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. In this interview, hear from Dr. Jean-Pierre Issa at 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.
Q: What is epigenetics, and how does it relate to cancer?
Jean-Pierre Issa: Perhaps the best example of an epigenetic phenomenon—you’re actually looking at it. You see, skin and eyes and teeth and hair and organs all have exactly the same DNA. You cannot genetically tell my skin from my eyes or my teeth. Yet these are very different cells. They behave differently. And that behavior remains the same for as long as I live.
That difference, not being genetic, has been termed epigenetic. It is a difference that is not due strictly to genetic changes but to the way we utilize these genes. And so the same process that can cause such a profound difference that one tissue looks like skin and one tissue looks like eye could actually cause less profound changes that result in cancer.