Muscle-to-tumor effects. During exercise, muscle contraction stimulates the production of myokines. Muscle-derived myokines enter the circulation, and affect tumor promotion and progression by modulating TME in an endocrine fashion. In particular, BDNF seems to regulate TME rather indirectly through muscle-to-brain effects. Overall, exercise-derived myokines exert anti-tumorigenic functions in both direct and/or indirect manners.