Common Cancer Gene Suppressed

By studying laboratory mice with skin cancer, scientists have found a way to suppress a mutant gene called Ras, which is found in up to 30% of human tumors.

Ras is a cancer-causing gene, also known as an oncogene; normal copies of this gene are important in the cell-signaling process. However, when mutated, Ras becomes an oncogene and can trigger the growth of tumors in the lung, colon, pancreas, as well as leukemia and thyroid cancer.

Efforts to inhibit activated Ras has had little success to date. However, researchers at the Huntsman Cancer Institute (Salt Lake City, UT, USA) reported that they have found an enzyme that, when inhibited, seems to reduce the incidence of Ras-induced tumors in mice. They published their findings in the May 9, 2005, online early edition of the Journal of the Proceedings of the [U.S.] National Academy of Sciences.

Matthew K. Topham, M.D., assistant professor of internal medicine at the University of Utah School of Medicine (Salt Lake City, UT, USA; www.utah.edu) and lead investigator on the study, explained that the researchers had initially been evaluating a group of enzymes that control the function of the Ras gene. These enzymes, called diacylglycerol kinases (DGKs), are implicated in tumor growth.

"When we began our investigation using a type of DGK, called DGK iota, we thought that its absence would cause more tumors to develop, as has happened with other DGKs we have tested. This time, though, when we tested mice with an activated Ras gene, but an absent DGK iota gene, the number of tumors was significantly reduced,” Dr. Topham remarked. "This result is interesting because it happened when the Ras gene was activated. The implication is that a drug therapy could be developed to reduce tumors caused by Ras without significant side effects.”

The investigators used mice that were bred to have a highly expressed mutant form of the Ras oncogene. Earlier studies showed that these mice were very prone to tumors. For the new study, the group of scientists removed the DGK iota gene in the mice and discovered they developed a small number of tumors, whereas mice with an intact DGK iota gene and an activated Ras gene showed considerably more tumor activity. Dr. Topham said his team will now more closely evaluate the process behind how DGK iota works to inhibit tumor formation.




Related Links:
Huntsman Cancer Institute