title: A novel PKC-ι inhibitor abrogates cell proliferation and induces apoptosis in neuroblastoma.
abstract: Protein Kinase C-iota (PKC-ι), an atypical protein kinase C isoform manifests its potential as an oncogene by targeting various aspects of cancer cells such as growth, invasion and survival. PKC-ι confers resistance to drug-induced apoptosis in cancer cells. The acquisition of drug resistance is a major obstacle to good prognosis in neuroblastoma. The focus of this research was to identify the efficacy of [4-(5-amino-4-carbamoylimidazol-1-yl)-2,3-dihydroxycyclopentyl] methyl dihydrogen phosphate (ICA-1) as a novel PKC-ι inhibitor in neuroblastoma cell proliferation and apoptosis. ICA-1 specifically inhibits the activity of PKC-ι but not that of PKC-zeta (PKC-ζ), the closely related atypical PKC family member. The IC(50) for the kinase activity assay was approximately 0.1μM which is 1000 times less than that of aurothiomalate, a known PKC-ι inhibitor. Cyclin dependent kinase 7 (Cdk7) phosphorylates cyclin dependent kinases (cdks) and promotes cell proliferation. Our data shows that PKC-ι is an in vitro Cdk7 kinase and the phosphorylation of Cdk7 by PKC-ι was potently inhibited by ICA-1. Furthermore, our data shows that neuroblastoma cells proliferate via a PKC-ι/Cdk7/cdk2 cell signaling pathway and ICA-1 mediates its antiproliferative effects by inhibiting this pathway. ICA-1 (0.1μM) inhibited the in vitro proliferation of BE(2)-C neuroblastoma cells by 58% (P=0.01). Additionally, ICA-1 also induced apoptosis in neuroblastoma cells. Interestingly, ICA-1 did not affect the proliferation of normal neuronal cells suggesting its potential as chemotherapeutic with low toxicity. Hence, our results emphasize the potential of ICA-1 as a novel PKC-ι inhibitor and chemotherapeutic agent for neuroblastoma.
authors.affiliation: Department of Chemistry, University of South Florida, Tampa, FL 33620, USA.
authors.forename: Prajit
authors.initials: P
authors.lastname: Pillai
authors.forename: Shraddha
authors.initials: S
authors.lastname: Desai
authors.forename: Rekha
authors.initials: R
authors.lastname: Patel
authors.forename: Mini
authors.initials: M
authors.lastname: Sajan
authors.forename: Robert
authors.initials: R
authors.lastname: Farese
authors.forename: David
authors.initials: D
authors.lastname: Ostrov
authors.forename: Mildred
authors.initials: M
authors.lastname: Acevedo-Duncan
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001667:Binding, Competitive; D053148:Caspase 3 / Q000378:metabolism; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D042002:Chromatin Assembly and Disassembly / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D010755:Organophosphates / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D000095043:Cyclin-Dependent Kinase-Activating Kinase; D000099293:Protein Kinase C-lambda
chemical_list: D053148:Caspase 3; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D007093:Imidazoles; D007527:Isoenzymes; D010755:Organophosphates; D011065:Poly(ADP-ribose) Polymerases; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D000095043:Cyclin-Dependent Kinase-Activating Kinase; D000099293:Protein Kinase C-lambda; C559837:(4-(5-amino-4-carbamoylimidazol-1-yl)-2,3-dihydroxycyclopentyl) methyl phosphate; C000722416:CDK7 protein, human