New insights into the cellular response to radiation using microbeams

Microbeams are now being used to study a number of novel 'non-targeted' responses that do not follow the standard radiation model based on direct DNA damage and are now known to occur when living cells and tissues are irradiated. One such response is the so-called 'bystander effect' where unirradiated cells are damaged through signalling pathways initiated by a nearby irradiated cell. This effect predominates at low doses and profoundly challenges our understanding of environmental radiation risk. Furthermore, we now have evidence that simple molecules (such as nitric oxide) are involved in the signalling process, such that it may be possible to chemically influence the bystander response. If so, then this could eventually lead to improvements in the treatment of cancer by radiotherapy. Other studies have shown that the bystander effect is induced with equal effectiveness if either the nucleus or the cytoplasm of a cell is targeted.