MEDICAL SCIENCES. For the article “Mutations in the G-quadruplex silencer element and their relationship to c-MYC overexpression, NM23 repression, and therapeutic rescue,” by Cory L. Grand, Tiffanie J. Powell, Raymond B. Nagle, David J. Bearss, Denise Tye, Mary Gleason-Guzman, and Laurence H. Hurley, which appeared in issue 16, April 20, 2004, of Proc. Natl. Acad. Sci. USA (101, 6140–6145; first published April 12, 2004; 10.1073/pnas.0400460101), the authors wish to note the following: “After an unsuccessful effort to expand the observations that were reported in our article, we have determined that certain data contained in the manuscript are incorrect. The error is a result of contamination of genomic DNA with plasmid DNA, which affects the results represented in Fig. 2 and Table 1 of this article. Our conclusion that the erroneous results were due to a plasmid contamination has been confirmed by an independent laboratory, at our request. We have been unable to reproduce the experiments indicating the presence of tumor-derived mutations in the G-quadruplex silencer element of the nuclease hypersensitivity element region of the c-MYC gene in the tumor samples reported in the article or in additional tumor samples that we have analyzed. We therefore retract the article. We deeply regret this error and apologize for any inconvenience publication of this study may have caused.”