Autophagy and the functional roles of Atg5 and beclin-1 in the anti-tumor effects of 3beta androstene 17alpha diol neuro-steroid on malignant glioma cells.
In this study, we demonstrate that the anti-tumor activity of the neuro-steroid, 3beta androstene 17alpha diol (17alpha-AED) on malignant glioma cells is mediated by the induction of autophagy. 17alpha-AED can inhibit the proliferation an induce cell death of multiple, unrelated gliomas with an IC(50) between 8 and 25muM. 17alpha-AED treatment induced the formation of autophagosomes and acidic vesicular organelles in human malignant gliomas which was blocked by bafilomycin A1 or 3-methyladenine. Cleavage of microtubule-associated protein-light chain 3 (LC3), an essential step in autophagosome formation, was detected in human malignant glioma cells exposed to 17alpha-AED. In 17alpha-AED treated T98G glioma cells there was an increase in the autophagy related proteins Atg5 and beclin-1. Silencing of ATG5 or beclin-1 with small interfering RNA significantly reduced the incidence of autophagy in 17alpha-AED treated malignant gliomas and attenuated the cytotoxic effects of the neuro-steroid indicating that the induction of autophagy mediates the anti-glioma activity of 17alpha-AED rather than serving as a cyto-protective response. These results demonstrate that 17alpha-AED possesses significant anti-glioma activity when used at pharmacologically relevant concentrations in vitro and the cytotoxic effects are resultant from the induction of autophagy.
Graf
Martin R
MR
Department of Neurosurgery - Harold F. Young Neurosurgical Center and Massey Cancer Center, Virginia Commonwealth University Medical Center, PO Box 980631, Richmond, VA 23298-0631, USA. mgraf@hsc.vcu.edu
Jia
Wentao
W
Johnson
Ross S
RS
Dent
Paul
P
Mitchell
Clint
C
Loria
Roger M
RM
D045930:Anabolic Agents / Q000737:chemistry / Q000494:pharmacology*; D015113:Androstane-3,17-diol / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D001343:Autophagy / Q000187:drug effects*; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; D045744:Cell Line, Tumor / Q000187:drug effects*; D005910:Glioma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D015388:Organelles / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D058570:TOR Serine-Threonine Kinases
C502778:ATG5 protein, human; D045930:Anabolic Agents; D051017:Apoptosis Regulatory Proteins; D000071187:Autophagy-Related Protein 5; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; D015113:Androstane-3,17-diol; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases