Novel extranuclear-targeted anthracyclines override the antiapoptotic functions of Bcl-2 and target protein kinase C pathways to induce apoptosis

Mol Cancer Ther. 2002 May;1(7):469-81.

Abstract

Bcl-2 inhibits apoptosis induced by numerous antitumor drugs, including doxorubicin and daunorubicin and is, thus, a major impediment to successful cancer chemotherapy. Here, we report the ability of a novel family of nonnuclear targeted anthracyclines to induce rapid apoptosis in cells despite Bcl-2 or Bcl-X(L) expression. Typified by N-benzyladriamycin-14-valerate (AD 198) and N-benzyladriamycin-14-pivalate (AD 445), this family of compounds binds to the C1 regulatory domain of protein kinase C (PKC), competitively inhibits phorbol ester binding in cell-free studies, and induces PKC translocation in intact cells. PKC-delta has an established role as a pro-apoptotic protein through the association of the holoenzyme or catalytic fragment with mitochondria. In proliferating 32D.3 myeloid cells, or in 32D.3 cells engineered to overexpress Bcl-2, substantial levels of PKC-delta are associated with mitochondria. However, after a 1-h exposure to 5 microM AD 198, cytochrome c release, caspase-3 activation, poly(ADP-ribose) polymerase (PARP) cleavage, PKC-delta cleavage, and DNA fragmentation are observed. Pretreatment of 32D.3 cells with the selective PKC-delta inhibitor, rottlerin, but not the general PKC inhibitor, GF 109203X, or PKC-alpha and -beta inhibitor, Gö 6976, delayed the 50% cell kill to >24 h for control and Bcl-2 overexpressing 32D.3 cells treated with 5 microM AD 198. Rottlerin delayed PKC-delta and PARP cleavage to >20 h post-drug exposure and also delayed mitochondrial membrane depolarization. In contrast, the pan-caspase inhibitor Z-Val-Ala-Asp-CH2F blocked PKC-delta and PARP cleavage, but not mitochondrial membrane depolarization. These results suggest that AD 198 induces mitochondrial-dependent apoptosis in 32D.3 cells by activating PKC-delta holoenzyme on mitochondria, which, in turn, overrides the antiapoptotic effects of Bcl-2.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibiotics, Antineoplastic / therapeutic use*
  • Antineoplastic Agents / therapeutic use*
  • Apoptosis*
  • Biological Transport
  • Caspase 3
  • Caspases / metabolism
  • Cell Line
  • Cell Membrane / metabolism
  • Cell Survival
  • Cytochrome c Group / metabolism
  • DNA Fragmentation
  • Dose-Response Relationship, Drug
  • Doxorubicin / analogs & derivatives
  • Humans
  • Immunoblotting
  • Intracellular Membranes / metabolism
  • Isoenzymes / metabolism
  • Mice
  • Microscopy, Fluorescence
  • Mitochondria / metabolism
  • Models, Chemical
  • Poly(ADP-ribose) Polymerases / metabolism
  • Protein Kinase C / metabolism*
  • Protein Kinase C-alpha
  • Protein Kinase C-delta
  • Protein Structure, Tertiary
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Signal Transduction
  • Subcellular Fractions
  • Time Factors
  • Transfection
  • Tumor Cells, Cultured

Substances

  • Antibiotics, Antineoplastic
  • Antineoplastic Agents
  • Cytochrome c Group
  • Isoenzymes
  • Proto-Oncogene Proteins c-bcl-2
  • Doxorubicin
  • Poly(ADP-ribose) Polymerases
  • Prkcd protein, mouse
  • PRKCA protein, human
  • PRKCD protein, human
  • Prkca protein, mouse
  • Protein Kinase C
  • Protein Kinase C-alpha
  • Protein Kinase C-delta
  • CASP3 protein, human
  • Casp3 protein, mouse
  • Caspase 3
  • Caspases