Reversibility of Carcinogen-induced Rat Forestomach Basal Cell Hyperplasia Is Due to Squamous Cell Differentiation

The mechanisms of reversibility of basal cell hyperplasia in the rat forestomach were investigated. Male F344 rats were given an initial single gastric intubation of N-methyl-N'-nitro-N-nitoroso-guanidine and then received 2% butylated hydroxyanisole in the diet from the third week to the 26th week. Rats were killed at weeks 26 and 46 after return to basal diet and their forestomachs were removed. Bromouracil deoxyriboside (BUdR) was administered as a single i.p. injection 1 h before death or by osmotic minipump (120 μg/h) continuously for 7 days before death. Additional animals were maintained for 2 or 4 weeks after removal of osmotic minipumps to allow assessment of the fate of proliferating populations. In each case BUdR-labeled cells were demonstrated by immunohisto-chemistry. At week 26, hyperplastic changes were more pronounced than at week 46. Squamous cells above basal cell hyperplasias were strongly labeled even 4 weeks after cessation of continuous BUdR administration, in clear contrast to those in normal-appearing epithelium. Three-dimensional reconstruction of persisting basal cell hyperplasias showed almost all basal cells limited to a thin sheet in direct contact with the squamous cell layer, occasional separate islands demonstrating differentiation to squamous cells and formation of epidermal cysts. The results thus showed that the mechanism of reversibility of basal cell hyperplasia involves differentiation of basal cells to squamous cells.     

Dose Dependence of 1-O-Hexyl-2,3,5-trimethylhydroquinone Promotion of Forestomach Carcinogenesis in Rats Pretreated with N-Ethylnitrosourethane

Post-initiation dose-dependent effects of the chemopreventive antioxidant 1- O -hexyl-2,3,5-trimethylhydroquinone (HTHQ), a potent inhibitor of heterocyclic amine-induced mutagenesis and carcinogenesis, on the development of forestomach and tongue tumors were investigated in male F344 rats. Groups of 22 rats were treated with 0.01% ethylnitrosourethane (ENUR) as an initiator in the drinking water for 4 weeks, then placed on diet containing 1.0%, 0.5%, 0.25% or 0.125% HTHQ, or basal diet alone for 36 weeks. Further groups of 12 rats each were similarly treated with the different doses of HTHQ or given basal diet alone for 36 weeks without prior ENUR treatment. All animals were killed at week 40. Tongue papillary hyperplasia and papillomas tended to be increased in the groups treated with ENUR followed by 0.5–0.125% HTHQ, though there was no effect at the highest dose, in line with increased bromodeoxyuridine labeling indices. In the forestomach, the incidences of papillomas and carcinomas were also significantly elevated only in the group treated with ENUR followed by 0.125% HTHQ. Without ENUR pretreatment, papillary hyperplasia was found in the 1–0.125% HTHQ groups and the labeling index was also increased, though without clear dose dependence. The results indicate that HTHQ may have very weak or weak promotion potential for tongue and forestomach carcinogenesis, but that both minimum and maximum thresholds for active dose levels may exist.     

Effect of Butylated Hydroxyanisole on the Level of DNA Adduction by Aristolochic Acid in the Rat Forestomach and Liver

Administration of butylated hydroxyanisole (BHA) orally at either 0.5 g or 1 g/kg daily for 14 days to rats did not produce any DNA adducts in the forestomach as measured by the ³²P-postlabeling method using (1) limiting concentrations of ³²P-ATP; (2) nuclease P₁ enhancement; or (3) butanol extraction. Experiments were conducted to establish the effects of BHA administration on aristolochic acid (AA) DNA adduct formation in the forestomach and liver, when BHA was administered prior to, together with or after AA administration. Adduct levels per 10⁹ nucleotides in the liver after oral dosing daily for 5 days with 1 mg/kg AA and BHA (1 g/kg) or corn oil (5 ml/kg) for 7 days were as follows: (a) BHA and AA given simultaneously; 235±71, (b) AA+corn oil; 63±39, (c) AA followed by BHA; 57±13, (d) AA followed by corn oil; 91±38, (e) BHA followed by AA; 90±12, (f) corn oil followed by AA; 83±24. For the forestomach the values were: (a) 236±86, (b) 77±25, (c) 367±97, (d) 296±47, (e) 217±81, (f) 70±64. These data suggest that BHA could have an enhancing effect on AA-induced lesions in the forestomach if dosed together with, or prior to, AA as adduct levels are significantly higher than in controls.     

