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  • Title: Requirement for caspase activation in monocytic differentiation of myeloid leukemia cells.
    Author: Pandey P, Nakazawa A, Ito Y, Datta R, Kharbanda S, Kufe D.
    Journal: Oncogene; 2000 Aug 10; 19(34):3941-7. PubMed ID: 10951587.
    Abstract:
    Human myeloid leukemia cells respond to 12-tetradecanoylphorbol-13-acetate (TPA) and other activators of protein kinase C (PKC) with the induction of terminal monocytic differentiation. The present studies demonstrate that TPA treatment of U-937 leukemia cells is associated with release of mitochondrial cytochrome c, activation of caspase-3 and induction of internucleosomal DNA fragmentation. By contrast, the TUR cell variant, which is deficient in PKCbeta, failed to respond to TPA with release of cytochrome c and induction of the caspase-3 cascade. Moreover, stable overexpression of PKCbeta in TUR cells reconstituted sensitivity to TPA-induced cytochrome c release and activation of caspase-3. The results also demonstrate that treatment of cells with the caspase inhibitor Z-VAD-fmk blocks both TPA-induced apoptosis and monocytic differentiation. Similar results were obtained in U-937 cells stably expressing the CrmA caspase inhibitor. These findings demonstrate that TPA induces cytochrome c release by a PKCbeta-dependent mechanism and that activation of caspase-mediated signaling is required for induction of the differentiated monocytic phenotype.
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