Exercise May Rewire the Tumor Battlefield to Empower Cancer-Killing T Cells
A workout may do more than strengthen muscles and improve cardiovascular fitness: it could also help the immune system hunt down cancer. A review published in the Journal of Molecular Medicine describes how physical exercise can enhance the activity of CD8+ T cells, the immune system’s specialized tumor-killing agents, while simultaneously making tumors more accessible to immune attack. The authors argue that exercise acts through several connected biological systems, including hormones, muscle-derived signaling molecules, cellular energy metabolism, tumor blood vessels and immune-suppressive pathways. Together, these effects could turn exercise into a low-cost supportive strategy for cancer immunotherapy—although the evidence remains strongest in laboratory and preclinical studies, and large clinical trials are still needed.
CD8+ T cells are central to the body’s adaptive immune response. After recognizing fragments of abnormal proteins displayed by tumor cells on major histocompatibility complex class I molecules, these lymphocytes form an immunological synapse with their targets. They then release cytotoxic proteins, including perforin and granzymes, which trigger the cancer cell to self-destruct. CD8+ T cells can also secrete interferon-γ and other signaling molecules that alter surrounding cells and help coordinate a broader immune response. But solid tumors rarely provide a friendly environment for these defenders. Low oxygen, scarce glucose, high acidity, abnormal lipids and suppressive immune cells can gradually push infiltrating T cells into a dysfunctional or “exhausted” state, in which they remain present but lose the ability to kill efficiently.
The review by Li Liu, Zhihao Deng, Ruiying Fang and colleagues focuses on how exercise may counter this collapse in immune performance. During physical activity, contracting skeletal muscle releases signaling proteins known as myokines. Among the molecules discussed are interleukins 6, 7 and 15, each of which can influence immune-cell behavior. Interleukin-15 is particularly important for the maintenance, proliferation and survival of cytotoxic lymphocytes. Exercise can engage the IL-15/IL-15Rα signaling axis, a molecular communication system that helps present IL-15 to T cells and natural killer cells. This may increase the number of immune cells available for tumor surveillance and improve their capacity to persist. Interleukin-7, meanwhile, supports T-cell survival and memory formation, potentially helping generate populations capable of responding more effectively over the long term.
Exercise also produces a rapid redistribution of immune cells through the bloodstream. As heart rate and blood flow rise, the sympathetic nervous system releases adrenaline and noradrenaline. These hormones act partly through β2-adrenergic receptors on lymphocytes, loosening the cells from blood-vessel walls and mobilizing them into circulation. The cells most readily recruited include differentiated effector-memory CD8+ T cells, which have previously encountered antigens and can respond quickly when they find a target. This surge is not simply a temporary numerical change. Once circulating immune cells reach tissues, the combination of exercise-induced signals and chemokines may help direct them toward tumors. In preclinical models, the effect has been linked to stronger recruitment of CD8+ T cells and improved control of tumor growth.
The tumor microenvironment, however, is an obstacle course of its own. Cancer cells and nearby stromal and immune cells can produce PD-L1, a surface protein that binds PD-1 on T cells and transmits an inhibitory signal. This interaction acts like a molecular brake, reducing T-cell activation and promoting exhaustion. Tumors also accumulate myeloid-derived suppressor cells, or MDSCs, which interfere with T-cell proliferation and function through mechanisms involving nutrient depletion, suppressive cytokines, reactive oxygen species and other metabolic disruptions. The review highlights evidence that exercise can reduce PD-L1 expression in some tumor settings and lower the proportion or suppressive activity of MDSCs. Rather than merely adding more immune cells to the bloodstream, physical activity may therefore alter the tissue landscape that determines whether those cells can function once they arrive.
Blood vessels inside tumors are often malformed, leaky and poorly organized. Their chaotic architecture restricts the delivery of oxygen and therapeutic drugs, while also creating a physical and chemical barrier to immune-cell entry. Exercise may partially normalize this vasculature by improving perfusion and reducing regions of severe hypoxia. Better-functioning vessels can make it easier for lymphocytes to cross the endothelial barrier and penetrate the tumor. The review connects this process with chemokine signaling, especially the CXCR3-CXCL9/CXCL10 pathway. CXCR3 is a receptor found on activated T cells, while CXCL9 and CXCL10 are chemical attractants that can be produced within inflamed tumors. When this signaling route is active, it helps guide CD8+ T cells toward malignant tissue. Exercise-induced changes in tumor inflammation and vascular structure may strengthen this homing system, transforming an immunologically “cold” tumor with few infiltrating immune cells into a more accessible, “hotter” environment.
