Carcinogenicity of catechol in F344 rats and B6C3F1 mice

Carcinogenicity of catechol, a naturally occurring and industrialchemical which has been shown to have strong cell proliferatingpotential on rat glandular stomach epithelium, was investigatedin male and female F344 rats and B6C3F₁ mice. Groups of 30 maleand female F344 rats and B6C3F₁ mice were treated with 0.8%catechol in powdered diet continuously for 104 weeks (rats)or 96 weeks (mice). At necropsy, neoplastic lesions were observedmainly in the glandular stomach of both species. Adenomas werefound in all rats and in the majority of mice: 29 out of 30(97%) in males and 21 out of 29 (72%) females. In addition 15out of 28 (54%) and 12 out of 28 (43%) of the male and femalerats respectively, had well differentiated adenocarcinomas.No adenocarcinomas were found in mice of either sex. In theforestomach epithelium, although significant increase in papillomadevelopment was not evident, incidences of squamous cell hyperplasiawere significantly increased in rats and mice of both sexes.In other organs examined, incidence and numbers of liver hyperplasticfoci per cm² liver section were significantly lower in malerats. Although the incidence was not different, the numbersof hyperplastic foci were also significantly reduced in femalerats. Thus the present experiment clearly demonstrated thatcatechol exerts carcinogenic activity in rodent glandular stomachepithelium.     

Association between growth stimulation by phenobarbital and expression of cytochromes P450 1A1, 1A2, 2B1/2 and 3A1 in hepatic hyperplastic nodules in male F344 rats.

This study was conducted to examine relationships between phenobarbital (PB) treatment, specific cytochrome P450 gene expression patterns and growth rates of hepatic hyperplastic nodules. Nodules were induced in 8 week old male F344 rats by a Solt-Farber resistance protocol. Six weeks after diethylnitrosamine (DEN) initiation, subgroups of rats were either kept on control chow diet or transferred to a chow diet containing 0.05% PB, then killed 2 weeks later. [3H]Thymidine was delivered continuously via osmotic minipump during the final 3 days of the experimental to label dividing cells. PB treatment resulted in a 89% increase in the number of persistent gamma-glutamyl transpeptidase (GTT) nodules per cm2 section, a 278% increase in the area of persistent GGT nodules per cm2 section, and a 116% increase in the average area per persistent nodule. PB increased the number of [3H]thymidine-labeled persistent GGT nodules but did not significantly change the labeling index (LI) distribution pattern or the average LI. A slight but uniform increase in CYP1A2 expression (relative to surrounding, non-nodular tissue) was observed in 50% (23/46) and 59% (60/102) of persistent nodules in control and PB-treated animals respectively. In contrast, for nodules undergoing remodeling, CYP1A2 expression was elevated in only 9% (2/22) and 0% (0/24) in control and PB groups respectively. In the PB group, CYP2B1/2 was underexpressed in 53% (54/102) of persistent GGT nodules and in 0% (0/24) of the remodeling nodules. Comparing LI among the persistent GGT nodules, those that displayed simultaneous increases in CYP1A2 and decreases in CYP2B1/2 had the highest LI, and were followed in level by those expressing either increases in CYP1A2 or decreases in CYP2B1/2. Nodules that expressed both CYP1A2 and 2B1/2 in a manner similar to the surrounding tissue had the lowest LI. Thus, these data suggest that expression of specific forms of cytochrome P450 may be an important factor in determining other phenotypic characteristics, e.g. rate of cell proliferation and GGT expression, within specific nodules.     

DNA adduct formation in B6C3F1 mice and Fischer-344 rats exposed to 1, 2, 3-trichloropropane

1, 2, 3-Trichloropropane (TCP) is a multispecies, multisitecarcinogen which has been found to be an environmental contaminantIn this study, we have characterized and measured DNA adductsformed in vivo following exposure to TCP. [¹⁴C]TCP was administeredto male B6C3F1 mice and Fischer-344 rats by gavage at dosesused in the NTP carcinogenesis bioassay. Both target and nontargetorgans were examined for the formation of DNA adducts. Adductswere hydrolyzed from DNA by neutral thermal or mild acid hydrolysis,isolated by HPLC, and detected and quanti-tated by measurementof radioactivity. The HPLC elution profile of radioactivitysuggested that one major DNA adduct was formed. To characterizethis adduct, larger yields were induced in rats by intraperitonealadministration of TCP (300 mg/kg). The DNA adduct was isolatedby HPLC based on coelution with the radiolabeled adduct, andcompared to previously identified adducts. The isolated adductcoeluted with S-[1-(hydroxymethyl)-2-(N⁷-guanyl)-ethyljglutathione,an adduct derived from the structurally related carcinogen 1,2-dibromo-3-chloropropane (DBCP). Analysis by electrospray massspectrometry suggested that the TCP-induced adduct and the DBCP-derivedadduct were identical. The ¹⁴C-labeled DNA adduct was distributedwidely among the organs examined. Adduct levels varied dependingon species, organ, and dose. In rat organs, adduct concentrationsfor the low dose ranged from 0.8 to 6.6 µmol per mol guanineand from 7.1 to 47.6 µmol per mol guanine for the highdose. In the mouse, adduct yields ranged from 0.32 to 28.1 µmolper mol guanine for the low dose and from 12.2 to 208.1 µmolper mol guanine for the high dose. The relationship betweenDNA adduct formation and organ-specific tumorigenesis was unclear.Although relatively high concentrations of DNA adducts weredetected in target organs, several nontarget sites also containedhigh adduct levels. Our data suggest that factors in additionto adduct formation may be important in TCP-induced carcinogenesis.     

Forestomach neoplasm induction in F344/DuCrj rats and B6C3F1 mice exposed to sesamol.

Sesamol was administered at a dietary level of 2% to groups of 30 male and female F344/DuCrj rats and B6C3F1 mice for 104 and 96 weeks, respectively. Squamous cell carcinomas in the forestomach were induced in nine of 29 (31%) effective male rats, three of 30 (10%) female rats, eleven of 29 (38%) male mice and five of 30 (17%) female mice treated with sesamol. Papillomas developed in ten of 29 (34%) male rats and fourteen of 30 (47%) female rats, but not in any of the mice. Hyperplasias developed in almost all rats and mice of both sexes. Significant differences from control values were found for all three lesions in rats and for carcinoma and hyperplasia categories in mice. The incidences of other tumors in the 2% sesamol group were comparable with control values. In conclusion, sesamol induces squamous cell carcinomas in the forestomach of rats and mice, males being more susceptible than females.     

Carcinogenicity of 4-chloro-o-phenylenediamine, 4-chloro-m-phenylenediamine, and 2-chloro-p-phenylenediamine in Fischer 344 rats and B6C3F1 mice

In both male and female Fischer rats, feeding 4-chloro-o-phenylenediamineat 0.5 or 1% in the diet led to a significant increase in hyperplasia,papilloma and carcinoma of the urinary bladder. Neoplastic nodulesof the liver and squamous cell papillomas of the stomach werealso increased slightly. Similar levels of this compound inmale and female B6C3F₁ mice increased significantly the incidenceof hepatocellular adenomas and carcinomas. 4-Chloro-m-phenylenediamineat 0.2 or 0.4% in the diet led to a significant elevation inthe incidence of adrenal pheochromocytoma in male rats. At 1or 2% levels it caused hepatocellular carcinoma or hepatocellularcarcinoma and hepatocellular adenoma in female mice. Althoughthe analog, 2-chloro-p-phenyl-enediamine increased transitionalcell hyperplasia of the kidney in both male and female rats,it had no significant neoplastic effect at the 0.15 or 0.3%levels fed.     

