title: 18α-Glycyrrhetinic acid lethality for neuroblastoma cells via de-regulating the Beclin-1/Bcl-2 complex and inducing apoptosis.
abstract: 18α-Glycyrrhetinic acid (18-GA) is a known gap-junction inhibitor with demonstrated anticancer effects. However, the different modes of cell cytotoxicity for 18-GA remain to be characterized. In this study, 18-GA reduced the expression of cell-cell interaction proteins (N- and VE-cadherin), and led to a dose-dependent increase in cytotoxicity of the neuroblastoma cells tested, but was less toxic toward actively dividing human embryonic kidney cells. We found that 18-GA could induce both autophagy and apoptosis. 18-GA mediated autophagy was due to accumulation of Atg5, Atg7 and LC3II and degradation of p62. Individual siRNAs against Atg5 and Atg7 prevented autophagy and resulted in a further loss of viability with 18-GA. In addition, combination of 18-GA with autophagy inhibitor chloroquine produced a more significant cell death. This implied a pro-survival function for autophagy induction with 18-GA. 18-GA also led to the destabilization of Bcl-2/Beclin-1 interaction and cleavage of Beclin-1, a protein known to play role in apoptosis and autophagy induction. Treatment of cells by a pan-caspase inhibitor or a caspase-3 siRNA prevented a large portion of 18-GA mediated cytotoxicity, demonstrating that caspase-dependent apoptosis induction was responsible for most of the observed cytotoxicity. In terms of signaling, 18-GA led to reduced phosphorylation of all three classes of MAP kinases. Taken together, 18-GA or its pathways may lead to more effective, targeted therapeutics against neuroblastoma.
authors: Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, South Korea.
authors: Md Ataur
authors: MA
authors: Rahman
authors: Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, South Korea.
authors: Kausik
authors: K
authors: Bishayee
authors: Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, South Korea.
authors: Khadija
authors: K
authors: Habib
authors: Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, South Korea.
authors: Ali
authors: A
authors: Sadra
authors: Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, South Korea. Electronic address: sungohhuh@gmail.com.
authors: Sung-Oh
authors: SO
authors: Huh
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects; D000071186:Beclin-1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015820:Cadherins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D048430:Cell Shape / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006034:Glycyrrhetinic Acid / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D009447:Neuroblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats
chemical_list: D000970:Antineoplastic Agents; D000071186:Beclin-1; D015820:Cadherins; D019253:Proto-Oncogene Proteins c-bcl-2; C119129:18alpha-glycyrrhetinic acid; D006034:Glycyrrhetinic Acid
keywords: Apoptosis; Beclin-1; MAP kinase pathway; Macro-autophagy; Mitochondria membrane potential