A major part of the proposed benefit involves metabolism. T cells require energy not only to survive but also to divide, move, communicate and release cytotoxic molecules. In tumors, they compete with rapidly growing cancer cells for glucose and other nutrients. They are additionally exposed to lactate, an acidic by-product that accumulates when cancer cells rely heavily on glycolysis. The result can be mitochondrial damage, reduced energy production and impaired effector function. Exercise is associated with metabolic remodeling that may improve mitochondrial oxidative phosphorylation—the process by which mitochondria use fuel and oxygen to generate ATP. Healthier mitochondria could give CD8+ T cells the energy reserves needed to maintain activity in hostile tissue. Evidence cited in the review also indicates that moderate aerobic training can improve the function of tumor-infiltrating CD8+ cells by reducing mitochondrial loss.
Lactate illustrates why the biology is more complicated than the simple idea that exercise “clears toxins” from a tumor. High lactate concentrations can suppress immune activity, but research reviewed by the authors suggests that lactate can also, in specific contexts, support a stem-like state in CD8+ T cells. These stem-like cells are less terminally differentiated and may retain the ability to self-renew and generate fresh effector cells. Their persistence is important in cancer immunotherapy because durable responses often depend on a reservoir of T cells that can expand repeatedly rather than burn out after a single burst of activity. The effect likely depends on concentration, timing, cellular context and the wider metabolic state of the tumor. Exercise may help reshape this balance by improving systemic metabolism and the capacity of T cells to adapt to fluctuating nutrient conditions.
The review also describes a potential partnership between exercise and immune checkpoint inhibitors such as anti-PD-1 antibodies. Checkpoint blockade works by interrupting inhibitory signals, but releasing the brake is not enough if too few functional T cells can reach the tumor. Exercise could provide the missing logistical support by mobilizing effector-memory cells, improving vascular access and increasing CXCR3-dependent recruitment. In animal studies, combining exercise with checkpoint blockade has enhanced tumor control and helped counter features of T-cell depletion. The authors emphasize that this does not mean exercise replaces immunotherapy, chemotherapy or surgery. Instead, it may influence several resistance mechanisms at once, potentially increasing the probability that a drug-induced immune response becomes a sustained attack.
The biggest unanswered question is how much exercise is beneficial, for whom and at what stage of treatment. Intensity appears to matter. Moderate training has improved immune and tumor-related outcomes in several models, while excessive or poorly timed exertion may produce stress responses that limit immune-cell redistribution or recovery. Cancer type, treatment regimen, age, nutrition, fitness, sleep, chronic inflammation and the patient’s existing T-cell profile could all change the outcome. The authors call for future studies combining single-cell analysis, metabolomics, transcriptomics and repeated immune monitoring to identify which patients are most likely to benefit and how exercise should be scheduled around therapy. For now, the evidence supports viewing physical activity as a promising biological companion to cancer care, not as a stand-alone cure. The emerging message is nevertheless striking: by moving the muscles, patients may also send molecular instructions that mobilize immune cells, improve their fuel systems and make the tumor battlefield less hostile.
Subject of Research: Exercise-induced modulation of CD8+ T-cell antitumor immunity and the tumor microenvironment
Article Title: Exercise and CD8+ T cells: mechanisms of immune modulation in antitumor responses
Article References: Liu L, Deng Z, Fang R, et al. “Exercise and CD8+ T cells: mechanisms of immune modulation in antitumor responses.” Journal of Molecular Medicine 104, article 54 (2026). Original research page
Image Credits: AI Generated
DOI: 10.1007/s00109-026-02659-9
Keywords: exercise, CD8+ T cells, cancer immunotherapy, tumor microenvironment, immune checkpoint blockade, IL-15 signaling, myokines, T-cell metabolism, tumor vascularity
Tags: biological mechanisms of exercise in cancer therapyCD8+ T cell activation in tumor targetingexercise and cancer immunotherapyexercise as supportive cancer treatmentexercise-induced immune system modulationhormonal influence on antitumor immunityimmune-suppressive pathway inhibition by exerciselaboratory and preclinical evidence for exercise and cancermuscle-derived signaling molecules in cancer defensephysical activity and tumor microenvironmentpotential clinical applications of exercise in oncologytumor blood vessel normalization through exercise
