t10c12 conjugated linoleic acid suppresses HER2 protein and enhances apoptosis in SKBr3 breast cancer cells: possible role of COX2.
BACKGROUND
HER2-targeted therapy with the monoclonal antibody trastuzumab (Herceptin) has improved disease-free survival for women diagnosed with HER2-positive breast cancers; however, treatment resistance and disease progression are not uncommon. Current data suggest that resistance to treatment in HER2 cancers may be a consequence of NF-kappaB overexpression and increased COX2-derived prostaglandin E2 (PGE(2)). Conjugated linoleic acid (CLA) has been shown to have anti-tumor properties and to inhibit NF-kappaB activity and COX2.


METHODS
In this study, HER2-overexpressing SKBr3 breast cancer cells were treated with t10c12 CLA. Protein expression of the HER2 receptor, nuclear NF-kappaB p65, and total and phosphorylated IkappaB were examined by western blot and immunofluorescence. PGE(2) levels were determined by ELISA. Proliferation was measured by metabolism of 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), and apoptosis was measured by FITC-conjugated Annexin V staining and flow cytometry.


CONCLUSIONS
We observed a significant decrease in HER2 protein expression on western blot following treatment with 40 and 80 microM t10c12 CLA (p<0.01 and 0.001, respectively) and loss of HER2 protein in cells using immunoflourescence that was most pronounced at 80 microM. Protein levels of nuclear NF-kappaB p65 were also significantly reduced at the 80 microM dose. This was accompanied by a significant decrease in PGE(2) levels (p = 0.05). Pretreatment with t10c12 CLA significantly enhanced TNFalpha-induced apoptosis and the anti-proliferative action of trastuzumab (p = 0.05 and 0.001, respectively). These data add to previous reports of an anti-tumor effect of t10c12 CLA and suggest an effect on the HER2 oncogene that may be through CLA mediated downregulation of COX2-derived PGE(2).
Flowers
Margaret
M
Department of Nutritional Sciences, University of Arizona, Tucson, AZ, USA. mflowers@email.arizona.edu
Thompson
Patricia A
PA
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D018734:Genes, erbB-2; D006801:Humans; D044243:Linoleic Acids, Conjugated / Q000494:pharmacology*; D008954:Models, Biological; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics; D051996:Transcription Factor RelA / Q000378:metabolism; D000068878:Trastuzumab; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D051546:Cyclooxygenase 2; D015232:Dinoprostone; D044243:Linoleic Acids, Conjugated; D018719:Erb-b2 Receptor Tyrosine Kinases; D051996:Transcription Factor RelA; D000068878:Trastuzumab; D014409:Tumor Necrosis Factor-alpha; C498143:RELA protein, human; C496197:trans-10,cis-12-conjugated linoleic acid; C496540:PTGS2 protein, human; C508053:ERBB2 protein, human