Carriers Multimerize STING Protein Fragments to Activate Type I Interferon Signaling in STING-Deficient Cancer Cells.

Area of Science:

• Immunology
• Molecular Biology
• Cancer Research

Background:

• The stimulator of interferon genes (STING) pathway is crucial for innate immunity and cancer immunotherapy.
• Loss of STING expression in cancer cells limits the efficacy of current STING agonists.
• Activating the STING pathway can induce anti-tumor immune responses.

Purpose of the Study:

• To develop a novel strategy for activating the STING pathway in cancer immunotherapy.
• To overcome the challenge of STING deficiency in cancer cells.
• To investigate the mechanism by which cytosolic delivery of a STING fragment enables therapeutic activity.

Main Methods:

• Delivery of a soluble STING protein fragment into the cytosol of cancer cells.
• Assessing the activation of downstream signaling molecules TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3).
• Evaluating the induction of a Type I interferon response in STING-proficient and -deficient cancer cell lines.

Main Results:

• Cytosolic delivery of a STING fragment activates Type I interferon response, even in STING-deficient cells.
• Complexation by delivery vehicles promotes STING fragment multimerization, enabling sustained activity.
• STING fragment activity is independent of its crystallizable domain, suggesting non-canonical multimerization.
• The strategy successfully induced immune responses in various cancer cell lines.

Conclusions:

• Cytosolic delivery of STING fragments offers a promising approach to cancer immunotherapy by bypassing STING deficiency.
• Delivery vehicles can be engineered to modify protein therapeutics into active forms.
• This work provides a proof of concept for developing STING fragment delivery systems for immunotherapy.