Mammary Carcinogenesis In Female Rats Research Articles

Anticancer role of mango (Mangifera indica L.) peel and seed kernel extracts against 7,12- dimethylbenz[a]anthracene-induced mammary carcinogenesis in female rats

Breast cancer is the second leading cause of cancer death among women. The present study is an effort to reveal the antiproliferative and antioxidant actions of mango seed kernel extract (KE), peel extract (PE), and their combination (KEPE) on mammary tumors induced by 7,12 dimethylbenz[a]anthracene (DMBA). Seven groups of adult female Sprague–Dawley rats were prepared, including C: (control), DMBA: (rats were administered with DMBA), (DMBA-KE), (DMBA-PE), and (DMBA-KEPE): rats were administered with DMBA and then treated with KE, PE, and (both KE and PE), respectively, (KE) and (PE): rats were administered with KE and PE, separately. The study focused on the assessment of markers of endocrine derangement [serum 17-β estradiol (E2)], apoptosis [caspase-3 and deoxyribonucleic acid fragmentation (DNAF)], and oxidative stress [lipid peroxidation and antioxidants (glutathione, glutathione-S-transferase, glutathione reductase, glutathione peroxidase, and superoxide dismutase)]. Histopathological examination and immunohistochemical expression of caspase-3 and estrogen receptor-α (ER-α) in mammary gland tissues (MGTs) were determined, as well as the characterization of mango extracts. The results showed that DMBA administration induced mammary tumors by increasing cell proliferation and evading apoptosis. In addition, DMBA administration caused oxidative stress by the production of reactive oxygen species, which increased lipid peroxidation and decreased cellular antioxidants, allowing cancer to progress. In contrast, treatment with DMBA-KE, DMBA-PE, or DMBA-KEPE diminished mammary tumors induced by DMBA, where they reduced oxidative stress via increased antioxidant parameters including reduced glutathione, superoxide dismutase, total glutathione peroxidase, glutathione reductase, and glutathione S-transferase. Also, different treatments decreased proliferation through the reduction of E2, and ER-α expression levels. However, these treatments increased the apoptosis of unwanted cells as they increased caspase-3 activity and DNAF. All these changes led to the prevention of breast injuries and the reduction of mammary tumors. This demonstrates that the contents of mango extracts, especially phenolics and flavonoids, have an important role in mammary tumor treatment through their potential antioxidant, antiproliferative, proapoptotic, and anti-estrogenic effects. KE and PE administration for 4 weeks had no adverse effects. Conclusion: Each of KE, PE, and KEPE has a therapeutic effect against DMBA-induced mammary tumors via induction of apoptosis and reduction of each of the OS, proliferation, and estrogenic effects. So, they can play an important role in the pharmacological tole.

Effect of Eremomastax polysperma on some Tumour Markers of 7,12-Dimethylbenz(A) Anthracene Induced Mammary Carcinogenesis in Female Rats

Effect of Eremomastax polysperma on some Tumour Markers of 7,12-Dimethylbenz(A) Anthracene Induced Mammary Carcinogenesis in Female Rats

Studying humane endpoints in a rat model of mammary carcinogenesis.

Objective(s):The present work intended to clearly define the most adequate humane endpoints in an experimental assay of mammary carcinogenesis in rats. Materials and Methods:Animals were observed twice a day; all parameters were registered once a week and the euthanasia endpoints were established in order to monitor the animal welfare/distress during an experimental assay of chemically-induced mammary carcinogenesis in female rats. Results:Fourteen animals developed at least one mammary tumor with a diameter >35 mm. No animals exhibited alterations in the remaining parameters that implied their early sacrifice. Statistically significant changes were not observed in the quantitative parameters like the hematocrit and urine specific gravity among groups, not being valuable for the assessment of the health status of animals included in an assay of mammary carcinogenesis for 18 weeks. The remaining humane endpoints seemed to be helpful to monitor the animals’ health status.Conclusion:The alteration in only one humane endpoint (mammary tumor dimensions) does not imply the animals’ sacrifice; the endpoints should be evaluated in conjunction, in order to define the most adequate time in which the animals should be sacrificed.

Fruit peel polyphenols demonstrate substantial anti-tumour effects in the model of breast cancer.

Fruit and vegetable intake is inversely correlated with cancer; thus, it is proposed that an extract of phytochemicals as present in whole fruits, vegetables, or grains may have anti-carcinogenic properties. Thus, the anti-tumour effects of fruit peel polyphenols (Flavin7) in the chemoprevention of N-methyl-N-nitrosourea-induced mammary carcinogenesis in female rats were evaluated. Lyophilized substance of Flavin7 (F7) was administered at two concentrations of 0.3 and 3 % through diet. The experiment was terminated 14 weeks after carcinogen administration, and mammary tumours were removed and prepared for histopathological and immunohistochemical analysis. In addition, using an in vitro cytotoxicity assay, apoptosis and proliferation after F7 treatment in human breast adenocarcinoma (MCF-7) cells were performed. High-dose F7 suppressed tumour frequency by 58 % (P < 0.001), tumour incidence by 24 % (P < 0.05), and lengthened latency by 8 days (P > 0.05) in comparison with the control rats, whereas lower dose of F7 was less effective. Histopathological analysis of tumours showed significant decrease in the ratio of high-/low-grade carcinomas after high-dose F7 treatment. Immunohistochemical analysis of rat carcinoma cells in vivo found a significant increase in caspase-3 expression and significant decrease in Bcl-2, Ki67, and VEGFR-2 expression in the high-dose group. Both doses demonstrated significant positive effects on plasma lipid metabolism in rats. F7 significantly decreased survival of MCF-7 cells in vitro in MTT assay by dose- and time-dependent manner compared to control. F7 prevented cell cycle progression by significant enrichment in G1 cell populations. Incubation with F7 showed significant increase in the percentage of annexin V-/PI-positive MCF-7 cells and DNA fragmentation. Our results reveal a substantial tumour-suppressive effect of F7 in the breast cancer model. We propose that the effects of phytochemicals present in this fruit extract are responsible for observed potent anti-cancer activities.

Targeting breast cancer using retinoic acid trifloromethyl chalcone, a promising therapeutic strategy in the treatment of breast cancer

The study was devised to investigate the effect of retinoic acid trifloromethyl chalcone (RAFC) on mammary carcinogenesis in female rats. The data revealed a significant decrease in number of rats with mammary tumor, number of tumors per rat and tumor volume by 54, 72 and 75% respectively in RAFC group compared to control group. The ibuprofen treated rats also showed a significant decrease in number of rats with tumor, number of tumors per rat and tumor volumes by 43%, 55%, and 59%, respectively. Treatment of rats with RAFC also increased the latency period of tumor induction significantly. Median detection period (50% of tumors) was 92, 83 and 56 days respectively in the rats from RAFC, ibuprofen and control groups respectively after DMBA induction. These results demonstrate that RAFC possesses strong chemopreventive activity against mammary carcinogenesis.

Antineoplastic effects of Chlorella pyrenoidosa in the breast cancer model

ObjectivesThere has been considerable interest in both clinical and preclinical research about the role of phytochemicals in the reduction of risk for cancer in humans. The aim of this study was to determine the antineoplastic effects of Chlorella pyrenoidosa in experimental breast cancer in vivo and in vitro. MethodsIn this experiment, the antineoplastic effects of C. pyrenoidosa in the chemoprevention of N-methyl-N-nitrosourea–induced mammary carcinogenesis in female rats were evaluated. Chlorella powder was administered through diet at concentrations of 0.3% and 3%. The experiment was terminated 14 wk after carcinogen administration. At autopsy, mammary tumors were removed and prepared for histopathological and immunohistochemical analysis. In vitro cytotoxicity assay, parameters of apoptosis, and proliferation after chlorella treatment in human breast adenocarcinoma (MCF-7) cells were carried out. ResultsBasic parameters of experimental carcinogenesis, mechanism of action (biomarkers of apoptosis, proliferation, and angiogenesis), chosen metabolic variables, and side effects after long-term chlorella treatment in animals were assessed. Chlorella at higher concentration suppressed tumor frequency by 61% (P < 0.02) and lengthened tumor latency by 12.5 d (P < 0.02) in comparison with the controls. Immunohistochemical analysis of rat tumor cells showed caspase-7 expression increase by 73.5% (P < 0.001) and vascular endothelial growth factor receptor-2 expression decrease by 19% (P = 0.07) after chlorella treatment. In a parallel in vitro study, chlorella significantly decreased survival of MCF-7 cells in a dose-dependent manner. In chlorella-treated MCF-7 cells, a significant increase in cells having sub-G0/G1 DNA content and significant increase of early apoptotic and late apoptotic/necrotic cells after annexin V/PI staining assay were found. Decreases in mitochondrial membrane potential and increasing reactive oxygen species generation were observed in the chlorella-treated MCF-7 cells. ConclusionsThis study is the first report on the antineoplastic effects of C. pyrenoidosa in experimental breast cancer in vivo and in vitro.

Preventive effects of fluvastatin in rat mammary carcinogenesis

On the basis of preclinical and clinical evidence, statins lead to risk reduction of several types of neoplasia including breast cancer. This study is the first report on the preventive effects of fluvastatin in experimental breast cancer in vivo. In this experiment, the antineoplastic effects of fluvastatin in the chemoprevention of N-methyl-N-nitrosourea-induced mammary carcinogenesis in female rats were evaluated. The effects of fluvastatin on selected parameters of apoptosis, proliferation, and angiogenesis in mammary tumor cells were determined. The drug was dietary administered at two concentrations of 20 and 200 mg/kg. The experiment was terminated 17 weeks after carcinogen administration; mammary tumors were removed and prepared for histomorphological and immunohistochemical analysis. The basic parameters of experimental carcinogenesis, chosen metabolic variables, and side effects after long-term fluvastatin treatment in animals were assessed. Fluvastatin at higher concentrations suppressed tumor frequency by 63% and tumor incidence by 33% in comparison with the controls. After fluvastatin treatment, immunohistochemical analysis of tumor cells showed a decrease in vascular endothelial growth factor receptor-2 expression by 86% and an increase in caspase-3 by 8.5%. Fluvastatin in both treated groups significantly increased the parameters of serum lipid metabolism and significantly decreased femur compact bone thickness and body weight in animals. Our results suggest that fluvastatin and other statins should be further evaluated for tumor-preventive characteristics.

Synergistic effect of lycopene and tocopherol against oxidative stress and mammary tumorigenesis induced by 7,12-dimethyl[a]benzanthracene in female rats

Breast cancer is one of the most serious problems in oncology. We investigated the antitumor potential of lycopene (Lyco) alone or combined with tocopherol (Lyco + Toco) for 90 days against a single oral dose of (50 mg/kg body weight) 7,12-dimethyl[a]benzanthracene (DMBA)-induced oxidative stress and mammary carcinogenesis in female rats. The treatment protocol started from the day immediately after DMBA administration. Results obtained indicated that there was a significant elevation in the levels of malondialdehyde (MDA) and nitric oxide (NO) in serum and breast tissues of DMBA-injected rats. The combined treatment (Lyco + Toco) group showed a potential reduction of these parameters more than Lyco alone group. The activities of superoxide dismutase, catalase, and glutathione peroxidase were found to be significantly higher when compared to rats treated with Lyco alone. In DMBA group, a positive significant correlation between NO and MDA (r = 0.92) was observed. Histopathological examination revealed the formation of tumor and angiogenesis in DMBA-induced rats and these abnormal changes were ameliorated by combined treatment with Lyco + Toco. In conclusion, these results suggested that supplementation of diet with Lyco and Toco provided antioxidant defense, with strong chemopreventive activity against DMBA-induced mammary tumors.

Antitumor effects of atorvastatin in the chemoprevention of rat mammary carcinogenesis

Epidemiological studies indicate that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, play a role in inhibition of several human neoplasia including breast cancer. In this study, chemopreventive effects of atorvastatin in N-methyl-N-nitrosourea-induced mammary carcinogenesis in female rats were evaluated. Atorvastatin was administered in the diet at two concentrations: 10 mg/kg (ATOR 10) and 100 mg/kg (ATOR 100). Atorvastatin treatment began 8 days prior to carcinogen administration and subsequently continued for 15 weeks till the end of the experiment. Atorvastatin at a higher dose suppressed tumor frequency by 80.5% (P = 0.0008) and tumor incidence by 49.5% (P = 0.015), and extended latency period by 14 days (P = 0.076) when compared to the control group. Atorvastatin at a lower dose did not significantly alter tumor parameters in comparison with the control group. In the specimens of mammary tumors, atorvastatin (in the ATOR 100 group) significantly decreased mRNA expression of Bcl-2 gene but non-significantly increased Bax mRNA expression compared to control group. Atorvastatin administration did not alter serum concentration of triacylglycerols, total cholesterol, and LDL cholesterol in comparison with controls. This study is the first report on tumor suppressive effect of atorvastatin in rat mammary carcinogenesis.

Diets High in Corn Oil or Extra-Virgin Olive Oil Provided From Weaning Advance Sexual Maturation and Differentially Modify Susceptibility to Mammary Carcinogenesis in Female Rats

Based on the importance of early-life events in breast cancer risk, we have investigated the effects of high-fat diets on maturation, mammary gland development, and its susceptibility to transformation. Female Sprague-Dawley rats were fed a lowfat (LF), high corn oil (HCO), or high extra-virgin olive oil (HOO) diet from weaning and gavaged with 7,12-dimethylbenz[a]anthracene. Body weight and mass increased in the HCO group compared to the LF group. The vaginal opening was advanced in both high-fat groups, especially in the HCO group. This HCO group also had increased body weight around puberty, more corpora lutea at post-puberty, and tended to have higher kisspeptin levels in the hypothalamus. Both high-fat diets induced subtle modifications in the morphology of the mammary gland, with no changes on β-casein or hormone receptors expression in the gland. The HCO diet had a clearly stimulating effect of carcinogenesis, inducing the earliest appearance of tumors and the highest tumor incidence and yield, whereas the HOO diet seemed to have a weak enhancing effect, increasing tumor yield. Our data suggest a strong influence of the HCO diet in sexual maturation and mammary cancer risk, while rats fed the HOO diet were more similar to the controls.

Rosuvastatin in the chemoprevention of N-methyl-N-nitrosourea-induced mammary carcinogenesis in female rats

The results of preclinical research have indicated anticarcinogenic effects of statins in diverse tumors including breast cancer. Lipophilic atorvastatin and simvastatin have demonstrated high anticarcinogenic effects in experimental breast cancer in our previous experiments. In this study, the chemopreventive potential of hydrophilic rosuvastatin in N-methyl-N-nitrosourea induced mammary carcinogenesis in female rats was evaluated. Chemoprevention started 7 days before carcinogen administration and subsequently continued 17 weeks - until the end of the experiment. Dietary administered rosuvastatin (250 mg/kg) decreased tumor frequency by 39% (p=0.146), average tumor volume by 64% (p=0.236), as well as lengthened the latency period by 11 days (p=0.143) compared to controls. Moreover, rosuvastatin (250 mg/kg) decreased average tumor volume by 85% (p=0.0082) compared to the group with rosuvastatin at lower dose in the diet (25 mg/kg). A histopathological analysis of mammary tumors has revealed a shift from poorly differentiated to well differentiated tumors after treatment with rosuvastatin (250 mg/kg).With the exception of HDL-cholesterol, the parameters of plasma lipid metabolism did not differ after rosuvastatin treatment. Rosuvastatin did not change the food intake and body weight in rats. This study is the first about rosuvastatin used in rat mammary carcinogenesis. Hydrophilic rosuvastatin have shown lower antineoplastic activity than lipophilic statins in this model of experimental breast cancer.

