Tandem BRAF mutations in primary invasive melanomas.
The RAS/RAF/MAPK pathway likely mediates critical cell proliferation and survival signals in melanoma. BRAF mutations have been found in a high percentage of melanoma cell lines and metastases; however, only a few studies with a limited number of specimens have focused on primary melanomas. We examined BRAF exon 15 mutational status in 37 primary invasive melanomas of varying thicknesses, which had undergone a standardized pathology review. BRAF mutational status was determined using direct manual sequencing of PCR products, followed by resequencing separately amplified DNA aliquots to confirm each mutation. BRAF exon 15 mutations were found in 17 of 37 (46%) primary melanomas. Tumor-specific tandem mutations, encoding either V599K, V599R, or V599E, were found in 5 of 17 (29%) melanomas with BRAF exon 15 mutations. Cloning of BRAF double base-pair substitutions confirmed that both base changes were on the same allele and can result in a positive charge at codon 599. BRAF mutations, including tandem mutations, were frequently found in both thin and thick primary melanomas, implying that these mutations can occur early in the progression of melanoma. The finding of tandem mutations in thin melanomas makes it more likely that they arise as a simultaneous rather than sequential event.
Thomas
Nancy E
NE
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, USA. nthomas@med.unc.edu
Alexander
Audrey
A
Edmiston
Sharon N
SN
Parrish
Eloise
E
Millikan
Robert C
RC
Berwick
Marianne
M
Groben
Pamela
P
Ollila
David W
DW
Mattingly
Dianne
D
Conway
Kathleen
K
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D006801:Humans; D008297:Male; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D008875:Middle Aged; D008969:Molecular Sequence Data; D017354:Point Mutation; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics*; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology
C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf