title: AT-101 simultaneously triggers apoptosis and a cytoprotective type of autophagy irrespective of expression levels and the subcellular localization of Bcl-xL and Bcl-2 in MCF7 cells.
abstract: The effects of autophagy on cell death are highly contextual and either beneficial or deleterious. One prime example for this dual function of autophagy is evidenced by the cell responses to the BH3 mimetic AT-101 that is known to induce either apoptotic or autophagy-dependent cell death in different settings. Based on previous reports, we hypothesized that the expression levels of pro-survival Bcl-2 family members may be key determinants for the respective death mode induced by AT-101. Here we investigated the role of autophagy in the response of MCF7 breast cancer cells to AT-101. AT-101 treatment induced a prominent conversion of LC3-I to LC3-II and apoptotic cell death characterized by the appearance of Annexin-positive/PI-negative early apoptotic cells and PARP cleavage. Inhibition of the autophagy pathway, either through application of 3-MA or by lentiviral knockdown of ATG5, strongly potentiated cell death, indicating a pro-survival function of autophagy. Overexpression of wild type Bcl-xL significantly diminished the net amount of AT-101-induced cell death, but failed to alter the death-enhancing effects of the ATG5 knockdown. This was also observed with the organelle-specific variants Bcl-xL-ActA and Bcl-2-ActA (mitochondrial) as well as Bcl-xL-cb5 and Bcl-2-cb5 (ER) which all reduced AT-101-induced cell death, but did not affect the death-enhancing effects of 3-MA. Collectively, our data indicate that in apoptosis-proficient MCF7 cells, AT-101 triggers Bcl-2- and Bcl-xL-dependent apoptosis and a cytoprotective autophagy response that is independent of the expression and subcellular localization of Bcl-xL and Bcl-2.
authors.affiliation: Experimental Neurosurgery, Goethe University Hospital, Frankfurt am Main, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Antonietti
authors.affiliation: Dept. of Neurosurgery, Goethe University Hospital, Frankfurt am Main, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Gessler
authors.affiliation: Dept. of Physiology and Centre for Medical Physics and Systems Medicine, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: H
authors.initials: H
authors.lastname: Düssmann
authors.affiliation: Experimental Neurosurgery, Goethe University Hospital, Frankfurt am Main, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Reimertz
authors.affiliation: Edinger Institute, Goethe University Hospital, Frankfurt am Main, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Mittelbronn
authors.affiliation: Dept. of Physiology and Centre for Medical Physics and Systems Medicine, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: J H M
authors.initials: JH
authors.lastname: Prehn
authors.affiliation: Experimental Neurosurgery, Goethe University Hospital, Frankfurt am Main, Germany. Electronic address: koegel@em.uni-frankfurt.de.
authors.forename: D
authors.initials: D
authors.lastname: Kögel
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D019610:Cytoprotection / Q000187:drug effects / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006072:Gossypol / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D061986:MCF-7 Cells; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein / Q000235:genetics* / Q000378:metabolism
chemical_list: C494811:BCL2L1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D006072:Gossypol; C028178:gossypol acetic acid
keywords: Apoptosis; Autophagy; BH3 mimetic; Bcl-2 family; Caspases