Until 2003, scientists knew that the principal distinction between the “normalcy” of a cell and the “abnormalcy” of a cancer cell lay in the accumulation of genetic mutations—ras, myc, Rb, neu, and so forth—that unleashed the hallmark behaviors of cancer cells. But this description of cancer was incomplete. It provoked an inevitable question: how many such mutations does a real cancer possess in total? Individual oncogenes and tumor suppressors had been isolated, but what was the comprehensive set of such mutated genes that exists in any true human cancer?