Chemopreventive effect of lycopene alone or with melatonin against the genesis of oxidative stress and mammary tumors induced by 7,12 dimethyl(a)benzanthracene in sprague dawely female rats

Breast cancer is the principle cause of death among women worldwide. In this study, we investigated the anti-tumor potential of lycopene (Lyco) alone or combined with melatonin (Lyco + Mel) for 120 days against a single oral dose of (50 mg/kg B.W.) 7,12-dimethylbenz(a)anthracene (DMBA)-induced oxidative stress and mammary carcinogenesis in female rats. The treatment protocol started from the day immediately after DMBA administration. Results obtained indicated that there was an elevation in the levels of malondialdhyde and nitric oxide in serum and breast tissues of DMBA injected rats. The combined treatment (Lyco + Mel) group showed a potential reduction of these parameters more than lyco individually. The activities of SOD, CAT, and GPx were found to be significantly high than lyco alone treated rats. In DMBA group a negative significant correlation between weight and serum nitric oxide (r = -0.59), and a positive significant correlation between NO and MDA (r = 0.81) was observed. Histopathological examination revealed the formation of tumor and angiogenesis in DMBA-induced rats and these abnormal changes were ameliorated by combined treatment with Lyco + Mel. In conclusion, these results suggested that supplementation of diet with lycopene with melatonin provided antioxidant defense with strong chemo preventive activity against DMBA-induced mammary tumors.

Effect of a Short-Term and Long-Term Melatonin Administration on Mammary Carcinogenesis in Female Sprague-Dawley Rats Influenced by Repeated Psychoemotional Stress

The aim of this study was to evaluate the effect of melatonin (MEL) on N-methyl-N-nitrosourea (NMU)-induced mammary carcinogenesis in female Sprague-Dawley rats exposed to repeated psychoemotional stress - immobilization in boxes. NMU was applied intraperitoneally in two doses each of 50 mg/kg b.w. between 40 - 50 postnatal days. Melatonin was administered in drinking water at a concentration of 4 μg/ml daily from 15:00 h to 8:00 h. The application was initiated 5 days prior to the fi rst NMU dose and lasted 15 days, i.e. during the promotion phase of tumour development, or long-term until the end of the experiment (week 20). Immobilization (2 h per day) began on the third day after the second carcinogen application and lasted for 7 consecutive days. Short-term MEL administration to immobilized animals increased incidence by 22%, decreased tumour frequency per animal by 26% and reduced tumour volume gain (by 21%) when compared to the immobilized group without MEL application. Decreased frequency per animal by 28% and more than a 40% decrease in tumour volume gain and cumulative volume were the most pronounced changes in the animals drinking MEL until the end of the experiment. Long-term MEL administration reduced the number and size of mammary tumours more markedly than its short-term administration. Melatonin decreased certain attributes of mammary carcinogenesis in female rats influenced by psychoemotional stress.

Inhibition of PhIP-induced mammary carcinogenesis in female rats by ingestion of freeze-dried beer

This study evaluated the modulating effect of non-alcoholic constituents of beer on 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP)-induced mammary carcinogenesis. Female Sprague–Dawley (SD) rats at 6 weeks of age were divided into four groups ( n=26–30) and fed either a high fat diet or high fat diets containing 1, 2 or 4% freeze-dried beer (FD beer). One week after the start of feeding, rats received PhIP at a dose of 85 mg/kg by gavage four times weekly for 2 weeks. There were no differences in the body weights or diet intakes of rats between the control and the experimental groups. Weekly observation of palpable tumors indicated that tumor incidence and tumor multiplicity in the 2 and 4% FD beer groups were lower than in the control group throughout the experiment. Neoplastic lesions were pathologically examined at the end of the 22-weeks experiment. Tumor development was inhibited by FD beer intake in a dose-dependent manner. Tumor incidence (38.5%) and tumor multiplicity (0.8±0.4) for the group fed with a diet containing 4% FD were significantly reduced as compared with the control group (73.3% and 1.8±0.7). Supplementation with FD beer for 3 weeks together with the PhIP treatments resulted in increased liver GST activity, decreased liver CYP1A2 activity and a decrease in the number of DNA adducts in the mammary tissue, though these values were not significant. In conclusion, our results suggest that intake of FD beer may reduce the risk of carcinogenesis caused by heterocyclic amines.

Chemoprevention of mammary carcinogenesis in female rats by rofecoxib

Epidemiological and experimental studies indicate that non-steroidal anti-inflammatory drugs play role in the prevention of human neoplasia including mammary gland cancer. In this study, tumour suppressive effects of a selective inhibitor of cyclooxygenase-2 (COX-2) rofecoxib in the prevention of N-methyl- N-nitrosourea (NMU)-induced mammary carcinogenesis in female Sprague–Dawley rats were evaluated. Rofecoxib was dietary administered in two concentrations—0.01 mg/1 g (ROFE 0.001%), or 0.05 mg/1 g (ROFE 0.005%). Rofecoxib decreased the incidence by 40% (ROFE 0.001%) and by 42.5% (ROFE 0.005%) ( P=0.043) when compared to the control group. Similarly, tumour frequency and tumour volume decreased depending on an increasing rofecoxib dose by 18.5 or 40% (tumour frequency) and by 35 or 43% (tumour volume). Rofecoxib shifted the rate of fibroadenomas from 15% (control group) to 32% (ROFE 0.001%), or 38% (ROFE 0.005%), respectively. The present study points to pronounced dose-dependent tumour suppressive effects of rofecoxib in mammary carcinogenesis.

Lack of significant inhibitory effects of a plant lignan tracheloside on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mammary carcinogenesis in female Sprague-Dawley rats.

Tracheloside, one of the plant lignans which can be extracted from the debris after safflower oil is produced from the seeds of Carthamus tinctorious, is an analogue of another plant lignan, arctiin, the side-chain C-2 of the five-membered ring being changed from a hydrogen to a hydroxyl group. We have already demonstrated that arctiin has chemopreventive effect on mammary carcinogenesis. Therefore, chemopreventive effects of tracheloside on the initiation or post-initiation period of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mammary carcinogenesis in female rats were examined. For initiation, female Sprague-Dawley (SD) rats at the 6 weeks of age were given intragastric administrations of 100 mg/kg body weight of PhIP once a week for 8 weeks. The animals were treated with 0.2 or 0.02% tracheloside during or after this carcinogen exposure. Control rats were fed basal diet with PhIP initiation or 0.2% tracheloside or basal diet alone without initiation throughout the experimental period. All surviving animals were necropsied at the week 52 of administration. There were no clear treatment-related changes with statistical significance in all parameters for mammary carcinomas measured in this experiment. These results indicate that tracheloside may not exert significant effects on PhIP-induced mammary carcinogenesis at least under the present experiment condition.

Retinyl Acetate and Melatonin in Chemoprevention of Mammary Carcinogenesis in Female Rats: Metabolic Changes

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Possible mechanisms underlying mammary carcinogenesis in female Wistar rats by nitrofurazone

Mechanisms underlying mammary carcinogenesis in female rat given nitrofurazone (NF) were examined. Experiment I: female Wistar rats were divided into three groups, and given diets containing 0, 500 or 1000 ppm NF for 5 weeks. At terminal sacrifice, body and uterus weights were the same in all groups, although ovary weights in NF-treated animals were significantly higher than in control animals, the increase being dose-dependent. Serum prolactin (PRL) concentrations in NF-treated groups at 17:00 h on the day of proestrus were also dose-dependently higher than that in control group. Experiment II: a two-stage rat mammary carcinogenesis protocol was performed. Rats were divided into four groups, Groups 2 and 4 being treated by 9,10-dimethyl-1,2-benzanthracene (DMBA) at 7-weeks-old. Groups 3 and 4 were given diets containing 1000 ppm of NF between 8 and 27 weeks of age, when all surviving rats were autopsied. DMBA-treated animals demonstrated mammary tumors at high incidences, 91.1 and 90.5%, respectively, in Groups 2 and 4, no tumor development being observed without the initial carcinogen exposure (Groups 1 and 3). The mean tumor weights and the mean numbers of tumors per tumor-bearing rats in Group 4 were increased as compared with Group 2, albeit not significantly. Serum PRL (proestrus day at 17:00 h) and progesterone (PG) (diestrus day at 10:00 h) concentrations in NF-treated animals (Groups 3 and 4) were significantly higher than those in untreated rats (Groups 1 and 2). These results suggest that increases of serum PRL and PG concentrations by NF may be the most important factors regarding its promotion of mammary tumor growth and/or enhancement of mammary carcinogenesis in female rats.

Effects of arctiin on PhIP-induced mammary, colon and pancreatic carcinogenesis in female Sprague–Dawley rats and MeIQx-induced hepatocarcinogenesis in male F344 rats

Chemopreventive effects of arctiin, a lignan isolated from Arctium lappa (burdock) seeds, on the initiation or post initiation period of 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) induced mammary carcinogenesis in female rats and on 2-amino-3,8-dimethylimidazo[4,5- f]quinoxaline (MeIQx)-associated hepatocarcinogenesis in male rats were examined. In experiment 1, female Sprague–Dawley (SD) rats were given intragastric doses of 100 mg/kg body wt of PhIP once a week for 8 weeks as initiation. Groups of 20 rats each were treated with 0.2 or 0.02% arctiin during or after PhIP initiation. Control rats were fed 0.2 or 0.02% arctiin, or basal diet alone during the experimental period. Animals were killed at the end of week 48. Although the incidence of mammary carcinomas did not significantly differ among the PhIP-treated groups, multiplicity was significantly decreased in rats given 0.2 (0.7±0.7, P<0.05) or 0.02% (1.0±1.1, P<0.05) arctiin after PhIP initiation as compared with the PhIP alone controls (2.1±2.5). The average number of colon aberrant crypt foci was also significantly decreased in these two groups. Pancreas acidophilic foci were induced in PhIP treated animals with slight decrease in the multiplicity with arctiin during the initiation phase. For liver carcinogenesis, groups of 15 male F344 rats were given a single intraperitoneal injection of diethylnitrosamine (DEN) and starting 2 weeks later, they were administered 0.03% MeIQx in the diet, MeIQx together with 0.5% arctiin, 0.1% arctiin or basal diet for 6 weeks. They were subjected to two-third partial hepatectomy 3 weeks after DEN initiation and killed at the end of week 8 for glutathione S-transferase placental form (GST-P) immunohistochemistry. The numbers and areas of preneoplastic GST-P positive foci were elevated by the treatment with MeIQx, and further increased by the simultaneous treatment with arctiin. These results indicate that arctiin has a protective effect on PhIP-induced carcinogenesis particularly in the mammary gland in the promotion period. On the other hand, it may have a weak co-carcinogenic influence on MeIQx-induced hepatocarcinogenesis. In addition, the results suggested that PhIP is a weak pancreatic carcinogen in female SD rats, targeting acinar cells.

Dietary lipotrope-mediated mammary carcinogenesis in female rats

Dietary deficiency of lipotropes is known to be carcinogenic in itself. This study examined 1) the susceptibility of female rats previously exposed to lipotrope-modified diets to nitrosomethylurea (NMU)-induced mammary carcinogenesis; and 2) how lipotrope-modified diets modulate DNA methylation and gene expression in mammary tissue. Female rats (36 d of age) were assigned to one of the following groups: control-synthetic diet (CSD), containing all required lipotropes; methyl-deficient diet (MDD), lacking all lipotropes; and methyl-additive diet (MAD), containing 1.5-fold the amount of each lipotrope as in CSD. Rats were injected with NMU after a 2-wk dietary treatment period, and 2 d after NMU administration all treatment groups were fed CSD for the remaining experimental period. Mammary tissues were collected from rats just prior to NMU administration. The MDD group had the shortest latency period. The number of tumors and tumor volume were greatest in the MDD rats. Dietary modification of lipotropes altered the DNA methylation pattern of ornithine decarboxylase gene. DNA was significantly hypomethylated in mammary tissues of the MDD rats. These results suggest that dietary deficiency of lipotropes led to changes in DNA methylation and enhanced NMU-induced mammary carcinogenesis.