Comparative tumorigenicity of N-nitroso-2-hydroxymorpholine, N-nitrosodiethanolamine and N-nitrosomorpholine in A/J mice and F344 rats

N-Nitroso-2-hydroxymorpholine (NHMOR), a genotoxic metaboliteof the environmental carcinogens N-nitrosomor-pholine (NMOR)and N-nitrosodiethanolaraine (NDELA), was assayed for tumorigenidtyin A/J mice and F344 rats. Groups of female mice were givenNHMOR, NMOR or NDELA in the drinking water over a 10-week period;total doses were 53–55 µmol/mouse. The experimentwas terminated after 30 weeks. Whereas NMOR was a potent tumorigen,inducing 20.3 lung tumors/mouse, NHMOR and NDELA were only weaklytumorigenic, giving 1.2 and 1.4 lung tumors/mouse respectively.Groups of female F344 rats were also given these three nitrosaminesin drinking water for 50 weeks, as follows: NHMOR, total dose0.6 mmol/rat; NHMOR, 1.2 mmol; NMOR, 1.1 mmol and NDELA, 5.6mmol. The experiment was terminated after 120 weeks. NMOR wasa potent carcinogen, inducing liver tumors in 100% of the rats.NDELA gave hepatocelhilar tumors in 70% of the rats. NHMOR wasinactive even at the higher dose. The results of this studydo not support the hypothesis that NHMOR is a proximate carcinogenof NDELA or NMOR.     

Carcinogenicity of captafol in F344/DuCrj rats

Captafol was administered at dietary levels of 0 (control), 750 and 1,500 parts per million (ppm) to groups of 50 male and 50 female F344/DuCrj rats for 104 weeks, and then all animals were maintained without captafol for a further 8 weeks, and killed in week 113. Renal cell carcinoma was found in eight of 50 male rats treated with 1,500 ppm and in one of 50 male rats treated with 750 ppm of captafol. The incidences of renal adenomas, including micro-adenomas, and basophilic altered cell tubules were significantly higher in both sexes treated with captafol than in controls, and the increases were apparently dose-dependent except that of adenomas in females. The incidences of neoplastic and preneoplastic lesions of the kidney in captafol-treated animals were higher in males than in females. Captafol also induced hepatocellular carcinomas in four of 50 female rats in the 1,500 ppm group. The incidences of hyperplastic (neoplastic) nodules and foci of cellular alterations in the liver were also significantly increased in both sexes treated with captafol, the increases being dose-dependent. In conclusion, captafol induced renal cell carcinomas in male rats and hepatocellular carcinomas in female rats.     

CYP2E1*5B,CYP2E1*6, CYP2E1*7B,CYP2E1*2, and CYP2E1*3 Allele Frequencies in Iranian Populations

Background: CYP2E1 encodes an enzyme which is mainly involved in bioactivation of potential carcinogenssuch as N-nitrosamines. Polymorphisms in the gene have been reported to be associated with cancer. The aim ofthis study was to evaluate genotype distributions and allele frequencies of five CYP2E1 polymorphisms in IranMaterials and Methods: Two hundred healthy individuals of an Iranian population from the southwest wereincluded in this study. PCR-restriction fragment length polymorphism and Tetra-ARMS PCR methods wereapplied for CYP2E1 genotyping. Results: The allele frequencies for *5B, *6, *7B, *2, and *3 were calculated tobe 1.5%, 16%, 28.5%, 0%, and 2.75% respectively. Results of this study showed that no significant differencesin genotype and allele frequencies of five single nucleotide polymorphisms with respect to the gender andtribes. The chi-square test showed that the genotype frequencies of CYP2E1*5B were similar to Caucasians,but the distribution of CYP2E1*6 genotypes was similar to Asians. The frequencies of CYP2E1*2 (0%) andCYP2E1*3 (2.75%) alleles were within the range for Caucasians and Orientals. In the case of CYP2E1*7B, thedata werelimited. Accordingly, the results were only compared with Europeans and the comparison showedsignificant differences. Conclusions: In conclusion, ethnic and geographic differences may explain discrepanciesin the prevalence of CYP2E1 polymorphisms.     

黄曲霉毒素B1诱发大鼠肝癌过程中对CYP3A4活性的影响

目的 探讨黄曲霉毒素B1(AFB1)诱发肝癌过程中对CYP3A4活性的影响.方法 采用大鼠肝微粒体混合酶体外代谢体系,利用荧光定量法动态检测AFB1诱发肝癌过程中不同时期CYP3A4酶活性.结果 AFB1组CYP3A4含量从实验开始逐渐升高,至23周达顶峰,然后逐渐降低,到43周又升高,出现双波峰变化,阶段性比较差异有统计学意义(P=0.000);对照组CYP3A4含量在整个实验过程中,除33周和63周出现明显降低外,其他各阶段变化不大;组间比较显示AFB1组在诱癌过程中有抑制CYP3A4的趋势,于63周抑制最明显,但尚未达统计学意义(P=0.638);结论AFB1在诱癌过程中有抑制CYP3A4的趋势,可能是与早期癌变的细胞减少对特定基因毒性物质的活化有关.     

Liver carcinogenesis by methyl carbamate in F344 rats and not in B6C3F1 mice.

Short-term and long-term carcinogenicity of methyl carbamate (MCB) was evaluated in F344 rats and B6C3F1 mice. In experiments lasting 6, 12, and 18 months, MCB was given in water by gavage to groups of 10 male and 10 female rats at 0 or 400 mg/kg body weight, 5 days per week, and to similar groups of mice at 0 or 1,000 mg/kg. At 6 months, MCB induced atypical mitoses, cytologic alterations, cytomegaly, pigmentation, necrosis, and neoplastic nodules of the liver in rats. At 12 and 18 months, carcinomas of the liver were induced by MCB in 80-90% of male rats and in 60-80% of female rats. None was observed in control rats or in mice. In the 2-year studies, MCB was given to groups of 50 male and 50 female rats at 0, 100, or 200 mg/kg and to similar groups of mice at 0, 500, or 1,000 mg/kg, 5 days/week. Chronic focal inflammation, cytologic alteration, hyperplasia, and neoplastic nodules and carcinomas (200 mg/kg groups only) of the liver were induced by MCB in rats. Liver tumor incidence data for combined experiments in rats were: males--5% in controls, 0% in 100 mg/kg group, 14% in 200 mg/kg group, and 77% in 400 mg/kg group; females--5% in controls, 0% in controls, 0% in 100 mg/kg group, 12% in 200 mg/kg group, and 63% in 400 mg/kg group. MCB was not shown to be carcinogenic in mice.     

Differential effects of oltipraz on CYP1A and CYP2B in rat lung

Oltipraz (OPZ) is a potent chemopreventive agent against chemically-induced carcinogenesis in several animal models. It affects the expression and/or activity of xenobiotic-metabolizing enzymes and its effects are altered in the course of inflammation in liver. The present study was undertaken to analyse the effect of OPZ alone or in combination with Escherichia coli lipopolysaccharide (LPS) on the expression and activities of glutathione S-transferases (GSTs) and cytochrome P450 (CYPs) in rat lung and kidney. Male Wistar rats were fed a diet containing OPZ for 1-5 days. LPS was injected 24 h before the end of OPZ treatment (from 48 to 72 h). Total GST activity, measured using 1-chloro-2,4-dinitrobenzene as a substrate, increased slightly in both lung and kidney during OPZ treatment. As previously demonstrated in the liver, OPZ induced rat GSTP1 in both kidney and lung and this effect was totally (kidney) or partially (lung) inhibited by co-treatment with LPS. CYP1A expression and activity were strongly increased in both tissues 24 h after starting OPZ treatment and maintained for 5 days. This increase was suppressed during the acute-phase response to endotoxin. OPZ has no effect on CYP2B1 mRNA expression in the lung, but it dramatically decreased the amount and activity of the corresponding apoprotein. The OPZ-dependent decrease in the CYP2B1 apoprotein was abolished and its corresponding activity partially reversed during LPS treatment. In reconstitution experiments using cytosol from OPZ-treated or control rat lungs and microsomal fractions, CYP2B1 apoprotein was rapidly degraded in the presence of cytosol from treated rats. This effect was partially reversed in the presence of MG132, a proteasome inhibitor. These observations support the conclusion that the decrease of CYP2B1 by OPZ involves proteasome-dependent degradation and represents a new mechanism of regulation by this compound.     

