Anti-nucleolin-conjugated gold nanoparticle (AS1411-GNP) is an aptamer-based anticancer drug that can be used to treat virtually any type of cancer. A key component of this drug, the AS1411 aptamer, has been tested in over 100 cancer patients and is well tolerated with no evidence of severe side effects; with at least 7 patients having long-lasting clinical responses in which their cancers disappeared or shrank substantially. Binding the aptamer AS1411 to a gold nanoparticle furnishes it with increased potency and versatility. Preclinical studies in breast cancer with AS1411-GNP showed significantly enhanced activity compared to AS1411 alone. The broader versatility conferred on AS1411 by linking it to the nanoparticle includes such uses as enhanced radiation therapy, tumor imaging, and the delivery of other anti-cancer compounds directly to tumor cells.