Our data show that BRAF mutation is common in melanoma metastases, regardless of their site, that mutations include both exons 11 and 15, and suggest that anti-RAS/RAF strategies may be effective in metastatic melanoma patients.
Thirty-three samples (7 of 25 primaries, 15 of 25 regional metastases, 5 of 25 nodal metastases, and 6 of 10 distant metastases) harbored the V599EB-RAF mutation (39%), 12 contained a Q61R N-RAS mutation and 5 a Q61K N-RAS mutation.
Primary melanomas (n = 71) and corresponding metastases (n = 88) from 71 patients were screened for BRAF exon 11 and exon 15 mutations using single-strand conformational polymorphism and nucleotide sequence analysis
NRAS was exclusively mutated in nine of 47 (19%) cell lines and two of 16 (13%) metastases, whereas BRAF was solely mutated in 28 of 47 (60%) cell lines and nine of 16 (56%) metastases.
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.
BRAF(V599E) tended to be associated, although not significantly, with a greater volume and extension of the tumour and with lymph-nodal metastases at surgery.
Sixty-eight samples (20 of 36 primaries, 18 of 27 regional metastases, 16 of 40 nodal metastases, and 9 of 12 distant metastases) harbored the V599EB-RAF mutation (59%), 17 contained a Q61R N-RAS mutation, and 4 contained a Q61K N-RAS mutation.
In comparison to the primary melanomas that we recently investigated, the spectrum of predicted B-raf protein mutations narrowed significantly in the cutaneous/subcutaneous metastases.
In our study of 51 primary nodular melanomas and 18 paired metastases, we found mutations in BRAF (codon 600, previously denoted 599) in 15 primary tumors (29%) and eight metastases (44%).
In line with the previous reports, NRAS/BRAF mutations were rare; only one metastatic tumor had an NRAS E61R mutation, and one primary tumor and two metastases harbored BRAFV599E mutations.
With regard to the B-raf protein sequence, the acidic amino acid transitions V599E and V599K were predicted in 15 (62%) and five (21%) of the 24 positive metastases, respectively.
In summary, this study provides a mechanistic basis for targeting Mek and not B-Raf in the mutant (V600E)B-Raf signaling cascade to inhibit melanoma metastases.
The BRAF(V600E) mutation was detected in 88 of the tumors examined, with significant differences between groups with and without lymph node (LN) metastases; the mean age of patients with BRAF(V600E) mutation was significantly higher than that of patients without mutations.
BRAFV600E was associated with extrathyroidal invasion (P < 0.0001), multicentricity (P = 0.0026), presence of nodal metastases (P = 0.0009), class III vs. classes I and II (P < 0.00000006), and absence of tumor capsule (P < 0.0001), in particular in follicular- and micro-PTC variants.
Treatment of orthotopic thyroid tumors, initiated 1 week after tumor cell implantation with PLX4720, an orally available selective inhibitor of B-Raf(V600E), caused a significant tumor growth delay and decreased distant metastases, without evidence of toxicity.
We therefore analyzed the correlation of BRAFV600E and ERK-activation in 20 malignant melanomas and 21 subsequently evolved, paired metastases of the same donor by BRAF exon 15 DNA sequencing and phospho-specific immunohistochemistry for ERK.
Therefore, the mRNA expression of the four members of the HER family as well as the frequency of PTEN allelic loss and KRAS/BRAF mutations were determined in pretreatment biopsies from a series of 100 locally advanced rectal cancers and then their ability to predict distant metastases was evaluated.