title: Protein kinase D3 sensitizes RAF inhibitor RAF265 in melanoma cells by preventing reactivation of MAPK signaling.
abstract: RAS mutations occur in more than 30% of all human cancers but efforts to directly target mutant RAS signaling as a cancer therapy have yet to succeed. As alternative strategies, RAF and MEK inhibitors have been developed to block oncogenic signaling downstream of RAS. As might be expected, studies of these inhibitors have indicated that tumors with RAS or BRAF mutations display resistance RAF or MEK inhibitors. In order to better understand the mechanistic basis for this resistance, we conducted a RNAi-based screen to identify genes that mediated chemoresistance to the RAF kinase inhibitor RAF265 in a BRAF (V600E) mutant melanoma cell line that is resistant to this drug. In this way, we found that knockdown of protein kinase D3 (PRKD3) could enhance cell killing of RAF and MEK inhibitors across multiple melanoma cell lines of various genotypes and sensitivities to RAF265. PRKD3 blockade cooperated with RAF265 to prevent reactivation of the MAPK signaling pathway, interrupt cell cycle progression, trigger apoptosis, and inhibit colony formation growth. Our findings offer initial proof-of-concept that PRKD3 is a valid target to overcome drug resistance being encountered widely in the clinic with RAF or MEK inhibitors.
authors.affiliation: Department of Developmental and Molecular Pathways, Novartis Institute for BioMedical Research, Inc., Cambridge, Massachusetts 02139, USA. jian.chen@novartis.com
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Qiong
authors.initials: Q
authors.lastname: Shen
authors.forename: Mark
authors.initials: M
authors.lastname: Labow
authors.forename: L Alex
authors.initials: LA
authors.lastname: Gaither
mesh_terms: D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008545:Melanoma / Q000188:drug therapy* / Q000473:pathology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000235:genetics; D048490:raf Kinases / Q000037:antagonists & inhibitors*
chemical_list: C530104:CCND1 protein, human; D007093:Imidazoles; D011725:Pyridines; D034741:RNA, Small Interfering; D019938:Cyclin D1; C559019:RAF265; D011065:Poly(ADP-ribose) Polymerases; D019869:Phosphatidylinositol 3-Kinases; C119190:protein kinase C nu; D048490:raf Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases