Abstract P4-03-01: Inhibition of Fatty Acid Synthase (FASN) Sensitizes Breast Cancer Cells to Chemotherapy and Disrupts the Lipid Rafts

Abstract MN Background: Breast cancer is the second leading cause of cancer death of women worldwide. One of the major challenges for a better prognosis of breast cancer patients is the ineffectiveness of chemotherapy and drug resistance. To investigate the mechanisms of drug resistance, resistant cancer cell lines have been established with various anticancer agents. We found that FASN, an important metabolic enzyme overexpressed in aggressive carcinomas, is t responsible in part for the drug resistance phenotype of breast cancer cells. Our findings show that blockage of FASN augments the cytotoxicity of the anti-mitotic drug Taxol in breast cancer cells. Moreover, C75 and Taxol have a synergistic effect both drugs are combined. The in vivo effect of C75 and Taxol and the mechanism by which blockage of FASN sensitizes the cells to chemotherapy are unknown. Material and Methods: In this study first we show the effect of C75 plus Taxol in breast tumor growth. BT474 cells were injected into the mammary fat pad of nude mice to generate the tumors. When the tumors were measurable we treated the mice with C75, Taxol or with a combination of both drugs. Second we studied the lipid rafts disruption after treatments by sucrose gradient and immunofluorescence. Results: We found that C75 plus Taxol extensively inhibited the tumor growth 9 fold and reduced the tumor size in 4 fold comparedn to the control mice (no treatement). In comparison C75 alone reduced the tumor growth in 1.5 fold only; and Taxol 2.5 fold compared to the control mice. These results show for first time that blockage of FASN (with C75) sensitizes breast cancer tumors to Taxol treatment in vivo. In addition, we studied the possible mechanism involved in the sensitization of breast cancer cells to Taxol by FASN blockage. Previous studies reported that blockage of FASN or Taxol treatment decrease the sphingolipids synthesis. Sphingolipids and cholesterol are the most abundant fatty acid in the lipid rafts in the plasma membrane. Disruption of lipid rafts has been shown to induce apoptosis in different carcinoma cell lines. Based in these findings, we studied lipid rafts in BT474 cells treated with C75, Taxol or combination of both with sucrose gradient and immunofluorescence microscopy. Discussion: Our results show that C75 and Taxol disrupt the lipid rafts. Thesefindings show that FASN is a new mechanism of drug resistance and may be an ideal target for chemosensitization in breast cancer chemotherapy. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-03-01.