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  • Title: 1-beta-D-arabinofuranosylcytosine activates serine/threonine protein kinases and c-jun gene expression in phorbol ester-resistant myeloid leukemia cells.
    Author: Kharbanda S, Emoto Y, Kisaki H, Saleem A, Kufe D.
    Journal: Mol Pharmacol; 1994 Jul; 46(1):67-72. PubMed ID: 8058058.
    Abstract:
    1-beta-D-Arabinofuranosylcytosine (ara-C) is an effective antileukemic agent that misincorporates into DNA. Recent studies have demonstrated that ara-C treatment is associated with transient induction of the c-jun early response gene. The present studies have examined the effects of ara-C on c-jun expression in a phorbol ester-resistant variant of the HL-60 myeloid leukemia cell line, designated HL-525, that is deficient in protein kinase C (PKC)-mediated signal transduction and fails to respond to 12-O-tetradecanoylphorbol-13-acetate with induction of c-jun transcripts. The results demonstrate that treatment of HL-525 cells with ara-C is associated with transcriptional activation of the c-jun gene. We also demonstrate that ara-C treatment is associated with activation of a PKC-like activity. Partial purification of this Ca(2+)-independent activity has demonstrated phosphorylation of synthetic peptides derived from (a) amino acids 4-14 of myelin basic protein and (b) the pseudosubstrate region of PKC (amino acids 19-31), with substitution of Ala25 with serine. The finding that the ara-C-induced activity is inhibited by the pseudosubstrate PKC(19-36) supports the activation of a PKC-like enzyme. Because PKC can act upstream of the mitogen-activated protein (MAP) kinases, we studied the effects of ara-C treatment on MAP kinase activity. The results demonstrate that MAP kinase is activated in ara-C-treated cells and that the kinetics of this activation are similar to those of the PKC-like activity. Because 12-O-tetradecanoylphorbol-13-acetate has little, if any, effect on the PKC-like and MAP kinase activities in HL-525 cells, these findings suggest that ara-C activates a distinct signaling cascade that may contribute to induction of the c-jun gene.
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