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FP5

The role of intercellular communication and DNA double-strand breaks in the induction of bystander effects (INTERSTANDER), Final report (summary)

Project ID: FIGH-CT-2002-00218
Funded under: FP5-EAECTP C

Abstract

A commonly accepted assumption is that the biological effects of ionising radiation are a direct consequence of DNA damage in the exposed cells. However, recent studies have demonstrated 'non-targeted' effects (i.e. effects in cells not directly exposed to radiation, but which are in the vicinity of the exposed cells) at highly significant levels. Such non-targeted effects have been shown to cause cell killing, mutations, cancerous transformation and other cellular responses associated with DNA damage in "bystander", non-irradiated cells.
These observations question the validity of the International Commission on Radiation Protection (ICRP) extrapolated estimates of cancer risk for low-dose exposures, which do not consider bystander effects. Similarly, the practice of radiotherapy assumes that damage is inflicted only in tissues within the radiation field. Radiation is not thought to affect adjacent non-exposed areas. Thus, an evaluation of the relative contribution of bystander effects to the overall response of tissues to ionising radiation and an understanding of the underlying mechanisms is a prerequisite for accurate recommendations in radiation protection and valid predictions in radiation therapy. The main objective of the present proposal was to try to further our understanding of the molecular mechanisms underlying bystander responses. One hypothesis is that bystander effects are caused by the transfer of low-molecular-weight chemical factors excreted from irradiated cells which affect non-exposed, nearby cells. An alternative hypothesis is that the transfer of small molecules occurs from irradiated cells through 'gap junctions', cell-membrane channels, through which low-molecular-weight substances can pass between adjacent cells. Such intercellular passage could for example allow damaging reactive oxygen species, or signalling molecules, to pass from irradiated to non-irradiated cells.

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Record Number: 8942 / Last updated on: 2008-02-13
Category: PRJS
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