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Caspase proteases mediate apoptosis induced by anticancer agent preactivated MC540 in human tumor cell lines
S Pervaiz1, J L Hirpara, M V Clément
1Department of Physiology, Faculty of Medicine, National University of Singapore, Singapore. shazib@pacific.net.sg
Abstract:
The molecular events involved in tumor cell death induced by novel photoproducts of merocyanine 540 (pMC540) are poorly understood. Using HL60 leukemia and M14 melanoma cell lines we investigated the role of the apoptotic pathway in pMC540-mediated cell death. Tumor cells exposed to pMC540 showed cell size shrinkage and an increase in the sub-diploid DNA content. A loss of membrane phospholipid asymmetry associated with apoptosis was induced by pMC540 in both tumor cell lines as evidenced by the externalization of phosphatidylserine. A dose-dependent increase in caspase-3 protease activity suppressed by the tetrapeptide inhibitor DEVD-CHO was observed in both cell lines. Western blot analysis of poly (ADP-ribose) polymerase, a caspase substrate, showed the classical cleavage pattern (116 to 89 kDa) associated with apoptosis in pMC540-treated cell lysates. Furthermore, caspase inhibition blocked the externalization of membrane PS, indicating that the loss of membrane phospholipid asymmetry is a downstream event of caspase activation. These findings demonstrate that tumor cell death induced by pMC540 is mediated by caspase proteases.
Insights
Novel photoproducts of merocyanine 540 (pMC540) induce tumor cell death through the activation of caspase proteases, a key pathway in apoptosis. This research clarifies the molecular mechanisms behind pMC540
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- The molecular mechanisms of tumor cell death induced by merocyanine 540 photoproducts (pMC540) remain unclear.
- Investigating apoptotic pathways is crucial for understanding pMC540's anti-cancer effects.
Purpose of the Study:
- To elucidate the role of the apoptotic pathway in pMC540-mediated cancer cell death.
- To determine if caspase proteases are involved in pMC540-induced apoptosis.
Main Methods:
- Utilized HL60 leukemia and M14 melanoma cell lines.
- Assessed apoptosis markers: cell size, sub-diploid DNA content, phosphatidylserine externalization.
- Measured caspase-3 activity and poly (ADP-ribose) polymerase cleavage via Western blot.
Main Results:
- pMC540 induced cell shrinkage, increased sub-diploid DNA, and phosphatidylserine externalization in tumor cells.
- Dose-dependent caspase-3 activation and poly (ADP-ribose) polymerase cleavage were observed.
- Caspase inhibition prevented phosphatidylserine externalization, confirming it as a downstream event.
Conclusions:
- pMC540-induced tumor cell death is mediated by the activation of caspase proteases.
- The apoptotic pathway, involving caspase activation, is central to pMC540's cytotoxic effects.
- Understanding these molecular events can inform the development of pMC540-based cancer therapies.