PMEL and melanoma: Proteins identified in higher abundance in the tumors with negative PC2 were involved in melanogenesis, for example, PMEL (which negatively correlated with the MEKi resistance phenotype in cell lines) and proteins with lower abundance were those which positively correlated with the MEKi resistance phenotype observed in melanoma cell lines (i.e., Fascin 1, PDLIM5, PDLIM7, and Zyxin) (see Fig. 2 and Supplementary Figure S3).