KRAS and colorectal cancer: The most common cause for this deregulation is mutation in RAS/RAF family members, with mutant KRAS (40% of colorectal cancer cases) and BRAF (12% of cases) being the most prevalent16,18,19 Since MEK1/2 lies directly downstream of these mutations and uniquely phosphorylates ERK1/2, the MEK1/2 kinases have been identified as extremely attractive targets for therapeutic intervention.