Voluntary Wheel Running Slows Tumor Progression In A Murine Lymphoma Model

Abstract

PURPOSE: Acute bouts of dynamic exercise elicit a profound mobilization of effector lymphocytes into the blood compartment, resulting in cellular redistribution and increased immunosurveillance of peripheral tissues. This effect, in conjunction with the release of catecholamines and myokines, is now known to play a mechanistic role in the anti-cancer effects of regular exercise against many solid malignancies. However, little data exists in this arena concerning hematological malignancies such as lymphoma. We tested the hypothesis that exercising mice would demonstrate reduced tumor progression relative to sedentary mice in a subcutaneous murine lymphoma model. METHODS: 8-12 week old male and female Balb/C mice were injected subcutaneously in the right flank with 1 x 106 A20 lymphoma cells and assigned to either sedentary (n = 32) or exercise (n = 31) conditions. Mice assigned to exercise received a running wheel one day post A20 cell injections. Body weight and tumor progression (calipers) were assessed every 3-4 days until the end of the experiment on day 40. RESULTS: Both sedentary and exercising mice gained a significant amount of weight due to tumor growth (p < 0.0001) over 40 days. However, upon resection of the tumor after sacrifice, there was no difference in tumor-free body weight between sedentary and exercising mice (25.09 ± 5.63 vs. 24.67 ± 4.86 g, respectively; p = 0.7886). On average, mice with access to a running wheel ran ~5.2 km/day; this voluntary wheel running translated to a significantly slowed tumor progression over the course of the experiment relative to sedentary mice (170.52 ± 163.18 vs. 239.75 ± 182.21 mm2 on day 40, p = 0.0042). CONCLUSION: Regular physical activity is now known to be inversely related with the risk of acquiring many different forms of cancer, as well as disease progression after diagnosis. These data suggest that regular exercise in mice reduces the progression of lymphoma, adding a hematological malignancy to the list of solid cancers (e.g. breast, skin) that now have in vivo evidence of slowed progression with exercise training. Future work will determine the immune cells involved in exerting the anti-cancer effects of regular exercise against lymphoma and other hematologic malignancies.