Biology subjects

Mowat, C.

Publications and source records attributed to Mowat, C..

4 recordsLinked to original sources

bioRxiv2025

Cytosolic DNA structures produced by mismatch-repair deficiency coordinate anti-tumor immunity in colorectal cancer

Patients with the microsatellite instable (MSI) subtype of colorectal cancer (CRC) have better prognosis and immunotherapy response than patients with the chromosomally instable (CIN) subtype due to improved cytotoxic T cell responses from high neoantigen levels and production of the chemokines CXCL10 and CCL5 that recruit cytotoxic T cells. This high chemokine production in MSI CRCs is due to constitutive activation of the cytosolic DNA (cyDNA) sensor STING by specific features of MSI cyDNA that lead to more effective STING pathway activation. Here, we investigate the features of MSI and CIN cyDNA to identify structures that more effectively activate STING. We find that MSI cyDNA is enriched in G-quadruplexes which improve STING and CD8+ T cell activation. Additionally, MSI micronuclei are also more efficient at inducing chemokine expression than CIN micronuclei. However, micronuclei are less effective than free cyDNA at inducing anti-tumor immunity and instead lead to increased Treg activation and IL10 production. Overall, these data highlight the role of specific cyDNA structures in anti-tumor immunity and provide essential knowledge for improved design of therapeutic DNA-based STING agonists that could be combined with immune checkpoint therapies to improve the prognosis of poorly immunogenic tumors like CIN CRCs.

cancer biology↗

bioRxiv2024

Mechanisms of genomic instability dictate cytosolic DNA composition and dendritic cell mediated anti-tumor immunity

Patients with microsatellite instable (MSI) colorectal cancers (CRC) face better prognosis than those with the more common chromosomal instable (CIN) subtype due to improved anti-tumor immune responses characterized by high cytotoxic T cell infiltration. Previous investigation identified the cytosolic DNA (cyDNA) sensor STING as necessary for chemokine-mediated T cell recruitment in MSI CRCs. Here, we find cyDNA from MSI CRC cells is inherently more capable of inducing STING activation and induces improved cytotoxic T cell activation by dendritic cells (DCs). Sequencing indicates MSI cyDNA is enriched for microsatellites, which upon DC uptake induce anti-tumor immunity in a manner consistent with clinical MSI CRCs. Radiation also modulates cyDNA stimulation capacity through larger cyDNA size and increased mitochondrial DNA content. Identifying highly stimulatory cyDNA arising from genomic instability such as in MSI CRCs allows for optimized development of DNA-based STING agonist therapies to improve responses of CIN CRC patients to immunotherapies.

cancer biology↗

bioRxiv2023

cGAS/STING and NLRP3 cooperatively activate CD8+ T cell-mediated anti-tumor immunity in colorectal cancer

Colorectal cancer (CRC) is a highly prevalent and deadly disease that is largely refractory to immunotherapy. The only CRC subset that responds to these therapies is characterized by prevalent microsatellite instability (MSI), extensive CD8+ T cell infiltration and high expression of innate immune signaling pathways. Endogenous activation of the cGAS/STING pathway is essential for the CD8+ T cell antitumor response in MSI CRCs, suggesting that activating it in other CRCs could boost immunotherapy response rates. We show that cGAS/STING signaling can be enhanced by costimulation of the NLRP3 inflammasome and that dual stimulation increases CD8+ T cell-mediated antitumor immunity in both MSI and non-MSI CRCs. The ability of NLRP3 to boost cGAS/STING signaling was specific and did not occur with activation of other innate immune pathways such as AIM2 or TLRs. Cooperativity between cGAS/STING and NLRP3 proceeded via a positive feedback loop that was inflammasome-independent and required early crosstalk between the signaling mediators and regulation of their gene expression. Notably, increased cGAS/STING signaling enhanced CD8+ T cell activation when in conjunction with anti-PD1 immunotherapy, suggesting that signaling via NLRP3 could further boost this response and render otherwise resistant CRC susceptible to immunotherapy. SignificanceInnate immune signaling pathways cooperatively regulate CD8+ T cell-mediated antitumor immunity in both hot and cold tumors. In addition to serving as predictive biomarkers, these pathways can be therapeutically targeted to increase response rates to immunotherapy while minimizing undesirable adverse events.

cancer biology↗

bioRxiv2020

Antitumor immunity in dMMR colorectal cancers requires interferon-induced CCL5 and CXCL10

Colorectal cancers (CRCs) deficient in DNA mismatch repair (dMMR) are heavily infiltrated by CD8+ tumor infiltrating lymphocytes (TILs) and are associated with a better prognosis than the majority of CRCs. The immunogenicity of dMMR CRCs is commonly attributed to abundant neoantigen generation due to their extreme genomic instability. However, lack of neoantigenic overlap between these and other CRCs necessitates study of antigen-independent mechanisms of immune activation by dMMR CRCs in order identify therapeutic strategies for treating MMR proficient CRCs. We show here using organoid cocultures and orthotopic models that a critical component of dMMR CRCs immunogenicity is the activation and recruitment of systemic CD8+ T cells into the tumor epithelium by overexpression of the chemokines CCL5 and CXCL10. This is dependent on endogenous activation of the cGAS/STING and IFN signaling pathways by the damaged DNA in dMMR CRCs. These signaling pathways remain sensitive to exogenous stimulation in other CRCs, identifying an attractive therapeutic avenue for increasing TIL infiltration into normally immune resistant CRC subtypes. We have thus identified a key neoantigen-independent mechanism that underlies the ability for dMMR CRCs to recruit TILs into the tumor epithelium. Given that TIL recruitment is a prerequisite for effective tumor killing either by the endogenous immune system or in the context of immunotherapies, treatments that activate IFN-induced chemokine-production by tumor cells promise to improve the prognosis of patients with many different CRC subsets. Statement of SignificanceA critical component of antitumor immunity in dMMR CRCs is their ability to recruit T cells into the tumor epithelium as a prerequisite to tumor cell killing. This occurs because their extensive genomic instability leads to endogenous activation of cGAS/STING and overexpression of CCL5 and CXCL10.

cancer biology↗