Cancer is more common in older people than the young, and there is by no means agreement on why this is true. Antagonistic pleiotropy has been proposed as the genetic mechanism underlying life-history trade-offs. Dr. Sharpless studies the process of aging and its relationship to cancer and degenerative diseases. This is a video of an interview in which I think he does a good job to  explaining his research – both in mice and in humans. It’s long, but gives a good example of both scientific hypothesis testing and a bit of the history of this field.   

http://s3.amazonaws.com/thesciencenetwork/videos%2FGlenn2011%2FNorman+Sharpless.mov