Immunoblotting with an antibody to -actin was used to control for equal loading of proteins per lane. on human H460, A549 and H358 NSCLC cell lines ST7612AA1 were synergistic. ST7612AA1 Our observations show that combination of paclitaxel and TOS may offer a novel therapeutic strategy for improving paclitaxel drug efficacy in NSCLC patient therapy as well as for potentially lowering the harmful side effects of paclitaxel through reduced drug dosage. Keywords:apoptosis; carcinoma, non-small-cell lung; caspase 8; paclitaxel; -tocopherol == Introduction == -Tocopheryl succinate (TOS), which is usually obtained by the esterification of -tocopherol is usually a more stable powder form of -tocopherol, since the succinate group protects the hydroxyl group of the chromanol ring from oxidation. Despite their comparable chemical structures, TOS differs in activity from -tocopherol. For example, TOS is usually redox-insensitive prior to being cleaved to -tocopherol by intracellular esterases. In contrast to -tocopherol, TOS induces cytotoxic responses in a wide range of malignancy cells while sparing normal cells (Weber et al., 2002;Kang et al., 2004). The antitumor effect of TOS appears to be mediated primarily through the induction of apoptosis. TOS has been shown to induce apoptosis in tumor cell lines via multiple pathways. For example, TOS was observed to induce apoptosis in malignancy cells by ST7612AA1 transcriptional activation of activator protein-1 (AP-1)-controlled genes. In other cell lines, the apoptotic activity of TOS was linked to its blockade of cell cycle progression by inhibiting the transcriptional activity of E2F, or by enhancing the expression of p21waf1/cip1, a cell cycle checkpoint protein (Turley et al., 1997). TOS has also been shown to induce apoptosis by activating Fas signaling pathways (Israel et al., 2000). Recently, the proapoptotic activity of TOS has been linked to its ability to induce the accumulation of reactive oxygen species (Kang et al., 2004;Dong et al., 2008), leading to mitochondrial destabilization (Neuzil et al., 2007). TOS-induced apoptosis appears to be mediated by caspase activation in majority of malignancy cell lines, even though contribution of caspase 9 or caspase 8 differs depending on the cellular context (Swettenham et al., 2005). Recently, considerable attention have been given to combination treatment with reduced doses of two or more different anticancer brokers, since combination treatment may enhance the therapeutic efficacy of each agent alone, and/or enable the use of lower doses of each agent. With this regards, in addition to induction of apoptosis ST7612AA1 at higher doses, lower doses of TOS functions synergistically with anticancer brokers, including selenium, exisulind and SC-560 a selective Cox-1 inhibitor (Lee et al., 2006b;Lim et al., 2007;Reagan-Shaw et al., 2008) to induce apoptosis. The mechanisms supporting the synergistic effects observed in combination treatments remain largely undefined, but involve enhanced apoptosis through enforced caspase activation. These earlier studies suggest a possibility that TOS may be a clinically useful adjuvant in malignancy treatment since antitumor effects of chemotherapeutic drugs are mediated at least partly through caspase-mediated apoptosis induction. Lung malignancy is usually one of leading cause of cancer-related death worldwide. Majority of lung malignancy patients are diagnosed with already metastasized or advanced diseases, thus being refractory to current treatment modalities, warranting the requires for developing new preventive or therapeutic drugs. In particular, nonsmall cell lung malignancy (NSCLC) is usually a malignancy with poor prognosis despite recent progress made in early diagnosis and treatment. Chemotherapy is an established treatment for advanced NSCLC but still show poor response rates in NSCLC patients (Ihde Rabbit polyclonal to ATF1.ATF-1 a transcription factor that is a member of the leucine zipper family.Forms a homodimer or heterodimer with c-Jun and stimulates CRE-dependent transcription. and Minna, 1991). Paclitaxel is one of the chemotheraputic drugs widely used for the treatment of NSCLC. This drug binds and stabilize microtubules, and interferes with the dynamic changes that occur during the formation of the mitotic spindles, thereby arresting the cells at the G2/M phase (Honore et al., 2005). Paclitaxel also has the ability to induce apoptosis and its cell killing effects are mediated, at least partly, by inducing apoptosis (Wang et al., 2000). Although there are numerous reports about the mechanism underlying apoptosis induced by paclitaxel, how this.