Inhibition Of Mammary Carcinogenesis Research Articles

Abstract P5-05-15: Pregnancy inhibits mammary carcinogenesis by persistently altering the hypothalamic-pituitary axis

Abstract Pregnancy, carried to term at an early age, is probably the best natural protection against breast cancer development. The relative life-long breast cancer risk for women that give birth to their first child before the age of 20 years is approximately half that of nulliparous women. In contrast, if a woman undergoes her first full-term pregnancy after the age of 35, her risk for breast cancer is increased even more than nulliparous women. In the current generation many women are career oriented and have children later in life. Universally the average age at first birth is on the rise. It is critical to understand the underlying mechanism of this protective effect of pregnancy against breast cancer to develop novel prevention strategies to reduce the risk of breast cancer without women having to undergo pregnancy early in life. Earlier, we and others have demonstrated that post-pregnancy there were persistent changes in circulating levels of hormones. In order to understand the significance of these systemic changes we determined alterations in the hypothalamic-pituitary axis in parous rats. In particular, we examined the static and dynamic alterations in the hypothalamic-pituitary axis in response to pregnancy. Seven weeks old female Lewis rats were injected with the chemical carcinogen N-methyl-N-nitrosourea (MNU) at a dose of 50mg/kg body weight intraperitoneally. Two weeks post-carcinogen treatment these rats were housed with a male rat. On the observation of the vaginal plug the male was removed from the cage. Once the rats gave birth they nursed the pups for three weeks and were weaned after that period. Mammary tumorigenesis was monitored through weekly palpation for a period of nine months. A subset of rats at 6, 12 and 24 weeks post-weaning were used to study static and dynamic changes in the level of hormones. We investigated the static alterations in the hypothalamic-pituitary axis in response to pregnancy by measuring the levels of thyrotropin releasing hormone (TRH), growth hormone releasing hormone (GHRH), somatostatin (SS), dopamine (DA), growth hormone (GH) and prolactin (PRL). Next we investigated if the dynamic alterations in the hypothalamic-pituitary axis in response to pregnancy. Control and parous animals were subjected to secretogogue treatments (Growth Hormone Related Peptide 6 for GH and Perphenazine for PRL) and the levels of GH and PRL were measured. We also isolated the pituitary and treated them with the secretogogues and measured the levels of GH and PRL. Our data demonstrated that pregnancy resulted in persistent static and dynamic alterations in circulating levels of hormones. Parous rats response to the secretogogues was severely blunted compared to the control nulliparous rats. The levels of TRH, GHRH, GH and PRL were significantly lowered in parous rats while DA and SS levels were higher in nulliparous rats. As expected mammary carcinogenesis was significantly inhibited in parous rats. Overall, these preliminary results suggest that pregnancy induces persistent changes in hypothalamic-pituitary axis, which results in a lowered hormonal promotion environment resulting in inhibition of mammary carcinogenesis. Citation Format: Subramani R, Galvez A, Pedroza D, Lakshmanaswamy R. Pregnancy inhibits mammary carcinogenesis by persistently altering the hypothalamic-pituitary axis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-15.

Taxifolin possesses anti-cancer activity on the 7,12-Dimethylbenz(a)anthracene-Induced breast cancer in the sprague dawley rats by remodeling nuclear factor Erythroid 2- Kelch-Like ECH-Associated Protein 1-Heme Oxygenase 1 and anti-oxidant pathways

Background: In mammary cancer, alterations in various gene expressions and signaling pathways occurs due to the secondary effects of oxidative stress that facilitates cancer by causing genomic instability and mutagenic alterations. Several phenolic compounds are active against various malignancies. Taxifolin (TAX) exhibits diverse bioactivity profile that also contributes toward its anticancer efficacy. Objective: The present study has been designed for estimation of the anticancer potential of TAX on 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast cancer in Sprague Dawley (SD) rats. Materials and Methods: Molecular docking analysis of Kelch-like ECH-associated protein 1 (Keap-1) and heme oxygenase-1 (HO-1) was carried out using Maestro tool to rationalize the activity of TAX based on their binding potential. This was followed by DMBA administration in air pouch to induce mammary cancer in female SD rats (50–55 days old). After 90 days of cancer induction, the chemotherapeutic potential of TAX was evaluated by the administration of TAX at doses 10, 20, and 40 mg/kg/day. Besides this, the effect of TAX on Keap-1-nuclear factor erythroid-2 (Nrf-2) pathway associated with HO-1 and NADPH:quinoneoxidoreductase 1 (NQO1) expressions and their effect on the anti-oxidative and anti-proliferative activity was also evaluated through immunofluorescence analysis, real-time quantitative polymerase chain reaction, and biochemical estimations. Results: TAX revealed protective effect against lipid peroxidation, enzymatic (superoxide dismutase [SOD], manganese-containing SOD, copper- and zinc-containing SOD, catalase, and glutathione peroxidase), and nonenzymatic (reduced glutathione, α-tocopherol, and ascorbic acid) anti-oxidative markers in serum, liver, kidney, and breast tissue of both control and experimental groups. The study revealed upregulation of protective Nrf-2, HO-1, and NQO1 expressions with consequent suppression in Keap-1 mRNA expression. Conclusion: This study revealed the potency of TAX in the inhibition of mammary carcinogenesis through Nrf-2-Keap-1-HO-1 and antioxidant pathway. Abbreviations used: RT-qPCR: Real-time quantitative polymerase chain reaction; ODC: Ornithin decarboxylase; HO-1; Heme oxygenase-1; PAHs: Polyaromatic hydrocarbons; TBARS: Thiobarbituric acid reactive species; NQO1: NADPH:quinoneoxidoreductase 1; Keap-1: Kelch-like ECH associated protein 1; Nrf2: Nuclear factor erythroid 2; SD: Sprague Dawley.

Abstract A14: Hedgehog inhibition delays cancer growth in C3(1)/Tag transgenic murine mammary carcinoma model

Abstract In 1941 Apperly hypothesized that differential sunlight exposure is the cause of the latitudinal gradient in breast cancer mortality, and subsequently the effect was postulated to be due to the tumor inhibitory properties of skin produced vitamin D3. We first tested this latitudinal hypotheses using the C3(1)/Tag transgenic murine mammary carcinoma model and found that ultraviolet radiation (UVR) significantly prolongs tumor-free and overall survival but that dietary D3 has no such effect. The mechanism of this anti-mammary carcinogenesis effect of UVR is unclear but there is evidence that D3 is a potent inhibitor of the hedgehog (HH) - signaling pathway. To test this mechanistic hypothesis we compared the effects of the small molecule Smo-acting HH pathway inhibitor (HHI) BMS-833923/XL139 with those of UVR on breast cancer development in C3(1)/Tag mice. We have found that oral administration of the pharmacologic HHI delays Tag mammary carcinogenesis with an efficacy similar to that of UVR treatment (350 mJ/cm2, 3x/week), thus, time to first palpable tumor was delayed by 9 days by UVR treatment (p=0.016) and by 14 days by HHI treatment (p=0.009), compared control mice. Overall survival was delayed by 9 days by UVR treatment (p=0.19) and by 15 days by HHI treatment (p=0.011). And, we have found that HHI, like UVR, acts at an early stage of carcinogenesis (i.e. reduction of histologic changes at age 12 weeks), and initial studies of UVR + HHI treatments suggest that HHI and UVR have overlapping effects. Taken together our results are consistent with (albeit by no means proof of) our hypothesis that inhibition of mammary carcinogenesis by UVR-produced vitamin D3 underlies the latitudinal gradient and is mediated via HH inhibition. Moreover, our results suggest more broadly that HHI treatment before tumors develop may have more of an anti-cancer effect than does HHI treatment after tumors already have become clinically apparent. Note: This abstract was not presented at the conference. Citation Format: Anastasia M. Makarova, Subheksha KC, John A. Dolorito, Yefim I. Khaimskiy, Ervin H. Epstein, Jr. Hedgehog inhibition delays cancer growth in C3(1)/Tag transgenic murine mammary carcinoma model. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr A14.

Abstract 2272: Comparison of metformin, pheformin and buformin in mammary carcinogenesis in non-obese, non-diabetic rats.

