Arsenic trioxide induces autophagic cell death in malignant glioma cells by upregulation of mitochondrial cell death protein BNIP3

Arsenic trioxide (As₂O₃) has shown considerable efficacy in treating hematological malignancies with induction of programmed cell death (PCD) type I, apoptosis. However, the mechanisms underlying the antitumor effect of As₂O₃ on solid tumors are poorly defined. Previously, we reported that As₂O₃ induced autophagic cell death (PCD type II) but not apoptosis in human malignant glioma cell lines. The purpose of this study was to elucidate the molecular pathway leading to autophagic cell death. In this study, we demonstrated that the cell death was accompanied by involvement of autophagy-specific marker, microtubule-associated protein light chain 3 (LC3), and damage of mitochondrial membrane integrity, but not by caspase activation. Analysis by cDNA microarray, RT-PCR, and Western blot showed that cell death members of Bcl-2 family, Bcl-2/adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) and its homologue BNIP3-like (BNIP3L), were upregulated in As₂O₃-induced autophagic cell death. Exogenous expression of BNIP3, but not BNIP3L, induced autophagic cell death in malignant glioma cells without As₂O ₃ treatment. When upregulation of BNIP3 induced by As ₂O₃ was suppressed by a dominant-negative effect of the transmembrane-deleted BNIP3 (BNIP3ΔTM), autophagic cell death was inhibited. In contrast, BNIP3 transfection augmented As₂O ₃-induced autophagic cell death. These results suggest that BNIP3 plays a central role in As₂O₃-induced autophagic cell death in malignant glioma cells. This study adds a new concept to characterize the pathways by which As₂O₃ acts to induce autophagic cell death in malignant glioma cells.