Co-carcinogenic Effect of Retinyl Acetate on Forestomach Carcinogenesis of Male F344 Rats Induced with Butylated Hydroxyanisole

The potential modifying effect of retinyl acetate (RA) on butylated hydroxyanisole (BHA)-induced rat forestomach tumorigenesis was examined. Male F344 rats, 5 weeks of age, were maintained on diet containing 1% or 2% BHA by weight and simultaneously on drinking water supplemented with RA at various concentrations (w/v) for 52 weeks. In groups given 2% BHA, although marked hyperplastic changes of the forestomach epithelium were observed in all animals, co-administration of 0.25% RA significantly (P<0.05) increased the incidence of forestomach tumors (squamous cell papilloma and carcinoma) to 60% (9/15, 2 rats with carcinoma) from 15% (3/20, one rat with carcinoma) in the group given RA-free water. In rats given 1% BHA, RA co-administered at a dose of 0.05, 0.1, 0.2 or 0.25% showed a dose-dependent enhancing effect on the development of the BHA-induced epithelial hyperplasia. Tumors, all papillomas, were induced in 3 rats (17%) with 0.25% RA and in one rat (10%) with 0.05% RA co-administration. RA alone did not induce hyperplastic changes in the forestomach. These findings indicate that RA acted as a co-carcinogen in the BHA forestomach carcinogenesis of the rat.     

Demonstration of Initiation Potential of Carcinogens by Induction of Preneoplastic Glutathione S-Transferase P-Form-positive Liver Cell Foci: Possible in vivo Assay System for Environmental Carcinogens

In a development trial for an initiation bioassay system, 7 known carcinogens and 1 suspected carcinogen were examined. In experiment 1, group 1 animals were initially subjected to partial hepatectomy (PH) 12 h before administration of diethylnitrosamine, 2-amino-3-methylimidazo[4,5- F ]-quinoline (IQ), captafol, α-hexachlorocyclohexane or diethylstilbestrol (DES), then 2 weeks later underwent a promotion procedure comprising administration of phenobarbital (0.05% in diet) for 8 weeks and D-galactosamine (300 mg/kg, i.g.) at week 3. Group 2 received the promotion protocol alone as in group 1. Initiating potential was assayed on the basis of significant increase in values of preneoplastic placental form glutathione S-transferase-positive (GST-P⁺) foci of more than 3 cells in cross section at week 10. Numbers and areas of GST-P⁺ foci in group 1 given IQ, captafol and DES were significantly increased as compared to group 2, confirming the validity of the protocol as an initiation assay. In Experiment 2, group 1 rats were subjected to PH and 12 h later received a suspected carcinogenic mixture of opium pyrolysate (OP) or carcinogenic pesticide p, p' -dichlorodiphenyltrichloroethane or hexachlorobenzene. Application of a modified promotion procedure comprising cholic acid (0.15%) and carbon tetrachloride (1 ml/kg, i.g.) revealed significant initiation potential for OP. Overall the results indicate that the current protocols may be useful for detection of the initiation potential of carcinogens irrespective of their mutagenicity.     

Activation of the Ki-ras gene in spontaneous and chemically induced lung tumors in CD-1 mice.

As part of an evaluation of the effectiveness of using ras mutation analysis for distinguishing carcinogen-induced from spontaneous tumors, we examined the profile of ras gene point mutations in spontaneous, 7,12-dimethylbenz[a]anthracene (DMBA)-induced, and N-nitrosodiethylamine (DEN)-induced lung tumors from Crl:CD-1(ICR)BR (CD-1) mice. Although all of the lung tumors were assayed for mutations in the Ha-ras, Ki-ras, and N-ras genes (codons 12, 13, and 61), only Ki-ras mutations were found, which is consistent with other studies that have noted a strong preference for Ki-ras gene activation in mouse, rat, and human lung tumors. We found that spontaneous CD-1 mouse lung tumors had a very high frequency of Ki-ras gene activation (17 of 20 tumors; 85%), distributed among codons 12 (5 of 20), 13 (1 of 20), and 61 (11 of 20). DMBA-induced lung tumors had a slightly higher frequency of Ki-ras gene mutations (16 of 16; 100%), again distributed among codons 12 (5 of 16), 13 (2 of 16), and 61 (9 of 16). However, seven of the DMBA tumors had mutations qualitatively different from those found in spontaneous tumors. In contrast to DMBA-induced tumors, DEN-induced tumors had a lower frequency of Ki-ras mutations (36%) when compared with spontaneous lung tumors, suggesting that DEN primarily induces lung carcinogenesis by a mechanism other than ras gene activation. Thus, although spontaneous and induced CD-1 mouse lung tumors have a strong tissue-specific preference for carrying an activated Ki-ras gene, the nature of the initiating carcinogen can influence the frequency or profile of Ki-ras mutations.     

Demonstration of ras and p53 Gene Mutations in Carcinomas in the Forestomach and Intestine and Soft Tissue Sarcomas Induced by N-Methyl-N-nitrosourea in the Rat

The presence of ras family and p53 gene mutations in rat forestomach, intestine and liver tumors and soft tissue sarcomas induced by N methyl- N -nitrosourea (MNU) was examined using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) followed by direct sequencing analysis. In the forestomach squamous cell carcinomas (SCC), Ha- ros and p53 mutations were detected in 2 (40%) and 4 (80%) of 5 cases, respectively. The figures for Ki- ras and p53 gene mutations in adenocarcinomas of the large and small intestines were 3 (18.8%) and 5 (31.3%) of 16 cases. Soft tissue sarcomas in different sites were found to have mutations of Ki- ras in 7 (23.3%)and of p53 in 9 (30%) of 30 cases. One forestomach SCC and 2 soft tissue sarcomas had double p53 mutations in different exons. Single cases of forestomach SCC and intestinal adenocarcinoma had mutations in both Ki- ras and p53 genes. No mutations were found in counterpart benign tumors or hepatocellular adenomas. The p53 mutation spectrum revealed preferential clustering within exon 8 for the forestomach SCCs, and exons 5 and 8 for the intestinal adenocarcinomas, whereas the distribution was evenly spread through exons 5 to 8 in soft tissue sarcomas. All the detected ras or p53 mutations were G:C to A:T transitions. These results indicate firstly that specific Ki- ras , Ha- ras and p53 gene mutations in MNU-induced lesions are related to particular alkylation sites (G:C to A:T transitions) and secondly, although not essential, Ki- ras , Ha- ras or p53 gene mutations may be involved in the progression stage of forestomach, intestine and soft tissue neoplasms induced by MNU.     

Synergism of Environmental Carcinogens and Promoters on Bladder Cancer Development Initiated by N-Butyl-N-(4-hydroxybutyl)nitrosamine in F344 Rats

Synergistic or additive effects of combined treatments with carcinogens or promoters on N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-initiated rat bladder carcinogenesis were examined. Male F344 rats were given BBN as an initiator followed by low doses of 3 sodium salts (sodium bicarbonate, sodium L-ascorbate and sodium citrate) and/or 3 antioxidants (butylated hydroxyanisole, butylated hydroxytoluene and tertiary butylhydroxyquinone). Combined treatments with 3 sodium salts or 3 antioxidants, and especially all 6 chemicals together promoted bladder carcinogenesis. In addition, these combined treatments were associated with increased DNA synthesis of the bladder epithelium. Combined administration of the carcinogens, o-anisidine, p-cresidine, and 4-chloro-o-phenylenedi-amine at low doses also enhanced BBN-initiated bladder carcinogenesis. These results indicate that environmental carcinogens or promoters can exert synergistic or additive actions on bladder cancer induction.     

