Although the anticancer activities of vitamin E have been studied for decades, recent intervention studies with α-tocopherol (the isoform that is preferentially absorbed in humans) have been negative for cancer protection. However, in the June 15 issue of Clinical Cancer Research, Lee et al. demonstrate that a tocopherol mixture rich in the γ and δ isoforms inhibits mammary tumorigenesis by activating PPAR-γ signaling and antagonizing ER signaling– suggesting that γ- and δ-tocopherols should be studied as potential antitumorigenic agents.