BRAF is a therapeutic target in aggressive thyroid carcinoma.
OBJECTIVE
Oncogenic conversion of BRAF occurs in approximately 44% of papillary thyroid carcinomas and 24% of anaplastic thyroid carcinomas. In papillary thyroid carcinomas, this mutation is associated with an unfavorable clinicopathologic outcome. Our aim was to exploit BRAF as a potential therapeutic target for thyroid carcinoma.


METHODS
We used RNA interference to evaluate the effect of BRAF knockdown in the human anaplastic thyroid carcinoma cell lines FRO and ARO carrying the BRAF V600E (V600EBRAF) mutation. We also exploited the effect of BAY 43-9006 [N-(3-trifluoromethyl-4-chlorophenyl)-N'-(4-(2-methylcarbamoyl pyridin-4-yl)oxyphenyl)urea], a multikinase inhibitor able to inhibit RAF family kinases in a panel of six (V600E)BRAF-positive thyroid carcinoma cell lines and in nude mice bearing ARO cell xenografts. Statistical tests were two sided.


RESULTS
Knockdown of BRAF by small inhibitory duplex RNA, but not control small inhibitory duplex RNA, inhibited the mitogen-activated protein kinase signaling cascade and the growth of ARO and FRO cells (P < 0.0001). These effects were mimicked by thyroid carcinoma cell treatment with BAY 43-9006 (IC50 = 0.5-1 micromol/L; P < 0.0001), whereas the compound had negligible effects in normal thyrocytes. ARO cell tumor xenografts were significantly (P < 0.0001) smaller in nude mice treated with BAY 43-9006 than in control mice. This inhibition was associated with suppression of phospho-mitogen-activated protein kinase levels.


CONCLUSIONS
BRAF provides signals crucial for proliferation of thyroid carcinoma cells spontaneously harboring the (V600E)BRAF mutation and, therefore, BRAF suppression might have therapeutic potential in (V600E)BRAF-positive thyroid cancer.
Istituto di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università di Napoli Federico II, Naples, Italy.
Giuliana
G
Salvatore
Valentina
V
De Falco
Paolo
P
Salerno
Tito Claudio
TC
Nappi
Stefano
S
Pepe
Giancarlo
G
Troncone
Francesca
F
Carlomagno
Rosa Marina
RM
Melillo
Scott M
SM
Wilhelm
Massimo
M
Santoro
D000818:Animals; D001557:Benzenesulfonates / Q000627:therapeutic use*; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000628:therapy*; D002291:Carcinoma, Papillary / Q000235:genetics / Q000378:metabolism / Q000628:therapy; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011725:Pyridines / Q000627:therapeutic use*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D000077157:Sorafenib; D013961:Thyroid Gland / Q000187:drug effects; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism / Q000628:therapy*; D014183:Transplantation, Heterologous
D001557:Benzenesulfonates; D010671:Phenylurea Compounds; D011725:Pyridines; D034741:RNA, Small Interfering; D009536:Niacinamide; D000077157:Sorafenib; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020928:Mitogen-Activated Protein Kinases