Caspase-8 deficiency induces a switch from TLR3 induced apoptosis to lysosomal cell death in neuroblastoma

Area of Science:

• Immunology
• Cell Biology
• Oncology

Background:

• Toll-like receptor 3 (TLR3) typically mediates apoptosis via Caspase-8 in cancer cells.
• Caspase-8 is a key protease in the extrinsic apoptosis pathway.

Purpose of the Study:

• To investigate alternative programmed cell death pathways induced by TLR3 activation in Caspase-8 deficient cancer cells.
• To elucidate the role of lysosomal membrane permeabilization (LMP) in TLR3-mediated cell death.

Main Methods:

• Activation of TLR3 in Caspase-8 negative neuroblastoma cell line (SH-SY5Y).
• Assessment of cell death, caspase activation, and lysosomal permeabilization.
• Inhibition of caspase activity to determine its role in the death pathway.

Main Results:

• TLR3 activation in Caspase-8 negative cells induced a form of programmed cell death distinct from apoptosis.
• Cell death was characterized by lysosomal permeabilization.
• Lysosomal permeabilization and cell death occurred independently of caspase activity, preceding caspase activation.

Conclusions:

• Lysosomal membrane permeabilization (LMP) serves as a default cell death mechanism in cancer cells lacking Caspase-8.
• TLR3 activation can initiate LMP-driven cell death when the apoptotic pathway is impaired.