Wednesday August 9

U.S. Scientists Unveil Cancer-Stopping Clue

By Bill Rosato

LONDON (Reuters) - A study of mice may have unveiled the secret of preventing the major types of adult cancers in humans from developing, U.S. scientists said in the journal Nature Wednesday.

The scientists said that a study using genetically engineered mice had shown that structures called telomeres which protect the tips of chromosomes (genetic material) were an integral part of the cause and prevention of cancer.

In living organisms, bodily tissues constantly renew themselves by cell division and as the cells divide, their genetic material, which is held in structures called chromosomes, is also divided.

Ronald DePinho from the Dana-Farber Cancer Institute of Harvard Medical School in Boston, said the division of chromosomes and the telomeres associated with them initiated certain cancers.

The division of chromosomes meant that eventually telomeres became too small to be effective, DePinho said.

Normally, cells stop dividing before telomeres grow too small but in some people a genetic defect means that the cells continue to divide and unprotected chromosomes fuse together to set people on the way to cancers, the scientists said.

``This process, known as 'crisis,' gives rise to pre-cancerous cells that begin to form a primary tumor,'' the lead author, Steven Artandi of the Dana-Farber Institute, said in a statement.

Mice Hold The Clue

Studies in mice showed that their telomeres did not shorten with cell division but continually rebuilt themselves and hence mice tended to develop cancers in different tissues to humans, the scientists said.

Mice develop cancers in bones and connective tissue while in adult humans tumors tend to arise in epithelial cells.

DePinho and colleagues engineered mice cells so they could experience ``crisis'' and sure enough the mice developed cancers like those in their human counterparts.

``We saw a dramatic shift in the types of tumors these animals developed. They much more closely resembled the tumor spectrum found in aged humans,'' DePinho said in a statement.

``Our conclusion is that 'crisis' is a major event in the development of cancer cells in older people. 'Crisis' is what enables cells to gain and lose the chromosomal material that leads cells down the pathway toward cancer,'' DePinho told Reuters.

The implication of the research is that if ``crisis'' could be prevented by rebuilding or maintaining telomeres in renewing tissues scientists could potentially reduce the chances of a cell becoming fully cancerous.

Cancer kills about six million people a year according to the latest statistics released by the World Health Organization.