Targeting the Tumour Microenvironment in Pancreatic Cancer: From Stromal Reprogramming to Emerging Therapeutics

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest solid tumours, driven by late diagnosis, early metastatic dissemination, and profound resistance to systemic therapies. Increasing evidence indicates that these hallmarks are not solely tumour cell intrinsic but are critically orchestrated by a complex and highly dynamic tumour microenvironment (TME) composed of pancreatic stellate cells (PSCs), cancer-associated fibroblast (CAF) subtypes, immune cells, endothelial and neuronal elements, and a dense extracellular matrix (ECM). This review provides an integrated overview of the cellular and acellular components of the PDAC TME and delineates how their reciprocal crosstalk drives desmoplasia, immune suppression, metabolic reprogramming, epithelial–mesenchymal transition (EMT), pre-metastatic niche formation, and metastatic outgrowth. Particular emphasis is placed on the context-dependent roles of stromal and immune niches in modulating drug delivery, chemoresistance, and failure of immunotherapy, highlighting why indiscriminate stromal depletion has yielded paradoxical outcomes. Building on these mechanistic insights, the review critically examines emerging therapeutic strategies targeting PSCs, CAF subsets, ECM components, myeloid and lymphoid populations, and key signalling pathways, including approaches that normalize stroma, reprogram immunity, or exploit nanocarrier-based delivery systems. Finally, a structured framework is proposed for rational TME-targeted combination regimens that integrate cytotoxic, targeted, and immunotherapeutic agents to overcome current therapeutic barriers in PDAC.