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Photodynamic therapy induces caspase-3 activation in HL-60 cells
D J Granville1, J G Levy, D W Hunt
1QLT Photo Therapeutics Inc., 520 West 6th Avenue, Vancouver, BC, Canada, V5Z 4H5. dgranvil@qlt-pdt.com
Cell Death and Differentiation
|October 14, 2003
Summary
Photodynamic therapy (PDT) with benzoporphyrin derivative monoacid ring A activates caspase-3, leading to DNA fragmentation in leukemia cells. This protease activation is crucial for PDT-induced apoptosis.
Area of Science:
- Biochemistry
- Cell Biology
- Oncology
Background:
- Caspases are key mediators of apoptosis, triggered by various stimuli.
- Photodynamic therapy (PDT) is a treatment modality utilizing photosensitizers and light to induce cell death.
Purpose of the Study:
- To investigate the role of caspases in photodynamic therapy (PDT)-induced apoptosis.
- To determine the specific caspases activated by benzoporphyrin derivative monoacid ring A (BPD-MA) mediated PDT.
Main Methods:
- Human promyelocytic leukemia HL-60 cells were treated with BPD-MA and exposed to light.
- Western blotting was used to detect cleavage of caspase-3, caspase-1, PARP, and DNA PK(CS).
- Inhibitors of caspases and serine proteases were employed to elucidate the signaling pathway.
Main Results:
- PDT with BPD-MA induced complete cleavage and activation of caspase-3, but not caspase-1.
- Poly(ADP-ribose) polymerase (PARP) and DNA-dependent protein kinase catalytic subunit (DNA PK(CS)) were cleaved within 60 minutes.
- General caspase and serine protease inhibitors blocked PARP and caspase-3 cleavage, respectively.
- Inhibitors also prevented PDT-induced DNA fragmentation.
Conclusions:
- PDT using BPD-MA triggers caspase-3 activation in HL-60 cells.
- Caspase-3 activation is a critical event in PDT-induced apoptosis, involving upstream serine proteases.
- These findings highlight the role of caspase-3 in mediating the cytotoxic effects of BPD-MA PDT.