Accumulation of cytosolic calcium induces necroptotic cell death in human neuroblastoma.

Necrosis has been studied extensively since the early days of medicine, with some patterns of necrosis found to be programmed like apoptotic cell death. However, mechanisms of programmed necrosis (necroptosis) are yet to be fully elucidated. In this study, we investigated how the hemagglutinating virus of Japan-envelope (HVJ-E) induces necrosis in mouse xenografts of human neuroblastoma cells. HVJ-E-induced necrosis in this system was found to depend on phosphorylation of the death receptor kinase receptor interacting protein kinase 1 (RIP1) and on the production of reactive oxygen species. This process was interpreted as necroptosis, based on its suppression by the small molecule necrostatin-1, and it did not involve the TNF-α receptor pathway. We also demonstrated that increased concentrations of cytoplasmic calcium triggered necroptosis by activating calcium-calmodulin kinase (CaMK) II. Finally, we determined that RIP1 phosphorylation was mediated by CaMK II activation. Together, our results define an upstream pathway for the activation of necroptosis in neuroblastoma cells, with potential therapeutic implications.