Autophagy and the functional roles of Atg5 and beclin-1 in the anti-tumor effects of 3β androstene 17α diol neuro-steroid on malignant glioma cells

In this study, we demonstrate that the anti-tumor activity of the neuro-steroid, 30 androstene 17 alpha diol (17 alpha-AED) on malignant glioma cells is mediated by the induction of autophagy. 17 alpha-AED can inhibit the proliferation an induce cell death of multiple, unrelated gliomas with an IC(50) between 8 and 25 mu M. 17 alpha-AED treatment induced the formation of autophagosomes and acidic vesicular organelles in human malignant gliomas which was blocked by bafilomycin All 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 17 alpha-AED. In 17 alpha-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 17 alpha-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 17 alpha-AED rather than serving as a cyto-protective response. These results demonstrate that 17 alpha-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. (C) 2009 Elsevier Ltd. All rights reserved.