Etoposide induces protein kinase Cδ- and caspase-3-dependent apoptosis in neuroblastoma cancer cells

Travis W. Day, Ching Huang Wu, Ahmad Safa

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

In this report, we reveal that etoposide inhibits the proliferation of SK-N-AS neuroblastoma cancer cells and promotes protein kinase Cδ (PKCδ)- and caspase-dependent apoptosis. Etoposide induces the caspase-3-dependent cleavage of PKCδ to its active p40 fragment, and active PKCδ triggers the processing of caspase-3 by a positive-feedback mechanism. Treatment of cells with the caspase-3-specific inhibitor N-benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethyl ketone or caspase-3-specific small interacting RNA (siRNA) prevented the etoposide-induced activation of caspase-8 and inhibited apoptosis. The silencing of the caspase-2 or caspase-8 genes using siRNAs did not affect the etoposide-induced processing of caspase-3, indicating that these caspases lie downstream of caspase-3 in this signaling pathway. Furthermore, the etoposide-induced processing of caspase-2 required the expression of caspase-8, and the etoposide-mediated processing of caspase-8 required the expression of caspase-2, indicating that these two caspases activate each other after etoposide treatment. We also observed that etoposide-mediated apoptosis was decreased by treating the cells with the caspase-6-specific inhibitor benzyloxycarbonyl-Val-Glu(OMe)-Ile-Asp-(OMe)- fluoromethyl ketone and that caspase-6 was activated by a caspase-8-dependent mechanism. Finally, we show that rottlerin blocks etoposide-induced apoptosis by inhibiting the PKCδ-mediated activation of caspase-3 and by degrading caspase-2, which prevents caspase-8 activation. Our results add important insights into how etoposide mediates apoptotic signaling and how targeting these pathways may lead to the development of novel therapeutics for the treatment of neuroblastomas.

Original languageEnglish
Pages (from-to)632-640
Number of pages9
JournalMolecular Pharmacology
Volume76
Issue number3
DOIs
StatePublished - Sep 2009

Fingerprint

Etoposide
Neuroblastoma
Caspase 3
Protein Kinase C
Caspase 8
Apoptosis
Caspase 2
Neoplasms
Caspases
Caspase 6
Ketones
Apoptosis Regulatory Proteins
RNA

ASJC Scopus subject areas

  • Pharmacology
  • Molecular Medicine

Cite this

Etoposide induces protein kinase Cδ- and caspase-3-dependent apoptosis in neuroblastoma cancer cells. / Day, Travis W.; Wu, Ching Huang; Safa, Ahmad.

In: Molecular Pharmacology, Vol. 76, No. 3, 09.2009, p. 632-640.

Research output: Contribution to journalArticle

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