Caspase-3 activation by lysosomal enzymes in cytochrome c-independent apoptosis in myelodysplastic syndrome-derived cell line p39

Terutoshi Hishita, Saeko Tada-Oikawa, Kaoru Tohyama, Yasuo Miura, Toshio Nishihara, Yumi Tohyama, Yataro Yoshida, Takashi Uchiyama, Shosuke Kawanishi

Research output: Contribution to journalArticle

106 Citations (Scopus)

Abstract

In most cases, apoptosis is considered to involve mitochondrial dysfunction with sequential release of cytochrome c from mitochondria, resulting in activation of caspase-3. However, we found that etoposide induced apoptosis in P39 cells, a myelodysplastic syndrome-derived cell line, without the release of cytochrome c. Furthermore, in etoposide-treated P39 cells, no changes in mitochondrial membrane potential (ΔΨm) were detected by flow cytometry. Flow cytometry using a pH-sensitive probe demonstrated that lysosomal pH increased during early apoptosis in P39 cells treated with etoposide. A reduction in the ATP level preceded the elevation of lysosomal pH. In addition, specific inhibitors of vacuolar H+-ATPase induced apoptosis in P39 cells but not in HL60 cells. Although etoposide-induced activation of caspase-3 was followed by DNA ladder formation in P39 cells, E-64d, an inhibitor of lysosomal thiol proteases, specifically suppressed etoposide-induced activation of caspase-3. Western blotting analysis provided direct evidence for the involvement of a lysosomal enzyme, cathepsin L. These findings indicate that lysosomal dysfunction induced by a reduction in ATP results in leakage of lysosomal enzymes into the cytosolic compartment and that lysosomal enzyme(s) may be involved in activation of caspase-3 during apoptosis in P39 cells treated with etoposide.

Original languageEnglish
Pages (from-to)2878-2884
Number of pages7
JournalCancer Research
Volume61
Issue number7
Publication statusPublished - 01-04-2001
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Oncology
  • Cancer Research

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