Preponderance of the oncogenic V599E and V599K mutations in the B-raf kinase domain is enhanced in melanoma lymph node metastases.

Abstract

Downstream of Ras, the serine/threonine kinase B-raf has been reported to be mutated, amongst other carcinomas, in a substantial subset of primary melanomas, with a preponderance of mutations within the kinase domain, including the activating V599E and V599K transitions. We investigated a representative series of 54 resection specimens of melanoma lymph node metastases for the presence of mutations within the activation segment (exon 15) of the B-raf kinase domain by polymerase chain reaction (PCR) and single-strand conformational polymorphism (SSCP) gel electrophoresis. Sequencing of cloned PCR-SSCP amplicons resulted in 24 (44%) samples harbouring somatic mutations, which is not significantly different from the mutation frequency found in recently investigated primary cutaneous melanomas (Deichmann M, Thome M, Benner A, Näher H. B-raf exon 15 mutations are common in primary melanoma resection specimens but not associated with clinical outcome. Oncology 2004; 66:411-419). The activating mutation T1796A was present in 20 (83%) of these resection specimens, followed in frequency by the oncogenic g1795A mutation in five (21%) cases. 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. The detection of mutations at this hot spot codon was significantly associated with subsequent visceral metastasis (P=0.03; Fisher's exact test). During the transition from primary melanomas (see reference above) to lymph node metastases, the spectrum of B-raf mutations narrows significantly (P=0.00047). The oncogenic B-raf mutations V599E and V599K, as early events in melanocyte transformation, persist throughout metastasis with important prognostic implications.

• Authors: Martin Kirschner, Burkhard Helmke, Hans Starz, Axel Benner, Marianne Thome, Martin Deichmann
• Journal: Melanoma research (Melanoma Res) Vol. 15 Issue 5 Pg. 427-34 (Oct 2005) ISSN: 0960-8931 [Print] England
• PMID: 16179870 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• BRAF protein, human
• Proto-Oncogene Proteins B-raf

Topics

• Exons
• Humans
• Lymph Nodes (pathology)
• Lymphatic Metastasis
• Melanoma (enzymology, genetics, pathology)
• Mutation
• Paraffin Embedding
• Polymerase Chain Reaction
• Polymorphism, Single-Stranded Conformational
• Proto-Oncogene Proteins B-raf (genetics)