Functional characterization of the novel T599I-VKSRdel BRAF mutation in a follicular variant papillary thyroid carcinoma.
BACKGROUND
Mutations in BRAF are rare in the follicular variant of papillary thyroid carcinoma (FV-PTC).


OBJECTIVE
We identified and functionally characterized a novel T599I-VKSR(600-603)del BRAF mutation in a FV-PTC patient. We analyzed in vitro the effects of this novel mutation in comparison with other thyroid cancer-associated mutations.


METHODS
Expression vectors for the BRAF mutants were generated and their in vitro kinase activity, signaling along the MAPK pathway, and capability of stimulating transcription from an AP1-responsive reporter evaluated.


RESULTS
BRAF kinase and signaling were increased to a similar extent by the T599I-VKSR (600-603)del, V600E, and K601E mutations. Instead, the G474R, a mutation previously found in a FV-PTC, knocked down the BRAF kinase and its intracellular signaling. Some cancer-associated low-activity BRAF mutants stimulate the MAPK cascade via CRAF; however, the G474R protein lacked also this property.


CONCLUSIONS
The T599I-VKSR(600-603)del is a novel gain-of-function mutation that targets BRAF in FV-PTC. Moreover, G474R is the first example of a mutation knocking down enzymatic BRAF activity in a FV-PTC. These findings underscore the importance of functional studies to characterize the role of BRAF mutations associated with thyroid cancer.
De Falco
Valentina
V
Istituto di Endocrinologia ed Oncologia Sperimentale, Dipartimento di Biologia e Patologia Cellulare e Molecolare, L. Califano, Università Federico II di Napoli, via S. Pansini 5, 80131 Naples, Italy.
Giannini
Riccardo
R
Tamburrino
Anna
A
Ugolini
Clara
C
Lupi
Cristiana
C
Puxeddu
Efisio
E
Santoro
Massimo
M
Basolo
Fulvio
F
D000328:Adult; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D018265:Carcinoma, Papillary, Follicular / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D002460:Cell Line; D005260:Female; D017930:Genes, Reporter; D014644:Genetic Variation; D005822:Genetic Vectors; D006801:Humans; D007668:Kidney / Q000196:embryology; D008969:Molecular Sequence Data; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D017384:Sequence Deletion; D013964:Thyroid Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D014162:Transfection
C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf