Science has made a significant stride in curing melanoma, a form of skin cancer, by using cloning cancer-fighting immune cells and injecting them back into the patient:
Scientists at the Fred Hutchinson Cancer Research Center in Seattle concentrated on a type of immune system cell called a CD4+ T cell.
From a sample of the man's white blood cells, they were able to select CD4+ T cells which had been specifically primed to attack a chemical found on the surface of melanoma cells.
These were then multiplied in the laboratory, and put back in their billions to see if they could mount an effective attack on the tumours.
Two months later, scans showed the tumours had disappeared, and after two years, the man remained disease-free. The new cells persisted in the body for months after the treatment.
Link - Thanks moronic50!