Activation of 2-Hydroxyamino-l-methyl-6-phenylimidazo[4,5-b]pyridne by cDNA-expressed Human and Rat Arylsulfotransferases

Sulfation plays an obligatory role in the activation of N-hydroxy derivatives of carcinogenic aryl-amiric(amide)s and heterocyclic amines. We found that the hepatic sulfotransferase-mediated covalent binding of ³H-labeled 2-hydroxyamino-1-inethy1-6-phenylimidazo[4,5- b ]pyridine (N-OH-PhIP) to calf thymus DNA was 3.3 and 12.9 times higher with human cytosol preparation than with male and female rat cytosol preparations, respectively, in the presence of 3'-phosphnadenosine 5'-phospho-sulfate. To assess the activating capacities of individual phenol-sulfating sulfotransferascs, five different forms, human ST1A2 and ST1A3 and rat ST1A1, ST1B1 and ST1C1, were expressed in heterologous cells. All five sulfotransferases mediated the activation of N-OH-PhIP to DNA-bound products. The extents of the binding, however, differed considerably among these forms. Human ST1A2 and ST1A3 mediated the activation of N-OH-PhIP at 5.2- and 6.2-fold higher rates than did rat ST1C1, a main N-hydroxy-2-acetylaminofluorene-activating sulfotransferase, in rat liver. Extents of the binding of N-OH-PhIP in human hepatic cytosols of different individuals were positively correlated with the contents of immunoreactive ST1A2/3. These results suggest a potential role of human liver sulfotransferases in N-OH-PhIP activation. In contrast, the low sulfotransferase-mediated activation of N-OH-PhIP in rat liver is consistent with the lack of PhIP hepatocarcino-genicity in this species.     

苏乐康胶囊抑制理化致癌因子诱发小鼠的肿瘤发生

本文用苏乐康胶囊,剂量为39mg,每天1次灌胃,连续7天,抑制~(60)钴γ线全身照射0.5Gy和二乙基亚硝胺(DENA)皮下注射,剂量为0.1mg,每周注射1次,共8次,诱发雄性LACA小鼠肺肿瘤的发生。该胶囊不仅明显地抑制和阻断肺肿瘤的发生,其发生率由80.0％降到26.1％,P<0.01,而且肺癌的发生率也明显降低,由26.7％降到0.0%,P<0.01。该胶囊阻断γ线和DENA的联合致癌作用机制与其中人参、黄芪、维生素E等具有还原和抗氧化作用有关,能捕获自由基,减轻或消除其对靶细胞的损伤。     

The Modifying Effects of Indomethacin or Ascorbic Acid on Cell Proliferation Induced by Different Types of Bladder Tumor Promoters in Rat Urinary Bladder and Forestomach Mucosal Epithelium

The effects of indomethacin (IM) or L-ascorbic acid (AsA) on cell proliferation induced by bladder tumor promoters such as butylated hydroxyanisole (BHA), sodium L-ascorbate (Na-AsA), sodium citrate (Na-Cit), and diphenyl (DP) in rat bladder and forestomach epithelium were investigated. Treatment with IM in combination with BHA or Na-AsA diminished DNA synthesis levels of bladder epithelium as compared to the BHA or Na-AsA alone values. On the other hand, AsA further amplified the increase of bladder epithelial DNA synthesis caused by Na-Cit treatment. Histopathologically, administration of Na-AsA in combination with IM reduced the incidence of simple hyperplasia. In contrast, simultaneous treatment with Na-Cit and AsA caused an increase of the hyperplasia development. No apparent combination effects were observed in the DP-treated groups. In forestomach epithelium, AsA enhanced the BHA-induced increase in DNA synthesis and epithelial hyperplasia, characterized by marked basal cell proliferation. The present results thus suggested that IM may exert inhibitory effects on promotion of bladder carcinogenesis by certain tumor promoter types, and AsA may enhance BHA forestomach carcinogenesis.     

Structure-Activity Relations in Promotion of Rat Urinary Bladder Carcinogenesis by Phenolic Antioxidants

The urinary bladder tumor-promoting potentials of the phenolic antioxidants, 2- tert -butyl-4-methyl-phenol (TBMP), propylparaben, catechol, resorcinol and hydroquinone, which are structurally related to butylated hydroxyanisole (BHA), were investigated in 170 male F344 rats. The animals were initially given 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) as an initiator in their drinking water for 4 weeks. Three days later, groups of 20 rats received diet containing 1.0% TBMP, 3% propylparaben, 0.8% catechol, 0.8% resorcinol, 0.8% hydroquinone or basal diet alone until the end of week 36. Significant increases in the incidences and average numbers of the putative preneoplastic lesions, papillary or nodular (PN) hyperplasia, and papillomas of the urinary bladder were only observed in the group given TBMP after BBN. Development of these lesions was not enhanced by diet containing the other test compounds and no induction was associated with any of the test chemicals alone. The results thus clearly showed that TBMP, which most closely resembles BHA, promoted urinary bladder carcinogenesis. The similar effects of TBMP and BHA on urinary bladder carcinogenesis suggest a direct link between chemical structure and biological potency.     

Potential Prophylactic Effect of Berberine against Rat Colon Carcinoma Induce by 1,2-Dimethyl Hydrazine

Introduction: Colon Cancer remains one of the major worldwide causes of cancer related morbidity and mortalityin both genders. Berberine (BBR), a major component of alkaloids that possess a variety of pharmacological properties.Objective: This study shows the ameliorating roles of berberine on 1,2 Di methyl hydrazine (DMH) induced coloncancer in male Swiss albino rats. Methods: The rats were segregated into four groups: group 1, control rats; group2, rats were orally received berberine (75 mg/kg b.wt./day) daily for ten weeks; group 3,rats were subcutaneouslyinjected with DMH (20 mg/kg b.wt) once a week for 8 weeks ,group 4, rats were treated firstly with berberine fortwo weeks before DMH intoxication and concurrently with DMH over 8 weeks. Result: DMH injection decreasedthe antioxidants levels (GSH and SOD) and increased inflammatory markers (MPO, MAPK and COX-2). Moreover,it downregulated apoptotic markers (Caspase-3 and P53) expression that confirmed by colon cell proliferation. Theprophylactic effect of berberine was noticed as its pre-and co-administration increased antioxidants status and apoptoticmarkers expression that associated with inflammatory markers down-regulation with absence of proliferated coloncells. Conclusion: Therefore, the overall findings proved that the anti-proliferative effect of berberine return to itsantioxidants and anti-inflammatory properties that activated the programmed cell death process.     

苦参碱和氧化苦参碱对二乙基亚硝胺诱发大鼠肝癌的预防阻断作用

目的 :研究苦参碱 (MT)和氧化苦参碱 (OMT)分别对二乙基亚硝胺 (DEN)诱发大鼠肝癌的预防阻断作用。方法 :采用 0 .0 1%的DEN诱发大鼠肝癌 90d ,同时分别腹腔注射MT和OMT注射液 15mg/kg ,停止诱癌及给药处理 30d后 ,处死大鼠 ,观察大鼠肝脏的病理改变、肝表面癌结节数、肝 /体重比和血清中丙氨酸氨基转移酶 (ALT)、γ 谷氨酰转肽酶 (γ GT)、碱性磷酸酶 (ALP)的变化。结果 :MT组和OMT组大鼠的体重明显高于模型组 ,肝表面癌结节数、肝 /体重比和血清ALT、γ GT明显低于模型组 (P<0 0 5) ,而ALP较模型组有所升高。另外 ,OMT组的肝重、肝 /体重比和血清ALP均明显低于MT组(P <0 0 5)。结论 :MT和OMT ,尤其是OMT ,尽管不能完全阻断DEN诱发大鼠肝癌的发生 ,但能保护肝细胞免受损伤 ,延缓DEN诱发大鼠肝癌的形成     

