Exercise-induced extracellular vesicles mediate apoptosis in human colon cancer cells in an exercise intensity-dependent manner

Regular exercise reduces the incidence and improves the prognosis of many cancer types, but the underlying mechanisms remain elusive. Evidence suggests that exercise exerts its therapeutic effects through extracellular vesicles (EVs), which are essential for cellular communication. Here, we hypothesized that exercise-induced EVs from serum of healthy individuals would exert anti-tumorigenic effects on human colon cancer HT-29 cells, in an exercise intensity-dependent manner. Ten healthy young active males participated in a randomized crossover trial, completing two workload-matched acute exercise bouts, moderate-intensity continuous exercise (MICE) and high-intensity interval exercise (HIIE), on a cycle ergometer. A control session of rest (PRE) was included. EVs were isolated from serum samples collected during PRE and immediately after each exercise session. EVs were co-incubated with HT-29 colon cancer cells, and the effects on cell viability, migration, and apoptosis were measured. EV treatment reduced cell viability in all groups (PRE, MICE, and HIIE) by 35%, 43% and 47%, respectively, vs. PBS. HIIE-EVs showed a significantly greater reduction in cell viability vs. PRE; therefore, only these groups were used for further analysis. PRE EVs reduced migration by 27%, and HIIE-EVs by 39%. HIIE-EVs increased expression of pro-apoptotic markers: Bax/Bcl-2 ratio by 56% and Caspase 3 by 30% vs. PBS, with no change observed in the PRE group. Further, 16% of cells in PRE and 28% of cells in HIIE were TUNEL-positive, indicating DNA fragmentation. To our knowledge, this is the first human study that illustrates the therapeutic potential of exercise-induced EVs in cancer treatment.