Dietary effects of mead acid on N-methyl-N-nitrosourea-induced mammary cancers in female Sprague-Dawley rats

  • Authors:
    • Yuichi Kinoshita
    • Katsuhiko Yoshizawa
    • Kei Hamazaki
    • Yuko Emoto
    • Takashi Yuri
    • Michiko Yuki
    • Hiroshi Kawashima
    • Nobuaki Shikata
    • Airo Tsubura
  • View Affiliations

  • Published online on: October 14, 2015     https://doi.org/10.3892/br.2015.530
  • Pages: 33-39
Metrics: Total Views: 0 (Spandidos Publications: | PMC Statistics: )
Total PDF Downloads: 0 (Spandidos Publications: | PMC Statistics: )


Abstract

The effect of mead acid (MA; 5,8,11-eicosatrienoic acid) on the suppression of the development and growth of N-methyl-N-nitrosourea (MNU)-induced mammary cancer in female Sprague-Dawley rats was examined. The MA diet (2.4% MA) or control (CTR) diet (0% MA) was started at 6 weeks of age, MNU was injected intraperitoneally at 7 weeks of age, and the rats were maintained on the respective diets for the whole experimental period (until 19 weeks of age). All induced mammary tumors were luminal A subtype carcinomas (estrogen and progesterone receptor positive and HER2/neu negative). The MA diet significantly suppressed the initiation and promotion phases of mammary carcinogenesis; MA suppressed the development (incidence, 61.5 vs. 100%; multiplicity, 2.1 vs. 4.5) and the growth (final tumor weight, 427.1 vs. 1,796.3 mg) of mammary cancers by suppressing cell proliferation, but not by accelerating cell death. There were evident changes in the major fatty acid composition of n‑3, n‑6, and n‑9 fatty acids in the serum of the MA diet group; there was a significant increase in MA and significant decreases in oleic acid (OA), linoleic acid, arachidonic acid and docosahexaenoic acid. In non‑tumorous mammary tissue, there was a significant increase in MA and a significant decrease in OA in the MA diet group. The n‑6/n‑3 ratios in serum and mammary tissue of the MA diet group were significantly decreased. The MA diet suppressed MNU‑induced luminal A mammary cancer by lowering cancer cell proliferation. Therefore, MA may be a chemopreventive and chemotherapeutic agent. In addition to hormone therapy, MA supplementation may be a beneficial chemotherapeutic agent for the luminal A subtype of breast cancer.

Introduction

Epidemiological investigation has shown the association between the risk of breast cancer and total fat intake (1). However, rather than total fat intake, subtypes of fatty acids are considered to have a more influential effect on breast cancer. Increased intake of n-3 fatty acids derived from marine products and decreased intake of n-6 fatty acids found in vegetable oils and processed foods results in a lower n-6/n-3 ratio and decreased breast cancer risk (2). Rat mammary cancer growth is suppressed by eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (3,4) and accelerated by n-6 fatty acids, such as linoleic acid (LA) (5). An increased n-6/n-3 ratio is associated with rat mammary carcinogenesis (6). In agreement with rat mammary carcinogenesis studies, laboratory experiments have shown that n-3 fatty acids, such as EPA, suppress human breast cancer cell growth (7), while n-6 fatty acids, such as LA and arachidonic acid (AA), promote the growth of human breast cancer cells (7,8). Experimental evidence shows critical roles for n-3 and n-6 fatty acids in association with breast cancer growth.

In contrast to n-3 and n-6 fatty acids, the role of n-9 fatty acids in breast cancer has not been studied in detail. One study showed that <15% of breast cancers could be prevented if the populations of high-income countries shifted to the traditional Mediterranean diet (9). The Mediterranean diet contains high amounts of olive oil rich in n-9 oleic acid (OA), and the possible effect of OA in suppressing breast cancer has received attention. However, another study was inconclusive in showing that olive oil consumption lowers the breast cancer risk (10). In cell culture, although OA causes growth inhibition at higher concentrations, it produces growth acceleration of human breast cancer cells at lower concentrations (11). Thus, the effects of OA on breast cancer appear to be complex. Mead acid (MA) is an n-9 fatty acid produced from OA when essential n-3 and n-6 fatty acids are deficient; mammals elongate and desaturate OA to make the end product MA (12,13). Epidemiologically, MA was inversely associated with breast cancer risk as well as overall cancer risk (14). Experimentally, MA suppressed MCF-7 and KPL-1 human breast cancer cell growth in culture (15,16). MCF-7 and KPL-1 are luminal A subtypes according to intrinsic subtype classification (17). MA also suppressed the growth and metastasis of KPL-1 cells transplanted in female athymic mice (16).

