Abstract
Arsenic trioxide (As(2)O(3)), used to treat promyelocytic leukemia, triggers cell death through unknown mechanisms. To further our understanding of As(2)O(3)-induced death, we analyzed its effects on transforming growth factor-β (TGFβ) signaling mediators in ovarian cells. Dysregulated TGFβ signaling is a characteristic of ovarian cancers. As(2)O(3) reduced the protein expression of EVI1, TAK1, SMAD2/3, and TGFβRII while increasing SnoN/SkiL. EVI1 protein was modulated by treatment with the proteasome inhibitors, MG132 and PS-341/Velcade, suggesting that degradation occurs through the ubiquitin-proteasome pathway. The sensitivity of ovarian cells to As(2)O(3)-induced apoptosis correlated with expression of multidrug resistance protein 1. Interestingly, expression of SnoN was similar to LC3-II (autophagy marker), which increased with induction of cytoplasmic vacuolation preceding apoptosis. These vesicles were identified as autophagosomes based on transmission electron microscopy and immunofluorescence staining with EGFP-LC3. The addition of N-acetyl-L-cysteine (ROS scavenger) to As(2)O(3)-treated cells reversed changes in SnoN protein and the autophagic/apoptotic response. In contrast to beclin-1 knockdown, siRNA targeting ATG5, ATG7, and hVps34 markedly reduced autophagy in As(2)O(3)-treated ovarian carcinoma cells. Further, treatment with SnoN siRNA markedly decreased LC3-II levels and increased PARP degradation (an apoptosis marker). Collectively, these findings suggest that As(2)O(3) induces a beclin-1-independent autophagic pathway in ovarian carcinoma cells and implicates SnoN in promoting As(2)O(3)-mediated autophagic cell survival.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Acetylcysteine / pharmacology
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Apoptosis Regulatory Proteins / genetics
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Apoptosis Regulatory Proteins / metabolism*
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Arsenic Trioxide
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Arsenicals
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Autophagy*
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Autophagy-Related Protein 5
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Autophagy-Related Protein 7
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Beclin-1
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Carcinoma / metabolism*
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Cell Line, Tumor
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Female
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Humans
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Microtubule-Associated Proteins / genetics
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Microtubule-Associated Proteins / metabolism
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Multidrug Resistance-Associated Proteins / metabolism
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Ovarian Neoplasms / metabolism*
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Oxides / toxicity*
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Poly(ADP-ribose) Polymerases / metabolism
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism*
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RNA Interference
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RNA, Small Interfering / metabolism
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Reactive Oxygen Species / metabolism
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Signal Transduction
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Transforming Growth Factor beta / metabolism
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Ubiquitin-Activating Enzymes / genetics
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Ubiquitin-Activating Enzymes / metabolism
Substances
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ATG5 protein, human
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Apoptosis Regulatory Proteins
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Arsenicals
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Autophagy-Related Protein 5
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BECN1 protein, human
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Beclin-1
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Intracellular Signaling Peptides and Proteins
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MAP1LC3A protein, human
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Membrane Proteins
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Microtubule-Associated Proteins
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Multidrug Resistance-Associated Proteins
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Oxides
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Proto-Oncogene Proteins
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RNA, Small Interfering
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Reactive Oxygen Species
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SKIL protein, human
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Transforming Growth Factor beta
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Poly(ADP-ribose) Polymerases
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ATG7 protein, human
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Autophagy-Related Protein 7
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Ubiquitin-Activating Enzymes
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Arsenic Trioxide
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Acetylcysteine
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multidrug resistance-associated protein 1