Marisa Sanchez's research while affiliated with Sanford Burnham Prebys Medical Discovery Institute and other places

The cellular stress response triggers a cascade of events leading to transcriptional reprogramming and a transient inhibition of global protein synthesis, which is thought to be mediated by phosphorylation of eukaryotic initiation factor-2α (eIF2α). Using mouse embryonic fibroblasts (MEFs) and the fission yeast S. pombe, we report that rapid translational arrest and cell survival in response to hydrogen peroxide-induced oxidative stress do not rely on eIF2α kinases and eIF2α phosphorylation. Rather, H2O2 induces a block in elongation through phosphorylation of eukaryotic elongation factor 2 (eEF2). Kinetic and dose-response analyses uncovered cross talk between the eIF2α and eEF2 phosphorylation pathways, indicating that, in MEFs, eEF2 phosphorylation initiates the acute shutdown in translation, which is maintained by eIF2α phosphorylation. Our results challenge the common conception that eIF2α phosphorylation is the primary trigger of translational arrest in response to oxidative stress and point to integrated control that may facilitate the survival of cancer cells.

The cellular stress response triggers a cascade of events leading to transcriptional reprogramming and a transient inhibition of global protein synthesis, which is thought to be mediated by phosphorylation of eukaryotic initiation factor-2α (eIF2α). Using mouse embryonic fibroblasts (MEFs) and the fission yeast S. pombe, we report here that rapid translational arrest and cell survival in response to hydrogen peroxide-induced oxidative stress do not rely on eIF2α kinases and eIF2α phosphorylation. Rather H 2 O 2 induces a block in elongation through phosphorylation of eukaryotic elongation factor 2 (eEF2). Kinetic and dose-response analyses uncovered crosstalk between the eIF2α and eEF2 phosphorylation pathways, indicating that, in MEFs, eEF2 phosphorylation initiates the acute shutdown in translation, which is then maintained by eIF2α phosphorylation. Our results challenge the common conception that eIF2α phosphorylation is the primary trigger of translational arrest in response to oxidative stress and point to integrated control that may facilitate the survival of cancer cells. HIGHLIGHTS Oxidative stress-induced translation arrest is independent of eIF2α phosphorylation Oxidative stress blocks translation elongation Oxidative stress triggers eEF2 kinase activation eEF2K KO cells are hypersensitive to oxidative stress

Di(1H-indol-3-yl)(4-trifluoromethylphenyl)methane (DIM-Ph-4-CF3) is an analog of orphan nuclear receptor 4A1 (NR4A1) ligand cytosporone B. We have synthesized several oxidation products of DIM-Ph-4-CF3, focusing on analogs with electronwithdrawing or donating groups at their phenyl ring 4-positions, and examined their anti-cancer activity and mechanism-of-action. Mesylates (DIM-Ph-4-X⁺ OMs⁻s) having CF3, CO2Me and Cl groups were more effective inhibitors of cancer cell viability than their precursors. ¹⁹F NMR spectroscopy and differential scanning calorimetry strongly indicated interactions of DIM-Ph-4-CF+³ OMs- with the NR4A1 ligand binding domain, and compound-induced apoptosis of prostate cancer cells was dependent on NR4A1. DIM-Ph-4-CF+³ OMs- showed robust inhibition of LNCaP prostate cancer xenografts with no apparent toxicity. In vitro and in vivo, DIM-Ph-4-CF+³ OMs- activated proapoptotic unfolded protein response (UPR) signaling in prostate cancer cells. Independently of DIM-Ph-4-CF+³ OMs⁻, the bulk of NR4A1 localized to the cytoplasm in various cancer cell lines, suggesting a cytoplasmic mechanism-of-action of DIMPh- 4-CF+³ OMs⁻ in UPR induction and cell death. In summary, the data suggest that oxidized analogs of DIM-Ph-4-CF3 possess potent and safe anti-cancer activity which is mediated through UPR signaling downstream of NR4A1 binding.