KRAS and non-small cell lung carcinoma: While both NF1 loss and KRAS activating mutation lead to MAPK pathway activation and sensitivity to MEK inhibition in vitro, the use of MEK inhibitors has failed to demonstrate efficacy for patients with KRAS-mutated non-small cell lung cancer, likely due to the presence of several mechanisms of bypass of the MAPK pathway inhibition, such as increased AKT signaling in KRAS-altered tumors (23).