Scientists are claiming that the body's own immune system could be used to fight the most serious form of skin cancer, malignant melanoma.
Two teams of researchers in the U.S. have been able to manipulate immune cells to boost the attack on cancer cells and the treatment appears to stop skin cancer progressing.
Experts say the studies are "significant", but much more research is needed before the treatment could be offered to patients.
Advanced melanoma is a devastating disease for which there is no effective treatment and the average life expectancy after diagnosis of the most serious form of the disease, stage four, is around nine months.
Though surgery or high doses of chemotherapy drugs are used to treat the cancer, while they can reduce the size of tumours they cannot prevent the disease recurring.
The immune system that attacks cancer cells is a delicately balanced defence system; the number of T cells, which recognise and attack foreign bodies such as tumour cells, are controlled by a T cells called Tregs.
Tregs role is to act as a break stop to prevent the immune attack going into overdrive and turning on the body.
One study found it was possible to suppress Tregs by blocking the activity of a protein on the cells' surface which left other parts of the immune system free to attack.
Dr. Jeffrey Weber, a professor of medicine at the University of Southern California in Los Angeles, and colleagues treated 25 patients with injections of an antibody to block the protein; eighteen months later, 24 of the patients are still alive and three are free of cancer.
In the second study, Dr. Jason Chesney from the J.G. Brown Cancer Center in Louisville, Kentucky found that when patients with advanced melanoma were given a drug combination of the diphtheria toxin and interleukin 2 to knock out their T-regulatory cells, tumors shrank or remained stable in five of seven participants.
The five patients on the higher dose saw their tumours shrink or remained stable and all seven are still alive 12 months after the treatment was given.