Department of Oral Medicine, The University of Tokushima Graduate Faculty of Dentistry, Tokushima, Japan.
Int J Oncol. 2013 Jan;42(1):75-82. doi: 10.3892/ijo.2012.1692. Epub 2012 Nov 8.
Taxanes, including docetaxel, are widely used for the treatment of squamous cell carcinoma of the head and neck. However, the gastrointestinal toxicity of docetaxel has limited its high-dose clinical use. In this study, we examined the synergistic anticancer effects of combined low-dose docetaxel and γ-tocotrienol treatment on human oral cancer (B88) cells. We treated B88 cells with docetaxel and γ-tocotrienol at concentrations of 0.5 nM and 50 µM, respectively. When cells were treated with either agent alone at a low dose, no significant cytotoxic effect was observed. However, the simultaneous treatment of cells with both agents almost completely suppressed cell growth. Whereas docetaxel stimulated the expression of nuclear factor-κB (NF-κB) p65 protein in B88 cells, γ-tocotrienol slightly inhibited the expression of constitutive nuclear p65 protein. Of note, the combined treatment with both agents inhibited docetaxel-induced nuclear p65 protein expression. Electrophoretic mobility shift assay (EMSA) revealed that the simultaneous treatment with these agents suppressed the NF-κB DNA binding activity in B88 cells. In addition, γ-tocotrienol downregulated the docetaxel-induced expression of NF-κB-regulated gene products associated with the inhibition of apoptosis. Furthermore, the activation of initiator caspases, caspases-8 and -9, and the effector caspase, caspase-3, was detected following treatment with both agents. Finally, apoptosis was also clearly observed as demonstrated by the cleavage of poly(ADP-ribose) polymerase (PARP) and nuclear fragmentation through the activation of caspase-3 by combined treatment with docetaxel and γ-tocotrienol. These findings suggest that the combination treatment with these agents may provide enhanced therapeutic response in oral cancer patients, while avoiding the toxicity associated with high-dose β-tubulin stabilization monotherapy.
紫杉烷类药物，包括多西紫杉醇，被广泛用于治疗头颈部鳞状细胞癌。然而，多西紫杉醇的胃肠道毒性限制了其在高剂量临床应用。在这项研究中，我们研究了低剂量多西紫杉醇与γ-生育三烯酚联合治疗对人口腔癌细胞（B88）的协同抗癌作用。我们用浓度分别为 0.5 nM 和 50 µM 的多西紫杉醇和γ-生育三烯酚处理 B88 细胞。当单独用低剂量的任一药物处理细胞时，没有观察到明显的细胞毒性作用。然而，同时用两种药物处理细胞几乎完全抑制了细胞生长。虽然多西紫杉醇刺激了 B88 细胞中核因子-κB（NF-κB）p65 蛋白的表达，但γ-生育三烯酚稍微抑制了组成型核 p65 蛋白的表达。值得注意的是，联合两种药物处理抑制了多西紫杉醇诱导的核 p65 蛋白表达。电泳迁移率变动分析（EMSA）显示，同时用这两种药物处理抑制了 B88 细胞中 NF-κB DNA 结合活性。此外，γ-生育三烯酚下调了多西紫杉醇诱导的与抑制细胞凋亡相关的 NF-κB 调节基因产物的表达。此外，在用两种药物处理后，检测到起始半胱氨酸蛋白酶 caspase-8 和 caspase-9，以及效应半胱氨酸蛋白酶 caspase-3 的激活。最后，通过 caspase-3 的激活证实了多西紫杉醇与γ-生育三烯酚联合治疗导致的凋亡，通过多聚（ADP-核糖）聚合酶（PARP）的切割和核片段化也可以清楚地观察到凋亡。这些发现表明，联合使用这些药物可能会为口腔癌患者提供增强的治疗反应，同时避免与高剂量β-微管蛋白稳定单药治疗相关的毒性。
