These pan-negative melanomas did not harbor mutations in MEK1 or 2 [29–31], nor did they display increased RAS activity [27, 28], both of which are implicated in previous citings of paradoxical MEK1/2 activation upon MEK1/2 inhibition, specifically in the BRAF V600-mutant setting (Supplementary Table S4). Here, MAP2K1 is linked to melanoma.