Mammary carcinogenesis is a multistep process in which normal breast epithelial cells experience DNA damage (initiation phase), followed by enhanced cell proliferation (promotion phase), and subsequently the acquisition of metastasis (progression phase) to acquire a malignant potential. According to in vivo and in vitro studies using breast cancer cell lines, MA suppressed the promotion/progression phase of carcinogenesis; however, the role of MA in the initiation phase remains to be elucidated. In contrast to using breast cancer cell lines, rodent mammary cancers induced by chemical carcinogens can be preferentially used to evaluate the initiation/promotion stage of mammary carcinogenesis. However, metastasis is hardly detectable in rodent systems. Therefore, the present study was designed to determine if MA can block the initiation/promotion stage of mammary carcinogenesis to explore the possible use of MA as a chemotherapeutic agent and a chemopreventive agent for mammary cancer. The intrinsic classification of breast cancer can recommend effective targeted therapy and predict responses to chemotherapy (18). Therefore, the intrinsic subtypes of chemically induced rat mammary cancers were determined to see the effects of MA in association with the intrinsic subtypes of induced mammary cancers.

Materials and methods

Diet

The experimental diets contained the same amount of nutrients but with different fatty acid compositions (Table I). In brief, the MA diet and control (CTR) diet were modifications of the AIN-76 diet. The MA diet contained 5% SUNTGM33 (Suntory Wellness, Tokyo, Japan), which contains 48.0% MA. SUNTGM33 is microbial oil obtained by fungal fermentation (19). The CTR diet contained 5% olive oil (Nacalai Tesque, Kyoto, Japan), which contains 74.7% OA; OA is a precursor of MA. The detailed fatty acid composition of SUNTGM33 and olive oil has been described previously; the MA diet contained 2.4% MA while the CTR diet contained 0% MA (16). Each experimental diet was formulated by Oriental Yeast (Tokyo, Japan).

Table I.

Composition of experimental diets.

Table I.

Composition of experimental diets.

ComponentsMA dietCTR diet
Casein  20  20
DL-Methionine0.30.3
Cornstarch  43  43
α-Cornstarch  12  12
Sucrose  10  10
Cellulose     5     5
AIN-76 mineral mix3.53.5
AIN-76 vitamin mix     1     1
Choline bitartrate0.20.2
SUNTGM33     5     0
Olive oil     0     5

[i] Values are expressed in g/100 g diet. MA, mead acid; CTR, control.

Carcinogen

N-methyl-N-nitrosourea (MNU) in a powder form was obtained from Sigma (St. Louis, MO, USA) and was stored at 4°C in the dark. Immediately prior to use, MNU was dissolved in physiological saline containing 0.1% acetic acid, and a 5 mg/ml solution was prepared. A single dose of 50 mg/kg body weight was administered intraperitoneally.

