New strategies to combat cancer use viruses to carry genes that can destroy tumour cells. One of the world"s leading figures in this field addressed these new developments during a conference in CIMA - the centre for the study of applied medicine at the University of Navarra. David T. Curiel is the director of the Gene Therapy Centre in the University of Alabama at Birmingham (USA), and leads a team of more than 50 scientists that includes doctors and biologists, along with specialist researchers expert in other disciplines of the life sciences. His goal is to establish gene therapy as a new approach in medical care, which will revolutionise existing practice and improve prognoses in the treatment of serious illnesses, including cancer.

Dr. Curiel took part in a conference on Gene Therapy and Hepatology organised at CIMA, and concurred with the fundamental principles set out by the conference organisers in his defence of a dynamic model of patient-centred research. The objective must be, he argued, the development of a "close relationship between laboratory and clinic, or what is sometimes referred to as "bench to bed", (from the laboratory bench to the patient"s bed)". At a critical point in his career as a medical practitioner, Dr. Curiel turned to biomedical inquiry in search of solutions to the problems posed by the limitations of classical medicine.

Virus as "lethal weapon"

During the conference, Dr. Curiel described the latest developments in gene therapy, which involve the transfer of genetic material into cells in order to treat illnesses: "We have compiled a great deal of information in recent times about which genes might have curative properties in the treatment of different diseases. The difficulty lies in finding a safe and effective method of introducing these genes into the cells which require treatment and regulating their function once they have been inserted".

The resolution of these problems has been the focus of Dr. Curiel"s research over the last number of years. He has settled on the strategy of using viruses as vehicles to carry the necessary genes, taking advantage of the nature and functioning of these micro-organisms to introduce genetic material into human cells.

The experiments in his laboratory are based on the production of various modifications to the structure of a relatively innocuous virus - the adenovirus, the cause of many common colds and intestinal infections. Through a process of genetic engineering, Dr. Curiel"s team has succeeded in modifying the adenovirus in such a way that the virus infects only the cancerous cells of a tumour and not the normal cells of healthy tissue.

"The process is a very delicate one, and is based on as precise a knowledge as possible not only of the virus, but also of the different types of tumour. The components of the virus that enable it to infect the cell must first be identified, and then replaced by others that allow the virus entry to the interior of the cell itself. It is not enough, however, that the virus penetrate the cancerous cell: it must destroy it".

One of the results of this new strategy to combat cancer has been the successful development of viruses that act as "lethal weapons" against tumours. By introducing toxic genes into the virus, or by limiting the virus" ability to reproduce itself to within the wall of the tumour cell, the cancerous cells are destroyed without negative consequences for the normal cells of healthy tissue. The virus builds up in the tumour cell until the cell is destroyed, and is then released from the dead cell to destroy other cells in the tumour, until the tumour as a whole has been eradicated. Dr. Curiel indicated that some of the approaches taken in his laboratory have yielded encouraging results in experiments on animals. They will shortly be tested on small groups of cancer patients in what are known as Type 1 clinical trials.