Chaetocin is a fungal mycotoxin, originally produced by Chaetomium species, that inhibits the lysine-specific histone methyltransferases (HMTs) SU(VAR)3-9 (IC₅₀ = 0.8 μM). HMTs are responsible for methylation of histones, thereby affecting heterochromatinization. Chaetocin is also known to inhibit G9a and DIM5 (IC₅₀ = 2.5 μM and 3 μM respectively; Cherblanc et al.; Greiner et al.). Chaetocin also acts as a competitive substrate and inhibitor of the central oxidative stress remediation enzyme thioredoxin reductase-1 (TrxR1; Km = 4.6 μM) more potently than glutathione reductase or thioredoxin (Tibodeau et al.).CANCER RESEARCH· Induces cellular oxidative stress, selectively killing cancer cells and rapidly-proliferating primary cells (Isham et al.; Spannhoff et al.)· Attenuates the growth of glioma xenografts accompanied by an increase in reactive oxygen species (ROS) production (Dixit et al.).