姜黄素对马兜铃酸诱发的膀胱肿瘤的预防作用

 目的 以马兜铃酸诱发的膀胱癌为模型，观察姜黄素对膀胱组织的病理变化、Ras蛋白和p53蛋白及细胞角质蛋白20（CK20）的变化，评价姜黄素对马兜铃酸诱导膀胱癌的化学预防作用及发生机制。方法 50只大鼠随机分为对照组、诱癌组、预防组三组。诱癌组：给予10mg（kg·d）马兜铃酸给大鼠灌胃,连续诱癌3个月；预防组：在诱癌的同时给予含2%姜黄素粉的饲料进行化学防护；对照组：为正常饮食和饮水。3个月后宰杀全部大鼠，取膀胱组织进行HE染色显微镜下观察病理变化，用免疫组化染色技术检测膀胱组织内Ras、p53蛋白的变化，荧光定量PCR技术检測CK20 mRNA。结果 经3个月诱癌，膀胱癌的发生率在诱癌组为95% (19／20)，而姜黄素预防组，膀胱癌的发生率仅为10%（2/20），对照组膀胱黏膜组织Ras、p53蛋白及CK20 mRNA均呈阴性表达，预防组及诱癌组膀胱黏膜组织Ras、p53蛋白及CK20 mRNA均呈阳性，且以诱癌组更明显，差异具有统计学意义（P<0.001）。结论 姜黄素对马兜铃酸诱导的膀胱癌具有良好的化学预防作用，可能分子机制与抑制 Ras、p53蛋白的过度表达能力有关。姜黄素有望成为一种有应用前景的膀胱癌预防药物。     

Effects of Sodium Nitrite and Catechol or 3-Methoxycatechol in Combination on Rat Stomach Epithelium

The effects of sodium nitrite (NaNO₂) and catechol or 3-methoxycatechol in combination were examined in male F344 rats. Animals were treated with 0.3% NaNO₂ in the drinking water and 0.8% catechol or 2% 3-methoxycatechol in powdered diet for 24 weeks. While catechol or 3-methoxycatechol alone induced low incidences of mild or moderate hyperplasia, simultaneous administration of NaNO₂ markedly enhanced the degree of hyperplasia and papilloma formation. In contrast, induction of submucosal hyperplasia and adenomas in the glandular epithelium was reduced. Thus, the results indicate that NaNO₂ can modulate the metabolism of antioxidants, so that, possibly via production of new active moieties, targeting of forestomach epithelium is enhanced.     

Simultaneous Measurement of Unscheduled and Replicating DNA Synthesis by Means of a New Cell Culture Insert DNA Retention Method: Rapid Induction of Replicating DNA Synthesis in Response to Genotoxic Carcinogens

In order to measure simultaneously replicating DNA synthesis (RDS) and unscheduled DNA synthesis (UDS) in rat hepatocytes responding to exposure to carcinogens, a new method, namely the "cell culture insert DNA retention (CDR)" method, was developed. All CDR procedures for cell culture, digestion of cytoplasm and retention of DNA were performed on membranes attached to cell culture containers. Four subgroups of primary cultures of hepatocytes prepared from rats were exposed to a genotoxic or non-genotoxic carcinogen with or without 10 m M hydroxyurea and incubated for 4 h with 10 μCi/ml [³H]thymidine. The membranes were then processed for both liquid scintillation and autoradiography. Among seven tested chemicals, three genotoxic agents, 3,2'-dimethyl-4-aminobiphenyl, 2-acetylaminofluorene and diethylnitrosamine, and two non-genotoxic carcinogens, nafenopin and phenobarbital, induced RDS within 4 h after the exposure, indicating that these carcinogenic agents induce cell proliferation in non-proliferating rat hepatocytes prior to the emergence of genotoxic changes. Several indices were devised to characterize the genotoxicity of the tested chemicals. The induction patterns obtained showed a wide variation in the individual characteristics of carcinogen-induced genotoxicity and mitogenicity in the early phase of initiation. This is the first report of simultaneous measurement, by using a combination of autoradiography and liquid scintillation, of UDS and RDS induced in rat hepatocytes. The described CDR approach will be useful for risk assessment and characterization of carcinogenic and tumor-promoting agents.     

