In many human cancers, including thyroid, breast, lung, colorectal cancers, and melanoma, the MAPK pathway is constitutively activated through mutations of its effectors: tyrosine kinases receptor (RTKs), their direct targets such as RAS, or downstream kinases belonging to the MAPK pathway [47,48,49,50,51,52,53,54,55,56]. The gene discussed is NTRK1; the disease is colorectal cancer.