Bilobalide isolated from the leaves of Ginkgo biloba has several pharmacological activities such as neuroprotective, anti-inflammatory, and anticonvulsant. However, the effect of bilobalide on cancer has not been clearly established. The main purpose of this study was to investigate the effect of bilobalide on cell growth and apoptosis induction in FaDu human pharyngeal squamous cell carcinoma. This was examined by 3-[4,5-dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide assay, nuclear 4′,6-diamidino-2-phenylindole dihydrochloride staining, DNA fragmentation analysis, and immunoblotting. Bilobalide inhibited the growth of FaDu cells in dose- and time-dependent manners. Treatment with bilobalide resulted in nuclear condensation and DNA fragmentation in FaDu cells. Furthermore, it promoted the proteolytic cleavage of procaspase-3/-7/-8/-9 with increase in the amount of cleaved caspase-3/-7/-8/-9. Bilobalide-induced apoptosis in FaDu cells was mediated by the expression of Fas and the activation of caspase-8, caspase-3, and poly (ADP-ribose) polymerase. Immunoblotting revealed that the antiapoptotic mitochondrial protein Bcl-2 was downregulated, but the proapoptotic protein Bax was upregulated by bilobalide in FaDu cells. Bilobalide significantly increased Bax/Bcl-2 ratio. These results suggest that bilobalide inhibits cell proliferation and induces apoptosis in FaDu human pharyngeal squamous cell carcinoma via both the death receptor-mediated extrinsic apoptotic pathway and the mitochondrial-mediated intrinsic apoptotic pathway.

Introduction
Materials and Methods
    1. Materials
    2. Cell line and cell cultures
    3. Cell viability test (MTT assay)
    4. DAPI staining
    5. DNA fragmentation analysis
    6. Immunoblotting
    7. Data analysis
Results
    1. Cytotoxic effect of bilobalide in FaDu cells
    2. Induction of apoptosis by bilobalide in FaDu cells
    3. Extrinsic death receptor-dependent and intrinsicmitochondria-dependent apoptotic signalingpathways induced by bilobalide in FaDu cells
Discussion
References

• Kyung In Jeong(The Institute of Dental Science, Chosun University)
• Su-Gwan Kim(The Institute of Dental Science, Chosun University)
• Dae-San Go(The Institute of Dental Science, Chosun University)
• Do Kyung Kim(The Institute of Dental Science, Chosun University) Correspondence to