MAPK1 and hepatocellular carcinoma: To validate the associations, causality should be tested by SSTR2 loss- and gain-of-function in HCC models with readouts of proliferation, apoptosis, migration/invasion, and MAPK/ERK and PI3K/AKT signaling, and by probing ligand dependence (somatostatin analogs/antagonists) with internalization/β-arrestin assays.