To study potential function of ISG15 downregulation in cisplatin‐resistant ovarian cancer cells, wild‐type (WT) or nonISGylatable mutant (G156/157A mutant, Mut) ISG15 was ectopically expressed in SKOV3/DDP and A2780/DDP cells using lentivirus (Figure 1C). The gene discussed is ISG15; the disease is ovarian carcinoma.