In the latest of a series of discoveries about colon cancer genes, researchers at the Johns Hopkins Oncology Center and the Howard Hughes Medical Institute have discovered a connection between two of them, APC and c-MYC, that conspires to initiate almost all colon cancers. Their findings are reported in the September 4, 1998, issue of SCIENCE.
The APC tumor suppressor gene, which acts like a brake on cell growth, loses that ability when mutated. The c-MYC gene has long been known as an oncogene, a type of gene that promotes cancer cell growth. Now, Hopkins scientists Bert Vogelstein, M.D., and Kenneth W. Kinzler, Ph.D., have found that the mutated APC gene controls the expression of c-MYC activation. APC was first identified and linked to colon cancer in 1991 by research teams including those led by Vogelstein and Kinzler.
Every person carries the c-MYC oncogene, but it remains under control in the colon until APC inactivation awakens it, generating the distinctive uncontrolled cell growth that mark cancers. "Cancer is like a car with the accelerator pushed to the floor and failing brakes," says Vogelstein, professor of oncology at Hopkins and a Hughes scholar.
"In this case, c-MYC is the accelerator and APC is the failed brakes," he explains. When suppressor genes, like APC, malfunction either through heredity or as a result of exposure to carcinogens, cells get signals to continue multiplying until they are out of control. "Now we know that in colon cancer a mutated APC gene signals to c-MYC," Vogelstein says.
The new findings about the APC pathway and how it functions may suggest
potential new drug strategies that could prevent colon cancer by blocking the
signal that activates c-MYC, says Kinzler, associate professor of oncology and
director of the study. "Just eight years ago, we didn't even know about APC
mutations. Now, we know this type of mutation is one of the earliest genetic
changes in most colon cancers, and we know what i
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Contact: Karin Twilde-Sheifer
oncpubaf@welchlink.welch.jhu.edu
(410) 955-1287
Johns Hopkins Medical Institutions
4-Sep-1998