Bryostatin 1 induces prolonged activation of extracellular regulated protein kinases in and apoptosis of LNCaP human prostate cancer cells overexpressing protein kinase calpha.
Previously, we reported that 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced apoptosis of LNCaP human prostate cancer cells was accompanied by prolonged translocation of protein kinase C (PKC)alpha to non-nuclear membranes and that TPA-resistant LNCaP cells had down-regulated PKCalpha. Here we show that 10 nM bryostatin 1 induced transient membrane translocation and down-regulation of PKCalpha, prolonged translocation of PKCdelta and epsilon to non-nuclear membranes, and did not induce cell death but blocked TPA-induced apoptosis. To test the hypothesis that inhibition of TPA-induced apoptosis by bryostatin 1 was due to down-regulation of PKCalpha, we inducibly overexpressed PKCalpha in LNCaP cells. Overexpression of PKCalpha alone did not induce apoptosis, even in clones that contained much more membrane-bound, active PKCalpha than was observed in TPA-treated untransfected LNCaP cells. However, the addition of 10 nM bryostatin 1 to PKCalpha-overexpressing LNCaP cells did not yield down-regulation of PKCalpha and induced extensive apoptosis. Immunoblot analysis revealed that TPA induced prolonged hyperphosphorylation of Raf-1 and activation of extracellular-regulated/mitogen-activated protein kinases 1 and 2 in untransfected LNCaP cells, as did bryostatin 1 in PKCalpha-overexpressing cells. On the other hand, bryostatin 1 induced only transient hyperphosphorylation of Raf-1 and activation of extracellular-regulated/mitogen-activated protein kinases 1 and 2 in untransfected LNCaP cells. These results confirm a role of prolonged membrane-associated PKCalpha in PKC activator-mediated LNCaP apoptosis and suggest involvement of the mitogen-activated protein kinase pathway.
Gschwend
J E
JE
Urologic Oncology Research Laboratory and George M. O'Brien Urology Research Center for Prostate Cancer, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
Fair
W R
WR
Powell
C T
CT
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001692:Biological Transport; D054713:Bryostatins; D002273:Carcinogens / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D015536:Down-Regulation; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis*; D007783:Lactones / Q000494:pharmacology*; D018942:Macrolides; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000473:pathology; D011493:Protein Kinase C / Q000096:biosynthesis*; D051571:Protein Kinase C-alpha; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D013347:Subcellular Fractions; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D054713:Bryostatins; D002273:Carcinogens; D007527:Isoenzymes; D007783:Lactones; D018942:Macrolides; C046785:bryostatin 1; D019908:Proto-Oncogene Proteins c-raf; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate