The panel of 49 melanoma cell lines shown in Figure 1, was further characterized for several molecular or phenotypic features associated with drug resistance [20–23], but no significant association was found, between the drug susceptibility groups and: a) the PTEN, MDM4 and MDM2 expression levels; b) the constitutive p-ERK, p-AKT and p-S6 levels (Supplementary Table 1A–1C and 1E–1G). Here, MDM4 is linked to melanoma.