Conjugated Linoleic Acid (CLA) Up-regulates the Estrogen-regulated Cancer Suppressor Gene, Protein Tyrosine Phosphatase γ (PTPγ), in Human Breast Cells

Abstract

Background: Conjugated linoleic acid (CLA), a naturally occurring compound found in ruminants products, has been shown to possess anticancer properties in vivo and in vitro. There are several CLA isomers in ruminant-produced foods, among which t10,c12-CLA and c9,t11-CLA are the most potent. Protein tyrosine phosphatase γ (PTPγ) has been implicated as a tumor suppressor gene in kidney and lung cancers. Our previous results indicated that estradiol-17β (E₂)-induced suppression of PTPγ may play a role in mammary tumorigenesis. Materials and Methods: The effects of t10,c12-CLA and c9,t11-CLA on PTPγ mRNA expression in human breast epithelial cells and stromal cells, isolated from surgical specimens of mammoplasty and breast cancer patients, were detected and quantified by RT-PCR. Results: The PTPγ mRNA expression was lower in cancer than in normal breast cells. Both t10,c12-CLA and c9,t11-CLA significantly (p<0.05) increased the PTPγ mRNA levels in primary cultured normal breast epithelial cells, normal breast stromal cells and breast cancer epithelial cells, but not in breast cancer stromal cells. t10,c12-CLA appeared to be the most active isomer in estrogen receptor α(ERα)-positive human breast cancer epithelial cells. Conclusion: The results indicate that dietary CLA might serve as a chemo-preventive and chemo-therapeutic agent in human breast cancers by up-regulating the estrogen-regulated tumor suppressor gene, PTPγ expression.