The IKK-related kinases: from innate immunity to oncogenesis

Over the past four years, the field of the innate immune response has been highly influenced by the discovery of the I kappa B kinase (IKK)-related kinases, TANK Binding Kinase 1 (TBK1) and IKKi, which regulate the activity of interferon regulatory factor (IRF)-3/IRF-7 and NF-kappa B transcription factors. More recently, additional essential components of the signaling pathways that activate these IKK homologues have been discovered. These include the RNA helicases RIGi and MDA5, and the downstream mitochondrial effector known as CARDIF/MAVS/VISA/IPS-1. In addition to their essential functions in controlling the innate immune response, recent studies have highlighted a role of these kinases in cell proliferation and oncogenesis. The canonical IKKs are well recognized to be a bridge linking chronic inflammation to cancer. New findings now suggest that the IKK-related kinases TBK1 and IKKi also participate in signaling pathways that impact on cell transformation and tumor progression. This review will therefore summarize and discuss the role of TBK1 and IKKi in cellular transformation and oncogenesis by focusing on their regulation and substrate specificity.