The present invention relates to compositions and methods for altering cell function. In particular, the present invention provides compositions comprising selenium (e.g., SEL-PLEX) and methods of using the same (e.g., as a therapeutic and/or prophylactic treatment). Additionally, the present invention demonstrates that specific forms of selenium (e.g., SEL-PLEX), when administered to a subject, possess the ability to alter (e.g., reduce) gene expression in various tissues (e.g., compared to expression in subjects not administered selenium).