The team also tested the effect of a number of chemotherapy agents on cells with and without p300 and found the same effect: cells with p300 frequently failed to die whereas identical cells lacking p300 triggered their suicide machinery.

Prof Caldas says: "The molecule seems to safeguard cancer cells from the effects of chemotherapy. Designing drugs to target p300 and block its action could make current anti-cancer drugs more potent particularly against the resistant forms of the disease.

"We could also use the molecule as a way to predict whether tumours will be responsive to chemotherapy prior to treatment," he adds.

Prof Caldas is currently running a large study to determine if the combined analysis of p53 and p300 status in patients' tumours could be used to determine prognosis.

Professor Robert Souhami, Director of Clinical and External Affairs at Cancer Research UK, says: "Chemotherapy is a very effective way of killing tumours but there are some cancer cells that are resistant to treatment. We need new approaches to tackle these difficult forms of the disease and targeting this molecule looks like a promising approach."