KRAS and lung adenocarcinoma: The MAPK/ERK pathway, which is critical for cellular responses to extracellular stimuli, has been demonstrated to be a key regulator of metabolism during tumorigenesis.[35] Constitutive activation of the MAPK/ERK pathway frequently occurs in lung adenocarcinoma due to mutations in genes such as EGFR or KRAS.[36, 37] However, whether the MAPK/ERK pathway regulates serine metabolism has not been determined.