The effects of Low α-Linolenic fatty acid Soybean Oil and Mid Oleic acid Soybean Oil on the growth of Her-2/neu and Fatty acid synthase over-expressing human breast cancer (SK-Br3) cells

A variety of soybean oils (SOs) were developed with improved functional properties. Some of the modified SOs contain altered fatty acid (FA) co mp sition by selective breeding methods. Currently, low αlinolenic acid soybean oil (LLSO) and low αlinolenic acid and mid oleic acid soybean oil (LLMOSO) are available FA modified SOs in the market. The consumption of FA modified SOs has been increased because the United States Food and Drug Administration required listing trans fat content in food products sold in U.S. as an eff ort to reduce possible health risks caused by trans fat beginning 2006. However, the effects of these F A modified SOs on human chronic diseases including breast cancer ( BC) have not been studied. BC has become the most frequently diagnosed cancer and is the sec ond leading cause of cancer death among American women. The type of dietary fat, FA composi ti n, and n-6/n-3 ratio are known to influence BC development. Therefore, it is possible that the changed FA composition and n-6/n3 ratio in the FA modified SOs may affect BC progre ssion, and its critical health concern needs to be investigated. Increased human epithelial grow th factor receptor 2 (Her-2/ neu) and fatty acid synthase (FAS) are associated with BC progression. In fact, FAS activity and expression are affected by dietary FA composition and FA metabolis m. Hypothesis of this research is that LLSO and LLMOSO may affect Her-2/ neu and FAS expressing human BC (SK-Br3) cell growth in vitro and in vivo. To test our hypothesis, we investigated the poten tial adverse or beneficial effects of LLSO and LLMOSO in comparison with conventional SO and lard on human BC cells and then examined the possible mecha nisms of action by evaluating the expression level of genes markers involved in growt h factor mediated signal transduction pathway, specifically Her-2/ nePI 3-kinase (phophoinositide 3kinase)-FAS signal transduction pathway. In vitro study demonstrated that all of the tested oils at 0-2 μl/ml had cytotoxic effects. LLMOSO showed less cytotoxic effects on the growth of SK-Br3 cells compared to SO. However, there was no difference in SK-Br3 cell gro wth between LLSO and SO. The apoptotic protein markers (mutant p53 and caspase-3) analysis revealed that the cell growth inhibition by oil treatments was cytotoxic by triggering apoptosi s. Western blot analysis demonstrated that LLSOand LLMOSOinduced changes on cell growth in volve Her-2/ neu and FAS signaling transduction pathway and sterol regulatory element bi ding protein-1 (SREBP-1), mitogen activated protein kinase (MAPK), and phosphatidylin ositol 3-kinase (PI 3-kinase) were possible down-stream effectors of Her-2/ neu signaling pathway. We also evaluated the dietary e ffects of LLSO (20% fat of total calorie), SO (20%), and lard (20%) on the growth of SK-Br3 tumors implanted in athymic mice. Changes in tumor surface rea, body weight, and food intake were monitored during the 6 months feeding study. After termination, tumor net weight, Her-2/ neu and FAS mRNA expression in tumors, FAS protein expr ssion in liver, lipid composition in diets, abdominal fat, and serum, as well as plasma total c ho esterol and triglyceride levels were analyzed. In vivo study showed that there were no statistical differe nces in tumor size and tumor net weight among SO, LLSO, and lard groups. No diff erences in FAS mRNA and protein iii expression levels between the LLSO and SO groups we re observed. Tumors from the lard group expressed higher Her-2/ neu and FAS mRNA than those from the LLSO and SO group. The lipid analysis demonstrated that LLSO was not significant ly distinct from SO in trans fat concentration after metabolism. Serum cholesterol a nd triglyceride levels were unchanged in LLSO fed compared to SO fed mice. In summary, LLSO which contained modification in αLA concentration showed similar effects on SK-Br3 as S O in both in vitro and in vivo. However, LLMOSO which contained more drastic modifications o n FA composition exhibited less cytotoxicity compared to SO in vitro.