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Characterization of the novel anti‐cancer therapeutic ONC201 and related analogs as non‐competitive antagonists of the D 2 dopamine receptor
Author(s) -
Cuoco Caroline A.,
Free R. Benjamin,
Willette Blair K.,
Day Marilyn M.,
Lane J. Robert,
Allen Joshua E.,
Sibley David R.
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.827.10
Subject(s) - radioligand , dopamine receptor d2 , receptor , pharmacology , chemistry , agonist , dopamine , protein kinase b , signal transduction , cancer research , biology , biochemistry , endocrinology
ONC201 is the first member of a new class of anti‐cancer small molecules called imipridones to be investigated in clinical trials for select advanced cancers. The anti‐cancer properties of the parent compound were first discovered in a phenotypic screen as a p53‐independent inducer of the immune cytokine TRAIL and tumor cell death. Tumor cell signaling studies revealed that ONC201 causes a dual inactivation of Akt/ERK that drives Foxo3a‐mediated TRAIL gene induction. Recent studies identified that ONC201 also selectively antagonizes D2‐like dopamine receptors (D2R, D3R, D4R) at therapeutically relevant concentrations. Notably, malignant overexpression of the D2R occurs in a variety of cancers and its antagonism imparts pro‐apoptotic and anti‐proliferative effects in tumor cells. In the current study, we sought to characterize the pharmacological properties of ONC201 and several novel analogs (ONC206 and ONC213) on D2‐like receptors. Both functional signaling (β‐arrestin recruitment and cAMP accumulation) and radioligand competition binding assays were employed. Radioligand binding assays with [ 3 H]‐methylspiperone determined that these compounds bind to D2‐like receptors with low μM affinity, consistent with their potencies for anticancer activities. When the compounds were tested in β‐arrestin recruitment assays (D2R, D3R, and D4R) and cAMP accumulation assays (D2R and D4R), all analogs were determined to be antagonists with no measurable agonist efficacy. Importantly, a resolved enantiomer of ONC201 that showed no anti‐cancer activity was found to be inactive in blocking the D2R. To gain further insight into the mode of action of ONC201 and analogs at the D2R, Schild‐like curve shift assays were performed in using the functional assays, where increasing concentrations of compound are used to shift the dopamine concentration‐response curve. Increasing concentrations of all compounds caused both a rightward shift in the dopamine concentration‐response curve and a depression of the maximum response. These data are consistent with a non‐competitive mode of action and could be fitted with an operational model of allostery. These analyses revealed a predominant modulatory effect upon dopamine efficacy and a smaller effect on dopamine potency. Further studies will aim to elucidate the nature in which these analogs interact with D2R binding pockets through site‐directed mutagenesis. Understanding the pharmacological profile of ONC201, including different signaling paradigms, may lead to a better understanding of its mechanism for anticancer targeting. