Gene therapy breakthrough to tackle skin cancer

GENE THERAPY which can switch on the body's immune system to kill cancerous cells could be tried this year.

British scientists announced yesterday that they had found a way to target skin cancer cells by introducing into them, by a simple injection, a gene for the immune system which attracts anti- cancer cells to the tumour.

Patents have been applied for and application will be made to the Clothier Committee on the Ethics of Gene Therapy within the next two weeks for permission to use the technique on patients. It would be the first time in Britain that gene therapy has been used on cancer patients.

The system is designed for melanoma, which is doubling in incidence every 10 years. The scientists hope that the therapy will be used on patients for whom other treatments have failed. About 4,000 people a year in the UK get melanoma. While it is treated successfully by surgery in two thirds of cases, more than 1,000 die patients every year.

Dr Michael Crumpton, director of the Imperial Cancer Research Fund's laboratory research, said: 'We believe we have an exciting and important discovery which has important clinical implications for the treatment of tumours in general - I guess we are talking about a period of 5 to 10 years.'

The work has been developed over the past year by Ian Hart, head of the ICRF biology of metastasis laboratory, and his colleague, Dr Richard Vile.

Dr Hart said they had exploited a function of certain skin cells, melanocytes, which produce the skin pigment melanin, which is spread through surrounding skin cells. The melanocytes also play a role in the development of the melanoma. 'The jump we made is that if this characteristic is a specific of melanocytes and is shared by many melanomas, then perhaps we could use the pathway that produces this melanin to target melanoma, and that is what we have done.'

The key is an enzyme, tyrosinase, essential for making melanin. The scientists found that close to the gene for tyrosinase is a piece of genetic material which acts as a chemical switch.

They confirmed that they could try to use a chemical switch that is active in most skin cancer cells but not in other cells in the body.

The final stage was to hook on to the chemical switch a gene for Interleukin 2 (IL2) which stimulates the 'killer' T cells of the immune system at the cancer sites.