Affiliation:
1. Department of Pathology Case Western Reserve University School of Medicine Cleveland OH USA
2. Triterpenoid Therapeutics Inc. Tunbridge VT USA
3. Trinity College of Arts and Sciences Duke University Durham NC USA
4. Department of Chemical and Biomolecular Engineering Case Western Reserve University Cleveland OH USA
5. The Angie Fowler Adolescent and Young Adult Cancer Institute University Hospitals Rainbow Babies & Children's Hospital Cleveland OH USA
6. The Case Comprehensive Cancer Center Cleveland OH USA
7. Department of Pediatrics Case Western Reserve University Cleveland OH USA
Abstract
Synthetic oleanane triterpenoids (SOTs) are small molecules with broad anticancer properties. A recently developed SOT, 1‐[2‐cyano‐3,12‐dioxooleana‐1,9(11)‐dien‐28‐oyl]‐4(‐pyridin‐2‐yl)‐1H‐imidazole (CDDO‐2P‐Im or ‘2P‐Im’), exhibits enhanced activity and improved pharmacokinetics over CDDO‐Im, a previous generation SOT. However, the mechanisms leading to these properties are not defined. Here, we show the synergy of 2P‐Im and the proteasome inhibitor ixazomib in human multiple myeloma (MM) cells and 2P‐Im activity in a murine model of plasmacytoma. RNA sequencing and quantitative reverse transcription PCR revealed the upregulation of the unfolded protein response (UPR) in MM cells upon 2P‐lm treatment, implicating the activation of the UPR as a key step in 2P‐Im‐induced apoptosis. Supporting this hypothesis, the deletion of genes encoding either protein kinase R‐like endoplasmic reticulum kinase (PERK) or DNA damage‐inducible transcript 3 protein (DDIT3; also known as CHOP) impaired the MM response to 2P‐Im, as did treatment with ISRIB, integrated stress response inhibitor, which inhibits UPR signaling downstream of PERK. Finally, both drug affinity responsive target stability and thermal shift assays demonstrated direct binding of 2P‐Im to endoplasmic reticulum chaperone BiP (GRP78/BiP), a stress‐inducible key signaling molecule of the UPR. These data reveal GRP78/BiP as a novel target of SOTs, and specifically of 2P‐Im, and suggest the potential broader utility of this class of small molecules as modulators of the UPR.
Funder
National Institutes of Health
National Cancer Institute
Subject
Cancer Research,Genetics,Molecular Medicine,General Medicine,Oncology
Cited by
1 articles.
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