Animals and experimental procedures

The study protocol and animal procedures were approved by the Animal Care and Use Committee of Kansai Medical University (Hirakata, Osaka, Japan; permit no. 14–111). In brief, 52 6-week-old virgin female Sprague-Dawley rats [Crl:CD(SD)] were purchased from Charles River Japan (Hino, Japan). They were housed in groups of 4 or 5 in plastic cages with paper bedding (Paper Clean, SLC, Hamamatsu, Japan) in a specific pathogen-free environment maintained at 22±2°C and 60±10% relative humidity with a 12-h light/dark cycle (lights on at 8:00 a.m. and lights off at 8:00 p.m.). The rats were randomly divided into four groups, which were the CTR diet group and the MA diet group with or without MNU (each n=13, Fig. 1). Fresh sterilized stocks of the pellet diet were provided to the animals twice a week starting at 6 weeks of age with any remaining diet being discarded to minimize the ingestion of oxidized fatty acid. Half of the animals received MNU at 7 weeks of age, and all animals remained on the same diets for the remainder of the experiment (until 19 weeks of age). Experimental diets and water were available freely. During the experiment, the dose of diet ingested, body weight and tumor volume were measured once a week. The tumor volume was calculated using the standard formula: Width2 x length × 0.5. At sacrifice, blood was sampled by inferior vena cava puncture and subsequently the animals were sacrificed by exsanguination from aortic transection. At necropsy, all the organs were examined macroscopically, and macroscopically abnormal organs, mammary glands and mammary tumors were examined histologically. Tissues were fixed in 10% neutral buffered formalin, embedded in paraffin, and stained with hematoxylin and eosin (HE); blood samples and sections of the non-tumorous inguinal mammary tissues were used for fatty acid analysis. Throughout the experiments, animals were cared for in accordance with the Guidelines for Animal Experimentation of Kansai Medical University.

Cell kinetics and microvessel density

The cell kinetics (cell proliferation and cell death) in the 6 largest MNU-induced tumors (Groups 1 and 2) were evaluated. Cell proliferation was evaluated by anti-Ki-67 (Clone SP6, ready to use; Nichirei Biosciences, Tokyo, Japan). Cell death was evaluated by anti-phospho-histone H2A.X (γ-H2A.X) antibody (Clone Ser139, 1:100; Cell Signaling, Danvers, MA, USA), an immunomarker of the DNA damage response. Microvessel density was evaluated by anti-CD34 antiserum (polyclonal, 1:50; Aviva Systemic Biology, San Diego, CA, USA). Immunohistochemistry was performed with the Histofine MAX-PO for rats kit (Nichirei Biosciences) according to the manufacturer's protocol. Each slide was scanned with a high-resolution digital scanner (NanoZoomer 2.0 Digital Pathology; Hamamatsu Photonics, Hamamatsu, Japan) to prepare digital images. The NDPI image files were opened in color mode with NDP.view software (Hamamatsu Photonics). The images were changed to JPEG files at magnification, ×40 in five randomly selected areas within each tumor that was used to analyze immunohistochemical staining (20,21). The Ki-67 and γ-H2A.X indexes were assessed by positive cells/1,000 cells as an index of cell kinetics, and CD34 was assessed by positive area/1 mm2 as a parameter of tumor angiogenesis.

Immunohistochemistry-based surrogate intrinsic subtyping of MNU-induced mammary tumors

The intrinsic subtype of the MNU-induced tumors was evaluated using the largest mammary tumor in each rat (Group 1, n=13; Group 2, n=8). Estrogen receptor (ER) was visualized by anti-ER antibody (Clone 6F11, 1:40; Leica Biosystems Newcastle, Newcastle upon Tyne, UK), progesterone receptor (PgR) by anti-PgR antibody (Clone PR6, 1:100; Abcam, Cambridge, UK), and HER2/neu by anti-c-erbB2/Her2/neu antibody (Clone e2–4000+H3B5 antibody cocktail, 1:300; Thermo Scientific, Waltham, MA, USA). Positive status was evaluated according to previous studies (2224). In brief, ER and PgR were considered positive when there were ≥1% positive tumor nuclei in the slide, and HER2 was considered positive when there were ≥10% positive tumor cells with complete and intense circumferential membrane staining.

Fatty acid analysis of serum and mammary tissue

To determine fatty acid composition, blood samples and mammary tissues were collected. Samples from Groups 1 and 2 were collected from the 5 and 6 rats that had the largest mammary tumors, respectively. Samples from Group 3 and 4 were collected from 5 and 6 randomly selected rats, respectively. Sera were separated from whole blood that was cooled on ice by centrifugation for 10 min at 1,640 × g. Non-tumorous mammary tissues stored at −20°C were thawed and homogenized. The fatty acid composition of the total phospholipid fraction of serum was determined. Total lipids were extracted by the method of Bligh and Dyer (25). The total phospholipid fraction was separated by thin-layer chromatography. For an internal standard, 1,2-diheptadecanoyl-sn-3-pfospfocholine (Avanti Polar Lipids, Inc., Alabaster, AL, USA) was added. Total phospholipid fractions were transmethylated with HCl-methanol, and subsequently the fatty acid composition was analyzed by gas chromatography (GC-2014, Shimadzu Corporation, Kyoto, Japan) with a capillary column DB-225 (0.25 mm ×30 m ×0.25 µm; J&M Scientific, Folsom, CA, USA). The entire system was controlled with gas chromatography software (GCsolution; Shimadzu Corporation). The fatty acid composition of the total lipid fraction of non-tumorous mammary tissues was determined. In brief, frozen tissues were thawed, minced and homogenized three times in 8 ml chloroform-methanol (2:1) by a polytron homogenizer (Kinematica, Lucerne, Switzerland) for 10 sec. The fatty acid analysis of total lipids in the mammary tissue was performed by the same method as previously mentioned (16).