Lack of carcinogenicity of quercetin in F344/DuCrj rats

Quercetin was administered at dietary levels of 0(control), 1.25 and 5.0% to groups of 50 male and 50 female rats for 104 weeks, and then all animals were maintained without quercetin supplement for a further 8 weeks. At 5.0% quercetin, both sexes showed growth retardation throughout the study. There were no treatment-ascribed effects regarding clinical signs, mortality, urinalyses or hematology. Although serum glucose in 5.0% quercetin-treated males was significantly decreased and some relative organ weights in 5.0% groups showed statistically significant increases, these latter changes seemed to be related to the growth retardation. An increased incidence of non-neoplastic hyperplastic polyps in the cecum was noted in the 5.0% males. The incidences of cystic changes and fibroadenomas of the mammary gland, and foci (areas) of hepatocellular alteration in the 5.0% females, and liver bile duct proliferations in the 5.0% males were significantly decreased. No proliferative lesions of the urinary bladder related to treatment with quercetin were found in any rats. The incidences of several other nonneoplastic and neoplastic lesions which demonstrated statistically significant changes appeared to be related to the growth retardation or to be within the normal range, and therefore none was considered to be significant biologically. Thus, the investigation did not demonstrate any clear carcinogenic effect of quercetin on F344 rats at dietary levels of up to 5.0%.     

CYP2W1, CYP4F11 and CYP8A1 polymorphisms and interaction of CYP2W1 genotypes with risk factors in Mexican women with breast cancer

Breast cancer (BCa) is the leading type of cancer in Mexican women. Genetic factors, such as single nucleotide polymorphisms (SNP) of P450 system, have been reported in BCa. In this report, and for the first time in the literature, we analyzed the rs3735684 (7021 G>A), rs11553651 (15016 G>T) and rs56195291 (60020 C>G) polymorphisms in the CYP2W1, 4F11 and 8A1 genes in patients with BCa and in healthy Mexican women to identify a potential association between these polymorphisms and BCa risk. Patients and controls were used for polymorphism analysis using an allelic discrimination assay with TaqMan probes and confirmed by DNA sequencing. Links with clinic-pathological characteristics were also analyzed. Statistical analysis was performed using the standard χ2 or Fisher exact test statistic. No significant differences were observed in the distributions of CYP2W1 (OR 8.6, 95%CI 0.43-172.5 P>0.05; OR 2.0, 95%CI 0.76-5.4, P>0.05) and CYP4F11 (OR 0.3, 95%CI 0.01-8.4 P>0.05) genotypes between the patients and controls. Only the CYP8A1 CC genotype was detected in patients with BCa and the controls. All polymorphism frequencies were in Hardy-Weinberg Equilibrium (HWE) in the controls (P>0.05). We found a significant association between BCa risk and smoking, use of oral contraceptives or hormonal replacement therapy (HRT), obesity, hyperglycemia, chronic diseases, family history of cancer and menopausal status in the population studied (P<0.05). Tobacco, oral contraceptive or HRT, chronic diseases and obesity or overweight were strongly associated with almost eight, thirty-five, nine and five-fold increased risk for BCa. Tobaco, obesity and hyperglycemia significantly increased the risk of BCa in the patients carrying variant genotypes of CYP2W1 (P<0.05). These results indicate that the CYP2W1 rs3735684, CYP4F11 rs11553651 and CYP8A1 rs56195291 SNPs are not a key risk factor for BCa in Mexican women. This study did not detect an association between the CYP2W1, 4F11 and 8A1 genes polymorphisms and BCa risk in a Mexican population. However, some clinico-pathological risk factors interact with CYP2W1 genotypes and modifies susceptibility to BCa.     

Effect of voluntary exercise on azoxymethane-induced hepatocarcinogenesis in male F344 rats.

The effect of voluntary exercise on azoxymethane-induced hepatocarcinogenesis was investigated in male F344 rats. Beginning at 5 weeks of age, all animals were divided into two groups (sedentary and exercise) and fed AIN-76A semipurified diet ad libitum. At 7 weeks of age, animals were given azoxymethane (AOM) s.c. at a dose level of 15 mg/kg of body weight, once weekly for 2 weeks. Four days after the second dose of AOM, all animals in the exercise group were housed in individual wheel-cage units and the animals in the sedentary group were housed in plastic cages. The experiment was terminated at 38 weeks post-AOM treatment. Body weights of animals in the exercise and sedentary groups were comparable. Immunohistochemical staining of glutathione S-transferase placental form (GST-P) was performed in the liver and measured GST-P positive foci. Density (number of GST-P positive foci/cm2 area of liver section), average area of foci and unit area of foci were significantly inhibited in the exercise group, although the incidence of neoplastic nodules and GST-P positive foci were unaffected by the exercise. Thus, energy expenditure due to exercise may reduce hepatocarcinogenesis in a laboratory animal model.     

