Imipridone ONC212 activates orphan G protein-coupled receptor GPR132 and integrated stress response in acute myeloid leukemia

Abstract

Imipridones constitute a novel class of anti-tumor agents. Here, we report that a second-generation imipridone, ONC212, possesses highly increased anti-tumor activity compared to the first-generation compound ONC201. In vitro studies using human acute myeloid leukemia (AML) cell lines, primary AML, and normal bone marrow (BM) samples demonstrate that ONC212 exerts prominent apoptogenic effects in AML, but not in normal BM cells, suggesting potential clinical utility. Imipridones putatively engage G protein-coupled receptors (GPCRs) and/or trigger an integrated stress response in hematopoietic tumor cells. Comprehensive GPCR screening identified ONC212 as activator of an orphan GPCR GPR132 and Gαq signaling, which functions as a tumor suppressor. Heterozygous knock-out of GPR132 decreased the anti-leukemic effects of ONC212. ONC212 induced apoptogenic effects through the induction of an integrated stress response, and reduced MCL-1 expression, a known resistance factor for BCL-2 inhibition by ABT-199. Oral administration of ONC212 inhibited AML growth in vivo and improved overall survival in xenografted mice. Moreover, ONC212 abrogated the engraftment capacity of patient-derived AML cells in an NSG PDX model, suggesting potential eradication of AML initiating cells, and was highly synergistic in combination with ABT-199. Collectively, our results suggest ONC212 as a novel therapeutic agent for AML.

Imipridone Anticancer Compounds Ectopically Activate the ClpP Protease and Represent a New Scaffold for Antibiotic Development

“…Interestingly, our proteomic analysis revealed depletion of several cell cycle proteins, which may explain a previously described cell cycle arrest phenotype caused by ONC201 (Kline et al 2016). We also did not recover HRI (EIF2AK1) or PKR (EIF2AK2) genes, or other mediators of the integrated stress response (Ishizawa et al 2016;Kline et al 2016), nor any dopaminergic receptors or other GPCR-related genes (Kline et al 2018;Madhukar et al 2019;Nii et al 2019;Prabhu et al 2019). Although it is possible that cell type-specific gene expression may explain the absence of these genetic hits, the most parsimonious explanation is that CLPP is the primary target of the imipridones.…”

“…20 phase II clinical trials for hematological malignancies and solid tumors (Allen et al 2016). Several mechanisms of action have been ascribed to ONC201 and its more potent derivate ONC212 (Wagner et al 2017), including: FOXO3A-mediated induction of TRAIL (Allen et al 2013) upon inhibition of the prosurvival AKT/ERK pathway (Allen et al 2013); activation of the integrated stress response (ISR) via the eIF2a kinases HRI and PKR, resulting in ATF4/CHOP-mediated upregulation of the TRAIL DR5 receptor (Kline et al 2016); activation of the ISR independent of eIF2a (Ishizawa et al 2016); and antagonism of dopaminergic G protein-coupled receptors (GPCRs) or activation of other GPCRs (Kline et al 2018;Madhukar et al 2019;Nii et al 2019;Prabhu et al 2019). Cell biological characterization suggests that ONC201 disrupts mitochondrial function and that cancer cells that do not depend on mitochondrial respiration are ONC201-insensitive (Greer et al 2018).…”

ONC201 and imipridones: Anti-cancer compounds with clinical efficacy

“…Another ONC201 analog synthesized was ONC212, a fluorinated ONC201-derivative which was found to be the most potent anti-cancer imipridone family member to date, exhibiting cytotoxicity at low nanomolar concentrations. The anti-cancer efficacy of ONC212 may be driven by agonism of the orphan GPCR GPR132 and hyperactivation of the mitochondrial protease ClpP, leading to induction of tumor-selective apoptosis [7] , [10] , [123] , [124] . GPCR profiling of ONC212 revealed no interaction with DRD2 or any other GPCRs with known ligands.…”

Targeting Mitochondria in Melanoma

“…According to the National Cancer Institute (USA) and several publications, the first-in-class analogue of the imipridone family, ONC201, is currently being tested for treatment of several types of solid tumors and hematological malignancies in clinical trials [ 39 , 83 , 85 , 86 , 87 ]. The anti-cancer activity of imipridones is linked to different mechanisms such as inactivation of Akt and ERK, activation of mitochondrial caseinolytic protease P (ClpP), protein quality control of the endoplasmic reticulum, the cellular stress response, apoptosis and cell-cycle arrest [ 40 , 44 , 88 ]. ONC212, another analogue of this family, displays enhanced anti-tumor effects in comparison with ONC201 [ 41 ].…”

“…Newly developed anti-tumor agents like the imipridone family including ONC201, ONC206, and ONC212 demonstrate anti-tumor effects in a variety of cancers. Remarkably, they had no effects on non-cancerous cells [ 39 , 40 , 41 ]. Recently, suppression of mitochondrial respiration has been reported as a novel mechanism of action of imipridone agents in glioblastoma and breast cancer [ 42 , 43 , 44 ].…”