Science Peels the Onion of Selenium Effects on Prostate Carcinogenesis

The role of the essential trace element selenium in prostate cancer was first (and last) editorialized in the Journal in 1998 in conjunction with the report of the first large prospective obser-vational study of selenium and the risk of advanced prostate cancer (1,2). Although the principals for the 1998 study were the same as those for the observational study by Li et al. (3) in this issue of the Journal, much has changed in the basic scientific understanding of selenium. The onion, an allium vegetable that concentrates selenium, is an apt metaphor for the scientific work of peeling back the layers of molecular effects and mechanisms underlying the strong selenium epidemiology in the prostate. The past 6 years have seen the publication of seven prospec-tive epidemiologic studies of selenium status and prostate cancer (including the study in this issue of the Journal) (2–8), with a collective total of nearly 2000 case subjects. The studies in-