I hadn't heard about this... They've apparently managed to create something that will hunt down and kill specific cancer cells. (It doesn't get 'em ALL, and they haven't figured out how to get the things safely inside a human, so, not a cure, but...)
http://arstechnica.com/science/news/2011/09/synthetic-genetic-circuitry-tuned-to-kill-specific-cancer-cell.ars