Biology subjects

Meier-Stephenson, V.

Publications and source records attributed to Meier-Stephenson, V..

3 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↗

bioRxiv2021

Identification and characterization of a G-quadruplex structure in the pre-core promoter region of hepatitis B virus

Worldwide, [~]250 million people are chronically infected with the hepatitis B virus (HBV) and are at increased risk of cirrhosis and hepatocellular carcinoma. The HBV persists as covalently closed circular DNA (cccDNA), which acts as the template for all HBV mRNA transcripts. Nucleos(t)ide analogs do not directly target the HBV cccDNA and cannot eradicate the HBV. We have discovered a unique structural motif, a G-quadruplex in HBVs pre-core promoter region that is conserved amongst nearly all genotypes, and is central to critical steps in the viral life-cycle including the production of pre-genomic RNA, core and polymerase proteins, and encapsidation. Thus, an increased understanding of the HBV pre-core may lead to the development of novel anti-HBV cccDNA targets. We utilized biophysical methods to characterize the presence of the G-quadruplex, employed assays using a known quadruplex- binding protein (DHX36) to pull-down HBV cccDNA, and compared HBV infection in HepG2 cells transfected with wild-type and mutant HBV plasmids. This study provides insights into the presence of a G-quadruplex in the HBV pre-core promoter region essential for HBV replication. The evaluation of this critical host-protein interaction site in the HBV cccDNA may ultimately facilitate the development of novel anti-HBV therapeutics against the resilient cccDNA template.

biophysics↗