By Stephen Ornes
Turning Cells On to Reading
Epigenetics research could lead to a new generation of diagnostic tools and treatments
By Stephen Ornes
Genes are commonly referred to as the book of life. But what good would that book be if there wasn’t a way for cells to read it?
The human body contains more than 200 types of cells, most of which contain a complete set of the blueprints necessary to create a human being. These blueprints, written with tightly wound strands of DNA, help determine fundamental traits unique to each person, from appearance to the ability to fight disease.
However, genes are simply instructions. They must be read by the special enzymes in the cell that can decipher the book of life and activate the specific genes a cell should turn on and use. This process of how and when genes are activated is called epigenetics—literally, on top of the genes—and it is of interest to cancer researchers because of the role it plays in cancer development and its potential to lead to new ways to treat, screen and diagnose cancer.
“Epigenetics represents the packaging of genes into different parcels and different cells in such a way that some pieces of the genome are used in some cells and some are used in others,” says cancer biologist Peter A. Jones, the director of the University of Southern California Norris Comprehensive Cancer Center in Los Angeles. “Epigenetics is really trying to understand how this packaging works.”
Most researchers define epigenetics as the ability of a cell to change and heritably transmit gene expression patterns without changing the primary sequence of the DNA. In other words, the genes stay the same, but the way they’re read differs from cell to cell. Stephen Baylin, a cancer biologist at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University in Baltimore, likens the relationship between DNA and epigenetic processes to a computer. “All the information you have in your genome, that’s the hard drive,” he explains. “But it can’t work without software.” Just as software specifies which information on the hard drive is used for a specific program, “epigenetics refers to those processes that specify which parts of the DNA are for gene expression and which parts aren’t.”
Because they turn genes on and off, epigenetic processes are crucial to life. Many scientists believe that harmful epigenetic mechanisms underlie a wide variety of diseases—from heart ailments to schizophrenia. It is also now known that an abnormal epigenetic alteration can silence a gene that would normally keep a cancer cell from growing, or activate a damaged gene that promotes tumor growth. Exposure to environmental agents like radiation, cigarette smoke and other chemicals has been shown to directly damage DNA. But it’s also now clear that these environmental agents can cause malicious epigenetic changes that could lead to cancer.