Statistical analysis

Values are expressed as the mean ± standard error of the mean. Body weight, tumor volume, tumor weight, cancer multiplicity, number of Ki-67 and γ-H2A.X-positive cells/1,000 cells, CD34-positive area/1 mm2, ER and PgR-positive cells/1 mm2, fatty acid composition, and the n-6/n-3 ratio among groups were analyzed by the t-test. The cancer incidence was analyzed with the χ2 test.

Results

Host animals

During the experiment, the daily dose of food ingestion was compatible among groups, and although MNU treatment tends to decrease the body weight, the MA diet did not significantly influence the weight as compared with the CTR diet group. At necropsy, except for the development of mammary tumors, no organs or tissues were macroscopically abnormal.

Mammary carcinogenesis

All mammary tumors examined were histologically confirmed as mammary cancers. Therefore, the mammary tumors in the present study are referred to as mammary cancers. In MNU-treated rats, the MA diet (Group 2) tended to have a delayed development of palpable mammary cancer as compared to the CTR diet group (Group 1), and at the end of the experiment, the mammary cancer incidence was significantly lower in MA dietfed rats (Group 2 vs. 1: 61.5 vs. 100%; P<0.05; Fig. 2A). At the end of the study, the MA diet group had a significantly decreased average cancer volume (data not shown) and final average cancer weight (Group 2 vs. 1: 427.1±106.9 vs. 1,796.3±378.8 mg; P<0.01; Fig. 2B) when MNU-induced macroscopic mammary cancers were compared. Including histologically detectable microscopic cancers, the MA diet significantly lowered cancer multiplicity (Group 2 vs. 1: 2.1±0.4 vs. 4.5±0.9; P<0.05; Fig. 2C. No mammary cancer was detected in the MNU-unexposed rats on either the CTR or MA diet (Groups 3 and 4, respectively).

Proliferation and apoptotic ratio of MNU-induced mammary cancer

To compare the cell kinetics of MNU-induced mammary cancers (cell proliferation and cell death), the number of Ki-67-positive and γ-H2A.X-positive cells/1,000 cancer cells from the CTR and MA diet groups was compared. The proliferation and apoptotic cell number are shown in Fig. 3A and B, respectively. The proliferation ratio in the CTR and MA diet group was 44.3±3.9 and 29.3±3.9, respectively (Group 2 vs. 1: P<0.05), while the apoptotic ratio in the CTR and MA diet group was 1.7±0.4 and 1.3±0.5 (P>0.05). MA significantly suppressed cancer cell proliferation but did not alter the cell death ratio.

Microvessel density of MNU-induced mammary cancer

Although the cell growth was suppressed in the MA diet group, microvessel density of MNU-induced tumors, as evaluated by the CD34-positive area, was compatible between the CTR and MA diet groups (Fig. 4). Therefore, the MA diet did not affect tumor angiogenesis in the MNU-induced mammary tumor system (Group 2 vs. 1: P>0.05).

Intrinsic subtype of MNU-induced mammary cancer

In the CTR and MA diet group (13 and 8 mammary cancers, respectively), all tumors were ER- and PgR-positive and HER2-negative (all luminal A subtype). Representative staining is shown in Fig. 5A. Therefore, MA effectively suppressed the growth and development of luminal A subtype tumors without affecting the number of ER- and PgR-positive cells/1 mm2 (Group 2 vs. 1: not significant; Fig. 5B). However, the effect of MA against other intrinsic subtype tumors could not be evaluated from the MNU-induced mammary tumor system.

Fatty acid composition of serum and mammary tissue

The different diet groups had different fatty acid compositions of serum and mammary tissue that reflected the differences in the fatty acid composition of the respective diets. MNU treatment did not affect the fatty acid composition (Groups 1–4; Fig. 6A and B). Evident changes in the major n-3, n-6 and n-9 fatty acid composition of serum in the MA diet group were significant increase in MA concentration and significant decreases in OA, LA, AA and DHA, as compared to the CTR diet (Fig. 6A). Changes in the fatty acid composition of non-tumorous mammary tissues were a significant increase in MA and a significant decrease in OA (Fig. 6B). Changes in the fatty acid composition of serum and mammary tissue resulted in significantly decreased n-6/n-3 ratios in the sera and mammary tissues of the MA group (Group 2 vs. 1: P<0.01 and P<0.05, respectively; Fig. 7).

Discussion

The use of pharmacological or natural agents that inhibit the development of invasive breast cancer either by blocking the DNA damage that initiates cancer (blocking agent) or by arresting or reversing the progression of premalignant cells in which such damage has already occurred (suppressing agent) is desired (26,27). In the present study, 2.4% MA in the diet significantly suppressed MNU-induced mammary cancer incidence, multiplicity and average cancer volume and final cancer weight. These results indicate that MA suppressed the initiation and promotion phases of carcinogenesis. Our previous study on KPL-1 human breast cancer cells showed that 2.4% MA in the diet suppressed the promotion (growth) and progression phases (metastasis) (16). Taken together, 2.4% MA in the diet acted as a blocking and suppressing agent that suppressed all stages of mammary carcinogenesis; thus, MA is a candidate molecule to be used as a chemotherapeutic and chemopreventive agent.

The effects of n-9 OA on breast cancer remain controversial (11). By contrast, epidemiological results and experimental data show the beneficial effects of n-9 MA against breast cancer (1416); MA suppressed the growth of MCF-7 and KPL-1 human breast cancer cells in culture. In the present study, in agreement with a study of KPL-1 cells transplanted into female athymic mice (16), MA suppressed the development and growth of MNU-induced mammary cancer. In these two experiments, the mechanism of growth suppression was decreased cell proliferation, not accelerated apoptosis. Studies of the effects of MA on breast cancer in humans and animals are limited (1416). MA dose-dependently inhibits vascular endothelial growth factor (VEGF)-stimulated angiogenesis (28). The VEGF pathway may act indirectly via endothelial cells and may be involved in tumor angiogenesis; or the VEGF pathway may act directly via the VEGF receptor in cancer cells and participate in the growth modification of breast cancer cells (16). The VEGF-VEGFR interaction on cancer cells may partially explain the actions of MA in modifying cancer cell growth. However, the microvessel density in MNU-induced tumors was not affected by MA, which is consistent with findings from athymic mice implanted with KPL-1 cells (16). In contrast to the lack of detailed studies on n-9 fatty acids, the growth inhibitory action of n-3 fatty acids and the growth stimulatory action of n-6 fatty acids have been studied in detail (26). Changes in the n-6/n-3 ratio appear to be noteworthy (6,29). The present study showed that MA decreased the n-6/n-3 ratio in serum and in mammary tissue, which may have been indirectly involved in suppressing cell proliferation of MNU-induced mammary cancers. However, more precise mechanisms of the MA-mediated decrease in cell proliferation should be determined.

Detailed molecular characterization of individual cancers will enable cancer patients to receive tailored targeted therapies that improve outcomes and decrease therapy toxicity. Immunohistochemistry-based surrogate intrinsic subtyping is convenient when specimens for gene analysis are not available (18). Immunohistochemical staining for ER, PgR, and HER2 can differentiate breast cancer into luminal A (ER+ and/or PgR+, HER2), luminal B (ER+ and/or PgR+, HER2+), HER2 (ER and PgR, HER2+), and triple negative (ER and PgR, HER2) subtypes (18,30). Endocrine therapy for luminal A subtype, endocrine therapy and trastuzumab plus chemotherapy for luminal B subtype, trastuzumab plus chemotherapy for HER2 subtype, and chemotherapy for triple negative cases are recommended (18,31). MCF-7, KPL-1 (17), and all the MNU-induced mammary cancers were luminal A, which means that MA supplementation in addition to endocrine therapy may further improve the outcome of luminal A breast cancer. However, assessments of the efficacy of MA against other breast cancer subtypes are required.

