Low-dose radiation action: possible implications of bystander effects and adaptive response

Several experimental studies performed in the last decade have suggested the occurrence of low-dose-specific phenomena such as the bystander effect (BE, damage induction in cells not directly hit by radiation) and adaptive response (AR, induction of resistance to subsequent irradiation with higher doses). Although the underlying mechanisms are still not known in detail, cellular communication is widely regarded as a key factor. BE and AR may have a non-negligible role in modulating low-dose radiation effects not only in cells, but also in tissues and organs. Whether these phenomena would imply an increase or a decrease of low-dose cancer risk is still an open question. In this context a few representative findings are discussed, focusing on their possible implications for low-dose risk.