Anticancer Activities Study Of Oel And Fluopsin C And Their Underlying Mechanisms

At present, the malignant tumor has become one of the factors, which are seriously harmful to human health. The increased incidence of cancer and the clinical resistance to anticancer agents highlight the need to search for new anticancer drugs. Breast cancer is the prevalent disease and its pathogenesis is complex. Many treatments, such as chemotherapy which is still the most effective clinical therapy, have been developed to improve prognosis and decrease the risk of recurrent diseases. Therefore, the development of novel therapeutic agents becomes greatly needed. The current study was undertaken to investigate the effects and mechanisms that underlie the anticancer activity of two compounds, one is a novel eudesmane-type sesquiterpene compound,1-oxoeudesm-11(13)-eno-12,8a-lactone (OEL), which was isolated from the Chinese herb Aster himalaicus, and another is Fluopsin C, an antibiotic isolated from Pseudomonas Jinanesis.The3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide (MTT) assay showed that OEL substantially reduced cell viability in KB, MCF-7, U87, A172and MG-63cells. Compared with tumor cell lines, OEL had a lower cytotoxicity on normal cells, EVC304and HL7702. MCF-7cells were employed to further evaluate anti-tumor effect and explore anti-cancer mechanisms of OEL. First, OEL displayed significant cytotoxicity in MCF-7cells in a dose-and time-dependent manner. OEL-induced apoptosis was characterized by chromatin condensation, formation of apoptotic bodies and exposure of phosphatidylserine on extracellular surface, which was confirmed by DAPI nuclear staining and flow cytometry, respectively. The increased expression of Bax and deceased expression of Bcl-2were also observed in OEL-treated MCF-7cells by western bloting. Further experiments demonstrated that OEL could induce the loss of mitochondria membrane potential, release of cytochrome C, activation of caspase-9and generation of reactive oxygen species (ROS). Therefore, ROS generation and mitochondria activation were involved in OEL-treated MCF-7cells. OEL will be a novel promising pro-apoptotic leading compound for anticancer drug developing.Fluopsin C, an antibiotic isolated from Pseudomonas Jinanesis, has antitumor effect in several cancer cell lines. The results of the MTT showed that Fluopsin C substantially reduced the viability of cancer cells (A172, K562, Hela, MCF-7and MD-MBA-231) in dose-and time-dependent manners. Additionally, Fluopsin C was of low toxicity in normal cells, EVC304and HL7702. In the current study, the oncotic cell death induced by Fluopsin C was investigated in human breast adenocarcinoma cells. Fluopsin C-induced oncosis was morphologically characterized by the formation of membrane blebbing and swelling through time-lapse microscopy. Fluopsin C treatment also made propidium iodide (PI) permeate into the cells and permitted lactate dehydrogenase release, suggesting that rupture of the plasma membrane may be involved in Fluopsin C-induced oncosis. Further experiments demonstrated that Fluopsin C induced the increase of reactive oxygen species (ROS), the depletion of adenosine triphosphate (ATP), and the decrease of the mitochondrial membrane potential (△ψm). In addition, the degradation of the cytoskeletal system was observed using the western-blot analysis and immunostaining of Fluopsin C-treated cells, the result showed that Fluopsin C destroys the cell skeleton including the microfilament and microtubule network, and decreases β-actin and a-tublin protein levels in a time-dependent manner.In summary, OEL, a novel eudesmane-type sesquiterpene isolated from Aster himalaicus, was firstly found to significantly inhibit proliferation of several cancer cells and increase apoptosis of MCF-7cells. The underlying anticancer mechanism of Fluopsin C was also demonstrated for the first time. About its anticancer activity, we found Fluopsin C can induce oncosis. Apoptosis is a process of programmed cell death and has little effect on surrounding tissue. However, oncosis resulting from cell membrane damage and the leakage of contents can cause inflammation of surrounding tissue. OEL and Fluopsin C may merit further investigation as a potential therapeutic agent for the treatment of cancer or leading compound for the development of novel anti-cancer drugs.