RNA interference (RNAi) is fast becoming an essential tool for academic and industrial labs searching for genes that promote or inhibit cancer. Munich-based Xantos Biomedicine, for example, once relied on cDNA overexpression, a decades-old approach, to identify novel genes with tumor-suppressor phenotypes. But the small five-year-old company is now supplementing its gain-of-function, high-throughput cDNA technology with loss-of-function RNAi. "I don't see any really stringent advantage of one versus the other," says chief scientific officer Ulrich Brinkmann. "It's really different questions that you can ask and different answers. You need both." The journal Oncogene devoted its entire November 1, 2004, issue to high-throughput RNAi screens in cancer research.