Glioblastoma constitute the most frequent and deadliest brain tumors of 
astrocytic origin. They are resistant to all current therapies and are 
associated with a high rate of recurrence. Glioblastoma were previously shown to 
respond to treatments by 5-aminolevulinic acid (5-ALA)-based photodynamic 
therapy (PDT) mainly by activating a necrotic type of cell death. The 
receptor-interacting protein 3 (RIP3) has recently been outlined as a key 
mediator of this caspase-independent form of programmed cell death. In the 
present study, we analyzed the necrotic mechanism induced by 5-ALA-PDT in human 
glioblastoma cells and explored the role of RIP3 in this context. Our results 
show that PDT-induced necrosis is dependent on RIP3, which forms aggregates and 
colocalizes with RIP1 following photosensitization. We demonstrate that 
PDT-mediated singlet oxygen production is the cause of RIP3-dependent necrotic 
pathway activation. We also prove that PDT induces the formation of a 
pro-necrotic complex containing RIP3 and RIP1 but lacking caspase-8 and FADD, 
two proteins usually part of the necrosome when TNF-α is used as a stimulus. 
Thus, we hypothesize that PDT might lead to the formation of a different 
necrosome whose components, besides RIP1 and RIP3, are still unknown. In most 
cases, glioblastoma are characterized by a constitutive activation of NF-κB. 
This factor is a key regulator of various processes, such as inflammation, 
immune response, cell growth or apoptosis. Its inhibition was shown to further 
sensitize glioblastoma cells to PDT-induced necrosis, however, no difference in 
RIP3 upshift or aggregation could be observed when NF-κB was inhibited.