This study was supported by Uniformed Services University Grant RO 7439 and USPHS grant CA-34994 from the National Cancer Institute (to O.T. Preble). Initial portions of this work were also supported by USPHS Grants AI-07057 and AM 2948 (to J. Vilcek) and by a grant from the Kroc Foundation (to R.M. Friedman). The opinions or assertions contained herein are the private views of the authors and should not be construed as official or as necessarily reflecting the views of the Uniformed Services University of the Health Sciences or the Department of Defense.