A mutation and expression analysis of the oncogene BRAF in pituitary adenomas.
OBJECTIVE
BRAF is an oncogene that is commonly mutated in both melanomas and papillary thyroid carcinomas, usually at position V600E that leads to constitutive activity in the Ras-mitogen-activated protein kinase (MAPK) pathway. We speculated that this same gene may be either mutated at this site, or overexpressed, in pituitary adenomas.


METHODS
We sequenced 37 pituitary adenomas for a mutation at the V600E position. In addition, we investigated B-Raf mRNA expression in normal pituitary (n = 5) and nonfunctioning pituitary adenomas (NFPA) (n = 6) by semiquantitative PCR, and in a further 27 pituitary adenomas of various types and 10 normal pituitaries using real-time quantitative PCR. Finally, we explored B-Raf protein expression in 10 normal pituitaries and 12 NFPAs.


RESULTS
No sequence mutations for the substitution V600E were identified. B-Raf mRNA was overexpressed in pituitary adenomas compared to normal pituitary, and this was entirely due to overexpression in NFPAs. NFPAs also showed very variable expression of B-Raf protein, but those tumours showing highest levels of B-Raf mRNA expressed the most B-Raf protein.


CONCLUSIONS
Mutations previously seen in the majority of melanomas and a substantial minority of papillary thyroid carcinomas are not a frequent finding in pituitary adenomas. However, overexpression of B-Raf mRNA and protein may be a feature of NFPAs, highlighting overactivity of the Ras-B-Raf-MAP kinase pathway in these tumours.
Ewing
Iain
I
Department of Endocrinology, Barts and the London School of Medicine, Queen Mary University of London, UK.
Pedder-Smith
Stephen
S
Franchi
Giulia
G
Ruscica
Massimiliano
M
Emery
Michelle
M
Vax
Vladimir
V
Garcia
Edwin
E
Czirják
Sándor
S
Hanzély
Zoltán
Z
Kola
Blerina
B
Korbonits
Márta
M
Grossman
Ashley B
AB
D049913:ACTH-Secreting Pituitary Adenoma / Q000737:chemistry; D000236:Adenoma / Q000737:chemistry*; D016022:Case-Control Studies; D004252:DNA Mutational Analysis; D015972:Gene Expression Regulation, Neoplastic; D049912:Growth Hormone-Secreting Pituitary Adenoma / Q000737:chemistry; D006801:Humans; D010911:Pituitary Neoplasms / Q000737:chemistry*; D016133:Polymerase Chain Reaction / Q000379:methods; D015175:Prolactinoma / Q000737:chemistry; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D018709:Statistics, Nonparametric
D012333:RNA, Messenger; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf