Saponin 6 derived from Anemone taipaiensis induces U87 human malignant glioblastoma cell apoptosis via regulation of Fas and Bcl­2 family proteins.

ABSTRACT

Glioblastoma multiforme (GBM) is the most common and aggressive type of brain tumor, and is associated with a poor prognosis. Saponin 6, derived from Anemone taipaiensis, exerts potent cytotoxic effects against the human hepatocellular carcinoma HepG2 cell line and the human promyelocytic leukemia HL­60 cell line; however, the effects of saponin 6 on glioblastoma remain unknown. The present study aimed to evaluate the effects of saponin 6 on human U87 malignant glioblastoma (U87 MG) cells. The current study revealed that saponin 6 induced U87 MG cell death in a dose­ and time­dependent manner, with a half maximal inhibitory concentration (IC50) value of 2.83 µM after treatment for 48 h. However, saponin 6 was needed to be used at a lesser potency in HT­22 cells, with an IC50 value of 6.24 µM. Cell apoptosis was assessed by flow cytometry using Annexin V­fluorescein isothiocyanate/propidium iodide double staining. DNA fragmentation and alterations in nuclear morphology were examined by terminal deoxynucleotidyl transferase­mediated dUTP nick end labeling and transmission electron microscopy, respectively. The present study demonstrated that treatment with saponin 6 induced cell apoptosis in U87 MG cells, and resulted in DNA fragmentation and nuclear morphological alterations typical of apoptosis. In addition, flow cytometric analysis revealed that saponin 6 was able to induce cell cycle arrest. The present study also demonstrated that saponin 6­induced apoptosis of U87 MG cells was attributed to increases in the protein expression levels of Fas, Fas ligand, and cleaved caspase­3, ­8 and ­9, and decreases in the levels of B­cell lymphoma 2. The current study indicated that saponin 6 may exhibit selective cytotoxicity toward U87 MG cells by activating apoptosis via the extrinsic and intrinsic pathways. Therefore, saponin 6 derived from A. taipaiensis may possess therapeutic potential for the treatment of GBM.