Schweinfurthin induces ICD without ER stress and caspase activation

Area of Science:

• Immunology
• Cancer Biology
• Pharmacology

Background:

• Previous studies demonstrated 5'-methoxyschweinfurthin G (MeSG) enhances anti-PD1 therapy and induces protective anti-tumor immunity.
• Investigating the precise mechanisms of MeSG-induced immunogenic cell death (ICD) is crucial for its therapeutic development.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying MeSG-induced immunogenic cell death (ICD).
• To characterize the differences between MeSG-induced ICD and the canonical pathway.

Main Methods:

• Assessed calreticulin (CRT) exposure on tumor cell surfaces following MeSG treatment.
• Evaluated dendritic cell phagocytosis of MeSG-treated tumor cells in vitro.
• Investigated the roles of ER stress, PERK, caspases, ERp57, and ER-to-Golgi transport in MeSG-induced ICD.

Main Results:

• MeSG induced time- and concentration-dependent cell surface CRT exposure and enhanced dendritic cell phagocytosis.
• MeSG-induced CRT exposure occurred independently of ER stress, PERK, and ERp57.
• Caspase inhibitors only partially rescued cells from apoptosis but did not affect CRT exposure.
• An intact ER to Golgi transport system was essential for MeSG-induced CRT exposure.

Conclusions:

• MeSG induces immunogenic cell death (ICD) through a novel pathway involving CRT exposure, distinct from canonical mechanisms.
• These findings support the development of schweinfurthins to augment immunotherapy responses.
• Further research into the specific mechanisms of MeSG-induced ICD is warranted.