Clinical detection and categorization of uncommon and concomitant mutations involving BRAF

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Selective BRAF inhibitors (vemurafenib, dabrafenib) and MEK inhibitors (trametinib) are approved for metastatic melanomas with BRAF p.V600E mutations.
• The clinical relevance of BRAF mutations outside codon 600 is not well understood due to varying kinase activity.
• BRAF mutations are implicated in various cancers, including melanoma, lung, and colorectal cancers.

Purpose of the Study:

• To categorize BRAF mutations based on their reported kinase activity.
• To investigate the prevalence and characteristics of non-codon 600 BRAF mutations in different cancer types.
• To explore the association of BRAF mutations with other genetic alterations, such as RAS mutations.

Main Methods:

• Categorization of BRAF mutations by kinase activity.
• Analysis of 1027 lung cancer, colorectal cancer, and melanoma specimens using next-generation sequencing.
• Assessment of mutation frequencies and co-occurrence with other mutations (KRAS, NRAS, PIK3CA).

Main Results:

• Non-codon 600 BRAF mutations were found in 37% of BRAF-mutated tumors.
• Kinetic activity profiles: 75% kinase-activated, 15% kinase-impaired, 10% kinase-unknown.
• Kinase-impaired BRAF mutants (e.g., p.D594G, p.D594N) were more frequent in lung cancers and associated with concurrent KRAS/NRAS mutations.

Conclusions:

• BRAF mutants with impaired or unknown kinase activity, and those co-occurring with RAS mutations, are present in lung, colorectal, and melanoma cancers.
• These findings highlight the heterogeneity of BRAF mutations beyond the V600E site.
• Tailoring therapeutic strategies based on BRAF mutant kinase activity and co-mutations is a promising direction for cancer treatment.