Retraction

Biochemistry. In the article “ATP-dependent uptake of natural product cytotoxic drugs by membrane vesicles establishes MRP as a broad specificity transporter” by Saptarshi Paul, Lisa M. Breuninger, Kenneth D. Tew, Hongxie Shen, and Gary D. Kruh, which appeared in number 14, July 9, 1996, of Proc. Natl. Acad. Sci. USA (93, 6929–6934), the authors request that the following be noted. “Due to the uncertain validity of the data and the irreproducibility of some of the results, we retract this article. We are currently unable to reproduce the experiments indicating that MRP transports natural product drugs. We apologize for any inconvenience that publication of this study may have caused.” Saptarshi Paul, Lisa M. Breuninger, Kenneth D. Tew, Hongxie Shen, Gary D. Kruh