[1] Johns Hopkins Univ, Sch Med, Predoctoral Program Human Genet, Baltimore, MD 21205 USA
[2] Johns Hopkins Univ, Sch Med, Dept Med, Baltimore, MD 21205 USA
[3] Johns Hopkins Univ, Sch Med, Dept Genet & Mol Biol, Baltimore, MD 21205 USA
[4] Johns Hopkins Univ, Sch Med, Dept Oncol, Baltimore, MD 21205 USA
[5] NCI, Radiat Oncol Branch, Canc Res Ctr, NIH, Bethesda, MD 20892 USA