掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

DOI： 10.1093/bbb/zbad164

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

DOI： 10.3390/biom14010036

PubMed

<p>Pulmonary emphysema is primarily attributable to prolonged exposure to cigarette smoke. Novel tobacco substitutes, such as heated tobacco products, have emerged as healthier alternatives to cigarettes. The effects of short-term inhalation of a heated tobacco product, Ploom TECH+ (PT+), on the lungs of mice were compared with those of 3R4F reference cigarettes. Male 10-week-old C57BL mice were exposed to clean air (control), 3R4F, or PT+ for 1 h/d, 5 d/week for two or four weeks. After four weeks of exposure, the number of inflammatory cells and proportion of neutrophils and lymphocytes in the bronchoalveolar lavage fluid and the number of macrophages in the lung tissue increased significantly in mice exposed to 3R4F but not in those exposed to PT+. Changes in the expression of genes related to inflammation-related factors were observed in the lung tissues of mice exposed to 3R4F for two and four weeks. Chemokine (C-C motif) ligand 17, resistin-like alpha, and lipocalin 2 were among the upregulated genes. In our previous short-term tobacco inhalation study, these genes were identified as useful markers of emphysema effects induced by exposure to cigarette smoke from Peace cigarettes, detectable before pulmonary histological changes appeared. These effects were not observed in the PT+-exposed mice. These data suggest that PT+ caused less damage to the lungs of mice than 3R4F, particularly regarding the induction of emphysema.</p>

DOI： 10.1293/tox.2024-0069

<p>Tobacco smoking is a major risk factor for human cancers including urinary bladder carcinoma. In a previous study, nicotine was shown to enhance rat urinary bladder carcinogenesis in a two-stage carcinogenesis model. In this study, we examined the progressive effects of nicotine on bladder carcinogenesis in F344 rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). Nicotine, administered in drinking water for 52 weeks following 4 weeks of BBN treatment, significantly increased the incidence and multiplicity of invasive urothelial carcinoma in a dose-dependent manner. The Ki67 labeling index of bladder papillomas was significantly increased by nicotine in a dose-dependent manner. However, nicotine treatment did not affect the incidence or total number of tumors, and nicotine administration alone for 52 weeks did not result in any neoplastic lesions. These data suggest that while nicotine does not initiate carcinogenesis, it has the potential to promote invasive urinary cancers.</p>

DOI： 10.1293/tox.2024-0087

<p>【背景】ヒトへの吸入暴露が想定される化学物質の毒劇物判定、並びに化学品の分類および表示に関する世界調和システム（GHS）分類は、動物を用いた急性吸入毒性試験による評価が必要である。しかし、大規模な暴露装置を用いた全身吸入暴露試験を実施可能な施設はわずかであり、毒性情報は限定的である。本研究では、吸入による毒劇物判定に利用可能な<i>in vivo</i>試験代替法の確立を目指し、経気管肺内噴霧投与（TIPS）法による急性毒性試験を行い、既報の全身吸入暴露による急性毒性情報との比較検討を実施した。【方法】12週齢の雄F344ラット（6匹/群）に14種の化学物質（GHS区分2：4物質、3：9物質、4以上：1物質）を1時間間隔で4回気管内投与し、投与後14日間観察して剖検した。媒体は生理食塩液を用い、2 mL/kgで投与を実施した。投与量は、<i>in vitro</i>試験代替法として検討しているヒト肺腺癌細胞株（A549）の細胞毒性を指標としたNeutral red assay（A549 NRU assay）におけるLC₅₀値を参考に設定した。また、TIPS法で得られたLD₅₀値の範囲を基に毒劇物/GHS分類を行った。【結果】TIPS法におけるLD₅₀値は、従来の全身吸入暴露法におけるLC₅₀値と同程度またはより低値を示した。毒劇物/GHS区分では、8物質でTIPS法による区分の範囲と全身吸入暴露法による区分が重なったが、6物質ではTIPS法で有害性がより強い区分に分類された。また、TIPS法でより強い急性毒性が認められた6物質のA549 NRU assayにおけるLC₅₀値は、その他の化学物質と比較して低値を示した。【考察】TIPS法によって分類される有害性区分は、細胞傷害性が比較的弱い物質では従来の全身吸入暴露法による分類と概ね一致した。一方、細胞傷害性が強い物質では、TIPS法は吸入暴露法と比較して毒性が強く表れる可能性が示唆された。現在、病理組織学的検査を実施しており、細胞傷害性とTIPS法による急性毒性の関連についての検討を行っている。</p>

DOI： 10.14869/toxpt.51.1.0_p-340

<p>【目的】</p><p>毒物又は劇物は、原則として動物を用いた急性毒性試験におけるLD50・LC50値から判定されており、投与方法には経口、経皮及び吸入が想定されている。一方、近年は<i>in vitro</i>試験等に基づく、毒性や刺激性等から判断する評価法も希求されている。そこで、本研究ではラットを用いた被験物質の経気管肺内噴霧投与法(Trans-tracheal intrapulmonary spraying；TIPS法)を行う際の<i>in vitro</i>投与量設定法として、細胞毒性評価法として使用されているマウス線維芽細胞 3T3を用いたNeutral Red Uptake Cytotoxicity Assay(OECD GD 129)を一部改変し、ヒト肺腺癌細胞株A549を用いた改変Neutral Red Uptake assay (A549 NRU assay)を構築し、試験プロトコールの最適化とその有用性について検討を行った。</p><p></p><p>【方法】</p><p>30種類の被験物質について、それぞれA549 NRU assayを実施し、IC50を算出した。さらに6物質(Acetylacetone、1,2-Dichloroethane、N,N-Dimethylacetamide、N-Dimethylformamide、Glycidol及びPolyacrylic Acid 5000)については、TIPS法で得られたLD50と比較し、A549 NRU assayで得られたIC50値との相関を検討した。</p><p></p><p>【結果と考察】</p><p>A549 NRU assayを用いて30物質の本試験におけるIC50を算出し、良好な再現性も確認できた。うち6物質ではTIPS法でのLD50値と高い相関が得られた。以上より、TIPS法の<i>in vitro</i>投与量設定試験としてA549 NRU assayを構築することができた。</p>

DOI： 10.14869/toxpt.51.1.0_p-299

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

Arsenic is a known human urinary bladder carcinogen. While arsenic is known to cause aberrant DNA methylation, the mechanism of arsenic-triggered bladder carcinogenesis is not fully understood. The goal of this study was to identify aberrant DNA methylation in rat bladder urothelial carcinoma (UC) induced by dimethylarsinic acid (DMAV), a major organic metabolite of arsenic. We performed genome-wide DNA methylation and microarray gene expression analyses of DMAV-induced rat UCs and the urothelium of rats treated for 4 weeks with DMAV. We identified 40 genes that were both hypermethylated and downregulated in DMAV-induced rat UCs. Notably, four genes (CPXM1, OPCML, TBX20, and KCND3) also showed reduced expression in the bladder urothelium after 4 weeks of exposure to DMAV. We also found that CPXM1 is aberrantly methylated and downregulated in human bladder cancers and human bladder cancer cells. Genes with aberrant DNA methylation and downregulated expression in DMAV-exposed bladder urothelium and in DMAV-induced UCs in rats, suggest that these alterations occurred in the early stages of arsenic-induced bladder carcinogenesis. Further study to evaluate the functions of these genes will advance our understanding of the role of aberrant DNA methylation in arsenic bladder carcinogenesis, and will also facilitate the identification of new therapeutic targets for arsenic-related bladder cancers.

DOI： 10.3390/cancers15215274

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

Dimethylarsinic acid (DMA) is a major metabolite in the urine of humans and rats exposed to inorganic arsenicals, and is reported to induce rat bladder carcinogenesis. In the present study, we focused on early pathways of carcinogenesis triggered by DMA that were also active in tumors. RNA expression in the bladder urothelium of rats treated with 0 and 200 ppm DMA in the drinking water for 4 weeks and in bladder tumors of rats treated with 200 ppm DMA for 2 years was initially examined using microarray analysis and Ingenuity Pathway Analysis (IPA). Expression of 160 genes was altered in both the urothelium of rats treated for 4 weeks with DMA and in DMA-induced tumors. IPA associated 36 of these genes with liver tumor diseases. IPA identified the amphiregulin (Areg)-regulated pathway as a Top Regulator Effects Network. Therefore, we focused on Areg and 6 of its target genes: cyclin A2, centromere protein F, marker of proliferation Ki-67, protein regulator of cytokinesis 1, ribonucleotide reductase M2, and topoisomerase II alpha. We confirmed high mRNA expression of Areg and its 6 target genes in both the urothelium of rats treated for 4 weeks with DMA and in DMA-induced tumors. RNA interference of human amphiregulin (AREG) expression in human urinary bladder cell lines T24 and UMUC3 decreased expression of AREG and its 6 target genes and decreased cell proliferation. These data suggest that Areg has an important role in DMA-induced rat bladder carcinogenesis.

DOI： 10.1016/j.toxlet.2023.08.004

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

BACKGROUND: Radiotherapy (RT) has recently been highlighted as a partner of immune checkpoint inhibitors. The advantages of RT include activation of lymphocytes while it potentially recruits immunosuppressive cells, such as myeloid-derived suppressor cells (MDSCs). This study aimed to investigate the mechanism of overcoming treatment resistance in immunologically cold tumours by combining RT and MDSC-targeted therapy. METHODS: The abscopal effects of irradiation were evaluated using MB49 and cisplatin-resistant MB49R mouse bladder cancer cells, with a focus on the frequency of immune cells and programmed cell death-ligand 1 (PD-L1) expression in a xenograft model. RESULTS: MB49R was immunologically cold compared to parental MB49 as indicated by the fewer CD8+ T cells and lower PD-L1 expression. Polymorphonuclear MDSCs increased in both MB49 and MB49R abscopal tumours, whereas the infiltration of CD8+ T cells increased only in MB49 but not in MB49R tumours. Interestingly, PD-L1 expression was not elevated in abscopal tumours. Finally, blocking MDSC in combination with RT remarkably reduced the growth of both MB49 and MB49R abscopal tumours regardless of the changes in the frequency of infiltrating CD8+ T cells. CONCLUSIONS: The combination of RT and MDSC-targeted therapy could overcome treatment resistance in immunologically cold tumours.

DOI： 10.1038/s41416-023-02244-8

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

Diphenylarsinic acid (DPAA), a neurotoxic organic arsenical, is present in groundwater and soil in some regions of Japan owing to illegal dumping. The present study evaluated the potential carcinogenicity of DPAA, including investigating whether bile duct hyperplasia in the liver that was observed in a chronic study on 52 week mouse, develops into a tumor when administered to mice in their drinking water for 78 weeks. DPAA was administered to 4 groups of male and female C57BL/6J mice at concentrations of 0, 6.25, 12.5, and 25 ppm in drinking water for 78 weeks. A significant decrease in the survival rate was found for females in the 25 ppm DPAA group. Body weights of males in the 25 ppm and females in the 12.5 and 25 ppm DPAA groups were significantly lower than those of the controls. Histopathological evaluation of neoplasms in all tissues showed no significant increase in tumor incidence in any organ or tissue of 6.25, 12.5, or 25 ppm DPAA-treated male or female mice. In conclusion, the present study demonstrated that DPAA is not carcinogenic to male or female C57BL/6J mice. Taken together with the fact that the toxic effect of DPAA is predominantly restricted to the central nervous system in humans, and the finding that DPAA was not carcinogenic in a previous 104-week rat carcinogenicity study, our results suggest that DPAA is unlikely to be carcinogenic in humans.

DOI： 10.1293/tox.2022-0111

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

Occupational exposure to aromatic amines is one of the most important risk factors for urinary bladder cancer. When considering the carcinogenesis of aromatic amines, metabolism of aromatic amines in the liver is an important factor. In the present study, we administered ortho-toluidine (OTD) in the diet to mice for 4 weeks. We used NOG-TKm30 mice (control) and humanized-liver mice, established via human hepatocyte transplantation, to compare differences in OTD-induced expression of metabolic enzymes in human and mouse liver cells. We also investigated OTD-urinary metabolites and proliferative effects on the urinary bladder epithelium. RNA and immunohistochemical analyses revealed that expression of N-acetyltransferases mRNA in the liver tended to be lower than that of the P450 enzymes, and that OTD administration had little effect on N-acetyltransferase mRNA expression levels. However, expression of CYP3A4 was increased in the livers of humanized-liver mice, and expression of Cyp2c29 (human CYP2C9/19) was increased in the livers of NOG-TKm30 mice. OTD metabolites in the urine and cell proliferation activities in the bladder urothelium of NOG-TKm30 and humanized-liver mice were similar. However, the concentration of OTD in the urine of NOG-TKm30 mice was markedly higher than in the urine of humanized-liver mice. These data demonstrate differences in hepatic metabolic enzyme expression induced by OTD in human and mouse liver cells, and consequent differences in the metabolism of OTD by human and mouse liver cells. This type of difference could have a profound impact on the carcinogenicity of compounds that are metabolized by the liver, and consequently, would be important in the extrapolation of data from animals to humans.

DOI： 10.1016/j.tox.2023.153483

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

Carbonic anhydrases (CAs) play an important role in maintaining pH homeostasis. We previously demonstrated that overexpression of CA2 was associated with invasion and progression of urothelial carcinoma (UC) in humans. The purpose of the present study was to evaluate the effects of the CA inhibitor acetazolamide (Ace) on N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced bladder carcinogenesis in mice and explore the function of CA2 in muscle invasion by UC. Male mice were treated with 0.025% (experiment 1) or 0.05% BBN (experiment 2) in their drinking water for 10 weeks, then treated with cisplatin (Cis), Ace, or Cis plus Ace for 12 weeks. In experiment 1, the overall incidence of BBN-induced UCs was significantly decreased in the BBN→Ace and BBN→Cis+Ace groups. In experiment 2, the overall incidence of BBN-induced UCs was significantly decreased in the BBN→Cis+Ace group, and the incidence of muscle invasive UC was significantly decreased in both the BBN→Ace and the BBN→Cis+Ace groups. We also show that overexpression of CA2 by human UC cells T24 and UMUC3 significantly increased their migration and invasion capabilities, and that Ace significantly inhibited migration and invasion by CA2-overexpressing T24 and UMUC3 cells. These data demonstrate a functional association of CA2 with UC development and progression, confirming the association of CA2 with UC that we had shown previously by immunohistochemical analysis of human UC specimens and proteome analysis of BBN-induced UC in rats. Our finding that inhibition of CA2 inhibits UC development and muscle invasion also directly confirms that CA2 is a potential therapeutic target for bladder cancers.

DOI： 10.1111/cas.15467

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

In the present study, potential molecular biomarkers of NASH hepatocarcinogenesis were investigated using the STAM mice NASH model, characterized by impaired insulin secretion and development of insulin resistance. In this model, 2-days-old C57BL/6N mice were subjected to a single subcutaneous (s.c.) injection of 200 μg streptozotocin (STZ) to induce diabetes mellitus (DM). Four weeks later, mice were administered high-fat diet (HFD) HFD-60 for 14 weeks (STAM group), or fed control diet (STZ group). Eighteen-week-old mice were euthanized to allow macroscopic, microscopic, histopathological, immunohistochemical and proteome analyses. The administration of HFD to STZ-treated mice induced significant fat accumulation and fibrosis development in the liver, which progressed to NASH, and rise of hepatocellular adenomas (HCAs) and carcinomas (HCCs). In 18-week-old animals, a significant increase in the incidence and multiplicity of HCAs and HCCs was found. On the basis of results of proteome analysis of STAM mice HCCs, a novel highly elevated protein in HCCs, cache domain-containing 1 (CACHD1), was chosen as a potential NASH-HCC biomarker candidate. Immunohistochemical assessment demonstrated that STAM mice liver basophilic, eosinophilic and mixed-type altered foci, HCAs and HCCs were strongly positive for CACHD1. The number and area of CACHD1-positive foci, and cell proliferation index in the area of foci in mice of the STAM group were significantly increased compared to that of STZ group. In vitro siRNA knockdown of CACHD1 in human Huh7 and HepG2 liver cancer cell lines resulted in significant inhibition of cell survival and proliferation. Analysis of the proteome of knockdown cells indicated that apoptosis and autophagy processes could be activated. From these results, CACHD1 is an early NASH-associated biomarker of liver preneoplastic and neoplastic lesions, and a potential target protein in DM/NASH-associated hepatocarcinogenesis.

DOI： 10.3390/cancers13061216

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

To uncover mechanisms and explore novel biomarkers of obesity, type 2 diabetes (T2DM) and nonalcoholic steatohepatitis (NASH)-associated hepatocarcinogenesis, cellular and molecular alterations in the liver, and hepatocellular carcinomas (HCCs) were investigated in NASH model 60-week-old Tsumura, Suzuki, Obese Diabetic (TSOD) mice and NASH HCC patients. Markedly elevated lipid deposition, inflammation, fibrosis, and peroxisome proliferation in the liver, preneoplastic lesions, and HCCs of TSOD mice were accompanied by accumulation of polysaccharides in the cellular cytoplasm and nuclei and increase of oxidative DNA damage marker, 8-hydroxydeoxyguanosine (8-OHdG) formation in the liver and altered foci. Metabolomics of TSOD mice HCCs demonstrated significant elevation of the concentration of amino acid L-arginine, phosphocreatine, S-adenosylmethionine/S-adenosylhomocysteine ratio, adenylate, and guanylate energy charges in coordination with tremendous rise of glucose metabolites, mostly fructose 1,6-diphosphate. L-arginine accumulation in HCCs was associated with significant under-expression of arginase 1 (ARG1), suppression of the urea cycle, methionine and putrescine degradation pathways, activation of Ser and Thr kinase Akt AKT, phosphoinositide 3-kinase (PI3K), extracellular signal-regulated kinase 1/2 (ERK1/2) kinases, β-catenin, mammalian target of rapamycin (mTOR), and cell proliferation. Furthermore, clinicopathological analysis in 20 metabolic syndrome/NASH and 80 HCV-positive HCC patients demonstrated significant correlation of negative ARG1 expression with poor tumor differentiation, higher pathological stage, and significant decrease of survival in metabolic syndrome/NASH-associated HCC patients, thus indicating that ARG1 could become a potential marker for NASH HCC. From these results, formation of oxidative stress and 8-OHdG in the DNA and elevation of glucose metabolites and L-arginine due to ARG1 suppression in mice liver cells are the important characteristics of T2DM/NASH-associated hepatocarcinogenesis, which may take part in activating oxidative stress resistance, synthesis of phosphocreatine, cell signaling, methylation, and proliferation.

DOI： 10.3390/ijms21207746

PubMed

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

Pregnant CD-1 mice received 200 ppm dimethylarsinic acid (DMA) in the drinking water from gestation day 8-18, and tumor formation was assessed in offspring at the age of 84 weeks. DMA elevated the incidence of lung adenocarcinoma (10.0%) and total tumors (33.3%) in male offspring compared to male control offspring (1.9 and 15.1%, respectively). DMA also elevated the incidence of hepatocellular carcinoma (10.0%) in male offspring compared to male control offspring (0.0%). DMA and its metabolites were detected in the lungs of transplacental DMA-treated neonatal mice. Transplacental DMA exposure increased cell proliferation in the epithelium in the lungs of both neonatal and 6-week-old male mice. Microarray and real-time PCR analyses detected high expression of keratin 8 (Krt8) in the lungs of both neonatal and 6-week-old DMA-treated mice. Western blot analysis indicated that DMA elevated methylation of histone H3K9, but not H3K27, in the lungs of male mice. Importantly, chromatin immunoprecipitation sequencing (ChIP-seq) analysis using an H3K9me3 antibody found differences in heterochromatin formation between mice exposed to DMA and the controls. Notably, ChIP-seq analysis also found regions of lower heterochromatin formation in DMA-treated mice, and one of these regions contained the Krt8 gene, agreeing with the results obtained by microarray analysis. High expression of Krt8 was also detected in adenoma and adenocarcinoma of the lung in male offspring. Overall, these data indicate that transplacental DMA treatment enhanced lung and liver carcinogenesis in male mice. In the lung, DMA caused aberrant methylation of histone H3K9, increased Krt8 expression, and enhanced cell proliferation.

DOI： 10.1007/s00204-020-02665-x

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

Recent epidemiological studies have indicated that occupational exposure to the aromatic amine acetoaceto-o-toluidide (AAOT) was associated with a marked increase in urinary bladder cancers in Japan. However, little is known about the carcinogenicity of AAOT. To evaluate the urinary bladder carcinogenicity of AAOT, male and female F344 rats were treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) for 4 weeks followed by dietary administration of 0, 0.167, 0.5, or 1.5% AAOT for 31 weeks. The incidences and multiplicities of bladder tumors were significantly increased in the 0.5 and 1.5% groups of male and female rats in a dose-response manner. AAOT and seven downstream metabolites were detected in the urine of the male and female rats administered AAOT with levels increasing in a dose-dependent manner. The most abundant urinary metabolite of AAOT was the human bladder carcinogen o-toluidine (OTD), which was at least one order of magnitude higher than AAOT and the other AAOT metabolites. In a second experiment, male F344 rats were administered 0, 0.167, or 1.5% AAOT for 4 weeks. Gene expression analyses revealed that the expression of JUN and its downstream target genes was increased in the urothelium of male rats treated with 1.5% AAOT. These results demonstrate that AAOT promotes BBN-induced urinary bladder carcinogenesis in rats and suggest that overexpressed of JUN and its downstream target genes may be involved the bladder carcinogenicity of AAOT. In conclusion, AAOT, like other carcinogenic aromatic amines, is likely to be a carcinogen to the urinary bladder, and OTD metabolized from AAOT is the ultimate carcinogen.

DOI： 10.1007/s00204-019-02605-4

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2019 The Author(s). Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved. Quantitative analysis of the mutagenicity and carcinogenicity of the low doses of genotoxic carcinogens present in food is of pressing concern. The purpose of the present study was to determine the mutagenicity and carcinogenicity of low doses of the dietary genotoxic carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Male F344 gpt delta transgenic rats were fed diets supplemented with 0, 0.1, 1, 10 or 100 ppm IQ for 4 weeks. The frequencies of gpt transgene mutations in the liver were significantly increased in the 10 and 100 ppm groups. In addition, the mutation spectra was altered in the 1, 10 and 100 ppm groups: Frequencies of G:C to T:A transversion were significantly increased in groups administered 1, 10 and 100 ppm IQ in a dose-dependent manner, and the frequencies of G:C to A:T transitions, A:T to T:A transversions and A:T to C:G transversions were significantly increased in the 100 ppm group. Increased frequencies of single base pair deletions and Spi- mutants in the liver, and an increase in glutathione S-transferase placental form (GST-P)-positive foci, a preneoplastic lesion of the liver in rats, was also observed in the 100 ppm group. In contrast, neither mutations nor mutation spectra or GST-P-positive foci were statistically altered by administration of IQ at 0.1 ppm. We estimated the point of departure for the mutagenicity and carcinogenicity of IQ using the no-observed-effect level approach and the Benchmark dose approach to characterise the dose-response relationship of low doses of IQ. Our findings demonstrate the existence of no effect levels of IQ for both in vivo mutagenicity and hepatocarcinogenicity. The findings of the present study will facilitate an understanding of the carcinogenic effects of low doses of IQ and help to determine a margin of exposure that may be useful for practical human risk assessment.

DOI： 10.1093/mutage/gez015

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© The Author(s) 2019. Published by Oxford University Press on behalf of the Society of Toxicology. Acetoaceto-o-toluidide (AAOT) is made from ortho-toluidine (OTD) and is used for the synthesis of pigments. A report of occupational urinary bladder carcinomas in Japanese workers chronically exposed to OTD and AAOT has recently been published. OTD is a well-known human urinary bladder carcinogen; however, little is known about the toxicity and the carcinogenicity of AAOT. The aim of the present study is to evaluate the toxic effects of AAOT on urinary bladder epithelium. In vitro, the cytotoxicities of AAOT and OTD were evaluated in rat (MYP3) and human (1T1) urothelial cells. The LC50 of AAOT was higher than that of OTD in both MYP cells and 1T1 cells. In vivo, 6-week-old male and female F344 rats were fed diets supplemented with 0%, 1.5%, or 3% AAOT for 4 weeks. Incidences of simple hyperplasia, cell proliferative activity, and γ-H2AX expression, which is a novel marker for the prediction of carcinogenicity, were significantly increased in a dose-dependent manner in the bladder urothelium of male and female rats administered AAOT. Furthermore, in male and female rats administered AAOT, the major urine metabolite of AAOT was OTD. These results demonstrate that AAOT has proliferation-enhancing activity and suggest that OTD metabolized from AAOT may play a pivotal role in the deleterious effects of AAOT in rats. The results of the present study also indicate that AAOT, like other carcinogenic aromatic amines, is likely to be a human bladder carcinogen.

DOI： 10.1093/toxsci/kfz051

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

© 2019, Japanese Society of Toxicology. All rights reserved. — Zinc (Zn) is an essential element, but excess amounts are known to cause neurotoxic effects. The risk of excessive Zn intake is increased by supplementing food intake with dietary supplements. Ageing affects many cellular processes that predispose individuals to neurodegeneration. Indeed, the prevalence of senile dementia such as Alzheimer’s disease, Parkinson’s disease, and vascular-type dementia increases with age. As such, we investigated the effects of long-term exposure to excess Zn on learning and memory in aged mice. ICR-JCL female mice (aged 26 weeks) were administered 0, 200, or 500 ppm Zn as zinc chloride in drinking water for 30 weeks. After 30-week administration, aged female animals were subjected to Y-maze, novel object recognition, and step-through passive avoidance tests. Chronic exposure to Zn did not inhibit learning and memory in the Y-maze test, but dose-dependently inhibited learning and memory in novel object recognition and step-through passive avoidance tests. These results indicate the potential for chronic Zn exposure to dose-dependently inhibit both long-term and novel object recognition memory. Results of microarray analysis revealed significant changes in gene expression of transthyretin and many olfactory receptors in the hippocampus of Zn-treated mice.

DOI： 10.2131/jts.44.681

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

© 2019 The Japanese Society of Toxicologic Pathology. Diphenylarsinic acid (DPAA), a neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping. The purpose of the present study was to evaluate the potential toxicity of DPAA when administered to mice in their drinking water for 52 weeks. DPAA was administered to mice at concentrations of 0, 6.25, 12.5, and 25 ppm in their drinking water for 52 weeks. There were no significant differences in final body weights between the control groups and the DPAA treatment groups in male or female mice. Relative liver weights were significantly increased in males treated with 25 ppm DPAA, and absolute liver weights were significantly decreased in female mice treated with 25 ppm DPAA. In female mice, cholangitis and simple bile duct hyperplasia were observed in the 12.5 and 25 ppm DPAA groups, and focal necrosis of hepatocytes was observed in the 25 ppm DPAA group. Proteomic analysis and Ingenuity Pathway Analysis identified 18 proteins related to hepatotoxicity that were overexpressed in the female 25 ppm group. The phase I metabolic enzyme CYP2E1 was one of these overexpressed proteins. Immunostaining confirmed high expression of CYP2E1 in the livers of females in the 25 ppm group. These results suggest that DPAA is toxic to the intrahepatic bile duct epithelium and hepatocytes in female mice and that CYP2E1 might be involved in DPAA-associated toxicity. The no-observed-adverse-effect levels of DPAA were 12.5 ppm (1.6 mg/kg bw/day) for males and 6.25 ppm (1.1 mg/kg bw/day) for females under the conditions of this study.

DOI： 10.1293/tox.2018-0067

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2018, Spandidos Publications. All rights reserved. Androgen signal has been recently suggested to be associated with the progression of bladder cancer. Steroid sulfatase (STS) is a steroid sulfate activation enzyme, considered to be one of the key enzymes in the androgen signaling pathway. However, the role of STS in bladder cancer has not been elucidated. The purpose of the present study was to determine the clinical and functional significance of STS in bladder cancer. Immunohistochemical analysis of surgical specimens obtained by radical cystectomy (n=114) demonstrated that overexpression of STS was associated with the invasion of bladder cancer, as evidenced by the incidence of STS-positive cancers (11.5 and 37.1% in non-muscle invasive and muscle invasive bladder cancers, respectively; P=0.003). STS-positive cancer demonstrated shorter recurrence-free survival and cancer-specific survival (P=0.0027 and 0.0030, respectively). Furthermore, knockdown of STS significantly reduced cell migration and invasion capacities of bladder cancer cells (P<0.001 and P=0.005, respectively), accompanied by the upregulation of E-cadherin and downregulation of vimentin. In summary, the present study demonstrated that STS promotes the invasion capability of bladder cancer via regulation of the epithelial-mesenchymal transition, and may be a useful marker for predicting the progression of bladder cancers.

DOI： 10.3892/etm.2018.6787

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Non-alcoholic steatohepatitis (NASH) can cause liver fibrosis and cirrhosis, with final progression to hepatocellular carcinoma (HCC) in some cases. Various factors have been suggested to be involved in the development of NASH. Considering the many possible contributing factors, we postulated that mechanisms of progression from NASH to HCC could differ depending on the risk factors. In the present study, we applied two mouse models of NASH–HCC and performed histopathological and proteome analyses of mouse liver tumors. Furthermore, to compare the mechanisms of NASH–HCC progression in mice and humans, we investigated HCCs in humans with a background of metabolic syndrome and NASH, as well as HCCs associated with hepatitis virus infection by immunohistochemistry. It was demonstrated that upstream regulators associated with the mammalian target of rapamycin (mTOR) pathway were altered in liver tumors of mice with metabolic syndrome characteristics (TSOD mice) using proteome analysis. Immunohistochemical analysis showed that mTOR was characteristically phosphorylated in liver tumors of TSOD mice and HCCs from metabolic syndrome cases in humans. These results indicated that the mTOR pathway is characteristically activated in liver tumors with metabolic syndrome and NASH, unlike liver tumors with other etiologies.

DOI： 10.3390/cancers10120465

PubMed

国際・国内誌：国際誌  

© 2018 Korean Society of Toxicology. Chemical carcinogenesis is a multistep process. Genotoxic carcinogens, which are DNA-reactive, induce DNA adduct formation and genetic alterations in target cells, thereby generating mutated cells (initiation). Subsequently, preneoplastic lesions appear through clonal proliferation of the mutated cells and transform into tumors (promotion and progression). Many factors may influence these processes in a dose-dependent manner. Therefore, quantitative analysis plays an important role in studies on the carcinogenic threshold of genotoxic carcinogens. Herein, we present data on the relationship between key carcinogenic events and their deriving point of departure (PoD). Their PoDs were also compared to those of the carcinogenesis pathway. In an experiment, the liver of rats exposed to 2-amino-3,8-dimethylimidazo-(4,5-f)quinoxaline (MeIQx) was examined to determine the formation of MeIQx-DNA adducts, generation of mutations at LacI transgene, and induction of preneoplastic glutathione S-transferase placental form (GST-P)-positive foci and tumors (benign and malignant). The PoDs of the above key events in the carcinogenicity of MeIQx were increased as the carcinogenesis advanced; however, these PoDs were lower than those of tumor induction. Thus, the order of key events during tumor induction in the liver was as follows: formation of DNA adducts < < Mutations < < GST-positive foci (preneoplasia) < < Tumor (adenoma and carcinoma). We also obtained similar data on the genotoxic and carcinogenic PoDs of other hepatocarcinogens, such as 2-amino-3,8-dimethylimidazo(4,5-f)quinoline. These results contribute to elucidating the existence of a genotoxic and carcinogenic threshold.

DOI： 10.5487/TR.2018.34.4.291

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. 1,4-Dioxane is a widely used synthetic industrial chemical and its contamination of drinking water and food is a potential health concern. It induces liver tumors when administered in the drinking water to rats and mice. However, the mode of action (MOA) of the hepatocarcinogenicity of 1,4-dioxane remains unclear. Importantly, it is unknown if 1,4-dioxane is genotoxic, a key consideration for risk assessment. To determine the in vivo mutagenicity of 1,4-dioxane, gpt delta transgenic F344 rats were administered 1,4-dioxane at various doses in the drinking water for 16 weeks. The overall mutation frequency (MF) and A:T- to -G:C transitions and A:T- to -T:A transversions in the gpt transgene were significantly increased by administration of 5000 ppm 1,4-dioxane. A:T- to -T:A transversions were also significantly increased by administration of 1000 ppm 1,4-dioxane. Furthermore, the DNA repair enzyme MGMT was significantly induced at 5000 ppm 1,4-dioxane, implying that extensive genetic damage exceeded the repair capacity of the cells in the liver and consequently led to liver carcinogenesis. No evidence supporting other MOAs, including induction of oxidative stress, cytotoxicity, or nuclear receptor activation, that could contribute to the carcinogenic effects of 1,4-dioxane were found. These findings demonstrate that 1,4-dioxane is a genotoxic hepatocarcinogen and induces hepatocarcinogenesis through a mutagenic MOA in rats. Because our data indicate that 1,4-dioxane is a genotoxic carcinogen, we estimated the point of departure of the mutagenicity and carcinogenicity of 1,4-dioxane using the no-observed effect-level approach and the Benchmark dose approach to characterize its dose–response relationship at low doses.

DOI： 10.1007/s00204-018-2282-0

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© Kitajima et al. Hypoxia-inducible factors (HIFs) facilitate cellular adaptation to environmental stress such as low oxygen conditions (hypoxia) and consequently promote tumor growth. While HIF-1α functions in cancer progression have been increasingly recognized, the contribution of HIF-2α remains widely unclear despite accumulating reports showing its overexpression in cancer cells. Here, we report that HIF-2α upregulates the expression of CD70, a cancer-related surface antigen that improves anchorage-independent growth in cancer cells and is associated with poor clinical prognosis, which can be induced via epigenetic modifications mediated by DNMT1. The ablation of CD70 by RNAi led to decreased colony forming efficiency in soft agar. Most strikingly, we identified the emergence of CD70-expressing cells derived from CD70-negative cell lines upon prolonged hypoxia exposure or DNMT1 inhibition, both of which significantly reduced CpG-nucleotide methylations within CD70 promoter region. Interestingly, DNMT1 expression was decreased under hypoxia, which was rescued by HIF-2α knockdown. In addition, the expression of CD70 and colony forming efficiency in soft agar were decreased by knockdown of HIF-2α. These findings indicate that CD70 expression and an aggressive phenotype of cancer cells is driven under hypoxic conditions and mediated by HIF-2α functions and epigenetic modifications. This provides additional insights into the role of HIF-2α in coordinated regulation of stem-like functions and epigenetics that are important for cancer progression and may www.oncotarget.com Oncotarget, 2018, Vol. 9, (No. 27), pp: 19123-19135 present additional targets for the development of novel combinatorial therapeutics.

DOI： 10.18632/oncotarget.24919

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Dammar resin is a natural food additive and flavoring substance present in many foods and drinks. The present study evaluates the chronic toxicity and carcinogenicity of dietary dammar resin in F344 rats. Dietary concentrations in the 52-week chronic toxicity study were 0, 0.03, 0.125, 0.5, or 2%. The major treatment-related deleterious effects were body weight suppression, increased relative liver weight, and low hemoglobin levels in males and females. Foci of cellular alteration in the liver were observed in the male 2% group, but not in any other group. The no-observed-adverse-effect level for chronic toxicity was 0.125% for males (200.4 mg/kg b.w./day) and females (241.9 mg/kg b.w./day). Dietary concentrations in the 104-week carcinogenicity study were 0, 0.03, 0.5, or 2%. Dammar resin induced hemorrhagic diathesis in males and females, possibly via the inhibition of extrinsic and intrinsic coagulation pathways. Incidences of hepatocellular adenomas and carcinomas were significantly increased in the male 2% group, but not in any other group. In the 4-week subacute toxicity study, the livers of male rat-fed diet-containing 2% dammar resin had increased levels of protein oxidation and increased the expression of two anti-apoptotic and seven cytochrome P450 (CYP) genes. There was also an increased tendency of oxidative DNA damage. These findings demonstrate that dammar resin is hepatocarcinogenic in male F344 rats and underlines the roles of inhibition of apoptosis, induction of CYP enzymes, and oxidative stress in dammar resin-induced hepatocarcinogenesis.

DOI： 10.1007/s00204-018-2316-7

PubMed

掲載種別：研究論文（学術雑誌）  

The role of deficiency of oxoguanine glycosylase 1 (Ogg1) Mmh homolog, a repair enzyme of the 8-hydroxy-2'-deoxyguanosine (8-OHdG) residue in DNA, was investigated using the multiorgan carcinogenesis bioassay in mice. A total of 80 male and female six-week-old mice of C57BL/6J background carrying a mutant Mmh allele of the Mmh/Ogg1 gene (Ogg1(-/-)) and wild type (Ogg1(+/+)) mice were administered N-diethylnitrosamine (DEN), N-methyl-N-nitrosourea (MNU), N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN), N-bis (2-hydroxypropyl) nitrosamine (DHPN) and 1,2-dimethylhydrazine dihydrochloride (DMH) (DMBDD) to induce carcinogenesis in multiple organs, and observed up to 34 weeks. Significant increase of lung adenocarcinomas incidence was observed in DMBDD-treated Ogg1(-/-) male mice, but not in DMBDD-administered Ogg1(+/+) animals. Furthermore, incidences of lung adenomas were significantly elevated in both Ogg1(-/-) males and females as compared with respective Ogg1(-/-) control and DMBDD-treated Ogg1(+/+) groups. Incidence of total liver tumors (hepatocellular adenomas, hemangiomas and hemangiosarcomas) was significantly higher in the DMBDD-administered Ogg1(-/-) males and females. In addition, in DMBDD-treated male Ogg1(-/-) mice, incidences of colon adenomas and total colon tumors showed a trend and a significant increase, respectively, along with significant rise in incidence of simple hyperplasia of the urinary bladder, and a trend to increase for renal tubules hyperplasia in the kidney. Furthermore, incidence of squamous cell hyperplasia in the forestomach of DMBDD-treated Ogg1(-/-) male mice was significantly higher than that of Ogg1(+/+) males. Incidence of small intestine adenomas in DMBDD Ogg1(-/-) groups showed a trend for increase, as compared to the wild type mice. The current results demonstrated increased susceptibility of Ogg1 mutant mice to the multiorgan carcinogenesis induced by DMBDD. The present bioassay could become a useful tool to examine the influence of various targets on mouse carcinogenesis.

DOI： 10.3390/ijms18081801

掲載種別：研究論文（学術雑誌）  

Background/Aim: Propolis has since long been utilized in numerous folk medicines with a variety of medicinal properties. In this study, the effects of ethanol-extracted (EEP) and water-extracted (WEP) Brazilian green propolis on the post-initiation phase of inflammation-Associated rat colon tumorigenesis were directly compared. Materials and Methods: Male F344 rats at 6 weeks of age were subcutaneously injected with 1,2-dimethylhydrazine (DMH) at 40 mg/kg body weight twice during the first week, followed by 1% dextran sodium sulfate (DSS) in drinking water for one week. After a 1-week no-Treatment period, animals were administered either basal Oriental MF powdered diet, or 1% EEP or 1% WEP in the basal diet until week 32. Results: Post-initiation treatment with EEP significantly reduced the multiplicity of colorectal carcinomas compared to the control (0.40±0.13/rat vs. 2.29±0.84/rat, respectively, <0.05), and EEP also reduced the tumor volume. Immunohistochemically, expression of inflammation-Associated proteins inducible nitric oxide synthase, tumor necrotic factor alpha, nuclear factor kappa B and glutathione peroxidase-2 were significantly diminished in colorectal tumors from EEP-Treated rats. Conclusion: Suppression of inflammation and oxidative stress, which had been triggered by DMH and promoted by DSS, was a primary mechanism by which EEP suppressed carcinogenesis.

DOI： 10.21873/invivo.11044

PubMed

掲載種別：研究論文（学術雑誌）  

Rat bladder cancer is nearly always papillary non-invasive urothelial carcinoma (UC). To establish an animal model mimicking invasive UC that arises from papillary non-invasive UC in the bladder, male human c-Ha-ras proto-oncogene transgenic rats (Hras128) were treated with 0.05% N-butyl-N-(hydroxybutyl) nitrosameine (BBN) in their drinking water and/or 0.1% phenylethyl isothiocyanate (PEITC) in their diet as follows: BBN (8 weeks)? PEITC (8 weeks); PEITC (8 weeks)? BBN (8 weeks); BBN alone (16 weeks); PEITC alone (16 weeks); and no treatment. At the end of week 16, the highest incidence of invasive UC was observed in the BBN? PEITC group. Therefore, we used Hras128 rats treated with BBN followed by PEITC as a model of invasive bladder cancer to identify invasion- associated proteins. Proteome analysis was performed to compare the protein profiles of invasive and non-invasive UC in Hras128 rats. We identified 49 proteins that were either overexpressed or underexpressed in invasive UC but not in non-invasive UC. Immunohistochemical analysis of carbonic anhydrase 2 (CA2), an overexpressed protein, showed that the relative number of CA2-positive UC was significantly higher for invasive UC compared to non-invasive UC in rats. Moreover, the incidence of CA2-positive cancers was also significantly higher for human muscle-invasive bladder cancer (MIBC) compared to non-MIBC (NMIBC) and was positively associated with the progression of NMIBC. Our findings indicate that CA2 is an invasion-associated factor and suggest that it could serve as a potential therapeutic molecular target for bladder cancers.

DOI： 10.1111/cas.13143

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2016 Elsevier GmbH Diphenylarsinic acid (DPAA), a chemical warfare-related neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. The purpose of the present study was to evaluate the potential toxicity of DPAA when administered to rats in their drinking water for 52 weeks. DPAA was administered to groups 1–4 at concentrations of 0, 5, 10, and 20 ppm in their drinking water for 52 weeks. There were no significant differences in the final body weights between the control groups and the treatment groups in male or female rats. In serum biochemistry, in females 20 ppm DPAA significantly increased alkaline phosphatase and γ-glitamyl transferase compared to controls, and 10 and 20 ppm DPAA significantly increased total cholesterol compared to controls. Absolute and relative liver weights were significantly increased in females treated with 20 ppm DPAA compared to the control group. Dilation of the common bile duct outside the papilla of Vater and stenosis of the papilla of Vater was observed in all male and female rats administered 20 ppm DPAA. The incidence of intrahepatic bile duct hyperplasia was significantly increased in male and female rats treated with 20 ppm DPAA compared to the control groups. These results suggest that DPAA is toxic to the bile duct epithelium in rats. The no-observed adverse effect levels of DPAA were estimated to be 10 ppm (0.48 mg/kg b.w./day) for males and 5 ppm (0.35 mg/kg b.w./day) for females under the conditions of this study.

DOI： 10.1016/j.etp.2016.10.002

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2017 Anna Kakehashi et al. The carcinogenic potential of phenobarbital (PB) was assessed in a mouse line carrying a mutant Mmh allele of the Mmh/Ogg1 gene encoding the enzyme oxoguanine DNA glycosylase (Ogg1) responsible for the repair of 8-hydroxy-2′-deoxyguanosine (8-OHdG). Mmh homozygous mutant (Ogg1-/-) and wild-type (Ogg1+/+) male and female, 10-week-old, mice were treated with 500 ppm PB in diet for 78 weeks. Hepatocellular carcinomas (HCCs) were found in PB-treated Ogg1-/- mice, while Ogg1+/+ animals developed only hepatocellular adenomas (HCAs) at the same rate. This was coordinated with PB-induced significant elevation of 8-OHdG formation in DNA and cell proliferation in adjacent liver of Ogg1-/- mice. Proteome analysis predicted activation of transcriptional factor Nrf2 in the livers and HCAs of PB-administered Ogg1+/+ mice; however, its activation was insufficient or absent in the livers and HCCs of Ogg1-/- mice, respectively. Significant elevation of phase I and II metabolizing enzymes was demonstrated in both Ogg1-/- and Ogg1+/+ animals. Treatment of Ogg1-/- mice with PB resulted in significant elevation of cell proliferation in the liver. These results indicate that PB induced progression from HCA to HCC in Ogg1-/- mice, due to persistent accumulation of DNA oxidative base modifications and suppression of Nrf2-mediated oxidative stress response, resulting in significant elevation of cell proliferation.

DOI： 10.1155/2017/8541064

PubMed

国際・国内誌：国内誌  

Diphenylarsinic acid (DPAA), a neurotoxic organic arsenical used as a chemical warfare agent, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. We previously demonstrated that DPAA promotes diethylnitrosamine-induced liver carcinogenesis in a medium-term rat liver bioassay. The purpose of the present study was to evaluate the potential carcinogenicity of DPAA, including investigation of whether the bile duct hyperplasia in the liver that was observed in a previous 52 week rat chronic study develops into a tumor, when administered to rats in their drinking water for 104 weeks. DPAA was administered to groups 1-4 at concentrations of 0, 5, 10, and 20 ppm in their drinking water for 104 weeks. A significant decrease in survival rate was found for females in the 20 ppm DPAA group. Body weights of males in the 20 ppm and females in the 10 and 20 ppm DPAA groups were significantly decreased compared to the controls. Overall histopathological evaluation of neoplasms in all tissues showed no significant increase of tumor incidence in any organ or tissue of the 5, 10, or 20 ppm DPAA-treated male or female F344 rats. In conclusion, the present study demonstrated that DPAA is not a complete carcinogen in male or female F344 rats.

DOI： 10.2131/jts.42.475

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

© 2017 The Japanese Society of Toxicologic Pathology. We have previously demonstrated that diphenylarsinic acid (DPAA) promotes liver carcinogenesis in rats in a medium-term liver carcinogenicity bioassay. However, the effects of DPAA on other organs have not been determined. In the present study, the effects of DPAA on carcinogenesis were investigated using a rat multiorgan carcinogenicity bioassay. A total of 60 six-week-old male F344 rats were treated with the carcinogens diethylnitrosamine, N-butyl-N-(4-hydroxybutyl) nitrosamine, N-methyl-N-nitrosourea, N-bis (2-hydroxypropyl) nitrosamine, and 1,2-dimethylhydrazine dihydrochloride to initiate carcinogenesis in multiple organs. After initiation, DPAA was given at a dose of 0, 5, or 20 ppm in drinking water for 27 weeks. The incidences of moderate and severe bile duct hyperplasia were significantly increased in the 20 ppm DPAA group (29.4%, 70.6%, respectively) compared with the 0 ppm DPAA group (0%, 0%, respectively), and the incidence and multiplicity of cholangioma were significantly increased in the 20 ppm DPAA group (29.4%, 0.4 ± 0.8/rat) compared with the 0 ppm DPAA group (0%, 0/rat). The total number and average area of glutathione S-transferase placenta form-positive foci, preneoplastic lesions in rat livers, were significantly increased in the 20 ppm DPAA group (10.5 ± 2.2/cm2, 5.3 ± 1.7 mm2/cm2) compared with the 0 ppm DPAA group (6.2 ± 2.9/cm2, 2.4 ± 1.4 mm2/cm2). In conclusion, our results demonstrate that DPAA promotes hepatobiliary carcinogenesis in a rat medium-term multiorgan carcinogenicity bioassay; no promotion effects were observed in other organs.

DOI： 10.1293/tox.2016-0049

PubMed

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2016 Arsenic is a well-known human bladder and liver carcinogen, but its exact mechanism of carcinogenicity is not fully understood. Dimethylarsinic acid (DMAV) is a major urinary metabolite of sodium arsenite (iAsIII) and induces urinary bladder cancers in rats. DMAV and iAsIII are negative in in vitro mutagenicity tests. However, their in vivo mutagenicities have not been determined. The purpose of present study is to evaluate the in vivo mutagenicities of DMAV and iAsIII in rat urinary bladder epithelium and liver using gpt delta F344 rats. Ten-week old male gpt delta F344 rats were randomized into 3 groups and administered 0, 92 mg/L DMAV, or 87 mg/L iAsIII (each 50 mg/L As) for 13 weeks in the drinking water. In the mutation assay, point mutations are detected in the gpt gene by 6-thioguanine selection (gpt assay) and deletion mutations are identified in the red/gam genes by Spi− selection (Spi− assay). Results of the gpt and Spi− assays showed that DMAV and iAsIII had no effects on the mutant frequencies or mutation spectrum in urinary bladder epithelium or liver. These findings indicate that DMAV and iAsIII are not mutagenic in urinary bladder epithelium or liver in rats.

DOI： 10.1016/j.jes.2016.07.005

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2016 Kakehashi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The present study was conducted over a course of 104 weeks to estimate the carcinogenicity of ethanol-extracted Brazilian green propolis (EEP). Groups of 50 male and 50 female Wistar Hannover rats, 6-week-old at commencement were exposed to EEP at doses of 0, 0.5 or 2.5% in the diet. Survival rates of 0.5% and 2.5% EEP-treated male and female rats, respectively, were significantly higher than those of respective control groups. Overall histopathological evaluation of neoplasms in rat tissues after 2 years showed no significant increase of tumors or preneoplastic lesions in any organ of animals administered EEP. Significantly lower incidences of pituitary tumors in 0.5% EEP male and 2.5% EEP female groups, malignant lymphoma/leukemia in both 2.5% EEP-treated males and females and total thyroid tumors in 0.5% EEP male group were found. Administration of EEP caused significant decreases of lymphoid hyperplasia of the thymus and lymph nodes in 2.5% EEPtreated rats, tubular cell hyperplasia of kidneys in all EEP groups, and cortical hyperplasia of adrenals in EEP-treated females. In the blood, significant reduction of neutrophils in all EEP-treated males and band neutrophils in 2.5% EEP-treated females was found indicating lower levels of inflammation. Total cholesterol and triglicerides levels were significantly lower in the blood of 2.5% EEP-treated female rats. In conclusion, under the conditions of the 2-year feeding experiment, EEP was not carcinogenic, did not induce significant histopathological changes in any organ, and further exerted anti-inflammatory and antitumorigenic effects resulting in increase of survival of Wistar Hannover rats.

DOI： 10.1371/journal.pone.0158654

PubMed

国際・国内誌：国内誌  

Several studies have successfully detected hepatocarcinogenicity in rats based on gene expression data. However, prediction of hepatocarcinogens with certain mechanisms of action (MOAs), such as enzyme inducers and peroxisome proliferator-activated receptor α (PPARα) agonists, can prove difficult using a single model and requires a highly toxic dose. Here, we constructed a model for detecting non-genotoxic (NGTX) hepatocarcinogens and predicted their MOAs in rats. Gene expression data deposited in the Open Toxicogenomics Project-Genomics Assisted Toxicity Evaluation System (TG-GATEs) was used to investigate gene marker sets. Principal component analysis (PCA) was applied to discriminate different MOAs, and a support vector machine algorithm was applied to construct the prediction model. This approach identified 106 probe sets as gene marker sets for PCA and enabled the prediction model to be constructed. In PCA, NGTX hepatocarcinogens were classified as follows based on their MOAs: cytotoxicants, PPARα agonists, or enzyme inducers. The prediction model detected hepatocarcinogenicity with an accuracy of more than 90% in 14- and 28-day repeated-dose studies. In addition, the doses capable of predicting NGTX hepatocarcinogenicity were close to those required in rat carcinogenicity assays. In conclusion, our PCA and prediction model using gene marker sets will help assess the risk of hepatocarcinogenicity in humans based on MOAs and reduce the number of two-year rodent bioassays.

DOI： 10.2131/jts.41.281

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2016 Japanese Cancer Association. The role of cells expressing stem cell markers deltaNp63 and CD44v has not yet been elucidated in peripheral-type lung squamous cell carcinoma (pLSCC) carcinogenesis. Female A/J mice were painted topically with N-nitroso-tris-chloroethylurea (NTCU) for induction of pLSCC, and the histopathological and molecular characteristics of NTCU-induced lung lesions were examined. Histopathologically, we found atypical bronchiolar hyperplasia, squamous metaplasia, squamous dysplasia, and pLSCCs in the treated mice. Furthermore, we identified deltaNp63posCD44vposCK5/6posCC10pos clara cells as key constituents of early precancerous atypical bronchiolar hyperplasia. In addition, deltaNp63posCD44vpos cells existed throughout the atypical bronchiolar hyperplasias, squamous metaplasias, squamous dysplasias, and pLSCCs. Overall, our findings suggest that NTCU induces pLSCC through an atypical bronchiolar hyperplasia-metaplasia-dysplasia-SCC sequence in mouse lung bronchioles. Notably, Ki67-positive deltaNp63posCD44vpos cancer cells, cancer cells overexpressing phosphorylated epidermal growth factor receptor and signal transducer and activator of transcription 3, and tumor-associated macrophages were all present in far greater numbers in the peripheral area of the pLSCCs compared with the central area. These findings suggest that deltaNp63posCD44vpos clara cells in mouse lung bronchioles might be the origin of the NTCU-induced pLSCCs. Our findings also suggest that tumor-associated macrophages may contribute to creating a tumor microenvironment in the peripheral area of pLSCCs that allows deltaNp63posCD44vpos cancer cell expansion through activation of epidermal growth factor receptor signaling, and that exerts an immunosuppressive effect through activation of signal transducer and activator of transcription 3 signaling.

DOI： 10.1111/cas.12855

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© 2015 Elsevier Ltd. Ethanol-extracted propolis (EEP) is used for medical, dietetic and cosmetic purposes. In this study, the effects of EEP on urinary bladder carcinogenesis, its underlying mechanism and in vivo genotoxicity were investigated. In experiment 1, rats were treated with N-butyl-. N-(4-hydroxybutyl)nitrosamine (BBN) for 2 or 4 weeks followed by dietary administration of 0.125, 0.25, 0.5 or 1% EEP for 4 or 32 weeks, respectively. At week 6, the mRNA levels of top2a, cyclin D1 and survivin were significantly elevated in the 0.5 and 1% EEP groups. At week 36, the incidence and multiplicity of urothelial carcinomas and total tumors were markedly elevated in all EEP groups. In experiment 2, rats were fed basal diet or the 1% EEP diet for 13 weeks without carcinogen initiation. Increases in urinary precipitate, cell proliferation and incidence of simple hyperplasia were observed in the 1% EEP group. In experiment 3, dietary administration of 2.5% EEP to gpt delta rats for 13 weeks did not induce any obvious mutagenicity in the urinary bladder urothelium. Taken together, EEP enhanced BBN-initiated rat urinary bladder carcinogenesis in a non-genotoxic manner through increasing formation of urinary precipitate, enhancing cell proliferation and inhibiting apoptosis during the early stages of carcinogenesis.

DOI： 10.1016/j.fct.2015.06.007

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

© The Author 2015. 1,2-Dichloropropane (1,2-DCP) has recently been reclassified from not classifiable as to its carcinogenicity to humans (Group 3) to carcinogenic to humans (Group 1) by the International Agency for Research on Cancer. This was based on the findings of epidemiological studies in Japan that occupational exposure to paint stripers containing 1,2-DCP was associated with increased cholangiocarcinomas. It is known that 1,2-DCP is negative for cholangiocarcinogenicity in rats and mice. However, its toxicity and carcinogenicity has not been examined in hamsters and little is known about the regulation of its metabolism in hamsters. The purpose of this study was to determine the hepatobiliary toxicity of 1,2-DCP in hamsters and to characterize and compare the altered patterns of hepatic xenometabolic enzymes in hamsters and mice. Male Syrian hamsters and male B6C3F1 mice were treated with various doses of 1,2-DCP for 4h or 3 days or 4 weeks. These experiments demonstrated that a high dose of 1,2-DCP induced centrilobular hepatocellular necrosis in hamsters. CYP2E1 is possibly the key enzyme responsible for bioactivation and the consequent hepatocytotoxicity of 1,2-DCP, and GSH conjugation catalyzed by GST-T1 may exert a cytoprotective role in hamsters and mice. Notably, the expression pattern of GST-T1 in bile duct epithelial cells differed between hamsters and mice: GST-T1 was expressed in bile duct epithelial cells of mice but not hamsters. This indicates that responses to 1,2-DCP in the bile duct of hamsters might differ from that of mice, and suggests that long-termstudies are necessary to clarify the chalangiocarcinogenicity of 1,2-DCP in hamsters, though no biliary toxicity was observed in the present short-termexperiments.

DOI： 10.1093/toxsci/kfv045

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

Based on the findings of epidemiological studies in Japan that occupational exposure to 1,2-dichloropropane (1,2-DCP) was associated with increased cholangiocarcinomas, 1,2-DCP has recently been classified as being carcinogenic to humans (Group 1). However, the cholangiocarcinogenicity of 1,2-DCP has not been demonstrated experimentally, and it was negative for cholangiocarcinogenicity in rats and mice. The present study determined the effects of 1,2-DCP on N-nitrosobis(2-oxopropyl)amine (BOP)-induced cholangiocarcinogenesis in male hamsters. We found that 1,2-DCP did not enhance the development of BOP-induced atypical biliary hyperplasia and did not induce any lesions in liver bile duct when administered alone. Notably, 1,2-DCP had no effect on the proliferative activity of bile duct epithelial cells regardless of BOP-initiation. These results demonstrate that 1,2-DCP lacks promoting effects on BOP-induced cholangiocarcinogenesis and suggest the possibility that 1,2-DCP is not cholangiocarcinogenic to the hamster in the present model. In addition, 1,2-DCP also lacks promoting effects on pancreatic, lung, and renal carcinogenesis. As the occurrence of occupational cholangiocarcinomas in Japan might be attributed to exposure to multiple chemicals, the results of the present study indicate that it will be necessary to determine the cholangiocarcinogenic effects of concurrent exposure of 1,2-DCP and the other halogen solvents to which workers with cholangiocarcinomas were exposed.

DOI： 10.2131/jts.40.647

PubMed

掲載種別：研究論文（学術雑誌）  

Targeted treatments for lung cancer based on pathological diagnoses are required to enhance therapeutic efficacy. There are few well-established animal models for lung squamous cell carcinoma although several highly reproducible mouse models for lung adenoma and adenocarcinoma are available. This study was carried out to establish a new lung squamous cell carcinoma mouse model. In the first experiment, female A/J mice were painted topically on back skin twice weekly with 75 mu L 0.013 M N-nitroso-tris-chloroethylurea for 2, 4, and 8 weeks (n = 15-20 per group) as initiation of lung lesions, and surviving mice were killed at 18 weeks. In the second experiment, mice were treated as above for 4 weeks and killed at 6, 12, or 18 weeks (n = 3 per group). Lung lobes were subjected to histopathological, immunohistochemical, immunoblotting, and ultrastructural analyses. In the case of treatment for 2, 4, and 8 weeks, incidences of lung squamous cell carcinoma were 25, 54, and 71%, respectively. Cytokeratin 5/6 and epidermal growth factor receptor were clearly expressed in dysplasia and squamous cell carcinoma. Desmosomes and tonofilaments developed in the squamous cell carcinoma. Considering the carcinogenesis model, we conclude that 2 or 4 weeks of N-nitroso-tris-chloroethylurea treatment may be suitable for investigating new chemicals for promotional or suppressive effects on lung squamous cell carcinoma.

DOI： 10.1111/cas.12289

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

Diphenylarsinic acid (DPAA), a chemical warfare-related neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. Inorganic arsenic is carcinogenic in humans and its organic arsenic metabolites are carcinogenic in animal studies, raising serious concerns about the carcinogenicity of DPAA. However, the carcinogenic potential of DPAA has not yet been evaluated. In the present study we found that DPAA significantly enhanced the development of diethylnitrosamine-induced preneoplastic lesions in the liver in a medium-term rat liver carcinogenesis assay. Evaluation of the expression of cytochrome P450 (CYP) enzymes in the liver revealed that DPAA induced the expression of CYP1B1, but not any other CYP1, CYP2, or CYP3 enzymes, suggesting that CYP1B1 might be the enzyme responsible for the metabolic activation of DPAA. We also found increased oxidative DNA damage, possibly due to elevated CYP1B1 expression. Induction of CYP1B1 has generally been linked with the activation of AhR, and we found that DPAA activates the aryl hydrocarbon receptor (AhR). Importantly, the promotion effect of DPAA was observed only at a dose that activated the AhR, suggesting that activation of AhR and consequent induction of AhR target genes and oxidative DNA damage plays a vital role in the promotion effects of DPAA. The present study provides, for the first time, evidence regarding the carcinogenicity of DPAA and indicates the necessity of comprehensive evaluation of its carcinogenic potential using long-term carcinogenicity studies.© 2013 Elsevier Inc.

DOI： 10.1016/j.taap.2013.08.022

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

Cigarette smoking is one of the major risk factors of bladder cancer in humans. To date, however, there is no experimental evidence for the effects of inhalation exposure to mainstream cigarette smoke on bladder carcinogenesis. The purpose of the present study was to evaluate the effect of inhalation of mainstream cigarette smoke on mouse bladder carcinogenesis using a cigarette smoke inhalation exposure system. Six-week-old male C57BL mice were administered 0.025% N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in their drinking water for 8 weeks and then divided into 2 groups and exposed to 0 or 300 mg/m3 wet total particulate matter mainstream cigarette smoke for 2 h per day, five times per week, for 22 weeks. The incidences of bladder tumors (papilloma and urothelial carcinoma) tended to increase in the cigarette smoke-exposed group (25.0%) compared with the controls (15.8%), albeit without a statistically significant difference. We also evaluated mRNA expression levels of cytochrome P450 (cyp) enzymes and proliferating cell nuclear antigen (PCNA) in the bladder epithelium. Expression of cyp1a1 was significantly increased in the cigarette smoke-exposed group. Cigarette smoke exposure did not have a significant effect on the expression of cyp1a2, cyp 1b1, cyp 2a4, cyp 2b10, cyp 2e1, or PCNA. In conclusion, limited exposure to mainstream cigarette smoke for 22 weeks, caused a significant increase in cyp1a1 expression. This increase coupled with the nonsignificant increase in bladder tumors suggests that a longer period of exposure is required to clarify the effects of cigarette smoke on bladder carcinogenesis. © 2013 The Japanese Society of Toxicologic Pathology.

DOI： 10.1293/tox.2013-0039

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.mrgentox.2012.08.004

掲載種別：研究論文（学術雑誌）  

Dammar resin has long been used in foods as either a clouding or a glazing agent. In a recent study, 2% Dammar resin showed significant hepatocarcinogenicity in a rat 2-year bioassay. Therefore, for an accurate estimate of human risk, it is necessary to understand whether Dammar resin induces liver genotoxicity and the underlying mechanisms of its hepatocarcinogenicity. Modifying effects of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a typical genotoxic carcinogen produced during cooking of protein-rich foods, was also studied in the present study. Exposure of gpt delta mice to Dammar resin at a dose of 2% for 12 weeks did not induce any obvious mutagenicity in the liver. However, the index of cell proliferation, the level of 8-OHdG, and bax, bcl-2, p53, cyp1a2, cyp2e1, gpx1 and gstm2 gene expression were all significantly increased when compared with the control group. In the IQ treatment group, at a dose of 300. ppm, mutagenicity was readily detected, the index of cell proliferation increased, and p53, cyp2e1 and gpx1 gene expression was down-regulated in the liver. Down-regulation of p53, P450s, and gpx1 in the livers of IQ treated mice are consistent with its genotoxic mechanism of carcinogenicity observed in a 675-day study. In contrast, our results using gpt delta mice suggest that Dammar resin is not genotoxic. Instead, the Dammar resin-induced hepatocarcinogenicity seen in our previous 2-year study with rats may have been mediated by non-genotoxic mechanisms, including increased P450 enzyme activity, increased oxidative stress, altered gene expression, and promotion of cell proliferation. © 2012 Elsevier B.V.

DOI： 10.1016/j.mrgentox.2012.06.005

PubMed

掲載種別：研究論文（学術雑誌）  

The purposes of the present study were to investigate the modifying effects of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a genotoxic carcinogen produced during cooking of protein-rich foods, and elucidate underlying mechanisms in a two-stage hepatocarcinogenesis mice model. Six-week-old B6C3F1 mice were subjected to two-thirds partial hepatectomy at the beginning of the study, followed by an intraperitoneal injection of diethylnitrosamine on day 1. Starting 1 week later, they were fed diets containing IQ at doses of 30, 100, or 300 ppm for 39 weeks. A dose-dependent trend for increase in eosinophilic altered foci as well as eosinophilic hepatocellular adenomas was observed, along with significant elevation in the incidence of hepatocellular carcinomas in the 100- and 300-ppm IQ groups as compared with initiation control group. Furthermore, IQ elevated the protein expression levels of Wnt1, transforming growth factor-β (TGF-β), TGF-β receptors 1 and 2 (TβR1 and TβR2), and phosphorylated c-Jun (p-c-Jun), while suppressing those of E-cadherin and p21 WAF1/Cip1. Moreover, translocation of β-catenin to the nuclei as well as upregulated nuclear expression of c-Myc and cyclin D1, which are downstream targets of β-catenin and p-c-Jun, were detected at 100 and 300 ppm. These findings suggest that IQ exerts dose-dependent promoting effects on mice hepatocarcinogenesis by activating TGF-β and Wnt/β-catenin signaling pathways and inhibiting cell adhesion. © The Author 2011. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved.

