Epigenetics of Brain Aging: Lessons from Chemo Brain and Tumor Brain

The world's population is rapidly aging. Aging is a complex and multifaceted process of the loss of viability and increase in vulnerability that affects the entire organism, and encompasses a progressive decline on various levels-molecular, cellular, tissue, and organismal. Indeed, both internal and various external environmental factors-such as life style, diet, exercise, smoking, alcohol consumption, as well as exposures to physical, chemical factors, drugs, toxins, and pathogens can contribute to aging processes in the brain as a part of integrated genome and epigenome response orchestrated via altered expression of genes and pathways. It is also apparent that various environmental exposures which affect the brain may influence pathological processes implicated in aging. Moreover, various co-morbidities can impact the brain-such as age-related cardiovascular and other diseases, and cancer. Of the latter, cancer is of particular interest. Here, we discuss the effects of non-CNS tumor growth and chemotherapy on the brain and the effects of these phenomena on brain aging. We introduce the epigenetic theory of chemo and tumor brain, and the role of epigenetic mechanisms in tumor brain, chemo brain, neurodegeneration and aging.