title: Sorafenib inhibits non-small cell lung cancer cell growth by targeting B-RAF in KRAS wild-type cells and C-RAF in KRAS mutant cells.
abstract: Sorafenib is a multikinase inhibitor whose targets include B-RAF and C-RAF, both of which function in the extracellular signal-regulated kinase (ERK) signaling pathway but which also have distinct downstream targets. The relative effects of sorafenib on B-RAF and C-RAF signaling in tumor cells remain unclear, however. We have now examined the effects of sorafenib as well as of B-RAF or C-RAF depletion by RNA interference on cell growth and ERK signaling in non-small cell lung cancer (NSCLC) cell lines with or without KRAS mutations. Sorafenib inhibited ERK phosphorylation in cells with wild-type KRAS but not in those with mutant KRAS. Despite this difference, sorafenib inhibited cell growth and induced G(1) arrest in both cell types. Depletion of B-RAF, but not that of C-RAF, inhibited ERK phosphorylation as well as suppressed cell growth and induced G(1) arrest in cells with wild-type KRAS. In contrast, depletion of C-RAF inhibited cell growth and induced G(1) arrest, without affecting ERK phosphorylation, in cells with mutant KRAS; depletion of B-RAF did not induce G(1) arrest in these cells. These data suggest that B-RAF-ERK signaling and C-RAF signaling play the dominant roles in regulation of cell growth in NSCLC cells with wild-type or mutant KRAS, respectively. The G(1) arrest induced by either C-RAF depletion or sorafenib in cells with mutant KRAS was associated with down-regulation of cyclin E. Our results thus suggest that sorafenib inhibits NSCLC cell growth by targeting B-RAF in cells with wild-type KRAS and C-RAF in those with mutant KRAS.
authors.affiliation: Department of Medical Oncology, Kinki University School of Medicine, Sakai Hospital, Osaka, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Takezawa
authors.forename: Isamu
authors.initials: I
authors.lastname: Okamoto
authors.forename: Kimio
authors.initials: K
authors.lastname: Yonesaka
authors.forename: Erina
authors.initials: E
authors.lastname: Hatashita
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yamada
authors.forename: Masahiro
authors.initials: M
authors.lastname: Fukuoka
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakagawa
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D001557:Benzenesulfonates / Q000494:pharmacology* / Q000627:therapeutic use; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects*; D019927:Cyclin E / Q000235:genetics; D016503:Drug Delivery Systems; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D011905:Genes, ras / Q000502:physiology; D005838:Genotype; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D009154:Mutation / Q000502:physiology; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics*; D011725:Pyridines / Q000494:pharmacology* / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects; D000077157:Sorafenib; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001557:Benzenesulfonates; D019927:Cyclin E; D010671:Phenylurea Compounds; D011725:Pyridines; D009536:Niacinamide; D000077157:Sorafenib; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases