For decades, scientists and doctors assumed that cancer was caused by irreversible damage to some critical stretch of DNA within one's genome. But in the last few years, a much more complex picture has emerged, one that shows that some cancers are caused by epigenetic changes—tiny chemical tags that accumulate over time and can turn genes on or off. Unlike genetic damage, epigenetic changes can sometimes be reversed, and with treatments that are far less toxic to the patient. An interesting interview from Dr. Jean-Pierre Issa of the M.D. Anderson Cancer Center whose pioneering clinical work with a form of leukemia known as MDS is showing the promise of epigenetic therapy, may be found at http://www.pbs.org/wgbh/nova/genes/issa.html.