Abstract Emerging evidence from studies of human pharmacoepidemiology indicate that metformin, an antidiabetic drug, is associated with reduced breast cancer risk in diabetic individuals. Data from preclinical mammary carcinogenesis studies in the rat indicate that metformin also has protective activity against chemically-induced mammary cancer in non diabetic rats, but the dose required for inhibition is above that used clinically for the treatment of diabetes. Human breast cancer cell growth also is inhibited by metformin, but at concentrations far in excess of anti-diabetic plasma concentrations of the drug. It is likely that pharmacokinetic/pharmacodyanmic factors contribute to this blunted sensitivity, possibly due to carcinogenesis-associated down regulation of organic cationic transporters (OCT) required for cellular uptake of metformin. Since some biguanides such as phenformin and buformin are not dependent on OCT for cellular accumulation, their effects against mammary carcinogenesis were evaluated in comparison to metformin as a proof-in-concept study that could set the stage for development of second generation biguanides. The hypothesis evaluated was that inhibition of mammary carcinogenesis by phenformin and buformin would be superior to metformin. Female Sprague Dawley rats (n=30/group) were injected with 1-methyl-1-nitrosourea (50 mg/kg) at 21 days of age and 7 days thereafter randomized to metformin, phenformin or buformin dietary groups and fed respective biguanides (10 mmol/kg) diets for 6 weeks. Both phenformin and buformin significantly reduced the number of mammary adenocarcinoma per rat (3.6, 1.6, and 0.7 cancers/rat for metformin, phenformin and buformin respectively) and tumor burden (1.61, 0.63, and 0.12 g/rat for metformin, phenformin and buformin respectively) and elongated cancer latency compared to metformin (40, 45, and 48 days post carcinogen for metformin, phenformin and buformin respectively) (p<0.05). Mammary cancer incidence was also lower in animals fed phenformin (77%) or buformin (43%) diet vs metformin (93%), but the difference was only significant between metformin and buformin (p<0.001). Cell culture experiments confirmed the carcinogenesis data. The comparative effects of these biguanides on the LKB1/AMPK axis will be reported. The associated mechanisms of cell growth inhibiton are under investigation. Supported by PHS grant CA52626 from the National Cancer Institute. Citation Format: Zongjian Zhu, Weiqin Jiang, John N. McGinley, Henry J. Thompson. Comparison of metformin, pheformin and buformin in mammary carcinogenesis in non-obese, non-diabetic rats. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2272. doi:10.1158/1538-7445.AM2013-2272

Defining the Role of Histone Deacetylases in the Inhibition of Mammary Carcinogenesis by Dietary Energy Restriction (DER): Effects of Suberoylanilide Hydroxamic Acid (SAHA) and DER in a Rat Model

Dietary energy restriction (DER) inhibits experimentally induced mammary cancer, an effect accompanied by elevated levels of silent information regulator 2 (SIRT1), a class III histone deacetylase (HDAC). However, the effect of DER on targets of other classes of HDACs has not been reported, a highly relevant issue given evidence that HDAC induction favors the development of cancer and tumor growth. Experiments were carried out to determine whether suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor with broad activity, would affect the anti-cancer activity of DER. Female Sprague Dawley rats (n = 30/group) were injected with 1-methyl-1-nitrosourea (50 mg/kg) at 21 days of age and 7 days thereafter were randomized to groups fed: (i) control diet (AIN-93G), (ii) 0.1% SAHA (w/w), (iii) 40% DER, or (iv) 0.1% SAHA + 40% DER. An additional group was fed 0.1% SAHA + 40%DER for 5 weeks and released to control diet for 3 weeks. DER significantly reduced mammary cancer incidence, multiplicity, and cancer burden and prolonged cancer latency (P < 0.01). Cancer inhibition was maintained in SAHA + DER, despite evidence that histone (H2A(Lys9), H2B(Lys5), and H4(Lys5/8/12/16), but not H3(Lys9); P < 0.001) and non-histone protein deacetylation (p53(Lys373) and p53(Lys382); P < 0.001) induced by DER was reversed by SAHA. This indicates that the inhibition of DER of cancer is not dependent on HDAC induction. After releasing rats from DER + SAHA, cancer multiplicity remained lower than control (P < 0.05), consistent with apoptosis-mediated cell deletion. These findings support further investigation of the hypothesis that HDAC induction by DER blunts its anti-carcinogenic impact.

Effect of Cu supplementation on genomic instability in chemically-induced mammary carcinogenesis in the rat

BackroundThe aim of the present study was to assess the effect of dietary supplementation (copper or copper and resveratrol) on the intensity of carcinogenesis and the frequency of microsatellite instability in a widely used model of mammary carcinogenesis induced in the rat by treatment with 7,12-dimethylbenz[a]anthracene (DMBA).MethodsDNA was extracted from rat mammary cancers and normal tisues, amplified by PCR, using different polymorphic DNA markers and the reaction products were analyzed for microsatellite instability.ResultsIt was found that irrespectively of the applied diet there was no inhibition of mammary carcinogenesis in the rats due to DMBA. Besides, in the groups supplemented with Cu (II) or Cu (II) and resveratrol the tumor formation was clearly accelerated. Unlike the animals that were fed with standard diet, the supplemented rats were characterized by the loss of heterozygosity of microsatellite D3Mgh9 in cancer tumors (by respectively 50 and 40%). When the animals received Cu (II) and resveratrol supplemented diet the occurrence of genomic instability was additionally found in their livers in the case of microsatellite D1Mgh6 (which was stable in the animals without dietary supplementation).ConclusionsIdentification of the underlying mechanisms by which dietary factors affect genomic stability might prove useful in the treatment of mammary cancer as well as in the incorporation of dietary factors into mammary cancer prevention strategies.

Effects of dietary energy repletion and IGF-1 infusion on the inhibition of mammary carcinogenesis by dietary energy restriction

Dietary energy restriction (DER) is a potent inhibitor of mammary carcinogenesis, but the responsible mechanisms are not fully understood. In a number of model systems, DER is associated with a decrease in circulating levels of IGF-1. Moreover, we have recently reported that protection against cancer is lost, and plasma IGF-1 levels are restored to control values when animals are re-fed, i.e., energy repleted (DER-REP). Accordingly, an experiment was designed to determine if infusion of IGF-1 could mimic the effect of DER-REP on the carcinogenic response in animals that were DER. Following 1-methyl-1-nitrosourea injection (50 mg/kg), rats were fed either ad libitum (AL) or 40% DER. After 6 wk, the DER group was divided into three groups: (1) continued DER, (2) DER-REP, or (3) continued DER and infused with 120 mug rh-IGF-1/d (INF) for a duration of 8 d. DER reduced mammary cancer incidence and multiplicity (P < 0.01) versus AL rats. In rats that were DER-REP, cancer incidence increased 1.4-fold and multiplicity increased by 3.6-fold versus DER rats. Plasma IGF-1 were reduced by DER (P < 0.01), an effect that was reversed by DER-REP (P < 0.05). INF increased plasma IGF-1 versus DER rats (P < 0.01) but did not reverse the carcinogenic response. Plasma IGFBP-3 levels were reduced by DER (P < 0.01), but elevated by either REP or INF. Thus, an 8-d period of refeeding following chronic DER (DER-REP) reversed the anticancer effects of DER, and 8 d of IGF-1 infusion without refeeding (INF) did not mimic the effects of the DER-REP on the carcinogenic response.

Sulforaphane: a naturally occurring mammary carcinoma mitotic inhibitor, which disrupts tubulin polymerization.

Sulforaphane (SUL), an isothiocyanate found in broccoli and other cruciferous vegetables, has been shown to induce phase II detoxification enzymes, inhibit chemically induced mammary tumors in rats, and more recently to induce cell cycle arrest and apoptosis in cancer cells of the colon. Here, we provide evidence that SUL also acts as a breast cancer anti-proliferative agent. The BALB/c mouse mammary carcinoma cell line F3II was treated with SUL at concentrations up to 15 microM and examined for markers of cell cycle arrest and apoptosis. Treatment of asynchronous F3II cells with 15 microM SUL resulted in G2/M cell cycle arrest, elevated p34cdc2 (cdc2) kinase activity, Bcl-2 down-regulation, evidence of caspase activation, and aggregation of condensed nuclear chromatin. Subsequent exposure of synchronized cells to 15 microM SUL resulted in elevated numbers of prophase/prometaphase mitotic figures, indicating cell cycle progression beyond G2 and arrest early within mitosis. Moreover, cells treated with 15 microM SUL displayed aberrant mitotic spindles, and higher doses of SUL inhibited tubulin polymerization in vitro. In addition, BALB/c mice injected s.c. with F3II cells and subsequently injected daily i.v. with SUL (15 nmol/day for 13 days) developed significantly smaller tumors (approximately 60% less in mass) than vehicle-treated controls. Western blot analysis of tumor proteins demonstrated significantly (P<0.05) reduced PCNA and elevated PARP fragmentation in samples from animals dosed with SUL. Taken together, these results indicate that SUL has mammary cancer suppressive actions both in cell culture and in the whole animal. Inhibition of mammary carcinogenesis appears in part to involve perturbation of mitotic microtubules and early M-phase block associated with cdc2 kinase activation, indicating that cells arrest prior to metaphase exit.

Prevention of methylnitrosourea-induced mammary cancers by 9-cis-retinoic acid and/or vitamin D3

Two cancer chemopreventive agents, vitamin D3 and 9-cis-retinoic acid (9-cis-RA), were evaluated alone and in combination in the methylnitrosourea (MNU)-induced mammary cancer model. In this study, female Sprague-Dawley rats received MNU (50 mg/kg BW) at 50 days of age. Vitamin D3 and 9-cis-RA were administered in the diet beginning three days later. The groups were: Group 1, vehicle only; Group 2, 9-cis-RA (60 mg/kg diet); Group 3, vitamin D3 (10 microg/kg diet); Group 4, vitamin D3 (3.3 microg/kg diet); Group 5, 9-cis-RA (60 mg/kg diet) plus vitamin D3 (10 microg/kg diet); and Group 6, 9-cis-RA (60 mg/kg diet) plus vitamin D3 (3.3 microg/kg diet). Animals were observed daily for signs of toxicity and were palpated 2x/week for mammary tumors. The study was terminated 150 days after treatment with MNU. The average number of mammary cancers was 6.7 in the animals receiving only the carcinogen. 9-cis-RA alone caused a 23% decrease in mammary cancer multiplicity, while vitamin D3 alone actually caused slight increases of 17 and 16% at 10 and 3.3 microg/kg diet dose levels, respectively. When the agents were given in combination, however, the 9-cis-RA plus the high dose of vitamin D caused a statistically significant decrease (44%) in mammary cancer number, while the 9-cis-RA plus the low dose resulted in a 37% decrease. Thus, low doses of these agents that were not effective in preventing mammary cancer when given alone appeared to be active when given in combinations. Possible interactions between the retinoic acid receptors and vitamin D receptor may be responsible for the observed inhibition of mammary carcinogenesis.

N-3 Fatty acids and lipid peroxidation in breast cancer inhibition

Long-chain n-3 fatty acids (FA) consistently inhibit the growth of human breast cancer (BC) cells both in culture and in grafts in immunosuppressed mice. Large cohort studies have, however, failed to confirm a protective effect for fish oils rich in n-3 FA against BC risk. The present review examines new evidence on biological mechanisms which may be involved in the inhibition of mammary carcinogenesis by long-chain n-3 FA, focusing on an apoptotic effect by its lipid peroxidation products. Dietary intake of n-3 FA leads to their incorporation into cell membrane lipids. Increased apoptosis in human BC cells following exposure to long-chain n-3 FA such as eicosapentaenoic and docosahexaenoic acids is generally ascribed to their inhibition of cyclooxygenase 2 which promotes mammary carcinogenesis. In addition however, long-chain n-3 FA are particularly likely to activate peroxisome proliferator-activated receptor (PPAR)-γ, a key regulator of lipid metabolism but also capable of modulating proliferative activity in a variety of cells including mammary cells. Expression of PPAR-γ in the nucleus is activated by second messengers such as J series prostaglandins and the latter have been shown to cause apoptosis in vivo in explants of human BC cells in immunosuppressed mice. In mammary tumours, it is observed that long-chain FA not only increase apoptosis, but also increase lipid peroxidation, and the apoptotic effect can be reversed by antioxidants. The rationale for use of n-3 FA dietary supplements in counteracting BC progression needs to be tested clinically in a phase 2 pilot study, while at the same time, the effect on whole-body lipid peroxidation needs to be monitored. Dietary supplements of fish oil rich in n-3 FA are proposed for premenopausal women over the age of 40 years who are shown to be at increased BC risk. Biological markers in breast tissue of BC progression will be monitored, and observed changes related to serial plasma levels of isoprostanes as a measure of whole-body lipid peroxidation.

N-3 fatty acids and lipid peroxidation in breast cancer inhibition.

Long-chain n-3 fatty acids (FA) consistently inhibit the growth of human breast cancer (BC) cells both in culture and in grafts in immunosuppressed mice. Large cohort studies have, however, failed to confirm a protective effect for fish oils rich in n-3 FA against BC risk. The present review examines new evidence on biological mechanisms which may be involved in the inhibition of mammary carcinogenesis by long-chain n-3 FA, focusing on an apoptotic effect by its lipid peroxidation products. Dietary intake of n-3 FA leads to their incorporation into cell membrane lipids. Increased apoptosis in human BC cells following exposure to long-chain n-3 FA such as eicosapentaenoic and docosahexaenoic acids is generally ascribed to their inhibition of cyclooxygenase 2 which promotes mammary carcinogenesis. In addition however, long-chain n-3 FA are particularly likely to activate peroxisome proliferator-activated receptor (PPAR)-gamma, a key regulator of lipid metabolism but also capable of modulating proliferative activity in a variety of cells including mammary cells. Expression of PPAR-gamma in the nucleus is activated by second messengers such as J series prostaglandins and the latter have been shown to cause apoptosis in vivo in explants of human BC cells in immunosuppressed mice. In mammary tumours, it is observed that long-chain FA not only increase apoptosis, but also increase lipid peroxidation, and the apoptotic effect can be reversed by antioxidants. The rationale for use of n-3 FA dietary supplements in counteracting BC progression needs to be tested clinically in a phase 2 pilot study, while at the same time, the effect on whole-body lipid peroxidation needs to be monitored. Dietary supplements of fish oil rich in n-3 FA are proposed for premenopausal women over the age of 40 years who are shown to be at increased BC risk. Biological markers in breast tissue of BC progression will be monitored, and observed changes related to serial plasma levels of isoprostanes as a measure of whole-body lipid peroxidation.

4-(hydroxyphenyl)retinamide selectively inhibits the development and progression of ductal hyperplastic lesions and carcinoma in situ in mammary gland.

In most previous chemoprevention studies on inhibition of mammary carcinogenesis, the formation of palpable tumors has been used as an end-point. Little is known about whether chemopreventive agents may similarly or selectively suppress hyperplastic and premalignant stages of the neoplastic process. In this study, we evaluated the effect of 4-(hydroxyphenyl)retinamide (4-HPR) on the development and progression of hyperplastic lesions and carcinoma in situ (CIS) in the N-methyl-N-nitrosourea (MNU) mammary carcinogenesis model in rats. 4-HPR was used as the chemopreventive agent because of its proven inhibitory effect on both the early and late phases of mammary carcinogenesis. Treatment with 4-HPR (2.0 mM/kg diet), beginning 2 days after MNU administration and administered continuously for 10 weeks, suppressed all mammary gland lesions (hyperplasia, CIS and invasive carcinoma) in 35% of animals. In the remaining 65%, 4-HPR allowed the development of hyperplastic lesions, alone or combined with CIS, and/or invasive carcinomas (CA). 4-HPR also increased by 2-fold the ratio between CIS and CA (0.75 per animal in control versus 1.5 in 4-HPR-treated animals), suggesting that it may also suppress the transition of CIS into CA. 4-HPR, when administered beginning 4 weeks after MNU administration [when hyperplastic and premalignant (CIS) lesions are present in the mammary gland], inhibited the frequency of terminal end bud hyperplasia (TEBH) and CA but did not significantly suppress ductal hyperplasia, ductal alveolar hyperplasia, alveolar hyperplasia and CIS. In these animals, 4-HPR induced partial disintegration of mostly peripheral areas of lesions, including carcinomas. Taken together, our data indicate that 4-HPR selectively suppresses the development and progression of hyperplastic lesions and CIS in TEBs. Furthermore, it appears that, in addition to mammary carcinomas, TEBH and CIS could also be used as end-point biomarkers in breast cancer chemoprevention studies.

Allium vegetable consumption, garlic supplement intake, and female breast carcinoma incidence.

The risk of female breast carcinoma in relation to onion and leek consumption and the use of garlic supplements was evaluated in the Netherlands Cohort Study on diet and cancer. Onions, leeks, and garlic contain specific compounds which might act as antimutagens. Animal experiments also suggest a possible role for these compounds in inhibition of mammary carcinogenesis. The Netherlands Cohort Study was started in 1986 among 120,852 Dutch men and women, aged 55-69 years, with collecting information on usual diet and important lifestyle characteristics. After 3.3 years of follow-up, 469 incident female breast carcinoma cases and 1713 female members of a randomly sampled control subcohort were available for analysis. Intake of onions or leeks was not associated with breast carcinoma risk after controlling for dietary and nondietary risk factors: the rate ratios in the highest intake categories were 0.95 (95% confidence interval 0.61-1.47) and 1.08 (95% confidence interval 0.79-1.48), respectively, compared with the lowest intake categories. The tests for trend in the rate ratios were neither significant. Garlic supplement use was also not associated with breast carcinoma incidence (rate ratio = 0.87, 95% confidence interval 0.58-1.31). In conclusion, we found no association between the consumption of onions or leeks, or garlic supplement use, and the incidence of female breast carcinoma.

Inhibition of mammary carcinogenesis in rats by dietary restriction

Mammary tumors were induced by 7,12-dimethylbenz[ a] anthracene (DMBA) in Sprague—Dawley female rats kept under different dietary restrictions. Starting at 40 days of age, 4 groups of rats were either full-fed or fed 25%, 50% or 80% of their daily ration. At 55 days of age DMBA was given by intravenous injection. Rats were continued on the restricted diet until 150 days after carcinogen treatment. Rats on 25% diet lost weight rapidly and the experiment had to be terminated. Rats on the 50% diet maintained a lower body weight throughout the experiment; only 12% developed tumors. Rats on the 80% diet lost weight initially, but at the termination of the experiment, there was no significant difference in body weight between this group and the full-fed controls. Of the rats on 80% diet, 34% developed tumors, compared to 92% tumor incidence in the full-fed controls. Vaginal smears were normal in the animals fed the 80% diet, while some irregularity was observed in the 50% group. Breeding capability in rats on the 80% diet was not affected, since there was no observable difference in the pregnancy rate between these animals and their controls. There was also no difference in plasma level of estrogen between the 80% diet group and the full-fed controls at the time of carcinogen treatment. [ 3H]Thymidine labelling index was significantly affected by 50% restriction of diet while there was no significant change in the 80% group.

Methods of extraction and high-performance liquid chromatographic analysis of butylated hydroxytoluene from the tissues and serum of rats

Butylated hydroxytoluene (BHT) is a phenolic antioxidant which is widely used in foods and has been shown to inhibit chemical carcinogenesis in the mammary gland induced by 7,12-dimethylbenz( a)anthracene. However, its mechanism of action as a tumor inhibitor is unclear. The purpose of this work was first to develop a method for extracting and quantitating BHT and then to determine the amounts that accumulate in the tissues and serum of rats as a starting point for looking at mechanistic possibilities in the inhibition of mammary carcinogenesis. Methodology of extracting BHT from rat tissues and serum was developed using a modified lipid extraction procedure. The sensitive nature of reverse-phase high-performance liquid chromatography proved useful in detecting and quantifying BHT after its extraction from biological tissues. All tissues were taken from animals consuming semipurified diets with and without 0.3% BHT for various periods of time (weeks). BHT was found in much higher levels in mammary tissue than in the liver and serum of rats. The lipid content in mammary tissue appears to be predictive of the amount of BHT found in this tissue, presumably because of the lipophilic character of the antioxidant.

Anticarcinogenic effect of selenium in the dimethylbenz(a)anthracene‐induced mammary tumor model in rats

AbstractUsing the dimethylbenz(a)anthracene‐induced mammary tumor model in rats, our studies indicated that there was a dose‐response relationship between dietary selenium supplementation and the inhibition of mammary carcinogenesis. The degree of inhibition was proportional to the level of dietary selenium up to 5 ppm, at which point toxicity in the form of a reduction in weight gain was evident. Moreover, it was observed that the chemopreventive efficacy of selenium was influenced by the dose of carcinogen as well as the fat intake of the animals. By supplementing selenium for defined periods of time, we concluded that selenium inhibited both the initiation and the promotion phases of chemical carcinogenesis, and that a continuous intake of selenium was necessary to achieve maximal suppression of tumor growth. In an attempt to improve the efficacy of lower levels of selenium, we conducted another series of experiments in which selenium and vitamin E were tested in combination. Results showed that although vitamin E alone had no prophylactic effect against tumorigenesis, it potentiated the ability of selenium to inhibit the development of mammary tumors. Further investigation suggested that the anticarcinogenic action of selenium could not be explained by its antioxidant function in lipid peroxidation. On the other hand, vitamin E might be able to provide a more favorable environment against oxidant stress to assist selenium in exerting its inhibitory effect through some other mechanisms.