Apoptosis mediated cytotoxicity induced by isodeoxyelephantopin on nasopharyngeal carcinoma cells

Abstract

Isodeoxyelephantopin (IDOE), a sesquiterpene lactone isolated from chloroform extract of Elephantopus scaber has been shown anticancer effects in various cancer cell lines. In the present study, we investigated the cytotoxic effect of IDOE on human nasopharyngeal epidermoid carcinoma (KB) cells and its different mode of action. Data from MTT viability assay indicated that IDOE inhibited viability of KB cells in a dose and time dependent manner. IC50 obtained by IDOE was 11.45 μM for 48h exposure. The clonogenic assay showed a dose-dependent inhibition of colony formation in IDOE-treated cells. The results obtained from morphological analysis of apoptosis by AO/EtBr and Hoechst staining revealed the typical morphological features of apoptosis such as chromatin condensation and nuclear fragmentation. In addition, DNA fragmentation assay confirmed apoptosis by showing ladder pattern of DNA in IDOE treated cells. Flow cytometric analysis of annexin V-propidium iodide staining demonstrated that treatment of KB cells with IDOE increased apoptotic cell population in a dose dependent manner. G2/M phase cell cycle arrest and subG1 peak of DNA, characteristics of apoptosis, was observed in IDOE treated cells. These results indicated that isodeoxyelephantopin exhibited apoptosis mediated cytotoxicity in nasopharyngeal carcinoma cells. This might provide a potential therapeutic option in the management of nasopharyngeal carcinoma.