Targeting Oncogenic BRAF in Human Cancer

Abstract

MAPK pathway activation is a frequent event in human cancer and is often the result of activating mutations in the BRAF and RAS oncogenes. BRAF missense kinase domain mutations, the vast majority of which are V600E, occur in approximately 8% of human tumors. These mutations, which are non-overlapping in distribution with RAS mutations, are observed most frequently in melanoma but also in tumors arising in the colon, thyroid, lung and other sites. Supporting its classification as an oncogene, (V600E)BRAF stimulates ERK signaling, induces proliferation and is capable of promoting transformation. Given the frequent occurrence of BRAF mutations in human cancer and the continued requirement for BRAF activity in the tumors in which it is mutated, efforts are underway to develop targeted inhibitors of BRAF and its downstream effectors. These agents offer the possibility of greater efficacy and less toxicity than the systemic therapies currently available for tumors driven by activating mutations in the MAPK pathway. Early clinical results with the BRAF-selective inhibitors PLX4032 and GSK2118436 suggest that this strategy will prove successful in a select group of patients whose tumors are driven by oncogenic BRAF.