Corrections and Clarifications
The News & Comment article "Animal tests take back seat to clinical data" by Lisa Seachrist (10 June, p. 1525) misidentified the author of a study that found specific mutations in the tumor-suppressor gene p53 in 50% of liver tumors from rats fed tamoxifen. The work was done by Gary Williams and his colleagues at the American Health Foundation in Valhalla, New York, not by David Kupfer of the Worcester Foundation for Experimental Biology, as the article reported. Kupfer found that tamoxifen is converted to reactive metabolites in the rat liver that become covalently bound to liver proteins; however, it is not known if this is detrimental to the animal.