A team from the Cancer Research Campaign based at Manchester University is studying what prompts some cells to die and others to survive.

They hope their research will provide information needed to find new ways to kill cancer cells.

In normal circumstances, a healthy cell will die when it reaches the end of its natural life span or when it knows it is no longer needed.

Doctors on attack

Cells that are damaged will also "self destruct" as a safety mechanism so their faults are not replicated in future generations.

However, cancer cells do not die in the usual way, and go on reproducing themselves uncontrollably.

Most conventional treatments aim to force cancer cells to commit suicide by inflicting further damage on them.

However, some cancer cells can resist this bombardment.

The Manchester team is trying to identify how the cancer cells do this so doctors can attack their defence mechanisms.

Suicide molecule

The research has focused on a protein molecule called Bak that receives signals from the parts of the cell that assess and report damage caused by drugs, and then makes the cell self-destruct.

The researchers have discovered that Bak is normally held in check by another molecule.

To become active, it must separate from this "minder" and change shape.

Jump start

Once it changes shape it can receive the signals that the cell is damaged and commit it to die.

Scientists believe this does not happen in cancer cells.

Professor John Hickman, a member of the Manchester team, said: "The next question we hope to answer is why Bak does not get going in a cancer cell.

"If we can find out why it doesn't, then in theory we could find a way to jump-start it and force the cancer cell to die."