Scientists find gene trigger for cancer

SCIENTISTS ARE claiming a breakthrough in the understanding of what triggers cancer by discovering the key steps that turn healthy human cells into tumours.

The researchers believe that knowing the precise stages in cancer development could result in new drugs to block tumour growth.

By tinkering with the genes known to be involved in cancer, scientists led by Robert Weinberg of the Whitehead Institute at the Massachusetts Institute of Technology have for the first time stimulated the growth of an "artificial" human tumour.

"Until now, the human cancer cell has been a black box with an unknown number of regulatory changes," Dr Weinberg said.

"Now we have been able to catalogue the number of changes with precision," he added.

The team of scientists has shown that there are four crucial steps to the development of a cancer, which happen when a healthy cell suddenly begins to divide uncontrollably to form a tumour.

"If we can somehow rebuild one of these steps in the tumour cell, then we may stop the evolution of the tumour cell," said Moshe Yaniv of the Pasteur Institute in Paris and a member of the research team.

Dr Weinberg said that discovery of the genetic faults leading to cancer would be particularly useful in understanding what happens in the later stages of disease when cancer cells begin to spread in the body. One of the steps involves a naturally occurring enzyme called telomerase that is known to be involved in setting a cell's internal "clock", which limits its lifespan.

"The next question we asked ourselves was whether telomerase is [switched] on in cancer cells because the cells need the enzyme to grow or whether it just comes along for the ride," said William Hahn, a research scientist at the Whitehead Institute.

Two oncogenes - genes that can control the development of cancer - were also found to be necessary for the full sequence of events involved in the growth of a tumour to unfold.

"One important conclusion from this study is that there are not an infinite number of cellular changes separating cancer cells from normal cells, but that tumour development is a finite process," Dr Hahn said.

The research, published in the journal Nature, ends a 15-year search to find the precise stages leading to full cancer development.

Dr Gerard Evan, of the Imperial Cancer Research Fund, said: "Identification of these events in the process of cancer cell formation opens up ways of effectively identifying and targeting the errors peculiar to human cancer cells, paving the way for more effective therapies in the future."