Abstract
Molecular investigations of cancer cells have identified genes, proteins, and biochemical pathways that may be useful for diagnosing and classifying cancer, formulating a prognosis, or identifying people who are predisposed to cancer. These studies have revealed two classes of genes related to cancer: proto-oncogenes and tumor-suppressor genes. The latter are now under intense scrutiny; nine tumor-suppressor genes have been identified by molecular cloning techniques (three in the past year1), and investigations of a variety of cancers suggest the existence of at least two dozen others.Evidence implicating suppressor genes in the cause of cancer comes mainly from studies of . . .