“…Bystander signals may be transferred to surrounding cells either by gap junctional intercellular communication or by the production of soluble extracellular factors released from irradiated cells. Soluble signaling factors such as reactive oxygen species (ROS) (8)(9)(10)(11)(12), nitric oxide (NO) (12)(13)(14), secondary messengers like calcium (4,(8)(9)(10), cytokines such as interleukins (15)(16)(17), TGFb (18,19), TNFa and TRAIL (20,21) have been found to play a major role in radiation-induced bystander effects. A new mechanism for communication by soluble factors could be by intercellular communication by exosomes.…”