Oxidative stress serves as an important regulator of both apoptosis and metabolic reprogramming in tumor cells. Chaetocin, a histone methyltransferase inhibitor, is known to induce ROS generation. As elevating basal ROS level sensitizes glioma cells to apoptosis, the ability of Chaetocin in regulating apoptotic and metabolic adaptive responses in glioma was investigated. Chaetocin induced glioma cell apoptosis in a ROS-dependent manner. Increased intracellular ROS induced (i) Yes-associated protein 1 (YAP1) expression independent of the canonical Hippo pathway as well as (ii) ATM and JNK activation. Increased interaction of YAP1 with p73 and p300 induced apoptosis in an ATM-dependent manner. Chaetocin induced JNK modulated several metabolic parameters like glucose uptake, lactate production, ATP generation, and activity of glycolytic enzymes hexokinase and pyruvate kinase. However, JNK had no effect on ATM or YAP1 expression. Coherent with the in vitro findings, Chaetocin reduced tumor burden in heterotypic xenograft glioma mouse model. Chaetocin-treated tumors exhibited heightened ROS, pATM, YAP1 and pJNK levels. Our study highlights the coordinated control of glioma cell proliferation and metabolism by ROS through (i) ATM-YAP1-driven apoptotic pathway and (ii) JNK-regulated metabolic adaptation. The elucidation of these newfound connections and the roles played by ROS to simultaneously shift metabolic program and induce apoptosis could provide insights toward the development of new anti-glioma strategies.

We recently reported that the antineoplastic thiodioxopiperazine natural product chaetocin potently induces cellular oxidative stress, thus selectively killing cancer cells. In pursuit of underlying molecular mechanisms, we now report that chaetocin is a competitive and selective substrate for the oxidative stress mitigation enzyme thioredoxin reductase-1 (TrxR1) with lower K(m) than the TrxR1 native substrate thioredoxin (Trx; chaetocin K(m) = 4.6 +/- 0.6 microM, Trx K(m) = 104.7 +/- 26 microM), thereby attenuating reduction of the critical downstream ROS remediation substrate Trx at achieved intracellular concentrations. Consistent with a role for TrxR1 targeting in the anticancer effects of chaetocin, overexpression of the TrxR1 downstream effector Trx in HeLa cells conferred resistance to chaetocin-induced, but not to doxorubicin-induced, cytotoxicity. As the TrxR/Trx pathway is of central importance in limiting cellular reactive oxygen species (ROS)--and as chaetocin exerts its selective anticancer effects via ROS imposition--the inhibition of TrxR1 by chaetocin has potential to explain its selective anticancer effects. These observations have important implications not just with regard to the mechanism of action and clinical development of chaetocin and related thiodioxopiperazines, but also with regard to the utility of molecular targets within the thioredoxin reductase/thioredoxin pathway in the development of novel candidate antineoplastic agents.