Various anticancer drugs cause mitochondrial perturbations in association with apoptosis. Here we investigated the involvement of caspase- and Bcl-2-dependent pathways in doxorubicin-induced mitochondrial perturbations and apoptosis. For this purpose, we set up a novel three-color flow cytometric assay using rhodamine 123, annexin V-allophycocyanin, and propidium iodide to assess the involvement of the mitochondria in apoptosis caused by doxorubicin in the breast cancer cell line MTLn3. Doxorubicin-induced apoptosis was preceded by up-regulation of CD95 and CD95L and a collapse of mitochondrial membrane potential (Δψ) occurring prior to phosphatidylserine externalization. This drop in Δψ was independent of caspase activity, since benzyloxycarbonyl-Val-Ala-dl-Asp-fluoromethylketone did not inhibit it. Benzyloxycarbonyl-Val-Ala-dl-Asp-fluoromethylketone also blocked activation of caspase-8, thus excluding an involvement of the death receptor pathway in Δψ dissipation. Furthermore, although overexpression of Bcl-2 in MTLn3 cells inhibited apoptosis, dissipation of Δψ was still observed. No decrease in Δψ was observed in cells undergoing etoposide-induced apoptosis. Immunofluorescent analysis of Δψ and cytochrome c localization on a cell-to-cell basis indicates that the collapse of Δψ and cytochromec release are mutually independent in both normal and Bcl-2-overexpressing cells. Together, these data indicate that doxorubicin-induced dissipation of the mitochondrial membrane potential precedes phosphatidylserine externalization and is independent of a caspase- or Bcl-2-controlled checkpoint.
Differential Regulation of Doxorubicin-induced Mitochondrial Dysfunction and Apoptosis by Bcl-2 in Mammary Adenocarcinoma (MTLn3) Cells*
M. Huigsloot,I. Tijdens,G. Mulder,B. van de Water
Published 2002 in Journal of Biological Chemistry
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- Publication year
2002
- Venue
Journal of Biological Chemistry
- Publication date
2002-09-27
- Fields of study
Biology, Medicine
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Semantic Scholar, PubMed
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