Methylation/demethylation of DNA and/or histones, acethylation/deacethylation of histones and shortening of telomeres appear to be some of the epigenetic factors controlling gene expression over time. The epigenetic control mechanism is affected by the environment and seems to become progressively relaxed or disrupted as we age. Because of this disruption illnesses of aging can appear, including cancer. In fact, aging is one of the highest risk factors for cancer. Because cancer involves an uncontrolled cell replication, senescence of replication might appear as a compensatory mechanism. This seems to be at least partially mediated through changes in telomeres.
In a previous blog entry I mentioned that life events can change gene expression. The mechanism could be the one explained here. Because of this interaction with the environment, in my opinion, it seems that the control mechanism might respond to drug manipulations or specific changes in the environment. By doing this we could hope to delay or even stop the aging process and its consequences. One of the difficulties for doing this is the heterogeneity in different cells. There seems not to be a uniform response to epigenetic manipulations, and each cell seems to behave differently. A good paper in this topic is the following:
Gravina Silvia, etal, Epigenetic factors in aging and longevity, Pflugers Arch- Eur J Physiol 2010 459: 247-258
Adolfo Cotter, MD