Although IKK1 is a critical component of the non-canonical NF-κB pathway, it should be mentioned that this kinase also plays a prominent role in the negative regulation of both canonical and noncanonical NF-κB pathways. Macrophages from IKK1-deficient mice or knockin mice expressing inactive IKK1 show increased production of proinflammatory cytokines as a result of enhanced IKK2 activation and IκBα degradation [34]. IKK1 has also been shown to inhibit nuclear NF-κB and to downregulate proinflammatory signalling by phosphorylating STAT1 [35]. Interestingly, a recent study has demonstrated that IKK1 phosphorylates NIK in negative feedback regulation of the noncanonical NF-κB pathway [36], supporting the idea that IKK1 plays important roles in terminating both canonical and noncanonical NF-κB pathways with possible implications for chronic inflammatory diseases like RA.