Cardiorespiratory fitness and sex impact the colorectal cancer-suppressive effects of aerobic exercise serum

Post-exercise human serum treatment can exhibit anti-viability properties in various cancer cell lines. However, whether the presence and/or magnitude of the effect differs in different participant populations is yet to be established. Here, we characterised baseline differences in serum-stimulated colorectal cancer cell viability and the acute exercise-induced response in males and females with varying levels of cardiorespiratory fitness (CRF). Forty-one participants (13 female) were stratified by maximal exercise test-derived VO2peak into high (n = 20) and low CRF (n = 21) and completed two experimental trials in a randomised crossover design: (1) 30-min moderate-intensity aerobic exercise; and (2) 30-min seated rest. Serum samples were collected before (pre), immediately after (post0), and 60-min after (post60) each trial and used to treat the human colorectal cancer cell line Caco-2 for 48 h, with cell viability assessed by MTT assay. Exercise-induced alterations in Caco-2 cell viability were, at least in part, modulated by CRF and sex. Specifically, at post0 and post60, exercise serum significantly reduced cell viability compared with no-exercise control serum when derived from individuals with high but not low CRF, and when derived from males but not females. These findings provide the first insights into the role of individual characteristics in determining the effects of exercise on colorectal cancer cells, with potential implications for increasing the precision of exercise recommendations for colorectal cancer risk reduction.