ZUP1 and cancer: A recent study identified COP9 signalosome 5 (CSN5) as a DUB that mediates deubiquitination and stabilization of PD-L1 in cancer cells.100 Initially shown to remove the ubiquitin-like modifier Nedd8 from neddylated proteins,201 CSN5 was later on found to also possess DUB activity.202 Interestingly, CSN5 is required for PD-L1 stabilization and immunosuppression stimulated by the proinflammation cytokine TNFα.