Radiation link to cancer explained

Scientists are a step closer to discovering why radiation causes cancer.

They have identified a molecule which appears to play a crucial role in protecting cells against radiation.

It could help scientists understand how accidental or deliberate exposure to radiation from a nuclear attack or "dirty bomb" could affect cells.

The discovery could also have implications for the treatment of cancer, the UK researchers say, because targeting cancer cells with drugs to inactivate the molecule could make them much more sensitive to the effects of radiotherapy.

Exposing human cells to radiation sets off an emergency response system, which repairs mutated genes or kills off cells that have suffered irreparable damage.

This system is a key defence against the development of cancer.

Defenceless

The research was carried out by scientists at the Wellcome Trust/Cancer Research UK Institute of Cancer and Developmental Biology at Cambridge University.

Scientists grew cells in the laboratory and studied the effects of exposing them to beams of radiation.

It was discovered that a protein molecule called MDC1 played a key role in helping cells to detect and repair radiation damage.

If the molecule was prevented from doing its job, cells were no longer able to defend themselves against radiation, making them susceptible to developing a range of genetic errors.

The MDC1 molecule works together with others to detect damage to DNA and prevent cells from dividing until their genes have been repaired.

After cells have been exposed to radiation, MDC1 helps guide the other molecule to places within the DNA where damage has occurred, kick-starting the repair process.

Radiotherapy treatment harnesses the damaging effects of radiation to cause lethal damage to the DNA of cancer cells.

If the MDC1 can be prevented from working, it could make the treatment even more effective, the researchers say.

Reducing risk

Professor Steve Jackson, who led the research, said: "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."

He added: "Understanding what happens within our cells when they're pounded with radiation is important for a whole range of reasons, not least for predicting the effects of cancer radiotherapy.

"In addition, it may suggest how the effects of radiation might be curtailed following a possible nuclear attack.