Sorafenib functions to potently suppress RET tyrosine kinase activity by direct enzymatic inhibition and promoting RET lysosomal degradation independent of proteasomal targeting.
Germ line missense mutations in the RET (rearranged during transfection) oncogene are the cause of multiple endocrine neoplasia, type 2 (MEN2), but at present surgery is the only treatment available for MEN2 patients. In this study, the ability of Sorafenib (BAY 43-9006) to act as a RET inhibitor was investigated. Sorafenib inhibited the activity of purified recombinant kinase domain of wild type RET and RET(V804M) with IC(50) values of 5.9 and 7.9 nm, respectively. Interestingly, these values were 6-7-fold lower than the IC(50) for the inhibition of B-RAF(V600E). In cell-based assays, Sorafenib inhibited the kinase activity and signaling of wild type and oncogenic RET in MEN2 tumor and established cell lines at a concentration between 15 and 150 nm. In contrast, inhibition of oncogenic B-RAF- or epidermal growth factor-induced ERK1/2 phosphorylation required micromolar concentrations of Sorafenib demonstrating the high specificity of this drug in targeting RET. Moreover, prolonged exposure to Sorafenib resulted in inhibition of cell proliferation and RET protein degradation. Using lysosomal and proteasomal inhibitors, we demonstrate that Sorafenib induces RET lysosomal degradation independent of proteasomal targeting. Furthermore, we provide a structural model of the Sorafenib.RET complex in which Sorafenib binds to and induces the DFG(out) conformation of the RET kinase domain. These results strengthen the argument that Sorafenib may be effective in the treatment of MEN2 patients. In addition, because inhibition of RET is not impaired by mutation of the Val(804) gatekeeper residue, MEN2 tumors may be less susceptible to acquired Sorafenib resistance.
Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, SW3 6JB London, United Kingdom.
Iván
I
Plaza-Menacho
Luca
L
Mologni
Elisa
E
Sala
Carlo
C
Gambacorti-Passerini
Anthony I
AI
Magee
Thera P
TP
Links
Robert M W
RM
Hofstra
David
D
Barford
Clare M
CM
Isacke
D001557:Benzenesulfonates / Q000494:pharmacology*; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D006801:Humans; D020128:Inhibitory Concentration 50; D008247:Lysosomes / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D018813:Multiple Endocrine Neoplasia Type 2a / Q000378:metabolism; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism; D051096:Proto-Oncogene Proteins c-ret / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology*; D000077157:Sorafenib
D001557:Benzenesulfonates; D010671:Phenylurea Compounds; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D009536:Niacinamide; D000077157:Sorafenib; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human; D048493:Proto-Oncogene Proteins B-raf; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D046988:Proteasome Endopeptidase Complex