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The effect of dietary CLA on mammary tumorigenesis

ABSTRACT: Conjugated linoleic acid (CLA), a class of fatty acids found in beef and dairy products, has been shown to inhibit tumorigenesis in a variety of cancer model systems. Based on previously well-documented anti-tumor activity of CLA in rodent models of breast cancer, a pilot study was initiated to examine the effect of dietary CLA in a well-established transgenic model of breast cancer. Western blots were performed for the detection of AKT, c-Src, ERK1/2, and Cdc24. CLA significantly increased tumor burden (p<0.1) independent of an increase in oncogenic signaling. Mammary gland whole mounts indicated a loss of mammary adipose and extensive epithelial expansion in CLA-treated animals. Microarray analysis indicated a significant reduction in cytoskeletal related genes with at least a two-fold decrease in five out of six CLA-fed animals compared to untreated controls. Reduction of Cdc42, a key regulator of cell adhesion and cytoskeletal arrangements, was confirmed at the protein level by western blot (p<0.01). These findings suggest that dietary CLA may advance the malignant phenotype by promoting a loss of cell polarity and adhesion in the mammary gland epithelium. This action may have serious clinical implications for a subset high-risk population and warrants further investigation.

ORGANISM(S): Mus musculus

PROVIDER: GSE13553 | GEO | 2008/11/19

SECONDARY ACCESSION(S): PRJNA110737

REPOSITORIES: GEO

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Project description:Conjugated linoleic acid (CLA), a class of fatty acids found in beef and dairy products, has been shown to inhibit tumorigenesis in a variety of cancer model systems. Based on previously well-documented anti-tumor activity of CLA in rodent models of breast cancer, a pilot study was initiated to examine the effect of dietary CLA in a well-established transgenic model of breast cancer. Western blots were performed for the detection of AKT, c-Src, ERK1/2, and Cdc24. CLA significantly increased tumor burden (p<0.1) independent of an increase in oncogenic signaling. Mammary gland whole mounts indicated a loss of mammary adipose and extensive epithelial expansion in CLA-treated animals. Microarray analysis indicated a significant reduction in cytoskeletal related genes with at least a two-fold decrease in five out of six CLA-fed animals compared to untreated controls. Reduction of Cdc42, a key regulator of cell adhesion and cytoskeletal arrangements, was confirmed at the protein level by western blot (p<0.01). These findings suggest that dietary CLA may advance the malignant phenotype by promoting a loss of cell polarity and adhesion in the mammary gland epithelium. This action may have serious clinical implications for a subset high-risk population and warrants further investigation. Virgin, four-week-old PyV-mT mice were administered a diet of a mixed-isomer CLA formulation (1% wt/wt) (N=6) or control AIN96G diet (N=5) for four weeks. Measurements of food disappearance, weights and palpations were recorded weekly. All animals were euthanized at eight weeks of age. Formalin-fixed, paraffin-embedded mammary gland tissue was used for H&E and trichrome staining and immunohistochemistry for Ki67. Tissue levels of CLA were measured by gas chromatography. Thoracic mammary glands were fixed in glacial acetic acid:ethanol and carmine stained. cDNA microarray was performed on RNA from 6 CLA-fed mice and 4 control mice using the Affymetrix 430 2.0 mouse genome chips.

Project description:Cis-9, trans-11-conjugated linoleic acid (c9, t11-CLA), a functional fatty acid, is one of the research hotspots in the fields of functional dairy products development because of its multiple beneficial effects in humans and animals. In milk, most c9, t11-CLA is de novo synthesized from trans-11-octadecenoic acid (TVA) and it is confirmed that genes such as stearoyl-coA desaturase 1 (SCD1) play a key role in the synthesis. However, few studies have been reported to deeply elucidate the SCD1-dependent molecular mechanism of cis9, trans11-CLA synthesis and its relationship with the pathways of energy metabolism and lipid metabolism. Therefore, in the present study, MAC-T cells were divided into three groups: CAY group (SCD1-inhibited MAC-T cell model with the addition of CAY, TVA), TVA group (only TVA), and Control group (without CAY, TVA). The relative mRNA expression of SCD1 was measured using real-time PCR, while TVA accumulation and c9, t11 -CLA synthesis were analyzed using gas chromatography (GC). The SCD1-related proteins were firstly screened in MAC-T cells by Tandem Mass Tag (TMT)-based quantitative proteomics analysis, then their functions were annotated by bioinformatic analysis, and finally their relationships with SCD1 were evaluated by parallel reaction monitoring (PRM) analysis and small RNA interference. The results showed that the deficiency of SCD1 led by CAY10566 blocked the synthesis of c9, t11-CLA in MAC-T cells. Sixty-one SCD1-associated proteins were screened and found to be mainly involved in the pathways of energy metabolism and lipid metabolism, such as glycolytic pathway, pentose phosphate pathway, fatty acid elongation pathway, and unsaturated fatty acid biosynthesis. Among these genes, 17 proteins were validated under the PRM analysis. PGAM1 (phosphoglycerate mutase 1), TPI1 (triosephosphate isomerase 1), LDHB (lactate dehydrogenase B), and ALDOA (aldolase, fructose-bisphosphate A) were verified to have a negative relationships with SCD1. This study furthered our understanding of the molecular mechanisms of c9, t11-CLA synthesis in the mammary glands of dairy cows.

Project description:Overexpression of fatty acid synthase (FAS) has been reported in both malignant and premalignant breast lesions, and has been associated with poor outcome. FAS has gained interest as a metabolic target for the treatment of breast cancer based on evidence that blockade with the antifungal antibiotic, cerulenin or synthetic inhibitor C75 inhibits proliferation of breast cancer cells and delays tumor development. Conjugated linoleic acid (CLA), a class of fatty acids found in beef and dairy products, has been shown to inhibit FAS in bovine mammary adipose. Based on previously well-documented anti-tumor activity of CLA, we hypothesized that one mechanism of CLAâs anti-tumorigenic activity may be metabolic blockade of FAS. We fed virgin PyV-MT transgenic mice a diet supplemented with either 1% CLA, as mixed isomers, or control chow for four weeks. Tissue histology was determined by H&E staining. cDNA microarray and real-time quantitative PCR were performed to determine relative expression of lipogenic genes. Western blots were used to examine relative protein expression of FAS. Differences in protein densitometry were analyzed using Students 2-sided T-test. Probability was determined using the binomial sign test. Level of significance for all tests was 0.05. H&E staining revealed a shift towards advanced mammary lesions in the CLA-fed mice compared to control animals (24/26 vs. 11/26) (p for trend < 0.001). Microarray analysis revealed a >2-fold decrease in FAS in the CLA-fed group compared to controls, and was confirmed by quantitative RT-PCR (p < 0.001) and Western blot. The decrease in FAS mRNA expression was unexpectedly associated with more advanced disease (p for trend < 0.01). Conclusions: Dietary CLA suppressed fatty acid synthase in the mammary glands of the PyV-MT mouse while promoting mammary tumor progression. Experiment Overall Design: PyV-MT and wild type FVB mice were obtained from Jackson Laboratories (Bay Harbor, ME) and housed 2â4 per cage in micro insulator rooms. Mice were genotyped according to Jackson Laboratory protocols (http://jaxmice.jax.org/pub-cgi/protocols/protocols). PyV-MT positive females were randomly selected at four weeks of age to receive either a control AIN93G chow (n=5) or 1% CLA-supplemented chow (n=6). . Food disappearance and animal weights were recorded weekly. Animals were palpated three times a week, and tumor area (length x width) was measured by caliper. Only palpable masses with an area >/= 0.5 cm2 were considered established growths. Animals were euthanized by CO2 inhalation. Eight-week-old animals were selected for tissue histology and analysis of mRNA and protein expression. Mammary gland sections were collected and processed to obtain mRNA or protein lysate, paraffin embedded for histology, or stored in liquid nitrogen until further processing.

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The effect of dietary CLA on mammary tumorigenesis

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