PDCD1 and melanoma: Based on these findings, we speculate that the MM_Immune subgroup plays a crucial role in determining the efficacy of anti-PD-1 therapy in melanoma.We then mapped the gene regulatory networks that govern these subgroups and found that MM_Immune cells exhibited elevated regulon activity for CCAAT enhancer binding protein delta (CEBPD) and forkhead box D3 (FOXD3) (Figure 2E).