定期锻炼可以降低恶性肿瘤的风险并减少癌症复发。然而，这种保护的机制尚未阐明。自然杀伤细胞(NK细胞)是先天免疫系统的淋巴细胞，在免疫防御和有效预防癌症转移中起着重要作用。体育锻炼可以增加NK细胞的活性。白细胞介素15 (IL-15) 是研究最多的激活NK细胞的细胞因子，它被证明对提高NK细胞的抗肿瘤反应具有许多正向功能。本研究的目的是澄清耐力运动引起NK细胞功能变化背后可能重要的机制，这可能与IL-15高度相关。通过动物模型研究比较了跑步机锻炼后的IL-15表达水平、肿瘤体积、癌细胞凋亡和NK细胞浸润。尽管IL-15在骨骼肌中表达较高，但跑步机锻炼进一步提升了血浆和肌肉中的IL-15水平（P<0.05）。此外，经过12周跑步机锻炼的肿瘤带瘤小鼠的肿瘤重量和体积减少了（P<0.05），肝癌细胞凋亡也增加了（P<0.05）。跑步机锻炼小鼠的瘤内NK细胞浸润增加，胞内γ干扰素(IFN-γ)和IL-15水平较静坐小鼠高（P<0.05）。研究显示，定期耐力训练可以降低癌症风险，与增加IL-15表达、激活NK细胞的免疫杀伤效应以及促进肿瘤细胞凋亡有关，从而最终控制肿瘤生长。

Regular exercise reduces the risk of malignancy and decreases the recurrence of cancer. However, the mechanisms behind this protection remain to be elucidated. Natural killer (NK) cells are lymphocytes of the innate immune system, which play essential roles in immune defense and effectively prevent cancer metastasis. Physical exercise can increase the activity of NK cells. Interleukin-15 (IL-15) is the best-studied cytokine activator of NK cells, and it was shown to have many positive functional effects on NK cells to improve antitumor responses. The aim of this study was to clarify the possible important mechanisms behind endurance exercise-induced changes in NK cell function, which may be highly correlated with IL-15. An animal model was used to study IL-15 expression level, tumor volume, cancer cell apoptosis, and NK cell infiltration after treadmill exercise. Although IL-15 was highly expressed in skeletal muscle, treadmill exercise further elevated IL-15 levels in plasma and muscle (P<0.05). In addition, tumor weight and volume of tumor-bearing mice were decreased (P<0.05), and liver tumor cell apoptosis was increased after 12 weeks of treadmill exercise (P<0.05). NK cell infiltration was upregulated in tumors from treadmill exercise mice, and the level of interferon-gamma (IFN-γ) and IL-15 were higher than in sedentary mice (P<0.05). The study indicated that regular endurance training can reduce cancer risk, which was related to increased IL-15 expression, activation of the immune killing effect of NK cells, and promotion of tumor cell apoptosis, which can ultimately control tumor growth.