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ALSO KNOWN AS: Precursors of oncogenes

SIGNIFICANCE: The HRAS gene controls production of a protein that regulates cell division. It is a member of a gene class called proto-oncogenes, and mutations in this gene can cause unusual, sometimes cancerous, growths, particularly in the bladder. Mutations in HRAS are also linked to a rare syndrome called Costello syndrome. Testing for this mutation can help distinguish between this disease and other syndromes.

SIGNIFICANCE: At its root, cancer is a genetic disease. It is characterized by unrestrained growth and reproduction of cells, loss of contact inhibition, and, eventually, metastasis (the wandering of cancer cells from a primary tumor to other parts of the body). All of these changes represent underlying mutations or inappropriate expression of genes involved in controlling the cell cycle and related processes.

SIGNIFICANCE: Oncogenes are mutated forms of normal genes that, when activated, can transform normal cells into cancerous cells. The prefix “onco-” comes from the Greek word meaning “tumor.” Oncogenes originate in normal cellular genes, often ones that help control cell division. When normal cells become damaged or have completed their functions, they commit suicide through a process called apoptosis. Cancer disrupts that process, causing cells in effect to pursue immortality. Proto-oncogenes, in contrast, are normal genes involved in controlling cell division that, if damaged by mutations, can become oncogenes. The term “proto-oncogene” is misleading in that it implies that progression into an oncogene is inevitable when in fact it is not. Proto-oncogenes lack the ability of oncogenes to transform cells.