"Cancer is a disease of genes gone wrong. When certain genes mutate, they make cells behave in odd ways. The cells divide swiftly, they hide from the immune system that could kill them, and they gain the nourishment they need to develop into tumors.
"Scientists started identifying these cancer genes in the 1970s and their list slowly grew over the years. By studying them, scientists came to understand how different types of cancer develop and, in some cases, they were even able to develop gene-targeting drugs. Last May, for example, the U.S. Food and Drug Administration approved a drug known as Tarceva to treat lung cancer in which a gene called EGFR has mutated."