[1] NCI, Urol Oncol Branch, Ctr Canc Res, NIH, Bethesda, MD 20892 USA
[2] NCI, Mol Pharmacol Lab, NIH, Bethesda, MD 20892 USA
[3] NCI, Med Oncol Branch, NIH, Bethesda, MD 20892 USA
[4] Georgetown Univ, Sch Med, Dept Urol, Washington, DC USA
[5] Amgen Inc, Dept Canc Biol, Thousand Oaks, CA 91320 USA