The synthetic oleanane triterpenoid CDDO-2P-Im binds GRP78/BiP to induce unfolded protein response-mediated apoptosis in myeloma

by Selleckchem | Sep 21 2023

Synthetic oleanane triterpenoids (SOTs) are small molecules with broad anti-cancer 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 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 (qRT-PCR) revealed upregulation of the unfolded protein response (UPR) in MM cells upon 2P-lm treatment, implicating activation of the UPR as a key step in 2P-Im-induced apoptosis. Supporting this hypothesis, deletion of genes encoding either protein kinase R (PKR)-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 (DARTS) 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.

Comments:

The passage you provided describes a study that investigated the effects and mechanisms of a synthetic oleanane triterpenoid (SOT) called 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]-4(-pyridin-2-yl)-1H-imidazole (CDDO-2P-Im or '2P-Im'). This compound exhibited enhanced anti-cancer activity and improved pharmacokinetics compared to a previous generation SOT called CDDO-Im. The researchers focused on studying the effects of 2P-Im in human multiple myeloma (MM) cells and a murine model of plasmacytoma.

The study found that 2P-Im displayed synergy with the proteasome inhibitor ixazomib in MM cells, suggesting a potential combination therapy approach. RNA sequencing and quantitative reverse transcription PCR (qRT-PCR) analysis revealed that 2P-Im treatment led to the upregulation of the unfolded protein response (UPR) in MM cells. This indicated that activation of the UPR played a crucial role in the induction of apoptosis (programmed cell death) by 2P-Im.

Further experiments demonstrated that the deletion of genes encoding two UPR-associated proteins, protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) and DNA damage-inducible transcript 3 protein (DDIT3 or CHOP), impaired the MM cells' response to 2P-Im. Treatment with an integrated stress response inhibitor called ISRIB, which acts downstream of PERK to inhibit UPR signaling, also diminished the response to 2P-Im. These findings provided additional evidence for the involvement of the UPR in mediating the effects of 2P-Im.

The study also employed drug affinity responsive target stability (DARTS) and thermal shift assays to demonstrate that 2P-Im directly bound to an endoplasmic reticulum chaperone called BiP (also known as GRP78/BiP). BiP is a stress-inducible key signaling molecule of the UPR. This finding identified GRP78/BiP as a novel target of SOTs, specifically 2P-Im, and suggested the potential broader utility of this class of small molecules as modulators of the UPR.

In summary, the study showed that 2P-Im, a synthetic oleanane triterpenoid, synergized with ixazomib in MM cells and exhibited activity in a murine model of plasmacytoma. The activation of the UPR was identified as a key step in 2P-Im-induced apoptosis. The study also revealed that 2P-Im directly bound to the endoplasmic reticulum chaperone BiP, highlighting it as a novel target for SOTs and suggesting the potential for this class of compounds to modulate the UPR.