Hypoxia-driven tumor immune escape: mechanisms and therapeutic opportunities

Hypoxia is a common feature of solid tumors and a major driver of tumor immune escape. It arises from abnormal tumor vasculature and rapid tumor growth, leading to persistent or fluctuating oxygen deprivation within the tumor microenvironment. Under hypoxic conditions, hypoxia-inducible factors, especially HIF-1α and HIF-2α, activate transcriptional programs that support tumor survival, angiogenesis, glycolytic metabolism, invasion, and therapy resistance. Beyond these tumor-intrinsic effects, hypoxia also reshapes antitumor immunity by suppressing CD8⁺ T cells, natural killer cells, and dendritic cell antigen presentation, while promoting regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells. These changes establish a strongly immunosuppressive microenvironment and reduce the efficacy of immunotherapy. Hypoxia-driven immune escape is mediated by several interconnected mechanisms. HIF signaling promotes lactate accumulation, acidosis, adenosine signaling, PD-L1 expression, myeloid cell recruitment, and T cell exhaustion. In addition, emerging evidence indicates that RNA modifications, including m6A and ac4C, provide a post-transcriptional regulatory layer that links hypoxia signaling with immune checkpoint regulation, chemokine production, myeloid metabolism, and HIF-1α translation. Therapeutically, targeting hypoxia-related pathways may improve antitumor immunity, but single-agent approaches are often insufficient because hypoxic tumors use multiple overlapping escape mechanisms. Rational combinations involving HIF inhibitors, metabolic intervention, immune checkpoint blockade, cell therapy optimization, and RNA epitranscriptomic targeting may provide more effective strategies. In this review, we summarize how hypoxia coordinates metabolic barriers, immune remodeling, checkpoint activation, and RNA modification-dependent regulation to drive tumor immune escape, and discuss future directions for targeting the hypoxia-metabolism-immune axis in cancer immunotherapy.