiple foci. Twenty-four of the MRI-positive cases (92.3%) demonstrated coincidence of both MRI and histopathologically defined lesions. In the single focus cases, 78.6% (11/14) demonstrated exact coincidence, but in the multifocal cases there were no cases with exact coincidence of MRI and histopathological findings (0/23). CONCLUSION: MRI evaluation cannot be considered an effective diagnostic tool in itself for detection of prostate cancers because sensitivity is far from satisfactory, especially in multi-focal cases.

Aged↗

PubMed2006

Lack of hinokitiol (beta-thujaplicin) carcinogenicity in F344/DuCrj rats.

Chronic toxicity and carcinogenicity of hinokitiol (beta-thujaplicin), used as an antibiotic and fungicidal agent of a food additive, was examined in both sexes of F344/DuCrj (F344) rats. In this chronic toxicity study, groups of 10 rats of each sex were given a diet containing hinokitiol at doses of 0, 0.005, 0.015 and 0.05% for 52 weeks. No treatment-related adverse effects were noted in the survival rate, general condition, body weights, food consumption, urinalysis, hematology and clinical chemistry. Slight but significant elevation of spleen and liver weights was noted in both sexes given 0.05% hinokitiol, along with an increase in hemosiderin deposits in male spleens, related to chelator binding of iron, together with slight centrilobular hypertrophy of male hepatocytes. However, these alterations were negligible and not toxicologically significant. In the carcinogenicity study, groups of 50 female and 50 male rats were given a diet containing hinokitiol at doses of 0, 0.005, 0.015 and 0.05% (excluding 0.005% in females). No treatment-related changes in survival rate, general condition, body weight, food consumption, hematology and organ weights were noted. Detailed histopathological examination revealed no treatment-related increase in the incidences of any neoplastic lesions. The results demonstrate that hinokitiol is not carcinogenic in F344 rats of either sex.

Animals↗

PubMed2005

Lack of prophylactic effect of incadronate on skeletal lesions associated with implants of prostate cancer.

OBJECTIVES: To evaluate prophylactic effects of bisphosphonate (BP) on skeletal lesions induced by prostate cancer (CaP). METHODS: Incadronate, a third-generation BP, was administered weekly for 4 weeks, with or without 4-week pre-administration, to rats whose calvaria had been inoculated with syngeneic CaP tissue. RESULTS: The transplanted CaP grew up and caused bone resorption with osteoblastic changes regardless of incadronate treatment. Although decrease in bone resorption accompanied by reduced number of osteoclasts was shown by incadronate administration, pre-administration had no additional inhibitory effect on bone destruction and Ki-67 labeling indices of CaP cells were not altered. CONCLUSIONS: These results indicate that application of BP alone is not sufficient to prevent skeletal lesions due to CaP in patients with high risk of bone metastases although it is useful in inhibition of cancer-induced bone resorption with osteoblastic changes.

Animals↗

PubMed2005

Anticancer effect of hyperthermia on prostate cancer mediated by magnetite cationic liposomes and immune-response induction in transplanted syngeneic rats.

BACKGROUND: The hyperthermic effect of magnetic particles was examined in rat prostate cancer in vivo. Magnetic cationic liposomes (MCLs) have a positive surface charge and generate heat in an alternating magnetic field (AMF) due to hysteresis losses. METHODS: Rat prostate cancer cells (PLS 10; androgen independent) were injected subcutaneously into the flank of F344 rats. MCLs were injected into rat prostate cancer nodules that had grown to 5-6 mm in diameter, and were then exposed to an AMF. Tumor growth rates were measured. To examine whether hyperthermia caused immune induction for PLS 10, cytotoxicity assays and immunohistochemical staining for CD3, CD4, CD8, and Heat Shock Protein (HSP) 70 were performed. RESULT: The tumor temperature increased to 45 degrees C whereas the body temperature remained at around 38 degrees C. Tumor regression was observed in the hyperthermic group. CD3, CD4, and CD8 immunocytes were present in the tumor tissues of the rats exposed to hyperthermia, but they were not detected in any of the tumor tissue of untreated rats. HSP70 also appeared in the viable area at its boundary with the necrotic area. The cytotoxic activity of tumor-transplanted rats for PLS 10 cells increased in hyperthermic-treatment rats. CONCLUSION: These results suggest that hyperthermia using MCLs is an effective therapy for prostate cancer, since this treatment appears to kill the prostate cancer cells not only directly by heating but also by inducing an immune response. This therapy may cure not only the primary lesion but also metastatic lesions.

Animals↗

PubMed2005

Lack of carcinogenicity of L-isoleucine in F344/DuCrj rats.

The carcinogenic potential of L-isoleucine, used as a food fortifier, was examined in both sexes of F344 rats. Groups of 50 female and 50 male animals were given diet containing L-isoleucine at concentrations of 0%, 2.5% or 5.0%. No treatment-related changes in the survival rate, general condition, body weight, food consumption, urinalysis, hematology or clinical chemistry data and organ weights were noted. Detailed histopathological examination revealed no treatment-related increase in the incidences of any non-neoplastic or neoplastic lesions. The results indicate that L-isoleucine is not carcinogenic in F344 rats of either sex.