Acknowledgements

The present study was supported by a grant from MEXT-Supported Programs for the Strategic Research Foundations at Private Universities (no. S1201038).

References

1 

Freedman LS, Kipnis V, Schatzkin A and Potischman N: Methods of epidemiology: Evaluating the fat-breast cancer hypothesis-comparing dietary instruments and other developments. Cancer J. 14:69–74. 2002. View Article : Google Scholar

2 

Yang B, Ren XL, Fu YQ, Gao JL and Li D: Ratio of n-3/n-6 PUFAs and risk of breast cancer: A meta-analysis of 274135 adult females from 11 independent prospective studies. BMC Cancer. 14:1052014. View Article : Google Scholar : PubMed/NCBI

3 

Takata T, Minoura T, Takada H, Sakaguchi M, Yamamura M, Hioki K and Yamamoto M: Specific inhibitory effect of dietary eicosapentaenoic acid on N-nitroso-N-methylurea-induced mammary carcinogenesis in female Sprague-Dawley rats. Carcinogenesis. 11:2015–2019. 1990. View Article : Google Scholar : PubMed/NCBI

4 

Yuri T, Danbara N, Tsujita-Kyutoku M, Fukunaga K, Takada H, Inoue Y, Hada T and Tsubura A: Dietary docosahexaenoic acid suppresses N-methyl-N-nitrosourea-induced mammary carcinogenesis in rats more effectively than eicosapentaenoic acid. Nutr Cancer. 45:211–217. 2003. View Article : Google Scholar : PubMed/NCBI

5 

Cohen LA, Thompson DO, Maeura Y, Choi K, Blank ME and Rose DP: Dietary fat and mammary cancer. I. Promoting effects of different dietary fats on N-nitrosomethylurea-induced rat mammary tumorigenesis. J Natl Cancer Inst. 77:33–42. 1986.PubMed/NCBI

6 

Zhu Z, Jiang W, McGinley JN, Prokopczyk B, Richie JP Jr, El Bayoumy K, Manni A and Thompson HJ: Mammary gland density predicts the cancer inhibitory activity of the N-3 to N-6 ratio of dietary fat. Cancer Prev Res (Phila). 4:1675–1685. 2011. View Article : Google Scholar : PubMed/NCBI

7 

Senzaki H, Iwamoto S, Ogura E, Kiyozuka Y, Arita S, Kurebayashi J, Takada H, Hioki K and Tsubura A: Dietary effects of fatty acids on growth and metastasis of KPL-1 human breast cancer cells in vivo and in vitro. Anticancer Res. 18:1621–1627. 1998.PubMed/NCBI

8 

Chang NW, Wu CT, Chen DR, Yeh CY and Lin C: High levels of arachidonic acid and peroxisome proliferator-activated receptor-alpha in breast cancer tissues are associated with promoting cancer cell proliferation. J Nutr Biochem. 24:274–281. 2013. View Article : Google Scholar : PubMed/NCBI

9 

Trichopoulou A, Lagiou P, Kuper H and Trichopoulos D: Cancer and Mediterranean dietary traditions. Cancer Epidemiol Biomarkers Prev. 9:869–873. 2000.PubMed/NCBI

10 

Buckland G, Travier N, Agudo A, Fonseca-Nunes A, Navarro C, Lagiou P, Demetriou C, Amiano P, Dorronsoro M, Chirlaque MD, et al: Olive oil intake and breast cancer risk in the Mediterranean countries of the European prospective investigation into cancer and nutrition study. Int J Cancer. 131:2465–2469. 2012. View Article : Google Scholar : PubMed/NCBI

11 

Rose DP and Connolly JM: Effects of fatty acids and inhibitors of eicosanoid synthesis on the growth of a human breast cancer cell line in culture. Cancer Res. 50:7139–7144. 1990.PubMed/NCBI

