Tissue Factor Promotes TREX1 Protein Stability to Evade cGAS-STING Innate Immune Response in Pancreatic Ductal Adenocarcinoma

Academic Background

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most challenging malignancies worldwide, with increasing incidence and mortality rates, particularly in advanced stages. Despite significant progress in chemotherapy and immunotherapy for various cancers, PDAC remains largely refractory to these treatments. Recent studies have identified the fibrotic stroma as a physical barrier to chemotherapy and immune infiltration in PDAC, but the intrinsic mechanisms of immune evasion in tumor cells remain poorly understood. Tissue factor (TF), a glycoprotein overexpressed in many malignancies, is found in approximately 80% of PDAC cases. TF not only participates in coagulation but also promotes tumor growth, metastasis, and angiogenesis through multiple mechanisms. However, the specific role of TF in PDAC and its relationship with immune evasion remain unclear.

This study aims to explore how TF promotes immune evasion in PDAC by regulating the cGAS-STING innate immune pathway and to investigate the potential of TF as a therapeutic target.

Source of the Paper

This paper was co-authored by Yinyin Xue, Yue Wang, Zhiqiang Ren, and Ker Yu, all affiliated with the Department of Pharmacology, School of Pharmacy, Fudan University. The paper was published in Oncogene in 2024, with the DOI: 10.1038/s41388-024-03248-1.

Research Process and Results

1. High TF Expression in PDAC is Associated with Immune Suppression

The researchers first analyzed tissue microarrays (TMA) from 80 PDAC patients using immunohistochemistry (IHC) and multiplex fluorescence staining (TSA). They found that high TF expression (TF-high) accounted for 68.75% of the cases, and these patients had higher tumor stages and poorer prognosis. In TF-high tumors, levels of p-STING and p-TBK1 were significantly reduced, indicating suppression of the cGAS-STING pathway. Additionally, TF-high tumors showed reduced infiltration of immune effector cells (e.g., CD8+ T cells) and increased infiltration of immunosuppressive M2 macrophages. Analysis of the TCGA database further confirmed that TF-high tumors had significantly lower expression of interferon-stimulated genes (ISGs) and chemokines (e.g., CCL5, CXCL9-11).

2. TF Knockout Restores STING Signaling and Inhibits Tumor Growth

To validate the role of TF in tumor cells, the researchers used CRISPR/Cas9 technology to knockout the TF gene (TF-KO) in mouse KPC cells. The results showed that TF-KO did not affect the in vitro proliferation of KPC cells but significantly inhibited tumor growth in an orthotopic mouse model. Immunohistochemistry and multiplex fluorescence staining revealed that TF-KO tumors exhibited increased expression of DNA damage marker γ-H2AX and STING pathway activation markers (p-TBK1, p-STAT1), along with increased infiltration of cytotoxic T cells and dendritic cells. Furthermore, TF-KO cells showed reduced levels of p-AKT and p-ERK, while levels of p-TBK1, p-STAT1, and p-IRF3 were significantly elevated, indicating restoration of the STING pathway.

3. TF-Targeted Therapy Restores STING Signaling in Human PDAC Models

The researchers further validated the role of TF in human PDAC cell lines (HPAF-II and BXPC3). Treatment with TF-shRNA or the anti-TF antibody Husc1-39 significantly increased the expression of STING pathway activation markers (p-TBK1, p-STAT1, and p-IRF3). RNA sequencing analysis revealed that TF inhibition significantly upregulated the mRNA levels of ISGs and chemokines (e.g., CCL5, CXCL10). In a nude mouse model, orthotopic transplantation of HPAF-II cells followed by treatment with Husc1-39 or TF-shRNA significantly inhibited tumor growth and increased tumor cell apoptosis. Additionally, TF inhibition promoted the infiltration of NK cells, mature dendritic cells, and M1-like macrophages.

4. TF Inhibition Activates the cGAS-STING Pathway via TREX1 Degradation

The researchers found that TF inhibition led to significant accumulation of cytoplasmic micronuclei and cGAS in tumor cells, suggesting that TF promotes immune evasion by suppressing the cGAS-STING pathway. Further studies revealed that TF inhibition triggered rapid degradation of TREX1 protein, an established innate immune checkpoint exonuclease that degrades micronucleus DNA. Overexpression experiments confirmed that TREX1 degradation is a key step in the activation of the cGAS-STING pathway following TF inhibition. Moreover, TF inhibition-induced TREX1 degradation was dependent on the proteasome pathway.

5. Synergistic Effect of TF Inhibition and STING Agonists

The researchers also explored the synergistic effect of TF inhibition and STING agonists. In co-culture experiments with PBMCs and tumor cells, the combination of TF inhibition and the STING agonist AN014 significantly increased the secretion of CXCL10 and IFN-γ and enhanced tumor cell killing. Additionally, the researchers developed a TF antibody-STING agonist ADC (Husc1-39-AN014), which demonstrated significant antitumor activity both in vitro and in vivo, significantly enhancing STING pathway activation and immune effector cell infiltration.

Conclusions and Significance

This study is the first to reveal that TF promotes immune evasion in PDAC by stabilizing TREX1 protein to suppress the cGAS-STING innate immune pathway. TF inhibition reshapes the tumor microenvironment from an “immune-cold” to an “immune-hot” state. TF-targeted therapy can be used alone or in combination with immunotherapy, providing a new therapeutic strategy for TF-positive PDAC and triple-negative breast cancer (TNBC).

Research Highlights

1. TF Suppresses the cGAS-STING Pathway by Stabilizing TREX1 Protein: This study is the first to reveal that TF stabilizes TREX1 protein to suppress the cGAS-STING pathway, providing new insights into the role of TF in tumor immune evasion.
2. TF Inhibition Reshapes the Tumor Microenvironment: TF inhibition significantly increases the infiltration of immune effector cells and promotes chemokine secretion, thereby enhancing antitumor immune responses.
3. Development of a TF Antibody-STING Agonist ADC: The researchers developed a novel TF antibody-STING agonist ADC, which demonstrated significant antitumor activity in vitro and in vivo, offering a new therapeutic option for TF-positive PDAC and TNBC.

Research Value

The scientific value of this study lies in its revelation of the mechanism by which TF suppresses the cGAS-STING pathway through the stabilization of TREX1 protein, providing new theoretical insights into tumor immune evasion. Furthermore, the development of TF-targeted therapy and the TF antibody-STING agonist ADC offers new strategies for the treatment of PDAC and TNBC, with significant clinical application prospects.