title: The important roles of RET, VEGFR2 and the RAF/MEK/ERK pathway in cancer treatment with sorafenib.
abstract: OBJECTIVE
  To elucidate the roles of receptor tyrosine kinases RET and VEGFR2 and the RAF/MEK/ERK signaling cascade in cancer treatment with sorafenib.
  
  
  METHODS
  The cell lines A549, HeLa, and HepG2 were tested. The enzyme activity was examined under cell-free conditions using 384-well microplate assays. Cell proliferation was evaluated using the Invitrogen Alarmar Blue assay. Gene expression was analyzed using the Invitrogen SYBR Green expression assays with a sequence detection system. Protein expression analysis was performed using Western blotting.
  
  
  RESULTS
  Sorafenib potently suppressed the activities of cRAF, VEGFR2, and RET with IC(50) values of 20.9, 4 and 0.4 nmol/L, respectively. Sorafenib inhibited cRAF, VEGFR2, and RET via non-ATP-competitive, ATP-competitive and mixed-type modes, respectively. In contrast, sorafenib exerted only moderate cytotoxic effects on the proliferation of the 3 cell lines. The IC(50) values for inhibition of A549, HeLa, and HepG2 cells were 8572, 4163, and 8338 nmol/L, respectively. In the 3 cell lines, sorafenib suppressed the cell proliferation mainly by blocking the MEK/ERK downstream pathway at the posttranscriptional level, which in turn regulated related gene expression via a feed-back mechanism.
  
  
  CONCLUSIONS
  This study provides novel evidence that protein kinases RET and VEGFR2 play crucial roles in cancer treatment with sorafenib.
authors.affiliation: Biology Department, East China Normal University, Shanghai, China.
authors.forename: Wei-Feng
authors.initials: WF
authors.lastname: Mao
authors.forename: Min-Hua
authors.initials: MH
authors.lastname: Shao
authors.forename: Pin-Ting
authors.initials: PT
authors.lastname: Gao
authors.forename: Ji
authors.initials: J
authors.lastname: Ma
authors.forename: Hui-Juan
authors.initials: HJ
authors.lastname: Li
authors.forename: Gai-Ling
authors.initials: GL
authors.lastname: Li
authors.forename: Bao-Hui
authors.initials: BH
authors.lastname: Han
authors.forename: Chong-Gang
authors.initials: CG
authors.lastname: Yuan
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D015153:Blotting, Western; D018929:Cell Culture Techniques; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000235:genetics; D009369:Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D010671:Phenylurea Compounds / Q000494:pharmacology* / Q000627:therapeutic use; D051096:Proto-Oncogene Proteins c-ret / Q000037:antagonists & inhibitors* / Q000235:genetics; D034622:RNA Interference / Q000187:drug effects; D060888:Real-Time Polymerase Chain Reaction; D000077157:Sorafenib; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors* / Q000235:genetics
chemical_list: D000970:Antineoplastic Agents; D010671:Phenylurea Compounds; D009536:Niacinamide; D000077157:Sorafenib; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human; D040301:Vascular Endothelial Growth Factor Receptor-2