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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.

This study evaluated a prolonged effect of palm oil addition to lard-supplemented diet (PLD) on the oxidative status, lysosomal enzyme activities, markers of hepatotoxicity and basic lipid profile in female rats. Female Sprague-Dawley rats received PLD (10% of total fat: 7.5% from palm oil and 2.5% from lard), and the control group received lard-supplemented diet (2.5% fat) from 28 days of age for 14 weeks. Histopathological evaluation of the liver from animals fed the PLD showed slight steatosis and signs of mild chronic inflammation. Reduction of extramedullary hematopoiesis and an increased ratio of red/white pulp were observed in the spleen. PLD induced oxidative stress (evaluated in the liver, heart, spleen, muscle and kidney) evidenced by an increase in conjugated dienes and malondialdehyde in all tissues except the muscle; protein carbonyl derivatives were increased as well. The changes in the antioxidant enzyme activities in the evaluated tissues were ambiguous except for the prominent increase in the heart. Lysosomal enzyme activities showed a tendency to increase in the heart and kidney and to decrease in the muscle and spleen. The De Ritis ratio, which is a biomarker of hepatotoxicity, was higher in the heart from animals fed the PLD. The palm oil addition to the lard-supplemented diet-induced prominent oxidative stress, particularly in myocardial tissue with involvement of the authophagy-lysosome pathway., (© 2020 Wiley-VCH GmbH.)

A high-fat diet (HFD) induces changes in gut microbiota leading to activation of pro-inflammatory pathways, and obesity, as a consequence of overnutrition, exacerbates inflammation, a known risk factor not only for cancer. However, experimental data showed that the composition of dietary fat has a greater impact on the pathogenesis of cancer than the total fat content in isocaloric diets. Similarly, human studies did not prove that a decrease in total fat intake is an effective strategy to combat cancer. Saturated fat has long been considered as harmful, but the current consensus is that moderate intake of saturated fatty acids (SFAs), including palmitic acid (PA), does not pose a health risk within a balanced diet. In regard to monounsaturated fat, plant sources are recommended. The consumption of plant monounsaturated fatty acids (MUFAs), particularly from olive oil, has been associated with lower cancer risk. Similarly, the replacement of animal MUFAs with plant MUFAs decreased cancer mortality. The impact of polyunsaturated fatty acids (PUFAs) on cancer risk depends on the ratio between ω-6 and ω-3 PUFAs. In vivo data showed stimulatory effects of ω-6 PUFAs on tumour growth while ω-3 PUFAs were protective, but the results of human studies were not as promising as indicated in preclinical reports. As for trans FAs (TFAs), experimental data mostly showed opposite effects of industrially produced and natural TFAs, with the latter being protective against cancer progression, but human data are mixed, and no clear conclusion can be made. Further studies are warranted to establish the role of FAs in the control of cell growth in order to find an effective strategy for cancer prevention/treatment.

Objective: Numerous reports showed inhibition of carcinogenesis after metformin (MF) and melatonin (MEL) administration. However, most in vivo studies used standard diet type, with relatively low fat content. As increase in fat intake may have a considerable impact on malignant transformation, we evaluated the effects of these two substances in a model of mammary carcinogenesis in rats fed a high-fat diet (10%)., Methods: Mammary tumors were induced by N-methyl-N-nitrosourea (NMU) in female rats of sensitive Sprague-Dawley strain. MF was administered in a diet (0.2%), MEL was administered in drinking water (20 mg/L). The chemoprevention was initiated 12 days prior to tumor initiation, both substances were administered through the termination of the experiment on 16th week after carcinogen application. Analysis of basic parameters of tumor growth, histopathological profile, and serum IGF-1 level were performed together with immunohistochemical detection of Ki67 (proliferation marker) and caspase-3 and BCL-2 (apoptosis markers) in mammary cancer cells., Results: Although neither tumor incidence nor frequency were changed after MF and/or MEL administration, MF and MEL decreased high-grade/low-grade (HG/LG) tumor ratio. MEL decreased proliferation in mammary cancer cells; positive correlations between histological grade and Ki67 expressions were found after single administration of both MF and MEL. Serum IGF-1 levels were reduced to the level of intact rats in all groups receiving chemoprevention., Conclusions: MF and MEL administration did not inhibit growth of NMU-induced mammary tumors in rats in a significant manner but both substances ameliorated tumor histopathological profile. Surprisingly, combined treatment had no such effect., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Melatonin (N-acetyl-5-methoxytryptamine) is not only a pineal hormone, but also an ubiquitary molecule present in plants and part of our diet. Numerous preclinical and some clinical reports pointed to its multiple beneficial effects including oncostatic properties, and as such, it has become one of the most aspiring goals in cancer prevention/therapy. A link between cancer and inflammation and/or metabolic disorders has been well established and the therapy of these conditions with so-called pleiotropic drugs, which include non-steroidal anti-inflammatory drugs, statins and peroral antidiabetics, modulates a cancer risk too. Adjuvant therapy with melatonin may improve the oncostatic potential of these drugs. Results from preclinical studies are limited though support this hypothesis, which, however, remains to be verified by further research.

Oxidative stress is involved in the development of various cancers. In the present study, the effect of long-term administration of peroral antidiabetic metformin and pineal hormone melatonin on liver antioxidant and aerobic status in female Sprague-Dawley rats carrying mammary tumors induced by N-methyl-N-nitrosourea was evaluated. Both substances were administered in a preventive and curative manner (12 days before and 16 weeks after the carcinogen application). Carcinogen administration induced oxidative stress: the level of thiobarbituric acid reactive substances (TBARS) considered as a marker of reactive oxygen species (ROS) generation in liver increased as well as the level of oxidatively modified protein content (OMP; aldehyde and ketone derivates). Metformin administration restored succinate dehydrogenase and lactate dehydrogenase activity and associated ROS production and OMP content to the level of intact rats, with predominant activation of superoxide dismutase (SOD) and glutathione reductase (GR). Melatonin alone and in combination with metformin also decreased TBARS content. OMP content decreased in all groups receiving chemoprevention. The rise in total antioxidant capacity after melatonin and particularly metformin and melatonin combination might result from the initiation of anaerobic metabolism and increasing SOD, GR, and glutathione peroxidase activity. Long-term administration of metformin and melatonin exerts antioxidant properties in liver, especially in combination.

The data from in-vitro and in-vivo studies show that both peroral antidiabetic metformin (MF) and pineal hormone melatonin (MT) inhibit the growth of many cancers, including breast cancer. However, most in-vivo studies used standard-type diet with low fat content. Therefore, in this study, we evaluated the chemopreventive effect of MF and MT in an in-vivo model of breast cancer in rats on a high-fat diet (10% of total fat). Mammary carcinogenesis was induced by 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawley rats. Chemoprevention with MF (administered in a diet, 0.2%) and MT (administered in tap water, 20 mg/l) was induced 20 days before the carcinogen administration through the termination of the experiment (14 weeks after carcinogen administration). Tumor growth parameters were analyzed together with histopathological examination and immunohistochemical detection of KI67 (proliferation marker), caspase-3, BAX, BCL-2 (apoptosis markers), and CD24 and CD44 (cancer stem cell markers) in mammary tumor samples. The combination of chemopreventive agents decreased tumor incidence by 29%. Cumulative tumor volume was lower in all groups treated with chemoprevention. Histopathology did not show significant changes in high-grade/low-grade tumor ratio. Immunohistochemistry showed increased expression of BAX in the combination group, and caspase-3 expression increased in both MT and combination groups. MT, and particularly the MF and MT combination, inhibited DMBA-induced mammary tumor growth in rats by apoptosis stimulation in cancer cells. Our results indicate that MT supplements in patients treated with MF may have a considerable effect on the incidence of breast cancer.

It is evident that standard chemotherapy agents may have an impact on both tumor and host immune system. Paclitaxel (PTX), a very potent anticancer drug from a taxane family, has achieved prominence in clinical oncology for its efficacy against a wide range of tumors including breast cancer. However, significant toxicity, such as myelosuppression, limit the effectiveness of Paclitaxel-based treatment regimens. Immodin (IM) is low molecular dialysate fraction of homogenate made from human leukocytes. It contains a mixture of substances from which so far have been described e.g. Imreg 1 and Imreg 2 formed by the dipeptide tyrosine-glycine and the tripeptide tyrosine-glycine-glycine, respectively. The aim of this study was to explore immunopharmacological activities of IM, using the strongly immunogenic 4T1 mouse breast cancer model, and evaluate its effect on the reactivity and the efficiency of PTX cancer therapy. The results highlight a potentially beneficial role for IM in alleviating PTX-induced toxicity, especially on the nonspecific immunity, during breast cancer therapy. Co-treatment exhibited an antitumor effect including reduced tumor growth, prolonged survival of tumor bearing mice, increased number of monocytes and lymphocytes in peripheral blood. In spleens, IM+PTX therapy elevated proportion of whole lymphocytes in the account of myelo-monocytic cells characteristic with low expression of CD11c+ and bearing Fc receptor (CD16/32) as well as T-lymphocytes, NK cells and dendritic cells. Accumulation of tumor-associated granulocytes in stroma of PTX-treated group and intensive 4T1-necrosis/apoptosis in tumors after co-treatment were also recorded. These findings suggest the possibility of using IM alongside PTX treatment for maintaining the immune system functions and increasing patient survival., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Manumycin A is a natural antibiotic isolated from Streptomyces parvulus with broad range of biological activities including antineoplastic activity in several in vitro and in vivo cancer models. Immodin [dialyzable leukocyte extract (DLE)] is a dialysate released from disintegrated blood leukocytes of healthy donors which exerts immunonormalizing effects on cell-mediated immune responses. The aim of the present study was to explore the antitumor potential of the combination of manumycin A and Immodin in an experimental breast cancer model. Experiments were carried using a 4T1 tumor-bearing BALB/c mouse model. Survival analysis, tumor growth, hematological and biochemical profiles, leukocyte differential, phagocytic activity of leukocytes and histology of the primary tumor were examined. The combination treatment suppressed the tumor growth and prolonged the survival of tumor-bearing mice, decreased the number of monocytes, plateletes and plateletcrit in peripheral blood of the tumor-bearing mice and increased the infiltration of neutrophils and eosinophils in the primary tumor. Moreover, individual therapies enhanced the phagocytic activity of monocytes and neutrophils. These findings demonstrate the antitumor effect of the combination of manumycin A and Immodin in 4T1 tumor-bearing mice associated with strong antiplatelet activity and innate immunity activation.

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.

Purpose: 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., Methods: 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., Results: 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., Conclusions: 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.

Objectives: There 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., Methods: In 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., Results: Basic 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., Conclusions: This study is the first report on the antineoplastic effects of C. pyrenoidosa in experimental breast cancer in vivo and in vitro., (Copyright © 2015 Elsevier Inc. 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.

Background: High levels of prostaglandins found in many neoplastic tissues, especially in colon cancer and breast cancer, suggest a role of cyclooxygenase in the process of carcinogenesis., Material and Methods: The aim of this study was to analyse the chemopreventive potential of non-steroidal inflammatory drug indomethacin and its combination with pineal hormone melatonin in rat mammary carcinogenesis induced by N-methyl-N-nitrosourea. Indomethacin was administered 3 times a week and melatonin 4 times a week, both substances in a concentration of 20 µg/ml of drinking water. Chemoprevention began approximately 2 weeks before carcinogen administration and lasted until the end of the experiment 25 weeks later., Results: Indomethacin administered alone and in combination with melatonin stimulated the growth of mammary tumors. We found a significant increase in the average tumor volume caused by indomethacin alone by 126%, and in combination with melatonin by 104% compared to the control group. Indomethacin administered alone increased the incidence of tumors by 21.5% (also in combination with melatonin) and reduced the tumor latency by 17 days compared to controls. Melatonin alone significantly reduced tumor volume in comparison with control animals. During the long-term administration, both substances were well tolerated by animals., Conclusion: Indomethacin, a predominant cyclooxygenase inhibitor-1, showed significant neoplastic effects in the prevention of N-methyl-N-nitrosourea induced rat mammary carcinogenesis. This finding is in strong contrast to our previous experiment, where indomethacin in 7,12-dimethylbenz(a)anthracene-induced rat mammary carcinogenesis revealed marked antineoplastic effects.

In this paper, the effect of peroral antidiabetic pioglitazone, a thiazolidinedione derivate, on selected parameters of carbohydrate and lipid metabolism in N-methyl-N-nitrosourea-induced mammary carcinogenesis in female Sprague-Dawley rats was evaluated. Pioglitazone was administered in the diet at two concentrations (10 ppm and 100 ppm), the chemoprevention was initiated 12 days before carcinogenesis induction and lasted until the termination of the experiment. The experiment was terminated 17 weeks after carcinogenesis induction, selected organs and tissues were removed and weighed and basic metabolic and hormonal parameters were determined. Pioglitazone increased glycemia (without exceeding normal values) and glycogen concentration in both liver and heart muscle without altering insulinemia and increased triacylglycerol concentration in liver, these changes were more prominent in group with higher dose. Pioglitazone also reduced corticosterone serum concentration and attenuated lipid peroxidation. Pioglitazone and other glitazones may be useful in alleviation of unfavourable metabolic changes in cancer patients.

Backgrounds: Statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) have proven therapeutic and preventive effects on cardiovascular diseases. Preclinical evidence demonstrates tumor-suppressive effects of statins in several human neoplasias, including breast cancer., Materials and Methods: In this study, antineoplastic effects of simvastatin in chemoprevention of N-methyl-N-nitrosourea-induced mammary carcinogenesis in female rats were evaluated. The drug was dietary administered at two concentrations--18 mg/kg (SIMVA 18) and 180 mg/kg (SIMVA 180)., Results: Basic parameters of experimental carcinogenesis after long-term simvastatin treatment in animals were assessed. In the SIMVA 180 group, simvastatin significantly suppressed tumour frequency by 80.5% and tumour incidence by 58.5% in comparison to the controls. Higher dose simvastatin non-significantly decreased the mean tumor volume by 23.5%, as well as non-significantly lengthened the latency period by 14.5 days compared to the control animals. Simvastatin, administered at a lower dose did not change parameters of mammary carcinogenesis in comparison to the control group. Simvastatin in both treated groups significantly decreased serum levels of triacylglycerols and VLDL-cholesterol in comparison to the control animals. Compared to the controls, a significant increase in food intake by the animals was recorded in the SIMVA 18 and SIMVA 180 groups. No significant differences in the final body weight gain between the simvastatin-administered and the control group were found., Conclusion: This study represents the first report of simvastatin use in experimental mammary carcinogenesis in vivo.

Data available from in-vitro and in-vivo studies suggest oncostatic properties of peroral antidiabetics, thiazolidinediones, in many types of cancer. This study is the first report on the chemopreventive effect of pioglitazone in mammary carcinogenesis in rats. Mammary carcinogenesis was induced by N-methyl-N-nitrosourea administered in two intraperitoneal doses per 50 mg/kg bodyweight on the 43rd and 50th postnatal days. Pioglitazone was administered in the diet at concentrations of 10 and 100 ppm, respectively, 12 days before the first carcinogen dose until the termination of the experiment. During the experiment, the animals were weighed weekly and palpated for the presence of mammary tumors, and the incidence, latency, tumor frequency, and tumor volume were recorded. The experiment was terminated 17 weeks after the first carcinogen dose; basic tumor growth parameters and metabolic and hormonal variables were evaluated. Pioglitazone at higher concentration decreased incidence and frequency per group from the 11th week of experiment when compared with the control group and a group receiving a lower dose. Pioglitazone at a higher dose decreased the final incidence by 38%, frequency per group by 63%, and extended latency period by 32% when compared with the control group. Our data suggest that pioglitazone and other glitazones should be further investigated for oncopreventive effects.

The aim of the present study was to determine whether prolonged stress repeated immobilization in boxes during the period of 18 weeks (IMS) influenced development and progression of N-methyl-N-nitrosourea (NMU)-induced mammary tumors in female Sprague-Dawley rats and whether long-term MEL application affected changes caused by stress. NMU was applied intraperitoneally in two doses each of 50 mg/kg b.w. between 40-50 postnatal days. Melatonin (MEL) was administered in drinking water in a concentration of 4 microg/ml (daily from 3 p.m to 8 a.m), application was initiated 3 days prior to first NMU dose and lasted until the end of the experiment. Immobilization (2 h/day) began on the fifth day after second carcinogen application, animals were immobilized three times a week. Repeated immobilization of rats during 18 weeks decreased tumor frequency per group and per animal by 30% and tumor volume gain by 16% as opposed to control (NMU) animals. Combination of repeated immobilization and a long-term MEL application lowered incidence by 13% when compared to control, prolonged latency by 13%, decreased tumor frequency per group (by 44%) and per animal (by 35%). Tumor volume gain increased by 35% but their cumulative volume prominently decreased by 74% as opposed to control. Tumor volume was the most markedly influenced by MEL, induced tumors developed more rapidly tumor volume gain increased by 61%. However, their cumulative volume markedly decreased by 75% when compared to immobilized group drinking water. Prolonged stress inhibited development and progression of NMU-induced mammary gland tumors in female rats and this effect was enhanced by long-term melatonin administration.

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.

Epidemiological and experimental studies indicate psychoemotional stress as an important factor in carcinogenesis. The aim of this study was to evaluate the effect of restraint stress on N-nitroso-N-methylurea (NMU)-induced mammary carcinogenesis. Female Sprague-Dawley rats were injected with two intraperitoneal NMU doses each per 50 mg/kg b.w. between 39-49 postnatal days. Three experimental groups were created: 1. NMU (without restraint--control group, 12 animals), 2. NMU+1IMS (group with single restraint, IMS--immobilization stress, 12 animals), 3. NMU+7IMS (group restrained 7 times during a week, 12 animals). Animals were immobilized daily in special boxes for 120 minutes or 7 x 120 minutes, respectively from third day after carcinogen administration. The observation lasted for 20 weeks. The incidence, frequency, latency and volume of mammary tumors were evaluated. In repeatedly immobilized group NMU+7IMS increase in tumor incidence by 57% (p<0.05), marked increase in frequency per group by 153% (p<0.01), increase in frequency per animal by 61% and shortened latency period by 7 days were recorded. The effect of single restraint was not seen. In this experiment repeated immobilization carried out early after carcinogen administration had a remarkable stimulatory effect on chemically-induced mammary carcinogenesis in female rats.

Tumorsuppressive effects of a selective inhibitor of cyclooxygenase-2 (COX-2) nimesulide (NIM) activity and pineal hormone melatonin (MEL) and their combination in two chemopreventive studies of mammary carcinogenesis were evaluated. Mamary tumors in female Sprague-Dawley rats were induced by N-methyl-N-nitrosourea (NMU) and by 7,12-dimethylbenz(a)anthracene (DMBA), respectively. The treatment with NIM (applied subcutaneously twice a week in the dose of 5 mg/kg b.w.) and MEL (given daily diluted in drinking water in concentration 20microg/ml) began several days before carcinogen administration and lasted until the end of the experiment. The tumor incidence, frequency, latency period and tumor volume as parameters of mammary carcinogenesis were evaluated. Moreover, the effect of chemopreventives on body weight, food and water intake were recorded. Changes of selected parameters of lipid and carbohydrate metabolism in the serum and chosen organs were evaluated in the NMU experiment. In the NIM-treated group in the NMU experiment, the tumor incidence decreased by 34.5% (p < 0.05), tumor frequency per group by 40% (p < 0.05) and tumor volume gain by 39% when compared to the control group. Tumorsuppressive effect of MEL was not observed. In DMBA-induced carcinogenesis an oncostatic effect of NIM was not observed; MEL administration decreased tumor incidence by 21.5% (p < 0.05), tumor frequency per group by 22.5% and tumor volume gain by 43.5%. Combined chemoprevention of NIM+MEL was very similar to that of chemopreventives administered alone. MEL lowered food and water intake and body weight gain in DMBA-induced carcinogenesis. It increased glycogen and cholesterol content in the liver, triacyglycerol and phospholipid concentrations in the bone marrow and decreased malondialdehyde concentration at the same tissue of tumor-bearing animals. NIM did not significantly influence the selected metabolic parameters, excepting the decrease in serum glucose concentration in tumor-bearing rats.

It is important to determine and clarify the variability of mammary carcinogenesis induction in animal experimental studies particularly in connection with chemoprevention projects. The circannual seasonal rhythms of hormone levels or various parameters within the immune system may involve factors participating in mammary gland carcinogenesis. In our study, 19 experiments were conducted and all of them lasted for about 25 weeks after chemical carcinogen administration (DMBA or NMU) under standard laboratory conditions. Females of two rat strains - a medium susceptible Sprague-Dawley strain and a very low susceptible Wistar:Han were used. We observed not only the effect of seasonal changes but also the effect of age after single or repeated carcinogen administration. The seasonal dependence of mammary carcinogenesis with higher tumor incidence during long days in comparison with winter short days has been demonstrated in Sprague-Dawley rats. In experiments on the Wistar:Han strain, certain features of seasonal character were recorded, although the very low susceptibility of this strain to mammary carcinogenesis might have influenced the results. A limited period of carcinogen administration in early puberty around postnatal days 43-46 (higher susceptibility), when compared to the period after postnatal day 50, is the factor significantly increasing incidence and frequency of mammary carcinogenesis in the Sprague-Dawley strain. Our results indicate the need to consider the effect of season and age of animals at the time of carcinogen administration on rat mammary carcinogenesis induction. However, the application of the results obtained in one strain of experimental animals may only lead to misleading conclusions.

Chemopreventive effects were analysed of antioestrogen TAM and of MEL on NMU- or DMBA-induced mammary gland cancer, respectively, in female Sprague-Dawley rats. NMU was administered intraperitoneally in two doses each of 50 mg/kg b.w. between 46th-57th postnatal days. DMBA was given by gavage in one dose (20 mg per animal) between 50th-54th postnatal days. The treatment with MEL began 12 days and the treatment with TAM 10 days before carcinogen administration; both chemopreventive substances were administered until the end of the experiment (24 weeks after carcinogen application). TAM was administered subcutaneously twice a week in a dose 2.5 mg/kg b.w. MEL was given in tap water (20 mg/ml) daily between 3 p.m. to 8 a. m. The tumour incidence, tumour frequency per group and animal, latency period, tumour volume, body weight gain in the rats and weight of uterus (in the experiment with NMU) were evaluated. TAM suppressed carcinogenesis to 0% incidence like TAM+MEL in both the NMU and DMBA models. In NMU-induced mammary carcinogenesis MEL lowered the tumour volume (although statistically non-significantly) by 30% in comparison with the control group; in DMBA-induced mammary carcinogenesis it lowered the tumour volume (2.70 +/- 0.81 cm3 vs. 0.90 +/- 0.33 cm3) and lengthened (non-significantly) the latency period (by 12 days). The weight gain of animals in both NMU and DMBA models and relative uterus weight in the NMU model were significantly lower in the groups treated with TAM and TAM+MEL as compared to the control group and the group treated with MEL. Evaluation of the combined effect of TAM+MEL was not possible due to total suppression of carcinogenesis by TAM. TAM and TAM+MEL are highly effective agents in rat mammary carcinogenesis prevention, but the side effects of TAM in humans limits its use in clinical oncology.

The aim of the experiment was to analyse the oncostatic effect of nonsteroidal antiinflammatory drug INDO, hormone MEL and combination of both substances in DMBA-induced mammary carcinogenesis in female SD rats. Chemoprevention started 10 days before the application of the first dose of DMBA to 35-day-old rats. INDO was administered in tap water (20 microg/ml of water) for 3 days in a week (days 2, 4 and 6), MEL solution in the concentration of 20 microg/ml of tap water was administered between 3 p.m. and 8 a.m. for 4 days in a week (days 1, 3, 5 and 7); during other days the animals drank tap water only. In combined chemoprevention, rats were drinking solutions of INDO and MEL according to the above-mentioned scheme. DMBA in the dose of 10 mg/rat was administered intragastrically using a probe to all rats 3 times on postnatal days 45, 50 and 55. There were four experimental groups: group 1--without chemoprevention, group 2--INDO treatment, group 3 --MEL treatment, group 4--application of INDO + MEL. The experiment lasted 26 weeks from the first administration of DMBA, when the final incidence and frequency of tumours per animal and group, as well as latency and average volume of tumours were evaluated. The content/concentration of malondialdehyde (MDA) was determined in selected tissues as a criterion of lipoperoxidation, considering its potential influencing by chemoprevention. The tumour incidence in controls was 100%; INDO reduced the incidence (36.84%) and frequency per group and animal, decreased the mean volume of tumours and prolonged the latency. Chemoprevention using combination of INDO with MEL was successful like that with INDO; however, it did not influence the tumour volume. MEL decreased the incidence to 42.11% and pronouncedly reduced the tumour frequency per group. INDO, administered alone or in combination with MEL, reduced an increased content/concentration of MDA in the liver, bone marrow and serum of tumour-bearing rats. INDO, MEL and INDO + MEL had a pronounced chemopreventive effect and showed to be a favourable combination in prevention of experimental mammary carcinogenesis.

The aim of this study was to evaluate preventive effects of raloxifene (RAL), melatonin (MEL) and their combination in N-methyl-N-nitrosourea (NMU)-induced rat mammary carcinogenesis. MEL-treatment began 12 days and RAL treatment began 10 days prior to carcinogen administration and continued till the end of experiment (24 weeks after first carcinogen administration). RAL was administered subcutaneously twice a week in the dose of 5 mg/kg b.w. MEL was administered diluted in drinking water in a concentration 4 microg/ml daily from 3 p.m. to 8 a.m. At the end of experiment, tumor incidence, frequency, latency period and tumor volume as parameters of mammary carcinogenesis were evaluated. Moreover, the effect of chemopreventives on body and uterine weight, food and water intake were recorded. In RAL-treated group, tumor incidence was decreased by 67% (p < 0.001), tumor frequency per group was reduced by 90% (p < 0.0002) and latency period lengthened by 27 days in comparison with control group. After MEL-treatment tumor incidence was decreased by 19%, tumor frequency per group was decreased by 50% (p < 0.05) when compared to control animals. The effect of RAL+MEL-treatment was very similar to that of RAL-treatment. In groups with RAL administration, significant decrease (p < 0.0001) in body weight gain and relative uterine weight was recorded. As to food intake no significant differences in comparison with control group were found. Consequently, groups were pooled and in RAL-treated groups (RAL, RAL+MEL) a decrease in food intake, when compared to groups without RAL administration (control group, MEL) was recorded (p<0.04). The water intake was markedly decreased in RAL-treated groups (P < 0.0001). RAL and RAL+MEL proved to be very effective in prevention of experimental mammary carcinogenesis in female rats, isolated MEL appeared to be of lower oncostatic activity.