Inhibition of Fatty acid synthase and induction of apoptosis in human breast cancer cells by Cacalia deliphiniifolia

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Fatty acid synthase (FAS), a key enzyme in fatty acid biosynthetic pathway as well as in energy homeostasis, has been found to be over-expressed in a variety of human malignancies including breast cancer at a relatively early stage. Importantly, previous studies have demonstrated that inhibition of FAS expression resulted in induction of apoptosis in breast cancer cells. Therefore, FAS is considered to be an ideal target for anticancer therapy. Currently, there are several FAS inhibitors including siRNA and pharmacological compounds, however, they have limited clinical utility due to their relatively short half-life and various side effects. Therefore, it is desirable to develop a specific and non-toxic anti-FAS agent for clinical application. In this study, we screened extracts from various traditional Japanese edible herbal plants that are believed to have medicinal effects on cancer. Among them, Cacalia deliphiniifolia, strongly abrogated the expression of FAS in a dose and time dependent manner in breast cancer cell lines (MCF7 and MDA-MB-231). The extract also blocked cell growth and significantly induced apoptosis by activating the Caspase3. To identify an active component, a methanol extract of C. deliphiniifolia was fractionated by various chromatographies. We found that one of compounds, Cacalol, had significant anti-FAS activity in a dose- and time-dependent fashion and also showed significant induction of apoptosis in MCF7 and MDA231 cells compared to normal human mammary epithelial cells (HMEC). Cacalol has been known to be a strong anti-oxidant agent and we previously found that the FAS expression was partly controlled by Reactive oxygen species (ROS) which is often generated at a high level under hypoxic microenvironment of a growing tumor. Therefore, we examined whether Cacalol had the ability to block the generation of ROS in MCF7 and MDA-MB-231 cell lines. Indeed, Cacalol as well as C. deliphiniifolia extract significantly suppressed ROS in these cell lines, which was in parallel with its FAS-inhibitory activity, suggesting that the FAS inhibitory effect by Cacalol is partly due to its anti-oxidant activity. To further evaluate the potential anti-cancer activity of C. deliphiniifolia or Cacalol, we examined the synergistic effect of C. deliphiniifolia or Cacalol and Cyclophosphamide (CPA) which is commonly used for cancer chemotherapy. We found that a combination of C. deliphiniifolia or Cacalol and CPA synergistically enhanced apoptosis in MCF7 and MDA-MB-231 cell lines by blocking the FAS expression. Taken together, we demonstrated that C. deliphiniifolia and Cacalol induced apoptosis in breast cancer cells through its inhibitory effect on FAS expression which is likely to be mediated by their anti-oxidant activities. Therefore, C. deliphiniifolia and Cacalol have potential utility as chemopreventive as well as chemotherapeutic agents for breast cancer.