In certain conditions (e.g., downstream of certain viral receptors or in certain cancers), the IKKβ-related kinases IKKε and TBK1 can also activate NF-κB via IκBα, RelA and c-Rel phosphorylation [9], while IKK-independent mechanisms have also been reported (e.g., in response to DNA damage or hypoxia). Here, REL is linked to cancer.