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Mechanisms of apoptosis-induction by rottlerin: therapeutic implications for B-CLL

I Ringshausen1, M Oelsner, K Weick

  • 13rd Department of Medicine, Technical University of Munich, Munich, Germany. iringshausen@cc.ucsf.edu

Leukemia
|January 27, 2006
PubMed

Insights

Targeting protein kinase C-delta (PKC-delta) with rottlerin induces apoptosis in chronic lymphocytic leukemia (CLL) cells, even with survival factors present. This suggests PKC-delta is a promising therapeutic target for CLL treatment.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Death Research

Background:

  • Chronic lymphocytic leukemia (CLL) cells exhibit resistance to apoptosis due to constitutively activated signaling pathways.
  • Protein kinase C-delta (PKC-delta), a permanently activated kinase, is implicated as a downstream target of phosphatidylinositol-3 kinase in B-CLL.

Purpose of the Study:

  • To investigate the therapeutic potential of inhibiting PKC-delta in CLL.
  • To elucidate the downstream apoptotic mechanisms induced by PKC-delta inhibition.

Main Methods:

  • Co-culture of bone marrow stromal and CLL cells to assess rottlerin's efficacy in a survival-factor-rich environment.
  • Analysis of downstream events including mitochondrial membrane potential (Deltapsi) and expression of antiapoptotic proteins (Mcl-1, XIAP).
  • Evaluation of rottlerin's effect on ZAP-70-expressing versus ZAP-70-negative CLL cells and its synergy with chemotherapeutics.

Main Results:

  • The specific PKC-delta inhibitor rottlerin effectively induces apoptosis in CLL cells, irrespective of supportive survival factors.
  • Rottlerin treatment leads to decreased expression of antiapoptotic proteins Mcl-1 and XIAP and a loss of mitochondrial membrane potential.
  • ZAP-70-expressing CLL cells demonstrated significantly higher susceptibility to rottlerin-induced apoptosis.
  • Rottlerin enhanced the cytotoxic effects of conventional chemotherapeutic drugs.

Conclusions:

  • PKC-delta is a viable and promising therapeutic target for chronic lymphocytic leukemia.
  • Targeting PKC-delta triggers both mitochondrial and non-mitochondrial apoptotic pathways, culminating in caspase activation.
  • The combination of rottlerin with standard chemotherapy may offer a more effective treatment strategy for CLL patients.

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