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.

Resveratrol (3,4',5,-trihydroxystilbene), a phytoalexin present in grapes, exerts a variety of actions to reduce superoxides, prevents diabetes mellitus, and inhibits inflammation. Resveratrol acts as a chemo-preventive agent and induces apoptotic cell death in various cancer cells. However, the role of resveratrol in odontoblastic cell differentiation is unclear. In this study, the effect of resveratrol on regulating odontoblast differentiation was examined in MDPC-23 mouse odontoblastic cells derived from mouse dental papilla cells. Resveratrol significantly accelerated mineralization as compared with the control culture in differentiation of MDPC-23 cells. Resveratrol significantly increased expression of ALP mRNA as compared with the control in differentiation of MDPC-23 cells. Resveratrol significantly accelerated expression of ColⅠmRNA as compared with the control in differentiation of MDPC-23 cells. Resveratrol significantly increased expressions of DSPP and DMP-1 mRNAs as compared with the control in differentiation of MDPC-23 cells. Treatment of resveratrol did not significantly affect cell proliferation in MDPC-23 cells. Results suggest resveratrol facilitates odontoblast differentiation and mineralization in differentiation of MDPC-23 cells, and may have potential properties for development and clinical application of dentin regeneration materials.

Metformin (1,1-dimethylbiguanide hydrochloride), derived from French lilac (Galega officinalis), is a first-line anti-diabetic drug prescribed for patients with type 2 diabetes. However, the role of metformin in odontoblastic cell differentiation is still unclear. This study therefore undertook to examine the effect of metformin on regulating odontoblast differentiation in MDPC-23 mouse odontoblastic cells derived from mouse dental papilla cells. As compared to controls, metformin significantly accelerated the mineralization, significantly increased and accelerated the expressions of ALP and Col I mRNAs, and significantly increased the accelerated expressions of DSPP and DMP-1 mRNAs, during differentiation of MDPC-23 cells. There was no alteration in cell proliferation of MDPC-23 cells, on exposure to metformin. These results suggest that the effect of metformin on MDPC-23 mouse odontoblastic cells derived from mouse dental papilla cells, facilitates the odontoblast differentiation and mineralization, without altering the cell proliferation.

Tyrosol, a phenylethanoid and a derivative of phenethyl alcohol, possesses various biological properties, such as anti-oxidative and cardioprotective activity. Olive oil is the principal source of tyrosol in the human diet. However, so far the anti-cancer activity of tyrosol has not yet been well defined. This study therefore undertakes to examine the cytotoxic activity and the mechanism of cell death exhibited by tyrosol in KB human oral cancer cells. Treatment of KB cells with tyrosol induced the cell growth inhibition in a concentration- and a time-dependent manner. Furthermore, the treatment of tyrosol induced nuclear condensation and fragmentation of KB cells. Tyrosol also promoted proteolytic cleavage of procaspase-3, -7, -8 and –9, increasing the amounts of cleaved caspase-3, -7, -8 and –9. In addition, tyrosol increased the levels of cleaved PARP in KB cells. These results suggest that tyrosol induces the suppression of cell growth and cell apoptosis in KB human oral cancer cells, and is therefore a potential candidate for anti-cancer drug discovery.

β-carotene is present in carrots, pumpkins, and sweet potatoes. It suppresses many types of cancers by regulating cellular proliferation and apoptosis through a variety of mechanisms. However, the effects of β -carotene on oral cancer cells have not been clearly established. The main goal of this study was to investigate the effects of β-carotene on cell growth and apoptosis in oral cancer cells. Our results demonstrate that treatment with β-carotene induced inhibition of cell growth, and that the effect was dependent on β-carotene treatment time and concentration in KB cells. Furthermore, treatment with β-carotene induced nuclear condensation and fragmentation in KB cells. β-carotene promoted proteolytic cleavage of procaspase-3, -7, -8 and –9 with associated increases in the concentration of cleaved caspase-3, -7, -8 and –9. In addition, the level of cleaved PARP was increased by β-carotene treatment in KB cells. These results suggest that β-carotene can suppress cell growth and induce apoptosis in KB human oral cancer cells, and that it may have potential usefulness in anti-cancer drug discovery efforts.

MicroRNA (miRNA, miR) is essential in regulating cell differentiation either by inhibiting mRNA translation or by inducing its degradation. However, the role of miRNA in odontoblastic cell differentiation is still unclear. In this study, we examined the molecular mechanism of miR-27-mediated regulation of odontoblast differentiation in MDPC-23 mouse odontoblastic cells derived from mouse dental papilla cells. The results of the present study demonstrated that the miR-27 expression increases significantly during MDPC-23 odontoblastic cell differentiation. Furthermore, miR-27 up-regulation promotes the differentiation of MDPC-23 cells and accelerates mineralization without cell proliferation. The over-expression of miR-27 significantly increased the expression levels of Wnt1 mRNA and protein. In addition, the results of target gene prediction revealed that Wnt1 mRNA has an miR-27 binding site in its 3’UTR, and is increased by miR-27. These results suggested that miR-27 promotes MDPC-23 odontoblastic cell differentiation by targeting Wnt1 signaling. Therefore, miR-27 is a critical odontoblastic differentiation molecular target for the development of miRNA based therapeutic agents in dental medicine.

Curcumin (diferuloylmethane), a constituent of turmeric powder derived from the rhizome of Curcuma longa, has been shown to inhibit the growth of various types of cancer cells by regulating cell proliferation and apoptosis. However, a need exists to design more effective analogs because of curcumin's poor intestinal absorption. EF-24 (diphenyl difluoroketone), the monoketone analog of curcumin, has shown good efficacy in anticancer screens. However, the effects of curcumin and EF-24 on salivary gland epidermoid carcinoma cells are not clearly established. The main goal of this study was to investigate the effects of curcumin and EF-24 on cell growth and induction of apoptosis in human salivary gland epidermoid carcinoma cells. Our studies showed that curcumin and EF-24 inhibited the growth of HTB-41 cells in a dose- and time-dependent manner, and the potency of EF-24 was > 34-fold that of curcumin. Treatment with curcumin or EF-24 resulted in nuclear condensation and fragmentation in HTB-41 cells, whereas the control HTB-41 cell nuclei retained their normal regular and oval shape. Curcumin and EF-24 promoted proteolytic cleavages of procaspase-3/-7/-9, resulting in an increase in the amount of cleaved caspase-3/-7/-9 in the HTB-41 cells. Caspase-3 and -7 activities were detected in viable HTB-41 cells treated with curcumin or EF-24. These results suggest that the curcumin and EF-24 inhibit cell proliferation and induce apoptosis in HTB-41 human salivary gland epidermoid carcinoma cells, and that they may have potential properties as an anti-cancer drug therapy.