title: Protein kinase Cdelta amplifies ceramide formation via mitochondrial signaling in prostate cancer cells.
abstract: We studied the role of protein kinase C isoform PKCdelta in ceramide (Cer) formation, as well as in the mitochondrial apoptosis pathway induced by anticancer drugs in prostate cancer (PC) cells. Etoposide and paclitaxel induced Cer formation and apoptosis in PKCdelta-positive LNCaP and DU145 cells but not in PKCdelta-negative LN-TPA or PC-3 cells. In contrast, these drugs induced mitotic cell cycle arrest in all PC cell lines. Treatment with Rottlerin, a specific PKCdelta inhibitor, significantly inhibited drug-induced Cer formation and apoptosis in LNCaP cells, as did overexpression of dominant negative-type PKCdelta. Overexpression of wild-type PKCdelta had an opposite effect in PC-3 cells. Notably, etoposide induced biphasic Cer formation in LNCaP cells. The early and transient Cer increase resulted from de novo Cer synthesis, while the late and sustained Cer accumulation was derived from sphingomyelin hydrolysis by neutral sphingomyelinase (nSMase). Cer, in turn, induced mitochondrial translocation of PKCdelta and stimulated the activity of this kinase, promoting cytochrome c release and caspase-9 activation. Furthermore, the specific caspase-9 inhibitor LEHD-fmk significantly inhibited etoposide-induced nSMase activation, Cer accumulation, and PKCdelta mitochondrial translocation. These results indicate that PKCdelta plays a crucial role in activating anticancer drug-induced apoptosis signaling by amplifying the Cer-mediated mitochondrial amplification loop.
authors.affiliation: Department of Urology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan. mh712@me.nmdc.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Sumitomo
authors.forename: Motoi
authors.initials: M
authors.lastname: Ohba
authors.forename: Junichi
authors.initials: J
authors.lastname: Asakuma
authors.forename: Takako
authors.initials: T
authors.lastname: Asano
authors.forename: Toshio
authors.initials: T
authors.lastname: Kuroki
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Asano
authors.forename: Masamichi
authors.initials: M
authors.lastname: Hayakawa
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001578:Benzopyrans / Q000494:pharmacology; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002458:Cell Fractionation; D002518:Ceramides / Q000737:chemistry / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D017239:Paclitaxel / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000378:metabolism*; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051745:Protein Kinase C-delta; D015398:Signal Transduction; D013109:Sphingomyelins / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000098:Acetophenones; D000972:Antineoplastic Agents, Phytogenic; D001578:Benzopyrans; D061945:Caspase Inhibitors; D002518:Ceramides; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D013109:Sphingomyelins; D005047:Etoposide; C085746:rottlerin; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D020169:Caspases; D017239:Paclitaxel