Phosphorylation of the well-described RSK target Y-box binding protein 1 (YB-1) at serine 102 (PS102-YB-1), a surrogate marker for RSK activity, could be effectively and dose-dependently suppressed in 451LU and WM3918 melanoma cell lines as respective models for the BRAFMut and NF-1LOF mutational subgroups. The gene discussed is RPS6KA1; the disease is melanoma.