How genes interact with the environment to cause disease has been a mystery to scientists. But now, the field of Epigenetics is starting to give clues that will help with cancer and other diseases.
Epigenetics can be thought of as chemical switches that can turn on and off the expression of genes in response to environmental factors. These chemical changes alter whether certain genes are expressed but they don't alter the genetic DNA sequence. The epigenetic changes occur most commonly during pregnancy, neonatal development, puberty and old age. The effects of these changes can occur years or decades later and, because the genes are altered, they can effect offspring also.
One example is shown in some cancers where tumor suppressor genes can be inactivated epigenetically in human tumors. There are now cancer therapies that aim to reverse inappropriate DNA methylation of such genes to allow them to function properly. These therapies don't replace a mutated gene with a good one, but rather they remove epigenetic marks so growth regulatory genes function properly.
There is some evidence in animal models that there may be epigenetic causes for chronic diseases, addiction and mental illness also. The effects of food supply, smoking and chemicals in plastics may mediate epigenetic changes that affect transgenerational inheritance. Pregnant mice that were exposed to BPA , a building block of polycarbonate plastics and epoxy resins used to make water bottles and dental sealants, caused changes in the mice that later became obese, diabetic and developed cancer. It is too early to say if humans behave the same way but when you see how plastics have overtaken our environment and the rise in obesity, it is a compelling theory.
The National Children's Study will follow a large nationally representative sample of children from prior to conception until they are young adults. The samples collected during this study should enable scientists to see if early developmental changes in the epigenome are linked to the development of human disease later in life.
The advances in science are never static and our ability to map the human genome has just barely opened the window of new discoveries. The field of Epigenomics is still in its infancy but the discoveries will be swift and additive. We truly do live in exciting times and I suspect in the future we will be screening and treating disease at a molecular level before it occurs, not after.