Exome sequencing identifies recurrent somatic MAP2K1 and MAP2K2 mutations in melanoma

Area of Science:

• Oncology
• Genetics
• Molecular Biology

Background:

• Melanoma is a significant skin cancer with complex genetic underpinnings.
• Understanding somatic mutations is crucial for developing effective cancer therapies.

Purpose of the Study:

• To identify somatic mutations in melanoma cell lines and patient samples.
• To investigate the role of specific mutations in melanoma development and drug resistance.

Main Methods:

• Exome sequencing of melanoma cell lines and matched germline DNA.
• Analysis of somatic mutation signatures to identify UV-induced DNA repair patterns.
• Screening of a larger cohort for recurrent mutations in key genes.

Main Results:

• High numbers of somatic mutations with UV-repair hallmarks were observed in most melanoma samples.
• Two metastatic samples lacked UV-repair signatures.
• Gain-of-function mutations in MAP2K1 and MAP2K2 (MEK1/MEK2) were identified in melanomas with non-canonical BRAF mutations, leading to constitutive ERK phosphorylation and MEK inhibitor resistance.
• Recurring somatic MAP2K1/MAP2K2 mutations were found in 8% of the screened melanoma cohort.
• Frequent missense and nonsense somatic mutations were detected in candidate melanoma genes FAT4, LRP1B, and DSC1.

Conclusions:

• Somatic mutations, particularly those related to UV exposure, are prevalent in melanoma.
• MAP2K1/MAP2K2 mutations represent a significant mechanism of resistance to MEK inhibitors in melanoma.
• FAT4, LRP1B, and DSC1 are identified as potential novel cancer genes in melanoma.