How ageing increases cancer susceptibility: A tale of two opposing yet synergistic views.

It is well known that with increasing age, the risk of acquiring certain age-related diseases - such as diabetes, cancer, cardiovascular disease and neurodegenerative diseases, increases. Several theories have been proposed to explain the reason why ageing leads to higher susceptibility to disease. Over time, many of these theories have been proven wrong. Currently, the two theories holding the interest of researchers in this field are the oxidative damage theory and hyperfunction theory of ageing. The former is an old theory which explains that ageing is as a result of oxidative damage (to macromolecular components of the cell) by reactive oxygen species produced as a normal part of metabolism. The hyperfunction theory is a much newer theory which explains that ageing is as a result of the unnecessary and unwanted continuation of certain metabolic processes at old age. In this review, we discuss the mechanisms which underlie the development of age-related cancer. We also discuss the aforementioned theories of ageing. We conclude by explaining the opposing views of proponents of both theories and provide a new viewpoint by revealing a point of synergy in the two theories.