title: Pilot study on the effects of dietary conjugated linoleic acid on tumorigenesis and gene expression in PyMT transgenic mice.
abstract: Conjugated linoleic acid (CLA) is a class of commercially available fatty acids that have been associated with anticancer properties in rodent models of chemical carcinogenesis. We conducted a pilot study to examine the antitumor effect of dietary CLA in a polyoma virus-middle T antigen (PyMT) mouse model of invasive breast cancer. Virgin 4-week-old PyMT mice were administered a mixed-isomer CLA diet (1% wt/wt) or control AIN-93G diet for 4 weeks (N = 6 and 5, respectively) and tumor burden was assessed at 8 weeks of age. Thoracic mammary glands were prepared as whole mounts with other glands being formalin fixed and paraffin embedded for histology and immunohistochemistry (IHC). Total RNA was prepared for microarray and real-time reverse transcription-polymerase chain reaction analysis. Western blots were performed for protein expression analysis. Tumor incidence was significantly increased in CLA-treated animals compared with controls (P = 0.009) and occurred with extensive lobular-alveolar expansion and loss of mammary adipose tissue. More than 100 genes were downregulated > or = 2-fold in the CLA-treated group compared with controls, including adipose-specific markers, as wells as cytoskeletal and adhesion-related genes. This was supported by dramatic decreases in the epithelial adherens E-cadherin and beta-catenin as demonstrated by IHC. Taken together, these results suggest that dietary CLA affects the mammary stromal environment, leading to tumor progression and cellular expansion in the PyMT mouse model. Further studies of the potential for cancer promotion are needed, especially because mixed-isomer CLA formulations are sold commercially as a nutritional supplement.
authors.affiliation: Department of Experimental Therapeutics, John Wayne Cancer Institute, 2200 Santa Monica Boulevard, Santa Monica, CA 90404, USA. flowersm@jwci.org
authors.forename: Margaret
authors.initials: M
authors.lastname: Flowers
authors.forename: Joyce A
authors.initials: JA
authors.lastname: Schroeder
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Borowsky
authors.forename: David G
authors.initials: DG
authors.lastname: Besselsen
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Thomson
authors.forename: Ritu
authors.initials: R
authors.lastname: Pandey
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Thompson
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000502:physiology*; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D049109:Cell Proliferation; D004032:Diet; D005260:Female; D020869:Gene Expression Profiling; D007124:Immunoenzyme Techniques; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage*; D008325:Mammary Neoplasms, Experimental / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008822:Mice, Transgenic; D020411:Oligonucleotide Array Sequence Analysis; D010865:Pilot Projects; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000952:Antigens, Polyomavirus Transforming; D014408:Biomarkers, Tumor; D044243:Linoleic Acids, Conjugated; D012333:RNA, Messenger