CRKL and hepatocellular carcinoma: As an example, Liu et al, using an in situ proximity ligation assay to identify and quantify 67 endogenous protein-protein interactions among 21 interlinked pathways, found that CrkL, involved in extracellular-signal-regulated kinase (Erk) pathway, can be a prognostic marker in hepatocellular carcinoma that strongly correlates with disease-free and overall survival [13].