دانلود رایگان مقاله شناسایی استرس اکسیداتیو ناشی از مرگ سلول توسط سورافنیب

abstract

The lack of effective chemotherapies in hepatocellular carcinoma (HCC) is still an unsolved problem and underlines the need for new strategies in liver cancer treatment. In this study, we present a novel approach to improve the efficacy of Sorafenib, today’s only routinely used chemotherapeutic drug for HCC, in combination with triterpenoid oleanolic acid (OA). Our data show that cotreatment with subtoxic concentrations of Sorafenib and OA leads to highly synergistic induction of cell death. Importantly, Sorafenib/OA cotreatment triggers cell damage in a sustained manner and suppresses long-term clonogenic survival. Sorafenib/OA cotreatment induces DNA fragmentation and caspase-3/7 cleavage and the addition of the pan-caspase inhibitor zVAD.fmk shows the requirement of caspase activation for Sorafenib/OA-triggered cell death. Furthermore, Sorafenib/OA co-treatment stimulates a significant increase in reactive oxygen species (ROS) levels. Most importantly, the accumulation of intracellular ROS is required for cell death induction, since the addition of ROS scavengers (i.e. a-tocopherol, MnTBAP) that prevent the increase of intracellular ROS levels completely rescues cells from Sorafenib/ OA-triggered cell death. In conclusion, OA represents a novel approach to increase the sensitivity of HCC cells to Sorafenib via oxidative stress.

4. Discussion

HCC is the most frequent primary liver cancer and one of the most aggressive tumors worldwide with an increasing incidence [3,25]. Dysregulation in the apoptotic program caused by different underlying liver diseases could explain chemotherapy resistance of HCC [26]. Due to its aggressive tumor growth, the majority of patients are in need of a palliative treatment. At present, Sorafenib is the treatment of choice for advanced HCC, but only shows a modest ability to extend the median survival [4]. Sorafenib resistance of HCC cells highlights the need for new strategies in HCC treatment. In this study we identify a novel synergistic combination of Sorafenib and OA, which improves the efficacy of Sorafenib in HCC cells. In addition to increasing cell death in short-term assays, Sorafenib and OA also inhibit long-term clonogenic survival of HCC cells. Mechanistic studies showed that the combination of Sorafenib and OA triggers caspase-dependent cell death. This conclusion is supported by data showing that Sorafenib/OA cotreatment stimulates caspase activation and that the pan-caspase inhibitor zVAD. fmk partially prevents cell death. Furthermore, we demonstrate that Sorafenib/OA cotreatment leads to ROS production, which is required for cell death induction. In rescue experiments, ROS scavengers protect HCC cells from Sorafenib/OA-mediated cell death. Our findings are in line with recent publications reporting that ROS production is involved in OA-induced [8,22] or Sorafenibinduced cell death [6]. Different studies showed that Sorafenib inhibits the MEK/ERK pathway that controls ROS production in HCC [6,27,28]. Coriat et al. reported that Sorafenib dosedependently stimulates ROS production in the human HCC cell line HepG2 and that the ROS scavenger MnTBAP significantly reduces the Sorafenib-mediated effect on tumor growth of HCC in mice experiments, emphasizing the relevance of ROS for the antitumor activity of Sorafenib [6]. This conclusion is underlined by an in vivo ROS analysis of sera from patients treated with Sorafenib, as the best response to Sorafenib has been reported for patients with high ROS levels during the treatment with Sorafenib [6].