Marked genetic differences between BRAF and NRAS mutated primary melanomas as revealed by array comparative genomic...

Area of Science:

• Genomics
• Oncology
• Molecular Biology

Background:

• Somatic mutations in BRAF and NRAS oncogenes are early events in melanoma initiation.
• These mutations alone are insufficient for melanoma tumor progression.

Purpose of the Study:

• To investigate distinct genomic imbalances in primary melanomas with different BRAF or NRAS genotypes.
• To identify commonly co-occurring genomic regions in different melanoma subgroups.

Main Methods:

• Array comparative genomic hybridization (aCGH) for copy number changes in 47 primary melanomas.
• BRAF and NRAS mutation screening using melting curve analysis.
• Reverse transcription PCR and fluorescence in-situ hybridization for result confirmation.

Main Results:

• Distinct genomic profiles were observed between BRAF and NRAS mutated melanomas.
• BRAF-mutated melanomas showed more frequent losses on 10q23-q26 and gains on chromosome 7 and 1q23-q25.
• NRAS-mutated melanomas frequently exhibited loss on 11q23-q25; those without BRAF/NRAS mutations had alterations in chromosomes 17 and 4.
• Random forest analysis identified 15 classifiers for BRAF mutation with 87% prediction accuracy.
• Extensive alterations in EGF/MAPK-JAK pathways were noted in BRAF-mutated melanomas.

Conclusions:

• Significant genetic pattern differences exist between BRAF and NRAS mutated melanoma subgroups.
• These distinct genetic profiles suggest cooperating oncogenic events contribute to malignant melanoma development alongside BRAF or NRAS mutations.