MAPK3 and colorectal cancer: Another example is the relative insensitivity of BRAFV600E colorectal cancer cells to selective BRAF inhibitors [361] due to loss ERK1/2-mediated feedback inhibition of EGFR activity; treatment of these cells with BRAF inhibitors (or MEK inhibitors) in combination EGFR inhibitors is synergistic because it prevents the activation of EGFR that occurs following ERK1/2 inhibition.