From U.S. News: "Cancer is characterized by cells dividing wildly, with no brakes; if a cell can't divide, it can't become cancerous. One solution that evolved: a whole class of naturally occurring tumor suppressor molecules that can disable cells in danger of going haywire. They do it either by telling the cell to kill itself, through a process called apoptosis, or by simply turning off the potentially dangerous cell's ability to divide, a process called senescence. ... But there's a tradeoff. The problem is that those senescent cells, while they have lost their ability to divide out of control, may trigger inflammation in nearby cells and tissues, and inflammation is linked with a host of age-related disease, including late-life cancers. Experiments in mice show that goosing one important tumor suppressor gene, p53, so it's a little bit activated all the time, does certainly hold off cancer ... but the mice age prematurely. It has been possible to regulate the action of p53 in a kind of Goldilocks mode - not too much, not too little - and that produces mice that are both tumor-free and don't age prematurely ... that's easy to do in mice, but difficult to do in people ... Some other possible tactics include figuring out why the senescent cells are secreting molecules that promote the dangerous inflammation and whether suppressing that secretion would help. Or [maybe] there's a way to get rid of the senescent cells entirely."

Link: http://health.usnews.com/articles/health/cancer/2009/02/20/cancer-and-age-why-we-may-face-a-tradeoff-between-cancer-risk-and-aging.html