Adult stem cells may have smarts to guard against cancer

Some bewildering behavior seen in the stem cells of muscles has led researchers at the Stanford University School of Medicine to an unexpected discovery that could explain why cancer isn’t more common. Stem cells found in adult tissues, such as muscles, brain or bone marrow, survive the lifetime of an animal, dividing when needed to replace cells lost to the ravages of bodily wear and tear. Every time that cell divides, it produces one offspring that becomes the new stem cell and one shorter-lived cell that replaces the body’s tissues. In order to split one cell into two, the original must essentially photocopy its genome and then divvy up material so that each cell gets one of every chromosome. Each round of photocopying introduces new genetic errors, some of which could derail essential functions and drive the cell toward cancer.
Cairns suggested that adult stem cells might avoid cancer by shuffling off the newly created, error-ridden chromosome to the offspring that becomes an adult body cell. That keeps the pristine original chromosomes for the long-lived stem cell.

http://med.stanford.edu/research/spotlight/archive/rando-thomas.html