Methylation and Cancer April 2005 Scientists at the Max-Planck Institute of Biochemistry in Germany have isolated a gene important in the development of prostate cancer, a discovery that could lead to a highly sensitive diagnostic test. Early detection is critical to treating this condition which results in nearly 30,000 annual deaths in the United States alone. Cancer can develop when tumor suppressor genes are deactivated through a chemical modification, called CpG methylation, of their regulatory region. This modification acts as a signal that recruits proteins to silence the gene. By looking for changes in the methylation pattern of cancerous cells, scientists can isolate important genes involved in cancer development. For many years, however, identifying these genes was a tedious process as researchers had to individually analyze the tens of thousands of genes in the human genome. In the October 18 issue of Oncogene, Dr. Heiko Hermeking's group from the Max-Planck Institute in Germany reported a genome-wide screen that identified an important gene involved in prostate cancer. DNA microarray technology allowed the group to simultaneously examine possible differences in methylation in thousands of potential disease-causing genes. They discovered a number of genes that were turned off via methylation in patients with the disease. One gene strongly regulated by methylation was 14-3-3σ. When the team analyzed 41 additional patient samples, they found 14-3-3σ methylation in all prostate cancer cells, but never in normal prostate epithelial cells. In order to identify genes that were regulated through methylation, the researchers chemically de-methylated the DNA of several prostate cancer cell lines. This treatment allowed any genes repressed by CpG methylation to be expressed again. Hermeking's group then used Affymetrix microarrays to detect which of these genes were reactivated. They found that 14-3-3σ gene expression increased by 430 percent. "Since 14-3-3σ is also methylated in a number of other carcinomas, a combination of this marker with prostate cancer-specific methylation markers may allow development of a highly sensitive and specific diagnostic assay in the future," said Hermeking. "Because changes in DNA methylation seem to occur early in cancer formation, this assay may be well-suited for the early-detection of prostate cancer." Before microarray technology, researchers had to look at methylation, a process known to regulate up to 60% of human genes, on a gene-by-gene basis. Using the GeneChip® Human Genome U133 Array, Hermeking's group looked at the methylation pattern of over 14,500 genes simultaneously. This approach identified the 14-3-3σ gene with significantly less time and resources than individual screens could have accomplished. The discovery of the CpG methylation of 14-3-3σ gene in prostate cancer may lead to a highly sensitive diagnostic test. This could provide early detection for thousands of men and allow more timely treatment for improved therapy. Because the 14-3-3σ gene is implicated in other cancers as well, it may serve as an important target for therapy of different diseases such as breast cancer. In addition to 14-3-3σ, the research group identified a number of other genes with diagnostic potential. Hermeking says those results will be published in the near future. Lodygin, D., Diebold, J. and Hermeking, H. (2004) Prostate cancer is characterized by epigenetic silencing of 14-3-3sigma expression. Oncogene 23, 9034-9041 Contact Information: Dr. Heiko Hermeking Max-Planck-Institute of Biochemistry Molecular Oncology Am Klopferspitz 18A D-82152 Martinsried/Munich Germany Tel: ++ 49-(0)-89-8578-2875 FAX: ++ 49-(0)-89-8578-2540 e-mail: herme@biochem.mpg.de