Sodium butyrate induces autophagic apoptosis of nasopharyngeal carcinoma cells by inhibiting AKT/mTOR signaling.

Previously, we confirmed the anti-tumor effects of sodium butyrate (NaBu) in nasopharyngeal carcinoma (NPC). However, its molecular mechanisms have not be fully elucidated. In this study, we studied the effects of NaBu on autophagy and explored the relation between NaBu associated autophagy and apoptosis in NPC cells. EGFP-LC3 plasmids were introduced into NPC cells to observed the effects of NaBu on autophagy flux with or without chloroquine (CQ) addition. Autophagy markers were also detected by Western blot. Under NaBu treatment, autophagy and apoptosis markers were detected simultaneously at different time. Then, to explore the roles of autophagy in NaBu induced apoptosis, the effects of autophagy inhibition, via specific inhibitor treatment or key gene knockdown, were analyzed. At last, the upstream signaling and its roles in NaBu induced autophagy and apoptosis were also analyzed. Increased LC3 dots and LC3-II accumulation indicated that NaBu can promote autophagy flux in NPC cells. LC3-II accumulation was earlier than cleaved PARP increment suggesting autophagy activation is prior to apoptosis activation, which was validated by flow cytometry mediated apoptosis analysis. Moreover, autophagy inhibition, achieved by 3-MA treatment or BECN1 knockdown, can antagonize NaBu induced apoptosis reflecting by re-deregulated cPARP and apoptotic rates. Furthermore, NaBu treatment inhibited the AKT/mTOR axis indicated by deregulated p-AKT(S473) and p-mTOR(S2448) and ectopic AKT expression both suppressed NaBu induced autophagy and apoptosis. At last, Western blot showed that HDAC6 dependent EGFR deregulation may account for the NaBu associated AKT/mTOR inhibition. NaBu can induce autophagic apoptosis via suppressing AKT/mTOR axis in NPC cells. Our results suggest that combination of autophagy inhibitors and deacetylase inhibitors may not be recommended in NPC clinical treatment.

Huang W ，Zeng C ，Liu J ，Yuan L ，Liu W ，Wang L ，Zhu H ，Xu Y ，Luo Y ，Xie D ，Jiang X ，Ren C ... -  《-》

Pre-treatment with angiotensin-(1-7) inhibits tumor growth via autophagy by downregulating PI3K/Akt/mTOR signaling in human nasopharyngeal carcinoma xenografts.

Lin YT ，Wang HC ，Chuang HC ，Hsu YC ，Yang MY ，Chien CY ... -  《-》

Plac8-mediated autophagy regulates nasopharyngeal carcinoma cell function via AKT/mTOR pathway.

To explore the relationship between autophagy and cell function, we investigated how PLAC8-mediated autophagy influences proliferation, apoptosis and epithelial-mesenchymal transition (EMT) in NPC. Colony formation analyses and CCK8 assays were used to assess the proliferative capacity of NPC cells. Transmission electron microscopy (TEM) was used to identify autophagosomes. Autophagic flux was monitored using the tandem monomeric RFP-GFP-tagged LC3 (tfLC3) assay. The rate of apoptosis in NPC cells was analysed by flow cytometry. Western blot analysis was used to evaluate the activation of autophagy and the signalling status of the AKT/mTOR pathway. Our study reveals that knocking out PLAC8 (koPLAC8) induces autophagy and apoptosis, while suppressing NPC cell proliferation and EMT. However, inhibition of autophagy with 3-methyladenine or by knocking down Beclin-1 reverses the cell proliferation, apoptosis and EMT influenced by koPLAC8. We find that koPLAC8 inhibits the phosphorylation of AKT and its downstream target, mTOR. Moreover, immunofluorescence and co-immunoprecipitation reveal complete PLAC8/AKT colocalization and PLAC8/AKT interaction, respectively. Furthermore, knockout of PLAC8 induced autophagy and inactivated AKT/mTOR signalling pathway of NPC xenografts. Overall, our findings demonstrate that koPLAC8 induces autophagy via the AKT/mTOR pathway, thereby inhibiting cell proliferation and EMT, and promoting apoptosis in NPC cells.

Huang ML ，Qi CL ，Zou Y ，Yang R ，Jiang Y ，Sheng JF ，Kong YG ，Tao ZZ ，Chen SM ... -  《-》

Wogonin induces cross-regulation between autophagy and apoptosis via a variety of Akt pathway in human nasopharyngeal carcinoma cells.

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.

Chow SE ，Chen YW ，Liang CA ，Huang YK ，Wang JS ... -  《-》

Targeting nasopharyngeal carcinoma by artesunate through inhibiting Akt/mTOR and inducing oxidative stress.

Drug repurposing has become an alternative therapeutic strategy for cancer treatment given the known pharmacokinetics and toxicity. The inhibitory effects of artesunate have been reported in various cancers. In this work, we investigated the effects of artesunate in nasopharyngeal carcinoma (NPC). We demonstrate that artesunate significantly inhibits proliferation via arresting NPC cells at G2/M phase. It also induces apoptosis through caspase-dependent and mitochondria-independent pathways in multiple NPC cell lines. The combination of artesunate and cisplatin is synergistic in targeting NPC cells in in vitro cellular culture system and in vivo xenograft tumor models. Artesunate inhibits phosphorylation of essential molecules involved in Akt/mTOR pathway in NPC cells, such as Akt, mTOR, and 4EBP1, and its inhibitory effects are partially abolished by overexpression of constitutively active Akt. In addition, artesunate also induces mitochondrial dysfunction and oxidative stress via inhibiting mitochondrial respiration, increasing levels of mitochondrial superoxide and cellular reactive oxygen species (ROS), leading to decreased ATP levels. Two ROS scavengers partially abolish the inhibitory effects of artesunate in NPC cells. These data suggest that both inhibition of Akt/mTOR pathway and induction of ROS are required for the action of artesunate in NPC cells. Our work demonstrates that artesunate is a potential candidate for NPC treatment. Our work also highlights the critical roles of Akt/mTOR pathway and mitochondrial function in NPC cells.

Li Q ，Ni W ，Deng Z ，Liu M ，She L ，Xie Q ... -  《-》