DOI： 10.1093/toxsci/kfr314

PubMed

DOI： 10.1158/1538-7445.AM2011-1340

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）  

Objective: Germ line mutations of the LKB1 gene cause the autosomal dominant Peutz-Jeghers syndrome (PJS), and PJS has also been associated with an increased risk of developing cancers, suggesting LKB1 may act as a tumor suppressor in PJS. By contrast, LKB1 mutations are rare events in most sporadic tumors in non-PJS patients, except for lung cancers. To better understand the involvement of LKB1 gene alterations during lung carcinogenesis, we investigated the LKB1 gene mutations and expressions in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in rats. Methods: Male Wistar rats, 6 weeks old, were given 2,000 ppm BHP in their drinking water for 12 weeks and maintained without further treatment until they were sacrificed at 25 weeks. A total of 15 lung adenocarcinomas were obtained, and genomic DNA was extracted for the search of mutations using polymerase chain reaction (PCR)-single strand conformation polymorphism analysis. To assess altered expressions of the LKB1 gene, reverse transcription-PCR analysis was also performed. Results: No mutations were found throughout exons 1-9 in any of the tumors. Aberrant transcripts bearing deletions of nucleotides 216-1459, 289-1302, 268-1261, or 257-1378 were detected in 5 of 15 adenocarcinomas (33.3%). Conclusion: These results suggest that alterations of the LKB1 gene might be involved in the development of lung adenocarcinomas induced by BHP in rats. Copyright © 2010 S. Karger AG.

DOI： 10.1159/000305355

PubMed

掲載種別：研究論文（学術雑誌）  

Lysophosphatidic acid (LPA) is a bioactive phospholipid that stimulates cell proliferation and migration, and protects cells from apoptosis. It interacts with specific G protein-coupled transmembrane receptors. Recently, frequent mutations of the LPA receptor-1 (LPA1) gene were detected in rat lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP). In this study, to evaluate the involvement of other LPA receptor gene alterations during lung carcinogenesis, we investigated mutations of the LPA2, LPA3, LPA4 and LPA5 genes in lung adenocarcinomas induced by BHP in rats. Fifteen male Wistar rats, 6 weeks of age, were given 2000 ppm BHP in their drinking water for 12 weeks and then maintained without further treatment until sacrifice at 25 weeks, and 15 adenocarcinomas were obtained. Genomic DNAs were extracted from frozen tissues, and the LPA2, LPA3, LPA4 and LPA5 genes were examined for mutations, using polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis. No mutations of LPA2, LPA3, LPA4 and LPA5 were detected in the 15 adenocarcinomas. These results suggest that alterations due to LPA2, LPA3, LPA4 and LPA5 gene mutations might not be involved in the development of lung adenocarcinomas induced by BHP in rats.

DOI： 10.1293/tox.23.63

J-GLOBAL

J-GLOBAL

ヒ素は、自然環境中や食品中に広く存在する半金属元素である。無機ヒ素は疫学的に発がん性が認められており、国際がん研究機関（IARC）によりグループ１（ヒトに対する発がん性が認められる）と認定されている。現在、環境からのヒ素汚染によるアジア諸国、中南米諸国における慢性ヒ素中毒の危険にさらされている人々は数千万人にも及び、ヒ素曝露からの潜在的ながんの発生リスクが高まっている。しかしながら、実験動物においてヒ素の発がん性は十分に検証されておらず、実験モデルによるヒ素の発がん機序の解明及びリスク評価はいまだに課題が多い。我々は、無機ヒ素の哺乳類での主な尿中謝産物であるdimethylarsinic acid (DMA(V))に着目し、種々の実験モデルからラットにおける膀胱発がん性を明らかにした。それらの結果からIARC（2004）は、DMA(V)の動物における発がん性を判断している。さらに、尿中代謝物としてメチル化イオウヒ素であるdimethylmonothioarsinic acidを同定し、それがDMA(V)誘発ラット膀胱発がんにおける原因物質の1つである可能性を示してきた。一方、近年無機ヒ素では成熟ラット及びマウスに対して発がん性がみられないのに対して、経胎盤ばく露の場合には成熟した仔マウスで肝臓、肺、副腎などの腫瘍が有意に発生することが報告されているため、今後はDMA(V)の経胎盤ばく露による発がんリスク評価が急務であると考えられる。また、魚介類を多く摂取する日本人は、他の欧米人に比べヒ素摂取量が多く、尿中ヒ素代謝物の排泄が多いことが確認されている。ここでは、食品からのヒ素摂取のリスク評価も含めて論じたい。<br>文献：Yamamoto S. et al., Cancer Res. 55, 1995. Wanibuchi H. et al., Carcinogenesis, 1996. Wei M., Wanibuchi H. et al., Carcinogenesis, 1999. Wei M., Wanibuchi H. et al., Carcinogenesis, 2002. Wanibuchi H. et al., Toxicol Appl Pharmacol, 2004. Kinoshita A., Wanibuchi H. et al., Cancer Sci, 2007. Kinoshita A., Wanibuchi H. et al., Toxicol Appl Pharmacol, 2007. Gi M., Wanibuchi H. et al., Toxicol Appl Pharmacol, 2013. Fujioka M., Wanibuchi H. et al., J Environ Sci, 2016.

DOI： 10.14869/toxpt.44.1.0_S27-3

CiNii Article

Given the possibility that the occurrence of occupational cholangiocarcinoma in Japan might be attributed to exposure to multiple chemicals, studies are needed to determine the carcinogenic effects of concurrent exposure to 1,2-dichloropropane (1,2-DCP) and dichloromethane (DCM) or other organic solvents contained in the stripers to which the workers with cholangiocarcinoma were exposed. <br> The purpose of the present study is to determine the carcinogenic effects of concurrent administration of 1,2-DCP and DCM in mice. <br> Male C3H mice were divided into three groups and treated twice a week for 52 weeks as follows: vehicle (control group); 500 mg/kg 1,2 DCP; and co-administration of 500 mg/kg 1,2-DCP and 500 mg/kg DCM. <br> Incidence and multiplicity of hepatocellular adenomas were significantly increased in co-administered group compared with the 1,2-DCP alone group. Furthermore, The Ki-67 labeling index was significantly increased in the HCAs in the co-administered group compared with the HCAs in the 1,2-DCP alone group. In addition, microarray analysis revealed that expression of twelve tumor cell proliferation-related genes were significantly dysregulated in the HCAs induced by 1,2-DCP and DCM but not in the HCAs induced by 1,2-DCP alone.<br> These findings indicated that concurrent exposure of 1,2-DCP and DCM exerted a stronger hepatocarcinogenic effects than 1,2-DCP alone in mice.

DOI： 10.14869/toxpt.44.1.0_P-14

CiNii Article

掲載種別：研究発表ペーパー・要旨（国際会議）  

DOI： 10.1016/j.toxlet.2016.07.432

掲載種別：研究発表ペーパー・要旨（国際会議）  

DOI： 10.1016/j.toxlet.2016.07.229

J-GLOBAL

化学物質の発がん性・遺伝毒性の評価はリスク評価において必要不可欠である。しかし、発がん性試験では期間・費用等の面から評価できる物質の数に限りがある。一方、<i>in vitro</i>遺伝毒性試験では疑陽性のものも従来法では存在し、臓器特異性の判定が難しい。そこで、我々は <i>in vivo</i>変異原性を検索できる <i>gpt</i> deltaラットを用いたラット中期多臓器発がん性試験を実施し、遺伝毒性と発がん性の包括的な評価モデルの開発を行った。試験デザインは、発がん性評価系は実験開始から4週間にわたってイニシエーション処置として多臓器に標的性を持つ5種類の発がん物質を投与し、一方、<i>in vivo</i>変異原性評価系は同期間中無処置で飼育する。両評価系とも、その1週間後より、各群に被験物質を13週間投与する。検索項目は、発がん性評価系では前がん病変および増殖性病変を指標とした病理組織学的解析を行い、<i>in vivo</i>変異原性評価系では、点突然変異を検出する<i>gpt</i> assay、欠失変異を検出するSpi^- assayにより変異原性評価を行う。今回、評価した被験物質は、肝発がん物質であるダンマル樹脂、IQ及びコウジ酸で、発がん性評価系では、いずれも肝発がん促進作用が認められたが、<i>in vivo</i>変異原性評価系で、肝臓における<i>in vivo</i>変異原性が、それぞれ陰性、陽性、陰性となり、<i>in vitro</i>変異原性陽性であるコウジ酸が <i>in vivo</i>では陰性であることが判明した。因みにダンマル樹脂は <i>in vitro</i>変異原性陰性、IQは <i>in vitro</i>変異原性陽性であり、<i>in vitro</i>と<i>in vivo</i>変異原性は共に一致した。さらに、本モデルに改良DNA抽出法を導入することによって、これまで解析困難であった膀胱粘膜および甲状腺のような微小組織における様々な膀胱発がん物質及び甲状腺発がん物質の変異原性の評価に成功し、本モデルの汎用性をさらに高めることができた。以上より、本試験法は、遺伝毒性・発がん性の <i>in vivo</i>スクリーニング検索法として、さらにより短期間で発がん性を予測するモデルとして有用であることが考えられた。

DOI： 10.14869/toxpt.43.1.0_S20-1

CiNii Article

CiNii Article

掲載種別：研究発表ペーパー・要旨（国際会議）  

DOI： 10.1093/annonc/mdu359.13

掲載種別：研究発表ペーパー・要旨（国際会議）  

DOI： 10.1093/annonc/mdu359.9

CiNii Article

掲載種別：研究発表ペーパー・要旨（国際会議）