Not much is known about the way different proteins are produced and move around in living cells exposed to drugs. But a research team has now used a proteomics approach to study such processes in cancer cells exposed to the chemotherapy drug camptothecin (Science, DOI: 10.1126/science.1160165). Researchers could pursue the strategy to identify proteins associated with specific cell properties, such as enhanced drug resistance, and in their efforts to design more effective medications. Molecular cell biology graduate students Ariel A. Cohen, Naama Geva-Zatorsky, and Eran Eden of Weizmann Institute of Science, in Rehovot, Israel, and coworkers used time-lapse fluorescence microscopy to monitor the levels and locations of close to 1,000 different fluorescently tagged proteins in camptothecin-exposed human cancer cells. They found that levels of two proteins, the RNA helicase DDX5 and the replication factor RFC1, increase in cells that survive and decrease in those that die. They confirmed DDX5's effect on cell fate by showing that RNA-interference-induced reduction of protein levels boosted cell death after exposure to camptothecin.