PLSCR3 Deficiency Triggers mtDNA-Driven cGAS-STING Activation to Potentiate Antitumor Immunity in Colorectal Cancer

Area of Science:

• Mitochondrial biology
• Immunology
• Oncology

Background:

• Immunotherapy for colorectal cancer (CRC) is limited in microsatellite-stable (MSS) tumors.
• Mitochondrial DNA (mtDNA) leakage activates the cGAS-STING pathway, inducing antitumor immunity.
• Endogenous regulators of mtDNA release in CRC, especially in the inner mitochondrial membrane, are not well understood.

Purpose of the Study:

• To identify endogenous regulators of mtDNA leakage and cGAS-STING pathway activation in CRC.
• To investigate the role of Phospholipid Scramblase 3 (PLSCR3) in regulating mitochondrial integrity and immune response in CRC.
• To evaluate PLSCR3 as a potential therapeutic target for enhancing immunotherapy in MSS CRC.

Main Methods:

• Bioinformatic analysis of CRC cohorts (TCGA) to identify dysregulated mitochondria-associated genes.
• Functional validation using siRNA knockdown and CRISPR/Cas9 knockout in CRC cell lines (HT29, CT26).
• Assessment of mitochondrial integrity, mtDNA leakage, cGAS-STING activation, NK cell cytotoxicity, and in vivo anti-PD-1 therapy response in mouse models.

Main Results:

• PLSCR3 deficiency disrupted mitochondrial integrity, leading to increased cytosolic mtDNA and robust cGAS-STING pathway activation.
• PLSCR3 knockdown enhanced NK cell-mediated killing of CRC cells in vitro.
• PLSCR3 knockout potentiated anti-PD-1 therapy efficacy in vivo, increasing intratumoral T cell infiltration and activation in MSS CRC.

Conclusions:

• PLSCR3 is a novel negative regulator of mtDNA-associated cGAS-STING activation in CRC.
• PLSCR3 maintains mitochondrial homeostasis, thereby limiting innate immune signaling and reducing anti-PD-1 therapy sensitivity.
• Targeting PLSCR3 presents a promising strategy to improve immunotherapy outcomes in colorectal cancer.