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

Abstract

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.

• Authors: Wei Huang, Chong Zeng, Jie Liu, Li Yuan, Weidong Liu, Lei Wang, Hecheng Zhu, Yang Xu, Yi Luo, Dan Xie, Xingjun Jiang, Caiping Ren
• Journal: Biochemical and biophysical research communications (Biochem Biophys Res Commun) Vol. 514 Issue 1 Pg. 64-70 (06 18 2019) ISSN: 1090-2104 [Electronic] United States
• PMID: 31023529 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2019. Published by Elsevier Inc.

Chemical References

• Antineoplastic Agents
• Protein Kinase Inhibitors
• Butyric Acid
• MTOR protein, human
• Proto-Oncogene Proteins c-akt
• TOR Serine-Threonine Kinases

Topics

• Antineoplastic Agents (pharmacology)
• Apoptosis (drug effects)
• Autophagic Cell Death (drug effects)
• Butyric Acid (pharmacology)
• Cell Line, Tumor
• Humans
• Nasopharyngeal Carcinoma (drug therapy, metabolism)
• Nasopharyngeal Neoplasms (drug therapy, metabolism)
• Protein Kinase Inhibitors (pharmacology)
• Proto-Oncogene Proteins c-akt (antagonists & inhibitors, metabolism)
• Signal Transduction (drug effects)
• TOR Serine-Threonine Kinases (antagonists & inhibitors, metabolism)