Blockade of Tumor TAK1 Induces DNA Damage and Immunogenic cGAS-STING Pathway Activation in Pancreatic Cancer.

BACKGROUND & AIMS: Targeting the transforming growth factor-β (TGF-β) pathway to reverse the immunologically "cold" tumor microenvironment of pancreatic ductal adenocarcinoma (PDAC) remains clinically unsuccessful, warranting novel therapeutic strategies.

METHODS: We performed multiplex immunohistochemistry on human PDAC samples to correlate cell-type-specific TGF-β pathway activation and CD8+ T-cell abundance and developed a tumor and T-cell coculture to interrogate the TGF-β pathways that promote T-cell-mediated cytotoxicity. We employed newly generated genetically engineered mouse models and a specific pathway inhibitor and confirmed our findings using single-cell RNA sequencing, flow cytometry, and multiplex immunohistochemistry. We performed proteomics and various in vitro and in vivo assays to establish the mechanisms.

RESULTS: We found TGF-β-activated kinase 1 (TAK1, Map3k7) to be aberrantly activated in PDAC cells and correlates with T-cell dysfunction. Pharmacological inhibition with Takinib, or genetic deletion of tumor Map3k7 in an autochthonous p48-Cre/Trp53f/f/LSL-KrasG12D genetically engineered mouse model, enhances CD4+ and CD8+ effector T-cell infiltration and renders immune checkpoint blockade effective. Mechanistically, TAK1 inhibition induces DNA damage and cytoplasmic DNA leakage, which activates the cyclic GMP-AMP synthase-Stimulator of Interferon Genes DNA sensing pathway, triggering inflammatory responses that promote adaptive immune cell infiltration. At the molecular level, TAK1 phosphorylates Ephrin Receptor A2 at Serine 897, which in turn phosphorylates RAD51 at Tyrosine 315, a key DNA repair protein involved in homologous recombination.

CONCLUSIONS: We uncover TAK1 as a critical mediator in maintaining genomic integrity and highlight its potential as a therapeutic target to induce an inflamed tumor microenvironment that sensitizes PDAC to immune checkpoint blockade.