Brassinin (BSN) is a phytoalexin isolated from B. campestris that exhibits anticancer, chemopreventative, antiproliferative, and antifungal activities. Brassinin suppresses constitutive and IL-6-induced STAT3 activation in vitro and attenuates tumor growth in a xenograft lung cancer mouse model through modulation of E3 SUMO-protein ligase 3 (PIAS-3) and suppressor of cytokine signaling-3 (SOCS-3). Brassinin also induces apoptosis in PC3 cells through suppression of PI3K, Akt, mTOR, and S6K1.