Discovery of Small-Molecule Enhancers of Reactive Oxygen Species That are Nontoxic or Cause Genotype-Selective Cell Death

Abstract

Elevation of reactive oxygen species (ROS) levels has been observed in many cancer cells relative to nontransformed cells, and recent reports have suggested that small-molecule enhancers of ROS may selectively kill cancer cells in various in vitro and in vivo models. We used a high-throughput screening approach to identify several hundred small-molecule enhancers of ROS in a human osteosarcoma cell line. A minority of these compounds diminished the viability of cancer cell lines, indicating that ROS elevation by small molecules is insufficient to induce death of cancer cell lines. Three chemical probes (BRD5459, BRD56491, BRD9092) are highlighted that most strongly elevate markers of oxidative stress without causing cell death and may be of use in a variety of cellular settings. For example, combining nontoxic ROS-enhancing probes with nontoxic doses of l-buthionine sulfoximine, an inhibitor of glutathione synthesis previously studied in cancer patients, led to potent cell death in more than 20 cases, suggesting that even nontoxic ROS-enhancing treatments may warrant exploration in combination strategies. Additionally, a few ROS-enhancing compounds that contain sites of electrophilicity, including piperlongumine, show selective toxicity for transformed cells over nontransformed cells in an engineered cell-line model of tumorigenesis. These studies suggest that cancer cell lines are more resilient to chemically induced increases in ROS levels than previously thought and highlight electrophilicity as a property that may be more closely associated with cancer-selective cell death than ROS elevation.

Using Sensors and Generators of H2O2to Elucidate the Toxicity Mechanism of Piperlongumine and Phenethyl Isothiocyanate

“…Departments of 1 Biological Engineering and 2 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.…”

“…Given the role of GSH in the reduction of H 2 O 2 and the oxidation of sulfhydryl group, it is believed that GSH depletion will cause toxicity via accumulation of H 2 O 2 and oxidized proteins (6). It has been previously suggested that electrophilic small molecules such as buthionine sulfoximine (BSO), piperlongumine (PL), and phenethyl isothiocyanate (PEITC) convey at least part of their toxicity via this mechanism (9,16,39,49,51,56), and all of these drugs have been shown to be selectively toxic to certain in vitro and in vivo tumor models (1,5,13,39). Incubation of tumor cells with piperlongumine and PEITC results in depletion of GSH and elevation of fluorescence from dichloro-dihydro-fluorescein diacetate (DCFH-DA), a cell permeable dye that exhibits increasing fluorescence intensity upon oxidation (9,39,49,56).…”

Hypoxic Signaling and the Cellular Redox Tumor Environment Determine Sensitivity to MTH1 Inhibition

“…Therefore, the tightly balanced oncogenic redox system is presenting an attractive target for novel anticancer therapies (8)(9)(10). However, as solely increasing oxidative stress to induce cancer cell death seems to be insufficient (11), other strategies to target the cancer-specific redox environment might be more effective.…”

Piperlongumine Chemosensitizes Tumor Cells through Interaction with Cysteine 179 of IκBα Kinase, Leading to Suppression of NF-κB–Regulated Gene Products

“…Piperlongumine has multiple pharmacologic activities: it has been described as a platelet aggregation inhibitor (3), an anxiolytic agent (4), an antidepressant (5), an antinociceptive agent (6), an anti-atherosclerotic agent (7), an antidiabetic agent (8), an anti-inflammatory agent (9), and an infectious pathogen inhibitor (10). Furthermore, piperlongumine has been reported to kill multiple types of cancer cells, inhibit metastasis, and have antitumor activities in a variety of animal models (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22).…”