In the first set of experiments, the Johns Hopkins scientists sequenced nearly all protein-encoding genes in 10 of the 68 samples of pancreatic neuroendocrine tumors and compared these sequences with normal DNA from each patient to identify tumor-specific changes or mutations.
In another set of experiments, the investigators searched through the remaining 58 pancreatic neuroendocrine tumors to determine how often these mutated genes appeared.
The most prevalent mutation, in the MEN-1 gene, occurred in more than 44 percent of all 68 tumors. MEN-1, which has been previously linked to many cancers, creates proteins that regulate how long strands of DNA are twisted and shaped into dense packets that open and close depending on when genes need to be activated. Such a process is regulated by proteins and chemicals that operate outside of genes, termed "epigenetic" by scientists.
Two other commonly mutated genes, DAXX and ATRX, which had not previously been linked to cancer, also have epigenetic effects on how DNA is read. Of the samples studied, mutations in DAXX and ATRX were found in 25 percent and 17.6 percent, respectively. The proteins made by these two genes interact with specific portions of DNA to alter how its chemical letters are read.
"To effectively detect and kill cancers, it may be important to develop new diagnostics and therapeutics that take aim at both epigenetic and genetic processes," says Kenneth Kinzler, Ph.D., professor of oncology at the Johns Hopkins Kimmel Cancer Center and co-director of the Ludwig Center at Johns Hopkins.
|Contact: Vanessa Wasta|
Johns Hopkins Medical Institutions