The Mechanism By Which Fatty Acid Synthase(FAS) Inhibition Induces Apoptosis In Breast Cancer

Objectives Fatty acid metabolism is an important part of cell life activities, especially for cancer cells, with the fact that cancer cells need a lot of fatty acids to form their membrane systems to maintain their constant growth. Fatty acid synthase(FAS) is a key enzyme in the process of fatty acid synthesis. Overexpression of FAS is common in many cancer cells, by contrast, it is hard to find FAS in the vast majority of the normal tissue cells, which is closely related to clinic. Our previous studies have shown that there was abnormal metabolism of fatty acid synthesis- oxidation circulation balance in breast cancer cells, and it was essential for growth of breast cancer cells. In this study, breast cancer cell lines were used to explore the molecular mechanism of apoptosis of breast cancer cell lines causing by the FAS inhibition, so as to reveal the importance of abnormal metabolism of fatty acids for the development of tumor.Methods 1.Western blot was usesd to detect different expression levels of fatty acid synthase in breast cancer cell lines. 2.Cell counting method was used to detect different cell proliferation. 3.Key enzyme inhibitors(Cerulenin, Orlistat) of the fatty acid metabolism and sh RNA were used to treat breast cancer cells, and then their effects were detected. 4.Cerulenin was used to treat breast cancer cells and ROS levels in the cells was detected by DCFH- DA probe and DHE probe. 5.NAC, Trolox, BHA(antioxidants) and DPI(NADPH oxidase inhibitors) were used to check whether they can protect the apoptosis induced by suppressing FAS. 6.Cells flow was used to detect the mitochondrial membrane potential change and the release of cytochrome-C. 7.Bcl- 2 gene family was over expressed to check if they can protect cell apoptosis induced by suppressing fatty acid synthesis.Results 1.Western bloting showed high expression of FAS in breast cancer cells. 2.There was no positive correlation between the expression of fatty acid synthase in breast cancer cells and its cell growth. 3.Fatty acid synthesis inhibitors can inhibit the growth of tumor cells, or even kill tumor cells. 4.Knocking down the expression of FAS inhibited breast cancer cell growth and transformation. 5.Inhibition of fatty acid synthesis induced oxidative stress and caused redox metabolic disorders. 6.NAC could protect the cell apoptosis caused by inhibiting fatty acid synthesis.While,Trolox, BHA and DPI could not. 7.Inhibition of fatty acid synthesis caused mitochondrial membrane potential energy damage,release of the Cytochrome C and induced apoptosis. 8.The Bcl-2 family could maintain the stability of the mitochondrial membrane to protect the apoptosis induced by inhibition of fatty acid synthesis.Conclusions The abnormal metabolism of fatty acids in tumor cells provides nutrients and energy for the rapid proliferation of tumor cells, and it may has other biological functions. In this study, we confirmed that the metabolism of fatty acid circulation balance was necessary for the growth of breast cancer cells. Fatty acid synthesis inhibitor Cerulenin/Orlistat could disturb the balance of redox, then changed mitochondrial membrane potential energy which led to the release of cytochrome C and apoptosis. All the results proved that the abnormal metabolism of fatty acids in cells played an important role to maintain intracellular redox state.