Immune-excluded and immune-suppressive tumor microenvironments: mechanisms, spatial biomarkers, and therapeutic rewiring

Background: Immune checkpoint inhibitors have improved outcomes in several malignancies, yet durable benefit remains limited in most solid tumors because many lesions exhibit immune-excluded or immune-suppressive tumor microenvironments (TMEs). These resistant states are now understood to arise from coordinated stromal, myeloid, cytokine, vascular, and metabolic programs that prevent effective antitumor immunity and sustain therapeutic failure. Methods: This review synthesizes recent evidence on the biological architecture of immune-excluded and immune-suppressive TMEs, with particular emphasis on stromal remodeling, cancer-associated fibroblasts, myeloid-cell dominance, cytokine and chemokine networks, vascular dysfunction, metabolic stress, and organ-specific niche effects. We further integrate emerging data from spatial transcriptomics, multiplex imaging, spatial proteomics, and related platforms to evaluate how spatial biomarkers may refine patient stratification and therapeutic decision-making. Results: Current evidence indicates that resistant TMEs are spatially organized and dynamically evolving ecosystems rather than static histologic phenotypes. CAF/ECM remodeling, suppressive myeloid populations, cytokine circuits, vascular dysfunction, and metabolic stress cooperate to impair T-cell trafficking, infiltration, and effector fitness. Spatially resolved technologies may help refine patient stratification by identifying dominant resistance modules, although prospective clinical validation remains limited. Conclusion: Immune-excluded and immune-suppressive TMEs represent actionable but heterogeneous resistance states. Future progress will depend on integrating spatially informed biomarker systems, longitudinal profiling, and mechanism-based combination therapies to convert nonresponsive tumors into immunologically permissive niches.