A father spoke today of how a pioneering gene therapy eradicated his cancer, allowing him to attend his daughter's wedding.
Scientists have shown that ordinary immune system cells can be genetically engineered in the laboratory to become specialised tumour fighters.
In a small-scale trial, two patients with skin cancer were declared clinically free of the disease 18 months after starting the treatment.
One of the pair, Mark Origer, 53, from Wisconsin in the United States, underwent five years of unsuccessful cancer treatment before receiving the gene therapy in December 2004.
He was discharged the same month and by September 2005, when he attended his daughter Katie's wedding, there was only one small spot of cancer remaining in his liver, the Daily Telegraph reported.
Mr Origer told the paper of his daughter's delight that he was able to walk her down the aisle, saying: "She wanted me to be there for her, and she wanted me to be there for me."
The researchers, led by Dr Steven Rosenberg at the National Cancer Institute in Bethesda, Maryland, US, have also shown they can engineer immune cells to attack breast, lung and liver cancers.
Stephen Simpson, senior editor of the journal Science, which published the findings yesterday, said: "This work marks an important next step in harnessing the power of our immune systems to fight cancer."
The research showed that the modified cells - known as T cells - persisted in the bodies of another 15 cancer patients who underwent the gene therapy.
Although their cancers were not eliminated, for at least two months after the treatment the modified cells made up at least 10% of their circulating T cells.
T cells are white blood cells that can recognise and attack foreign invaders.
In earlier experiments, Dr Rosenberg's team isolated tumour-fighting T cells from skin cancer patients and multiplied them in the laboratory. They were then used to repopulate the patients' immune systems.
The new research goes a step further by making ordinary T cells capable of recognising skin cancer cells.
This was done by genetically arming them with a "receptor" protein that recognises skin cancer, or melanoma, tumours.
A virus was used to ferry the receptor genes into the T cells. The cells were then returned to the 17 volunteers with advanced skin cancer.
In the case of Mr Origer and a 39-year-old man, the tumours shrank to a point where all clinical signs of the disease disappeared.
Dr Rosenberg said engineered cells could be tailored to fight cancers other than melanoma.
"We've identified T cell receptors that will now recognise common cancers," he said.
The scientists are now searching for ways to fine-tune the treatment so that greater numbers of engineered T cells survive.