Fig. 3.

Biological responses to SOs are dependent on dose. Low concentrations (nanomolar) of SOs target Keap1 and activate the Nrf2/ARE cytoprotective and anti-inflammatory response. As the concentration of SO increases, SOs target Arp3 and other components of the cytoskeleton to inhibit cell proliferation, whereas even higher concentrations (micromolar) of SOs can selectively induce apoptosis in cancer cells by targeting a number of key regulatory proteins and pathways that are frequently constitutively activated or overexpressed in cancer cells. [Adapted from Liby KT, Yore MM, and Sporn MB (2007) Triterpenoids and rexinoids as multifunctional agents for the prevention and treatment of cancer. Nat Rev Cancer 7:357–369. Copyright © 2007 Nature Publishing Group. Used with permission.]