Reprogramming the Tumor Immune Microenvironment to Overcome Immunotherapy Resistance

Abstract

Immunotherapy has improved outcomes in selected cancers, but most patients either fail to respond or eventually develop resistance, highlighting a persistent gap between clinical efficacy and biological promise. Current evidence supports a role for the tumor immune microenvironment (TIME) in shaping therapeutic response, although its relative contribution varies across tumor types and remains incompletely resolved in clinical settings. This review integrates selected mechanistic and clinical observations of TIME organization, emphasizing how immunosuppressive cell populations, stromal remodeling, and cytokine-chemokine networks converge to establish immune “hot,” “cold,” and immune-excluded tumor states. We further examine how these features constrain the efficacy of immune checkpoint inhibitors (ICIs) and adoptive cell therapies (ACT), highlighting the roles of intratumoral heterogeneity, immune exclusion, and therapy-induced dysfunction. Notably, many proposed resistance mechanisms derive from preclinical or correlative studies, and their relative contribution in clinical settings remains incompletely defined. We propose a simplified framework in which immunotherapy resistance may arise from the interplay of three partially overlapping axes: immune suppression, stromal exclusion, and metabolic constraint. This framework provides a basis for rational combination strategies, including targeting immunosuppressive networks, remodeling tumor stroma, and integrating multi-omics-guided patient stratification. However, this model does not capture the full diversity of resistance mechanisms and may not be universally applicable across tumor contexts. A more precise understanding of TIME heterogeneity will be essential to convert immunologically refractory tumors into responsive states.