title: The protein kinase C inhibitor enzastaurin exhibits antitumor activity against uveal melanoma.
abstract: GNAQ mutations at codon 209 have been recently identified in approximately 50% of uveal melanomas (UM) and are reported to be oncogenic through activating the MAPK/Erk1/2 pathway. Protein kinase C (PKC) is a component of signaling from GNAQ to Erk1/2. Inhibition of PKC might regulate GNAQ mutation-induced Erk1/2 activation, resulting in growth inhibition of UM cells carrying GNAQ mutations. UM cells carrying wild type or mutant GNAQ were treated with the PKC inhibitor enzastaurin. Effects on proliferation, apoptosis, and signaling events were evaluated. Enzastaurin downregulated the expression of several PKC isoforms including PKCβII PKCθ, PKCε and/or their phosphorylation in GNAQ mutated cells. Downregulation of these PKC isoforms in GNAQ mutated cells by shRNA resulted in reduced viability. Enzastaurin exhibited greater antiproliferative effect on GNAQ mutant cells than wild type cells through induction of G1 arrest and apoptosis. Enzastaurin-induced G1 arrest was associated with inhibition of Erk1/2 phosphorylation, downregulation of cyclin D1, and accumulation of cyclin dependent kinase inhibitor p27(Kip1). Furthermore, enzastaurin reduced the expression of antiapoptotic Bcl-2 and survivin in GNAQ mutant cells. Inhibition of Erk1/2 phosphorylation with a MEK specific inhibitor enhanced the sensitivity of GNAQ wild type cells to enzastaurin, accompanied by p27(Kip1) accumulation and/or inhibition of enzastaurin-induced survivin and Bcl-2 upregulation. PKC inhibitors such as enzastaurin have activity against UM cells carrying GNAQ mutations through inhibition of the PKC/Erk1/2 pathway and induction of G1 arrest and apoptosis. Inhibition of the PKC pathway provides a basis for clinical investigation in patients with UM.
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Xinqi
authors.initials: X
authors.lastname: Wu
authors.forename: Meijun
authors.initials: M
authors.lastname: Zhu
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Fletcher
authors.forename: Anita
authors.initials: A
authors.lastname: Giobbie-Hurder
authors.forename: F Stephen
authors.initials: FS
authors.lastname: Hodi
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001973:Bromodeoxyuridine / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D006801:Humans; D007211:Indoles / Q000494:pharmacology / Q000627:therapeutic use; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008545:Melanoma / Q000188:drug therapy* / Q000201:enzymology* / Q000473:pathology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D014604:Uveal Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000473:pathology; D000098943:Uveal Melanoma
chemical_list: C530104:CCND1 protein, human; C554061:GNAQ protein, human; D044385:GTP-Binding Protein alpha Subunits; D007211:Indoles; D007527:Isoenzymes; D047428:Protein Kinase Inhibitors; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D001973:Bromodeoxyuridine; C504878:enzastaurin