Genetic Regulation of Development of Thymic Lymphomas Induced by N-Propyl-N-nitrosourea in the Rat

To clarify the linkage between Hbb and Tls-1 (thymic lymphoma susceptible-1) loci and to investigate other loci concerned in thymic lymphomagenesis, the BUF/Mna rat, which is highly sensitive to the lymphomagenic activity of N -propyl- N -nitrosourea (PNU), the WKY/NCrj rat, reported to be resistant, and their cross offspring were subjected to genetic analysis. F₁ hybrid and backcross generations were raised from the 2 strains, and 6 genetic markers including Hbb were analyzed in individuals of the backcross generation. However, no linkage between Hbb and Tls-1 loci could be demonstrated since WKY rats also developed a high incidence of thymic lymphomas in response to PNU. Nevertheless, thymic lymphomas developed more rapidly and reached a larger size in the BUF rats. F₁ rats expressed a rather rapid and large tumor growth phenotype, while the [(WKY × BUF) × WKY] backcross generation consisted of rats with either rapidly growing or slowly growing tumors. It was thus concluded that rapid development of thymic lymphomas is determined by a gene, provisionally designated Tls-3 . Analysis of the relationship between 6 genetic markers and development of thymic lymphoma in the backcross generation demonstrated that the Tls-3 locus is loosely linked to the Gc locus, suggesting a possible location on rat chromosome 14. Tls-3 may not be identical with Tls-1 and other genes known to be relevant to thymic tumors, but its relationship with Tls-2 remains obscure.     

Sequential Observation of Rat Prostate Lesion Development Induced by 3,2'-Dimethyl-4-aminobiphenyl and Testosterone

3,2'-Dimethyl-4-aminobiphenyl (DMAB), when combined with high doses of testosterone propionate (TP) induces invasive adenocarcinomas with metastatic potential in the rat prostate. The processes underlying this tumor development, including the involvement of atypical hyperplasias, were sequentially investigated in F344 rats. DMAB was given subcutaneously at a dose of 50 mg/kg body weight 10 times at 2-week intervals. TP was administered chronically (in Silastic tubes) from the beginning of the experiment or after the DMAB administration until termination (week 60). Invasive adenocarcinomas were induced in the lateral and anterior prostate as well as the seminal vesicles. Atypical hyperplasias appeared from an early stage, with the later appearance of cancers being closely associated with such foci of morphological alteration. The findings confirm that combined administration of DMAB and pharmacological doses of TP yields invasive adenocarcinomas in the rat prostate and provide further support for the conclusion that atypical hyperplasias are premalignant lesions.     

Expression and Localization of Ornithine Decarboxylase in Reversible Papillomatosis Induced by Uracil in Rat Bladder

Direct mechanical irritation by uracil calculi formed following feeding of 3% uracil in the diet to male rats produces severe papillary hyperplasia (papillomatosis, which is reversible) of bladder epithelium. To evaluate the mechanism of the appearance of uracil-induced papillomatosis, we examined the changes of the enzyme activity and the localization of ornithine decarboxylase (ODC), as well as polyamine biosynthesis, and epithelial proliferation, that accompany the sequential bladder epithelial changes following administration and withdrawal of uracil. Moreover, expression of ODC mRNA was investigated using northern blotting and localization of ODC mRNA was demonstrated using in situ hybridization. ODC activity during uracil administration was maintained at a high level compared to that in normal epithelium, but sharply decreased after cessation of uracil treatment. The accumulation of ODC protein was observed in the proliferating bladder epithelium by immunohistochemical examination and western blotting analysis, and even after cessation of treatment, the protein binding to anti-ODC antibody remained mildly elevated. Sequential changes of proliferating cell nuclear antigen (PCNA)-positive cells in the epithelium during the development and disappearance of papillomatosis correlated with ODC activity. ODC mRNA was expressed strongly in the proliferating epithelium in rats treated with uracil and weakly in normal epithelium, in accordance with the location of ODC protein. Consequently, our data demonstrate that cell proliferation in the development of papillomatosis is closely associated with polyamine metabolism, and moreover suggest that ODC activity is up-regulated at a post-translational step.