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From clinical practice, obvious positive effects of statins on plasma lipid metabolism are well known. On the other hand, there are several experimental rodent studies, where these beneficial effects were not confirmed. The effects of fluvastatin on selected serum lipid parameters in a rat model of experimental breast cancer were determined. The drug was dietary administered at two concentrations of 20 and 200 mg/kg. At the end of the study (experiment duration - 18 weeks) the blood from each animal was collected and serum lipid parameters were evaluated. Fluvastatin in both treated groups significantly increased parameters of serum lipids (mostly in a dose dependent manner). Fluvastatin in both treated groups of animals significantly increased serum levels of triacylglycerols, total cholesterol, and LDL-, HDL-, VLDL-cholesterol when compared to the control group. Our results pointed out to the apparent harmful effects of fluvastatin on plasma lipid metabolism in rat mammary carcinogenesis. Based on our previous results, it seems that rats commonly used in cancer model studies are generally unresponsive to the hypocholesterolemic effects of statins.

The risk of cancer may be modulated by drugs with pleiotropic effects and diet has been implicated in the efficacy of treatment. The oncopreventive effects of the antidiabetic drug pioglitazone (PIO) and the anti-insomnia drug melatonin (MT), in vivo, have been proven before, but using a standard-type diet. This study evaluated the impact of a high-fat diet on their efficacy in chemically induced mammary carcinogenesis in Sprague-Dawley rats. Mammary tumours were induced by N-methyl-N-nitrosourea (50 mg/kg, intraperitoneal, on the 41st postnatal day). PIO and MT administration was initiated 11 days before the carcinogen application and lasted until the termination of the experiment at 16 weeks. PIO was administered in a diet (10% fat) at a concentration of 100 ppm and MT was administered in tap water (20 mg/l). PIO, MT and the combination did not significantly alter the basic tumour growth parameters. However, histopathology showed a decrease in the high-grade/low-grade tumour ratio, particularly in animals that received combined treatment (P<0.01). Semiquantitative immunohistochemistry indicated the proapoptotic effect of chemoprevention, particularly in the drug combination group (P<0.01), but no changes in tumour cell proliferation and angiogenesis were recorded. Results were evaluated by one-way analysis of variance or the Mann-Whitney U-test, respectively. PIO and MT, alone or in combination, administered to rats fed a high-fat diet reduced the proportion of high-grade tumours and promoted apoptosis in an in-vivo breast cancer model, although it did not suppress tumour growth. The impact of high dietary fat content on the chemopreventive efficacy of these and other substances should be considered in human studies.

Background/aim: Chemopreventive activity of a new probiotic strain Lactobacillus plantarum LS/07 (PRO) and prebiotic oligofructose-enriched inulin (PRE) in rat mammary carcinogenesis induced by procarcinogen 7,12-dimethylbenz[a]anthracene has been reported before. This study evaluated the anticancer and immunomodulatory efficacy of PRO, PRE, PRO+PRE (PRO/PRE) and combination with melatonin (PRO+PRE+MEL) in a rat model, when breast cancer was induced by a direct-acting carcinogen N-nitroso-N-methylurea (NMU)., Materials and Methods: Daily administration of PRO (at a dose of 8.4×10(8) colony-forming units (c.f.u.)/rat), PRE (in the diet, 20 g/kg) and MEL (in tap water, 20 mg/l) started 14 days before the first NMU dose and lasted for 16 weeks., Results: Although tumor growth was not altered, a marked decrease in the ratio of high-/low-grade carcinomas and in tumoral Ki-67 expression was found after PRO+PRE treatment; melatonin augmented these effects. PRO+PRE+MEL combination enhanced CD4(+) and CD8(+) T-cell tumor infiltration induced by PRO/PRE and increased CD25(+)FoxP3(+) regulatory T-cells in tumors., Conclusion: In mammary carcinogenesis, Lactobacillus plantarum LS/07 and inulin exert prodifferentiating, antiproliferative and immunomodulatory activities, which are significantly amplified by melatonin co-administration., (Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Previous studies in the field of cancer research have suggested a possible role for statins in the reduction of risk in certain malignancies. The purpose of these studies was to examine the chemopreventive effects of pravastatin alone and in combination with pineal hormone melatonin in the N-methyl-N-nitrosourea-induced mammary carcinogenesis model. Pravastatin was given orally (1 00 mg/kg) and melatonin was added to the water (20 μg/ml). Chemoprevention began seven days prior to carcinogen administration and subsequently continued for 15 weeks until autopsy. At autopsy, mammary tumours were removed and prepared for histopathological and immunohistochemical analysis. Parameters of experimental carcinogenesis, mechanism of action (biomarkers of apoptosis, angiogenesis and proliferation) and side effects after long-term treatment in animals were assessed. Pravastatin alone suppressed tumour frequency by 20.5% and average tumour volume by 15% compared with controls. Combined administration of the drugs decreased tumour frequency by 69% and lengthened tumour latency by nine days compared with control animals. The ration between high and low grade carcinomas was apparently reduced in both treated groups. The analysis of carcinoma cells showed significant expression increase in caspase-3 and caspase-7 after pravastatin treatment; however, combined treatment even more pronounced increase in the expression of both caspases. Regarding VEGFR-2 expression, a small effect in carcinomas of both treated groups was found. In plasma metabolism evaluation, pravastatin alone significantly decreased levels of glucose and triacylglycerols. Our results suggest a mild anti-neoplastic effect of pravastatin in this rat mammary gland carcinoma model. Statins co-administered with other suitable drug (e.g. melatonin) should be further evaluated for tumour-preventive properties., (© 2014 The Authors. International Journal of Experimental Pathology © 2014 International Journal of Experimental Pathology.)

Resveratrol and celecoxib were used as chemopreventive agents in animal models of carcinogenesis, and exert antiproliferative and proapoptotic effects on cancer cells. Therefore, the aim of this study was to evaluate whether combining resveratrol with celecoxib may exert more potent anticarcinogenic effects than the single agents. Mammary carcinogenesis was initiated in 70 female Sprague-Dawley rats with N-methyl-N-nitrosourea (NMU). The chemoprevention with resveratrol, celecoxib, and their combination started 2 weeks before the first carcinogen dose and lasted until the end of the experiment. Tumor incidence and frequency, latency period, tumor volume, the expression of cyclooxygenase 2 (COX2) and growth differentiation factor 15 (GDF15), and also the formation of reactive oxygen species were analyzed using different methods. In addition, the levels of resveratrol and its metabolites in blood and selected tumor tissues were determined by high-performance liquid chromatography. Finally, the anticancer effects of the reagents were studied in the human breast cancer cell line MCF-7. Celecoxib as a single agent significantly decreased tumor frequency, prolonged tumor latency, and decreased the total number of malignant tumors compared with the NMU conditions. Tumor volume was nonsignificantly reduced (0.68±0.25 vs. 0.93±0.28 cm3). Importantly, the addition of resveratrol to celecoxib reduced tumor volume by 60% compared with celecoxib alone (from 0.68±0.25 to 0.27±0.07 cm3, P<0.05). Furthermore, the combination of resveratrol and celecoxib reduced tumor frequency by 29% compared with celecoxib alone (P=0.53). Tumor latency was not influenced by this combination compared with celecoxib alone (126.56±3.45 vs. 120.71±4.08 days). In addition, COX2 mRNA and immunoreactive protein stained on tumor sections were reduced and GDF15 protein increased significantly by the combination studied compared with the NMU conditions. In agreement with these data, a significant reduction in reactive oxygen species in blood lymphocytes of the combination was detected, which may have contributed toward the cancer-preventive effects of this application. This study showed that in NMU-induced mammary cancer in rats, the combination of resveratrol and celecoxib led to a significant reduction in all tumor parameters. In addition, in terms of tumor volume, the combination was more efficient than celecoxib as a single agent.

Our previous results indicated significant tumor-suppressive effects of different statins in rat mammary carcinogenesis. The purpose of this experiment was to examine the chemopreventive effects of Pitavastatin alone and in combination with the pineal hormone melatonin in the model of N-methyl-N-nitrosourea-induced mammary carcinogenesis in female Sprague-Dawley rats. Pitavastatin was administered dietary (10mg/kg) and melatonin in an aqueous solution (20μg/ml). Chemoprevention began 7 days prior to carcinogen administration and subsequently continued for 15 weeks until autopsy. At autopsy, mammary tumors were removed and prepared for histopathological and immunohistochemical analysis. Compared to controls, Pitavastatin alone reduced average tumor volume by 58% and lengthened latency by 8 days; on the other hand, the drug increased tumor frequency by 23%. Combined administration of Pitavastatin with melatonin decreased tumor frequency by 23%, tumor volume by 44% and lengthened tumor latency by 5.5 days compared to control animals. The analysis of carcinoma cells showed significant increase in caspase-3 expression in both treated groups and a tendency of increased caspase-7 expression after Pitavastatin treatment alone. Significant expression decrease of Ki67 was found in carcinoma cells from both treated groups. Compared to control carcinoma cells, Pitavastatin alone increased VEGF expression by 41%, however melatonin totally reversed its undesirable effect. Pitavastatin combined with melatonin significantly increased femur compact bone thickness in animals. Pitavastatin alone decreased plasma triglycerides and total cholesterol levels, however it significantly increased levels of glucose. In summary, our results show a partial antineoplastic effect of Pitavastatin combined with melatonin in the rat mammary gland carcinoma model., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

Aim: The purpose of the present study was to evaluate the chemopreventive efficacy of a new probiotic bacterial strain, Lactobacillus plantarum LS/07 (PRO), prebiotic oligofructose-enriched inulin (PRE) and PRO-PRE combination in a rat model of breast cancer., Materials and Methods: Mammary carcinogenesis was induced by 7,12-dimethylbenz[a]anthracene (DMBA). Daily oral administration of PRO (at a dose of 8.4×10(8) c.f.u./rat) and PRE (in the diet, 20 g/kg) started two weeks before the first DMBA dose and lasted until the end of the experiment (16 weeks)., Results: Administration of PRO, PRE and PRO-PRE combination significantly suppressed the tumor frequency, increased Cd4(+) T-cells in tumor tissue and reduced serum tumor necrosis factor-α concentration. In PRO and PRO-PRE groups, the decline of Cd8(+) T-cells in blood and their increase in tumor tissue was observed., Conclusion: Long-term administration of Lactobacillus plantarum LS/07 with and without inulin is effective against breast cancer, at least partially, through immunomodulatory mechanisms., (Copyright© 2014 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Diabetes increases cancer risk, which may be modulated by careful choice of treatment. Experimental reports showed efficacy of glitazones in various in vitro and in vivo models of carcinogenesis, but procarcinogenic effects in some models were reported too, and, similarly, data on cancer incidence in glitazone users are inconsistent. This review summarizes oncostatic effects of glitazones in preclinical and clinical studies and brings a brief summary of their impact on cancer risk in diabetic patients, with a focus on the association between pioglitazone use and bladder cancer., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

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.

The neurohormone melatonin is primarily involved in the regulation of circadian rhythms, but also acts as an antioxidant and anticarcinogenic agent, especially in breast cancer. Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a widely known polyphenolic agent from red wine, which has been shown to exert antioxidant, anti-inflammatory and anticarcinogenic effects. The objective of this study was therefore to investigate the effects of melatonin in combination with resveratrol in a rat model of experimental mammary carcinogenesis. Female Sprague-Dawley rats aged 31 days were used in the experiment. Mammary carcinogenesis was induced by N-methyl-N-nitrosourea (NMU), which was administered in two intraperitoneal doses (50 mg/kg of body weight). Chemoprevention with resveratrol and melatonin started 2 weeks before the first dose of NMU and lasted until the end of the experiment. The basic parameters evaluated were: tumour incidence, latency period, tumour frequency per group and tumour volume. In addition, oestrogen receptors ERα and ERß, melatonin receptor MT1, proliferating cell nuclear antigen and vascular endothelial growth factor were determined by immunohistochemical staining. The combination of resveratrol and melatonin reduced tumour incidence by approximately 17% and significantly decreased the quantity of invasive and in-situ carcinomas. Food intake declined in the second and seventh weeks after the administration of carcinogen. Resveratrol in combination with melatonin returned food intake to the level of intact controls. Resveratrol in combination with melatonin has some protective effects on NMU-induced rodent breast cancer. Further studies are necessary to confirm these effects of this promising combination.