bafilomycin-a1 and Nasopharyngeal-Carcinoma

Nedaplatin, a cisplatin analog, was developed to reduce the toxicity of cisplatin, whereas it can be cross-resistant with cisplatin in some circumstances. This study aimed to investigate the role of autophagy in nedaplatin induced cell death in cisplatin-resistant nasopharyngeal carcinoma cells. Here, we showed that HNE1/DDP and CNE2/DDP cells were resistant to nedaplatin-induced cell death with reduced apoptotic activity. Nedaplatin treatment resulted in autophagosome accumulation and increased expression of LC3-II, indicating the induction of autophagy by nedaplatin in HNE1/DDP and CNE2/DDP cells. Inhibition of autophagy by Bafilomycin A1 (Baf A1) and 3-Methyladenine (3-MA) remarkably enhanced the antitumor efficacy of nedaplatin in HNE1/DDP and CNE2/DDP cells, suggesting that the resistance to nedaplatin-induced cell death was caused by enhanced autophagy in nedaplatin-resistant NPC cells. Additionally, Baf A1 enhanced reactive oxygen species (ROS) generation and apoptosis induced by nedaplatin in HNE1/DDP cells. Mechanistically, nedaplatin treatment caused activation of ERK1/2 and suppression of Akt/mTOR signaling pathways. While inhibition of ERK1/2 by MEK1/2 inhibitor, U0126, could reduce the expression of LC3-II in nedaplatin-resistant NPC cells. Furthermore, suppression of ROS could inhibit nedaplatin-induced ERK activation in HNE1/DDP cells, indicating that ROS and ERK were involved in nedaplatin-induced autophagy. Together, these findings suggested that autophagy played a cytoprotective role in nedaplatin-induced cytotoxicity of HNE1/DDP and CNE2/DDP cells. Furthermore, our results highlighted a potential approach to restore the sensitivity of cisplatin-resistant nasopharyngeal cancer cells to nedaplatin in combination with autophagy inhibitors.

Topics: Adenine; Antineoplastic Agents; Apoptosis; Autophagy; Butadienes; Carcinoma; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cisplatin; Drug Resistance, Neoplasm; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; Humans; Macrolides; Microtubule-Associated Proteins; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Nitriles; Organoplatinum Compounds; Proto-Oncogene Proteins c-akt; Reactive Oxygen Species; Signal Transduction; TOR Serine-Threonine Kinases

Autophagy as well as apoptosis is an emerging target for cancer therapy. Wogonin, a flavonoid compound derived from the traditional Chinese medicine of Huang-Qin, has anticancer activity in many cancer cells including human nasopharyngeal carcinoma (NPC). However, the involvement of autophagy in the wogonin-induced apoptosis of NPC cells was still uninvestigated. In this study, we found wogonin-induced autophagy had interference on the process of apoptosis. Wogonin-induced autophagy formation evidenced by LC3 I/II cleavage, acridine orange (AO)-stained vacuoles and the autophagosome/autolysosome images of TEM analysis. Activation of autophagy with rapamycin resulted in increased wogonin-mediated autophagy via inhibition of mTOR/P70S6K pathway. The functional relevance of autophagy in the antitumor activity was investigated by annexin V-positive stained cells and PARP cleavage. Induction of autophagy by rapamycin ameliorated the wogonin-mediated apoptosis, whereas inhibition of autophagy by 3-methyladenine (3-MA) or bafilomycin A1 increased the apoptotic effect. Interestingly, this study also found, in addition the mTOR/P70S6K pathway, wogonin also inhibited Raf/ERK pathway, a variety of Akt pathways. Inactivation of PI(3) K/Akt by their inhibitors significantly induced apoptosis and markedly sensitized the NPC cells to wogonin-induced apoptosis. This anticancer effect of Akt was further confirmed by SH6, a specific inhibitor of Akt. Importantly, inactivation of its downstream molecule ERK by PD98059, a MEK inhibitor, also induced apoptosis. This study indicated wogonin-induced both autophagy and apoptosis through a variety of Akt pathways and suggested modulation of autophagy might provide profoundly the potential therapeutic effect.

Topics: Adenine; Apoptosis; Autophagy; Carcinoma; Cell Line, Tumor; Drugs, Chinese Herbal; Extracellular Signal-Regulated MAP Kinases; Flavanones; Flavonoids; Gene Expression Regulation, Neoplastic; Humans; Macrolides; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Phosphatidylinositol 3-Kinases; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; raf Kinases; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; TOR Serine-Threonine Kinases