PDCD1 and melanoma: Anti-PD-1 unresponsiveness in mouse models of melanoma was reversed by a small molecule, curaxin CBL0137, which potently activated Z-form nucleic acid binding protein 1 (ZBP1)-dependent necroptosis by triggering Z-DNA formation in tumor-infiltrating fibroblasts, irrespective of the potential for low necroptotic gene expression in melanoma cells [96].