Sorafenib potently inhibits papillary thyroid carcinomas harboring RET/PTC1 rearrangement.
OBJECTIVE
Papillary thyroid carcinomas (PTC) are the most common type of thyroid malignancy with one of the two mutations, RET/PTC rearrangement or BRAF mutation. Both mutations are able to activate the MEK/ERK signaling transduction pathway and result in the activation of transcription factors that regulate cellular proliferation, differentiation, and apoptosis. Sorafenib (Nexavar, BAY 43-9006) is a multikinase inhibitor, and in this study, we tested its effects on PTC cells carrying either mutation.


METHODS
The effects of sorafenib on cell proliferation and signaling were evaluated in vitro on PTC cells using growth curves, cell cycle analysis, and immunoblotting. Using an orthotopic mouse model, we determined the antitumor effects of sorafenib in vivo.


RESULTS
The concentration needed for 50% growth inhibition (GI(50)) by sorafenib was 0.14 mumol/L for the PTC cells with the RET/PTC1 rearrangement, and 2.5 mumol/L for PTC cells with a BRAF mutation, both readily achievable serum concentrations. After 3 weeks of oral administration of sorafenib (80 mg/kg/d) in mice, small (94% reduction compared with controls) or no tumor growth was detected in mice inoculated with PTC cells bearing the RET/PTC1 rearrangement, whereas the tumor volume of the orthotopic tumor implants of PTC cells with a BRAF mutation was reduced 53% to 54% (as compared with controls).


CONCLUSIONS
PTC cells carrying the RET/PTC1 rearrangement were more sensitive to sorafenib than PTC cells carrying a BRAF mutation. Because RET/PTC rearrangements are unique to thyroid carcinomas, our findings support the clinical evaluation of sorafenib for patients with PTC and the identification of patients most likely to respond to sorafenib treatment.
Henderson
Ying C
YC
Department of Head and Neck Surgery, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
Ahn
Soon-Hyun
SH
Department of Head and Neck Surgery, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
Kang
Ya'an
Y
Department of Head and Neck Surgery, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
Clayman
Gary L
GL
Department of Head and Neck Surgery, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.|Department of Cancer Biology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001557:Benzenesulfonates / Q000494:pharmacology*; D002291:Carcinoma, Papillary / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D009368:Neoplasm Transplantation; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics*; D011725:Pyridines / Q000494:pharmacology*; D015398:Signal Transduction; D000077157:Sorafenib; D013964:Thyroid Neoplasms / Q000188:drug therapy* / Q000378:metabolism
D000970:Antineoplastic Agents; D001557:Benzenesulfonates; D010671:Phenylurea Compounds; D011725:Pyridines; D009536:Niacinamide; D000077157:Sorafenib; D051096:Proto-Oncogene Proteins c-ret; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf