Cytokine circuitry in pancreatic cancer: Targets for overcoming immune checkpoint inhibitor resistance in PDAC.

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy with a poor prognosis due to its complex and highly immunosuppressive tumor microenvironment (TME). The PDAC TME, characterized by dense desmoplasia and enhanced infiltration of immunosuppressive immune cells, acts as a physical and immunological barrier, rendering most patients unresponsive to conventional and immune checkpoint inhibitor (ICI) therapies. This resistance is critically mediated by the cytokine network, where pro-tumorigenic factors such as IL-6 and TGF-β drive T-cell exclusion and myeloid-dependent suppression from PSCs, CAFs, and immune cells. The key to improving the therapeutic approaches lies in effectively reprogramming this hostile milieu. This review focuses on the dual and paradoxical role of cytokines as drivers of immune evasion (IL-6, TGF-β, MIF) and mediators of anti-tumor immunity (IL-12, IL-15). Herein, we outline the strategic shift toward cytokine-based combination immunotherapy designed to remodel the TME through the disruption of cytokine-driven resistance pathways. Key strategies currently under investigation include targeting TGF-β and IL-6 to sensitize tumors to ICIs, while antagonizing chemokines like CXCL12/CXCR4 to enhance T-cell trafficking. Furthermore, we detailed cutting-edge approaches to overcome systemic toxicity and poor drug delivery, specifically through cytokine-based nanotechnology, including nanocarriers and mRNA lipid nanoparticles, for localized expression of immunogenic signals. As well as the cutting-edge field of chimeric cytokine engineering, including VHH-fusions, to selectively activate anti-tumor immunity, highlighting promising candidates in late-stage clinical trials. The successful application of these engineered cytokine strategies is crucial to unlocking effective immunotherapy for PDAC patients.