Sequential changes of the forestomach of F344 rats, Syrian golden hamsters, and B6C3F1 mice treated with butylated hydroxyanisole

Butylated hydroxyanisole (BHA) was given to F344 rats, Syrian golden hamsters and B6C3F1 mice at 2 doses for up to 104 weeks. The two doses were 2.0% and 1.0% for rats and hamsters, and 1.0% and 0.5% for mice. Animals were sacrificed sequentially at 8-week intervals from week 8 to week 104, and the carcinogenic effects of BHA on the forestomach were examined histopathologically. Papillomas and carcinomas were found in rats, hamsters and mice. In rats, papillomas first appeared in week 8 in the group given the higher level of BHA and in week 56 in that given the lower level. The first carcinoma was observed in week 48 in rats given the high level, while no carcinoma was observed in rats given the lower level. In hamsters, papillomas appeared in week 8 in both BHA-treated groups, and in both groups, the incidence of papillomas was much higher than in BHA-treated rats. Squamous cell carcinomas were observed in 4 hamsters (10.0%) among those that survived more than 64 weeks on treatment with the higher level of BHA and in 4 (7.3%) among those treated with the lower level. In mice, papillomas were induced by BHA in both BHA-treated groups after more than 88 weeks. Although the incidence was not statistically significant, carcinoma was also seen in mice, suggesting that BHA may also be carcinogenic to mouse forestomach.     

Correlation of DNA adduct formation and riddelliine-induced liver tumorigenesis in F344 rats and B6C3F(1) mice

Riddelliine is a naturally occurring pyrrolizidine alkaloid that induces liver hemangiosarcomas in male and female F344 rats and male B6C3F(1) mice. We previously reported that eight dehydroretronecine (DHR)-derived DNA adducts were formed in liver DNA of rats treated with riddelliine. In order to examine the relationship between DNA adduct levels and the incidence of hemangiosarcomas, we have measured DHR-derived DNA adduct levels in purified rat and mouse liver endothelial cells, the cells of origin for the hemangiosarcomas. F344 rats and B6C3F(1) mice were treated by gavage 5 days per week for 2 weeks with riddelliine at 1.0 mg/kg for rats and 3.0 mg/kg for mice. One, 3, 7, and 28 days after the last dose, liver parenchymal and endothelial cell fractions were isolated, and the quantities of DHR-derived DNA adducts were determined by (32)Ppostlabeling/HPLC. The DHR-derived DNA adduct levels in the endothelial cells were significantly greater than in the parenchymal cells. The DNA adduct levels in rat endothelial cells were greater than in the mouse endothelial cells. These results indicate that the levels of riddelliine-induced DNA adducts in specific populations of liver cells correlate with the preferential induction of liver hemangiosarcomas by riddelliine.     

Effect of dietary fish oil on azoxymethane-induced colon carcinogenesis in male F344 rats

The effect of dietary intake of different levels of Menhaden fish oil on azoxymethane-induced carcinogenesis was examined in male F344 rats fed the semipurified diets. Starting at 5 weeks of age, groups of animals were fed the 5% corn oil (low corn oil) diet. At 7 weeks of age, all animals except the vehicle-treated controls were given s.c. injections of azoxymethane (15 mg/kg body weight/week for 2 weeks). After 4 days, groups of animals were fed the diets containing 4% Menhaden oil + 1% corn oil (low fish oil), 22.5% Menhaden oil + 1% corn oil (high fish oil), 5% corn oil, and 23.5% corn oil (high corn oil). Thirty-four weeks after azoxymethane injections, all animals were necropsied. High fish oil diet had no tumor promoting effect in the large intestine when compared to the high corn oil diet. There was no difference in large intestinal tumor incidence among the other dietary groups. The results of this study indicate that fish oils rich in highly polyunsaturated n-3 fatty acids do not enhance large bowel carcinogenesis and that the fatty acid composition of the dietary fat is one of the determining factors in large bowel carcinogenesis.