The RSK, being a common effector of the MAPK signalling pathway, was highly activated in the resistant melanoma cell lines as shown both by an increased activating phosphorylation of RSK (PT359/S363-RSK) and by an elevated phosphorylation of its target YB-1 (PS102-YB-1) (Figure 1B). This evidence concerns the gene RPS6KA2 and melanoma.