Cytotoxic Activity of Extracts against Nasopharyngeal Carcinoma Cells (HK1). Cardamonin, a Constituent, Inhibits Growth and Migration of HK1 Cells by Inducing Caspase-Dependent Apoptosis and G2/M-Phase Arrest.

(L.) Mansf. is an edible herb that is commonly used in the cuisine of several Asian countries. Studies have shown that it possesses high bioactivity against a variety of cancer cells. In this study, we investigated the cytotoxic activity of rhizomes and some of its constituents on nasopharyngeal carcinoma cells (HK1). MTT assay results showed that the methanolic and hexane extracts of decreased HK1 cell viability with IC values of 136 µg/ml and 66 µg/ml, respectively. Cardamonin, a constituent of , exhibited the highest cytotoxic activity with an IC value of 27 μg/ml. Further studies on cardamonin revealed that it inhibited the migration of HK1 cells, caused G2/M-phase arrest and induced apoptosis. Apoptosis was induced activating caspase-8 and caspase-3, but independent of caspase-9. This indicated that cardamonin induced extrinsic apoptosis. Western blot analysis further showed that cardamonin caused extrinsic apoptosis, as the expression levels of intrinsic apoptosis-related proteins (Bcl-X, Bcl-2 and Bax), were not affected. Finally, JC-1 staining of HK1 cells revealed an increase in the mitochondrial membrane potential after treatment, further proving that cardamonin did not induce apoptosis the intrinsic pathway. These results reflect cardamonin's potential as an anticancer agent.