STAT1 and melanoma: To address the role of PARP14 in spontaneously arising acquired resistance to α-PD-1 therapy, we firstly validated whether PARP14 expression could be induced by α-PD-1 therapy in our syngeneic mice models, as expression data from human melanoma biopsies32 indicated a modest but significant increase in PARP14 mRNA in α-PD-1 on-treatment melanoma biopsies compared to pre-treatment biopsies that correlated with increased IFNG and STAT1 mRNA (Supplementary Fig. 12A, B).