Image credit: Charlie Padgett
Most somatic mutations turn out to be harmless; many are even repaired by the body’s own quality-control processes. But some manage to wreak havoc, causing cells to reproduce uncontrollably. Many genes code for proteins, which do much of the work in cells. In the case of cancer, the harmful mutations tend to result in proteins that either actively promotes excessive replication or fail in their usual job of putting the brakes on cell proliferation.
Researchers refer to the abnormal changes that are integral to a tumor’s growth and survival as driver mutations; the others are known as passenger mutations because they appear to be unimportant and seemingly are just along for the ride. No one knows how many driver mutations are needed to promote each of the different kinds of cancers. One study determined that the average tumor requires as few as two or as many as eight driver mutations, whereas other studies found that tumors may frequently contain as many as 20 driver mutations.