Mutations in BRAF
Oncogenic mutations in the BRAF gene destroy the kinase domain, which results in constitutive activation of MAPK (mitogen-activated protein kinase) route, thereby stimulating the growth of abnormal cells. Activation of the MAPK pathway also occurs as a result of somatic mutations of other oncogenes, such as N-RAS. More than 30 mutations in the BRAF coding sequence have been detected, but the sequence encoding the kinase domain, in exon 15,contains a “hotspot” which accumulates more than 90% of mutations located in the BRAF gene, codon 600. The V600 mutation in the BRAF gene are found in approximately in 12-15% of sporadic colorectal cancers (CRC) as well as in premalignant lesions such as adenomas, hyperplastic polyps and early stages of cancer colorectal. It is also the most common mutation in melanoma.
Recent studies have detected mutations at codons 594 and 596 in BRAF, identifying a new molecular subtype of metastatic colorectal cancer with favorable prognosis.