12 

Fulco AJ and Mead JF: Metabolism of essential fatty acids. VIII. Origin of 5,8,11-eicosatrienoic acid in the fat-deficient rat. J Biol Chem. 234:1411–1416. 1959.PubMed/NCBI

13 

Ichi I, Kono N, Arita Y, Haga S, Arisawa K, Yamano M, Nagase M, Fujiwara Y and Arai H: Identification of genes and pathways involved in the synthesis of Mead acid (20:3 n-9), an indicator of essential fatty acid deficiency. Biochim Biophys Acta. 1841:204–213. 2014. View Article : Google Scholar : PubMed/NCBI

14 

Pouchieu C, Chajès V, Laporte F, Kesse-Guyot E, Galan P, Hercberg S, Latino-Martel P and Touvier M: Prospective associations between plasma saturated, monounsaturated and polyunsaturated fatty acids and overall and breast cancer risk-modulation by antioxidants: A nested case-control study. PLoS One. 9:e904422014. View Article : Google Scholar : PubMed/NCBI

15 

Heyd VL and Eynard AR: Effects of eicosatrienoic acid (20:3 n-9, Mead's acid) on some promalignant-related properties of three human cancer cell lines. Prostaglandins Other Lipid Mediat. 71:177–188. 2003. View Article : Google Scholar : PubMed/NCBI

16 

Kinoshita Y, Yoshizawa K, Hamazaki K, Emoto Y, Yuri T, Yuki M, Shikata N, Kawashima H and Tsubura A: Mead acid inhibits the growth of KPL-1 human breast cancer cells in vitro and in vivo. Oncol Rep. 32:1385–1394. 2014.PubMed/NCBI

17 

Kurebayashi J, Kanomata N, Moriya T, Kozuka Y, Watanabe M and Sonoo H: Preferential antitumor effect of the Src inhibitor dasatinib associated with a decreased proportion of aldehyde dehydrogenase 1-positive cells in breast cancer cells of the basal B subtype. BMC Cancer. 10:5682010. View Article : Google Scholar : PubMed/NCBI

18 

Sandhu R, Parker JS, Jones WD, Livas CA and Coleman WB: Microarray-based profiling for molecular classification of breast cancer and identification of new targets for therapy. Lab Medicine. 41:364–372. 2010. View Article : Google Scholar

19 

Sakuradani E, Kamada N, Hirano Y, Nishihara M, Kawashima H, Akimoto K, Higashiyama K, Ogawa J and Shimizu S: Production of 5,8,11-eicosatrienoic acid by a delta5 and delta6 desaturation activity-enhanced mutant derived from a delta12 desaturation activity-defective mutant of Mortierella alpina 1S-4. Appl Microbiol Biotechnol. 60:281–287. 2002. View Article : Google Scholar : PubMed/NCBI

20 

Kanematsu S, Yoshizawa K, Uehara N, Miki H, Sasaki T, Kuro M, Lai YC, Kimura A, Yuri T and Tsubura A: Sulforaphane inhibits the growth of KPL-1 human breast cancer cells in vitro and suppresses the growth and metastasis of orthotopically transplanted KPL-1 cells in female athymic mice. Oncol Rep. 26:603–608. 2011.PubMed/NCBI

21 

Redon CE, Weyemi U, Parekh PR, Huang D, Burrell AS and Bonner WM: γ-H2AX and other histone post-translational modifications in the clinic. Biochim Biophys Acta. 1819:743–756. 2012. View Article : Google Scholar : PubMed/NCBI

22 

Hammond ME, Hayes DF, Dowsett M, Allred DC, Hagerty KL, Badve S, Fitzgibbons PL, Francis G, Goldstein NS, Hayes M, et al: American society of clinical oncology/college of American pathologists guideline recommendations for immunohistochemical testing of estrogen and progesterone receptors in breast cancer. J Clin Oncol. 28:2784–2795. 2010. View Article : Google Scholar : PubMed/NCBI

23 

Wolff AC, Hammond ME, Hicks DG, Dowsett M, McShane LM, Allison KH, Allred DC, Bartlett JM, Bilous M, Fitzgibbons P, et al: Recommendations for human epidermal growth factor receptor 2 testing in breast cancer: American society of clinical oncology/college of American pathologists clinical practice guideline update. J Clin Oncol. 31:3997–4013. 2013. View Article : Google Scholar : PubMed/NCBI

24 

Russo J: Significance of rat mammary tumors for human risk assessment. Toxicol Pathol. 4:145–170. 2015. View Article : Google Scholar

25 

Bligh EG and Dyer WJ: A rapid method of total lipid extraction and purification. Can J Biochem Physiol. 37:911–917. 1959. View Article : Google Scholar : PubMed/NCBI

26 

Tsubura A, Uehara N, Kiyozuka Y and Shikata N: Dietary factors modifying breast cancer risk and relation to time of intake. J Mammary Gland Biol Neoplasia. 10:87–100. 2005. View Article : Google Scholar : PubMed/NCBI

27 

Cazzaniga M and Bonanni B: Breast cancer chemoprevention: Old and new approaches. J Biomed Biotechnol. 2012:9856202012. View Article : Google Scholar : PubMed/NCBI

28 

Hamazaki T, Nagasawa T, Hamazaki K and Itomura M: Inhibitory effect of 5,8,11-eicosatrienoic acid on angiogenesis. Prostaglandins Leukot Essent Fatty Acids. 86:221–224. 2012. View Article : Google Scholar : PubMed/NCBI

29 

Okuyama H, Kobayashi T and Watanabe S: Dietary fatty acids-the N-6/N-3 balance and chronic elderly diseases. Excess linoleic acid and relative N-3 deficiency syndrome seen in Japan. Prog Lipid Res. 35:409–457. 1996. View Article : Google Scholar : PubMed/NCBI

30 

Lips EH, Mulder L, de Ronde JJ, Mandjes IA, Koolen BB, Wessels LF, Rodenhuis S and Wesseling J: Breast cancer subtyping by immunohistochemistry and histological grade outperforms breast cancer intrinsic subtypes in predicting neoadjuvant chemotherapy response. Breast Cancer Res Treat. 140:63–71. 2013. View Article : Google Scholar : PubMed/NCBI

31 

Goldhirsch A, Wood WC, Coates AS, Gelber RD, Thürlimann B and Senn HJ: Panel members: Strategies for subtypes-dealing with the diversity of breast cancer: Highlights of the St. Gallen international expert consensus on the primary therapy of early breast cancer 2011. Ann Oncol. 22:1736–1747. 2011. View Article : Google Scholar : PubMed/NCBI

Related Articles

Journal Cover

January-2016
Volume 4 Issue 1

Print ISSN: 2049-9434
Online ISSN:2049-9442

Sign up for eToc alerts

Recommend to Library

Copy and paste a formatted citation
x
Spandidos Publications style
Kinoshita Y, Yoshizawa K, Hamazaki K, Emoto Y, Yuri T, Yuki M, Kawashima H, Shikata N and Tsubura A: Dietary effects of mead acid on N-methyl-N-nitrosourea-induced mammary cancers in female Sprague-Dawley rats. Biomed Rep 4: 33-39, 2016
APA
Kinoshita, Y., Yoshizawa, K., Hamazaki, K., Emoto, Y., Yuri, T., Yuki, M. ... Tsubura, A. (2016). Dietary effects of mead acid on N-methyl-N-nitrosourea-induced mammary cancers in female Sprague-Dawley rats. Biomedical Reports, 4, 33-39. https://doi.org/10.3892/br.2015.530
MLA
Kinoshita, Y., Yoshizawa, K., Hamazaki, K., Emoto, Y., Yuri, T., Yuki, M., Kawashima, H., Shikata, N., Tsubura, A."Dietary effects of mead acid on N-methyl-N-nitrosourea-induced mammary cancers in female Sprague-Dawley rats". Biomedical Reports 4.1 (2016): 33-39.
Chicago
Kinoshita, Y., Yoshizawa, K., Hamazaki, K., Emoto, Y., Yuri, T., Yuki, M., Kawashima, H., Shikata, N., Tsubura, A."Dietary effects of mead acid on N-methyl-N-nitrosourea-induced mammary cancers in female Sprague-Dawley rats". Biomedical Reports 4, no. 1 (2016): 33-39. https://doi.org/10.3892/br.2015.530