MEK (mitogen-activated protein kinase kinase-MAPKK) 1/2 is a transducer of the growth factor receptor-RAS-RAF-MAPK signalling cascade and plays a relevant role in development and progression of human cancers, such as colorectal cancer (CRC), non small cell lung cancer (NSCLC).
On the basis of the frequent involvement of the Ras-RAF-MEK-ERK signaling pathway in human non-small cell lung carcinoma (NSCLC), we have explored the target cell availability, reversibility, and cell type specificity of transformation by oncogenic C-RAF.
Direct inhibition of RAS is not yet possible, whereas inhibition of RAF is already established in malignant melanoma and under investigation in non-small-cell lung cancer (NSCLC).
Using a panel of non-small cell lung cancer (NSCLC) lines, we show here that MAP-ERK kinase (MEK) and RAF inhibitors are selectively toxic for the KRAS-mutant genotype, whereas phosphoinositide 3-kinase (PI3K), AKT, and mTOR inhibitors are not.
Although >90% of BRAF mutations in melanoma involve codon 599 (57 of 60), 8 of 9 BRAF mutations reported to date in NSCLC are non-V599 (89%; P < 10(-7)), strongly suggesting that BRAF mutations in NSCLC are qualitatively different from those in melanoma; thus, there may be therapeutic differences between lung cancer and melanoma in response to RAF inhibitors.