Abstract
Background:
Immunotherapy resistance in microsatellite-stable colorectal cancer (CRC) remains a major therapeutic challenge. Recent strategies to overcome the immunosuppressive tumor microenvironment have focused on reactivating innate immune pathways, particularly the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) axis, which links cytosolic DNA sensing to proinflammatory cytokine production and T cell activation. Although STING agonists show promise, their clinical application is limited by poor drug stability and cytokine storms triggered by excessive STING activation. This study establishes valosin-containing protein (VCP/p97) as a druggable target to potentiate cGAS-STING-driven antitumor immunity, offering a promising therapeutic strategy to overcome immunotherapy resistance in CRC.
Methods:
Bioinformatics analysis and compound screening were conducted to find potential regulators of the cGAS-STING pathway. Western blotting, co-immunoprecipitation, immunofluorescence staining, real-time PCR, molecular docking, and RNA sequencing (RNA-seq) were performed to identify VCP as a new regulator of STING proteostasis. Wild-type/Sting1-/- C57BL/6J mice with MC38 tumors and BALB/c mice with CT26 tumors were employed to evaluate the in vivo therapeutic effects of the VCP inhibitor and STING agonist/chemotherapy/immunotherapy combination. Flow cytometry, ELISA, immunofluorescence staining, and RNA-seq were performed to analyze the effectiveness of these interventions in remodeling the tumor microenvironment.
Results:
In this study, we determined the importance of the cGAS-STING pathway activity in macrophages for antitumor immunity by bioinformatics analysis and identified VCP as a critical negative regulator of STING through analyzing genome-wide CRISPR screening data and performing pharmacological validation. Mechanistically, VCP directly interacts with STING and modulates its protein stability. Pharmacological inhibition of VCP using CB-5083 stabilized STING protein, increased the pool of endoplasmic reticulum (ER)-localized STING, amplified STING agonist-induced signaling, and synergized with STING agonists to suppress tumor growth in murine models. Furthermore, CB-5083 significantly enhanced the antitumor efficacy of chemotherapy and immunotherapy in CRC models, while remodeling the immune microenvironment by increasing CD86+ macrophages and cytotoxic CD8+ T cell infiltration.
Conclusions:
Our study identifies VCP as a new regulator of STING proteostasis and provides a novel strategy to boost antitumor immunity by pharmacologically increasing ER-resident STING via VCP inhibition, offering a clinically actionable avenue to improve CRC therapy.