Research Grants Awarded
Preventive And Therapeutic Fffects Of Cacalia Delphiniifolia On Breast Cancer
Fatty acid synthase (FAS) plays a key role in fatty acid biosynthetic pathway. This enzyme has been found to be over-expressed in a variety of tumors including breast cancer, while the expression level of FAS in normal cell is minimum or undetectable except in the liver, embryonic and lactating cells. Although the exact role of the FAS gene in tumorigenesis is yet to be elucidated, treatment of tumor cells with a FAS-specific shRNA or pharmacological inhibitors of FAS such as cerulenin and C75 leads to cell cycle arrest and apoptosis, which makes FAS an ideal target for anticancer therapy. However, the use of these compounds in clinical setting is limited due to their relative short life and strong side effects. Therefore, it is desirable to develop more specific and less toxic agents to block the function of FAS. In search for such compounds, we screened extracts from various traditional Japanese edible plants that are believed to have medicinal effects and found that the extract of Cacalia delphiniifolia showed significant and specific inhibitory effect on the FAS expression. We also found that one of the components of Cacalia delphiniifolia extract, Cacalol, was indeed able to block the FAS expression followed by induction of apoptosis in various breast tumor cell lines but not in normal breast cells. While we were trying to understand the mechanism of the FAS inhibition by Cacalol, we found that the expression of FAS was significantly induced under a hypoxic condition which is a hallmark of malignant tumor. Furthermore, this induction was found to be mediated by ROS production followed by activation of the Akt pathway. Interestingly, Cacalol has strong anti-oxidant activity which is correlated to the ability of Cacalol to inhibit FAS expression. Therefore, we propose to examine the molecular mechanism of FAS inhibition by Cacalol and explore the possibility of using Cacalia delphiniifolia and Cacalol for breast cancer prevention and treatment.
We hypothesize that the expression of FAS in tumor cell is induced by hypoxia and ROS via the Akt pathway (Hypothesis 1). We also hypothesize that Cacalol induces apoptosis of breast tumor cells by blocking the FAS expression (Hypothesis 2).
RESEARCH AIMS AND DESIGN: Our specific aims are (1) to understand the mechanism of FAS induction by hypoxia and ROS, (2) to examine how Cacalol induces apoptosis to breast cancer cells, and (3) to examine the efficacy of Cacalol in mouse models of breast cancer. In order to pursue the specific aim (1), we will (a) examine whether activation of Akt, SREBP and HIF1 is involved in the up-regulation of FAS induced by hypoxia and ROS. We will also examine whether the induction of FAS is blocked by shRNA or specific chemical inhibitors to Akt, SREBP and HIF1, (b) determine the responsive sequence on the FAS promoter to hypoxia and ROS using a reporter assay and a ChIP analysis, and (c) examine the relationship between the expression level of FAS and hypoxic regions in an animal xenograft model. To accomplish the specific aim (2), we will (a) examine the level of activated Akt, SREBP and HIF1 in breast tumor cells treated with Cacalol. We will also examine the effect of ectopic expression of Akt and SREBP on the ROS and FAS expression in the presence and absence of Cacalol, and (b) examine the level of pro-apoptotic genes, BNIP3, TRAIL and DAPK2, in the Cacalol-treated cells. To accomplish the specific aim (3), we will (a) examine the tumor inhibitory effect of Cacalol using an animal xenograft model, and (b) examine a preventive effect of Cacalia delphiniifolia using the MMTV-Wnt mouse model.
UNIQUENESS AND CLINICAL SIGNIFICANCE:
FAS is significantly up-regulated in breast tumor cells which makes this gene an ideal target for breast cancer therapy for both primary and metastatic diseases. However, understanding how and why FAS is up-regulated in tumor cells is central question for the development of a targeted drug to FAS. We propose that hypoxia which is a hallmark of tumor progression is one of the culprits of FAS induction in tumor cells. We believe that this novel concept if proven to be true will significantly advance our knowledge of breast tumroigenesis. Furhtermore, we propose that Cacalia deliphiniifolia, a non-toxic edible plant, and its component Cacalol have strong anti-FAS activity and therefore, useful for the purpose of both prevention and therapy of breast cancer. It is our ultimate goal to bring these compounds into a clinical trial.
The fatty acid synthase gene is normally silent, but it is highly up-regulated in breast cancer. Importantly, when the expression of this gene is blocked, tumor cells stop growing and eventually die. Therefore, fatty acid synthase is considered to be an excellent target for breast cancer therapy. To develop an effective drug to attack fatty acid synthase, we need to answer two key questions: (i) why is the fatty acid synthase gene turned on in tumor cell?, and (ii) how can we effectively and specifically block this gene expression so that we can kill the cancer cells? Our hypotheses of this project are two folds: (i) tumor cells are usually under hypoxic condition (lack of oxygen) which generates reactive oxygen molecules, called ROS, and ROS eventually turn on the fatty acid synthase gene, and (ii) Japanese edible plant, Cacalia delphiniifolia, contains a substance which specifically inhibits fatty acid synthase and can be used for prevention and treatment of breast cancer.
HOW THE PROJECT ADVANCES OUR UNDERSTANDING OF BREAST CANCER:
Fatty acid synthase is a key enzyme which generates lipid to make the tissue membrane and also to store excess energy as fat. This enzyme is not normally produced in our body because we usually take fatty acids from diet. However, most tumor cells turn on this gene expression at relatively early stage of cancer development. Most importantly, inhibition of fatty acid synthase makes tumor cell die by itself. Therefore, if we develop a specific agent to block fatty acid synthase, it is likely to work as an effective anti-cancer drug. We screened many traditional Japanese edible plants to see if there is any plant which can block fatty acid synthase and found that one of the plants called, Cacalia delphiniifolia, contains strong antioxidant as well as anti-fatty acid synthase activity. We also purified an effective substance called Cacalol which strongly blocks fatty acid synthase. In this project, we try to understand the mechanism of action of Cacalol and explore the possibility of using this substance for breast cancer therapy.
IMPORTANCE OF RESEARCH TO PATIENTS WITH BREAST CANCER:
Tumor cells of almost all breast cancer patients express the fatty acid synthase gene. If we develop a drug which can block fatty acid synthase, such target-specific agent is expected to work as a highly effective and non-toxic drug for the treatment of breast cancer patients. We believe that Cacalol which was isolated from traditional Japanese food has great therapeutic and preventive potential for breast cancer.