Abstract
The details of molecular switching points between apoptosis and autophagy in tumor cells have still not been fully elucidated. This study focused on the role of cathepsin B and its substrate, BID as molecular links between apoptosis and autophagy in human breast cancer MCF-7 cells exposed to camptothecin. Apoptosis occurred rapidly with a peak in 60 min after drug administration, whereas autophagy developed at a much slower rate with continuous progression during 24 h of cell exposure to the drug. CPT induced very rapid activation of cathepsin B. Inhibition of cathepsins by E64d prevented CPT-induced BAX and BID aggregation on mitochondria and reduced significantly reduced apoptotic cell number. The above effects were accompanied by an increase in autophagosome formation, measured by expression of MAP I LC3. BID knock down resulted in strong suppression of CPT-induced apoptosis and a shift of cell death towards autophagy, manifesting with an increase of Beclin 1 and MAP I LC3 cellular content.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Antineoplastic Agents, Phytogenic / pharmacology*
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Apoptosis / drug effects*
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Apoptosis Regulatory Proteins / metabolism
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Autophagy / drug effects*
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BH3 Interacting Domain Death Agonist Protein / metabolism*
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Beclin-1
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Breast Neoplasms / enzymology
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Breast Neoplasms / metabolism*
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Breast Neoplasms / ultrastructure
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Camptothecin / pharmacology*
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Cathepsin B / antagonists & inhibitors
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Cathepsin B / metabolism*
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Cell Line, Tumor
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Cysteine Proteinase Inhibitors / pharmacology
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Enzyme Activation
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Female
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Humans
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Kinetics
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Laser Scanning Cytometry
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Leucine / analogs & derivatives
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Leucine / pharmacology
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Membrane Proteins / metabolism
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Microscopy, Confocal
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Microscopy, Electron, Transmission
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Microtubule-Associated Proteins / metabolism
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Mitochondria / drug effects
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Mitochondria / metabolism
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Signal Transduction / drug effects*
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bcl-2-Associated X Protein / metabolism
Substances
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Antineoplastic Agents, Phytogenic
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Apoptosis Regulatory Proteins
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BAX protein, human
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BECN1 protein, human
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BH3 Interacting Domain Death Agonist Protein
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BID protein, human
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Beclin-1
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Cysteine Proteinase Inhibitors
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Membrane Proteins
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Microtubule-Associated Proteins
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bcl-2-Associated X Protein
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Cathepsin B
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Leucine
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aloxistatin
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Camptothecin