[1] NCI, Occupat Epidemiol Branch, Div Canc Epidemiol & Genet, Bethesda, MD 20892 USA
[2] Rhein Westfal TH Aachen, Dept Dermatol, D-5100 Aachen, Germany
[3] NCI, Div Basic Sci, Human Carcinogenesis Lab, Bethesda, MD 20892 USA
[4] City Hope Beckman Res Inst, Div Mol Med, Duarte, CA USA