Scientists have reported in the journal Nature that they now have a better understanding of how exposure to radiation can cause cancer.
The research has important implications for cancer treatment
Experts believe it may be useful for predicting how our bodies would respond following exposure to radioactivity released either accidentally, or deliberately from a potential nuclear attack or 'dirty bomb'.
The research also has important implications for cancer treatment. Targeting cancer cells with drugs to inactivate the molecule could make them much more sensitive to the effects of radiotherapy.
In human cells, exposure to radiation sets off an emergency response system, which patches up mutated genes or kills off cells that have suffered irreparable damage. This system is a key defence against the development of cancer. Scientists at the Wellcome Trust/Cancer Research UK Institute of Cancer and Developmental Biology at Cambridge University grew cells in the laboratory and studied the effects of exposing them to beams of radiation.
Doctors take advantage of the damaging effects of radiation with radiotherapy
Researchers found that a mystery protein molecule, which they have called MDC1, plays a key role in helping cells to detect and repair radiation damage. When they knocked out the activity of the molecule, cells lost their ability to mount the necessary responses to radiation, making them susceptible to accumulating a host of genetic errors. Professor Steve Jackson, team leader on the study, says: "The molecule we've discovered seems to play a crucial role in recognising genetic damage and setting into motion the chain of events that will lead to its repair. By helping cells to patch up radiation damage, we speculate that it is acting as a key barrier against the development of cancer.
The MDC1 molecule works together with three others called MRE11, RAD50 and NBS1 to detect damage to DNA and prevent cells from dividing until their genes have been repaired. After exposure to radiation, MDC1 helps guide its partners to places within the DNA where breaks have occurred, flagging up the damage and kick starting the process of gene repair.
Doctors take advantage of the damaging effects of radiation with radiotherapy, which works by causing lethal damage to the DNA of cancer cells. Preventing MDC1 from working could therefore be a valuable way of making the treatment more effective.
Professor Jackson adds: "At the moment, we're investigating how much of the new molecule is found within tumours, so that we can see whether differences in MDC1 levels may influence clinical outcome."