ERBB2 and melanoma: We identified epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), melanoma-associated chondroitin sulfate proteoglycan (MCSP), and programmed death ligand 1 (PD-L1) as being expressed by A375 tumor cells (Supplemental Figure 6B, top panel) and by established tumors (Supplemental Figure 6B, bottom panel).