National Cancer Institute - Dictionary of Cancer Terms

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5-FU

A drug that is used in the treatment of cancer. It belongs to the family of drugs called antimetabolites. Also called fluorouracil.

5-hydroxyindoleacetic acid

5HIAA. A breakdown product of serotonin that is excreted in the urine. Serotonin is a hormone found at high levels in many body tissues. Serotonin and 5HIAA are produced in excess amounts by carcinoid tumors, and levels of these substances may be measured in the urine to test for carcinoid tumors.

5-hydroxytryptamine

A hormone found in the brain, platelets, digestive tract, and pineal gland. It acts both as a neurotransmitter (a substance that nerves use to send messages to one another) and a vasoconstrictor (a substance that causes blood vessels to narrow). A lack of 5-hydroxytryptamine in the brain is thought to be a cause of depression. Also called serotonin.

506U78

A substance that is being studied in the treatment of cancer. It belongs to the family of drugs called antimetabolites. Also called nelarabine.

5Q- syndrome

5Q minus syndrome. A rare disorder caused by loss of part of the long arm (Q arm) of human chromosome 5. This syndrome affects myeloid (bone marrow) cells, causing treatment-resistant anemia, and myelodysplastic syndromes that may lead to acute myelogenous leukemia.