Animals↗

PubMed2005

Parp-1 deficiency does not enhance liver carcinogenesis induced by 2-amino-3-methylimidazo[4,5-f]quinoline in mice.

The susceptibility of poly(ADP-ribose) polymerase-1 (Parp-1) knockout mice to 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)-induced liver carcinogenesis was analyzed. Twelve-week-old male Parp-1(+/+), Parp-1(+/-) and Parp-1(-/-) mice of the C57BL/6 congenic strain were fed a diet containing IQ at a concentration of 300 ppm or a control diet for 60 weeks. Hepatocellular carcinomas were observed only in 1/19, 2/18 and 1/17 of the Parp-1(-/-), Parp-1(+/-) and Parp-1(+/+) mice, respectively. Parp-1 deficiency did not affect the susceptibility of mice to carcinogenicity of IQ, which produces bulky DNA adducts that are repaired mainly through the nucleotide excision repair pathway. This result is in sharp contrast to the increased susceptibility of Parp-1(-/-) mice to carcinogenesis induced by alkylating agents that produce DNA damage repaired mainly through base excision repair and DNA strand break repair pathways.

Adenoma, Liver Cell↗

PubMed2005

Lack of potential of low dose N-nitrosodimethylamine to induce preneoplastic lesions, glutathione S-transferase placental form-positive foci, in rat liver.

Induction of liver lesions in male F344 rats by the genotoxic and carcinogenic N-nitrosodimethylamine (NDMA) was studied at a wide range of dose levels, i.e. from 0.001 to 10 ppm, in drinking water for 16 weeks. Dose related and statistically significant increase of glutathione S-transferase placental form-positive foci, endpoint markers for hepatocarcinogenesis in rats, at 1 and 10 ppm dose groups was obtained, but no increment in foci could be detected with the lower doses (0.001, 0.01, and 0.1 ppm). This finding of a no-observed effect level supports our hypothesis that a threshold, at least in practical terms, exists in carcinogenesis proposed on the basis of extensive wide range dose-dependence studies of other genotoxic carcinogens.

Animals↗

PubMed2005

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. Therefore, mRNAs extracted from GST-P positive foci and the surrounding liver tissue in each group were analyzed to explore mechanisms in detail. The results suggest that suppression of syndecan-2 (Sdc2) and induction of cell cycle arrest through a p21-dependent pathway might have counter-acted any promotion effects of up-regulation of CYP1A2.

Acetyltransferases↗

PubMed2005

Linkage and microarray analyses of susceptibility genes in ACI/Seg rats: a model for prostate cancers in the aged.

ACI/Seg (ACI) rats develop prostate cancers spontaneously with aging, similar to humans. Here, to identify genes involved in prostate cancer susceptibility, we did linkage analysis and oligonucleotide microarray analysis. Linkage analysis was done using 118 effective rats, and prostate cancer susceptibility 1 (Pcs1), whose ACI allele dominantly induced prostate cancers, was mapped on chromosome 19 [logarithm of odds (LOD) score of 5.0]. PC resistance 1 (Pcr1), whose ACI allele dominantly and paradoxically suppressed the size of prostate cancers, was mapped on chromosome 2 (LOD score of 5.0). When linkage analysis was done in 51 rats with single or no macroscopic testicular tumors, which had larger prostates and higher testosterone levels than those with bilateral testicular tumors, Pcs2 and Pcr2 were mapped on chromosomes 20 and 1, respectively. By oligonucleotide microarray analysis with 8,800 probe sets and confirmation by quantitative reverse transcription-PCR, only two genes within these four loci were found to be differentially expressed >1.8-fold. Membrane metalloendopeptidase (Mme), known to inhibit androgen-independent growth of prostate cancers, on Pcr1 was expressed 2.0- to 5.5-fold higher in the ACI prostate, in accordance with its paradoxical effect. Cdkn1a on Pcs2 was expressed 1.5- to 4.5-fold lower in the ACI prostate. Additionally, genes responsible for testicular tumors and unilateral renal agenesis were mapped on chromosomes 11 and 14, respectively. These results showed that prostate cancer susceptibility of ACI rats involves at least four loci, and suggested Mme and Cdkn1a as candidates for Pcr1 and Pcs2.

Animals↗

PubMed2005

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. We have found the rat bladder carcinoma cell line, BC31, to feature Tbx3 expression detectable by RT-PCR. To investigate its role in such cancer cells, they were transfected with an anti-sense Tbx3 expression vector. The obtained stable transfectant clones showed reduced expression of Tbx3 and much slower cell growth, as compared with mock transfectants, and many apoptotic cells were observed under normal culture conditions. These results indicate that Tbx3 is a negative regulator of apoptosis in bladder normal epithelial cells and suppression of Tbx3 expression causes inhibition of cell proliferation and induction of apoptosis in BC31, a rat bladder carcinoma cells.

Animals↗