A central role of IKK2 and TPL2 in JNK activation and viral B-cell transformation

I kappa B kinase 2 (IKK2) is well known for its pivotal role as a mediator of the canonical NF-kappa B pathway, which has important functions in inflammation and immunity, but also in cancer. Here we identify a novel and critical function of IKK2 and its co-factor NEMO in the activation of oncogenic c-Jun N-terminal kinase (JNK) signaling, induced by the latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV). Independent of its kinase activity, the TGF beta -activated kinase 1 (TAK1) mediates LMP1 signaling complex formation, NEMO ubiquitination and subsequent IKK2 activation. The tumor progression locus 2 (TPL2) kinase is induced by LMP1 via IKK2 and transmits JNK activation signals downstream of IKK2. The IKK2-TPL2-JNK axis is specific for LMP1 and differs from TNF alpha, Interleukin-1 and CD40 signaling. This pathway mediates essential LMP1 survival signals in EBV-transformed human B cells and post-transplant lymphoma, and thus qualifies as a target for treatment of EBV-induced cancer. IKK2 is the main mediator of the NF-kappaB pathway. Here, the authors demonstrate that LMP1 sustains the survival of Epstein-Barr virus-transformed human B cells and post-transplant lymphoma through IKK2 that induces JNK signaling through TPL2.