Certain types of cancer seem to run in some families, and in the early 1970s a geneticist named Alfred Knudson came up with one explanation: genes that normally protect against the cancer somehow get lost or damaged. Other scientists suggested that these genes serve as "off" switches, restraining cells from replicating ceaselessly and forming malignancies. If the switches are not inherited or are somehow disabled by, say, radiation, chemicals or viruses, cancerous growth might start. Logical enough; but as years passed without hard evidence, people questioned whether such genes existed.
Last week brought vindication for Knudson, now at Philadelphia's Fox Chase...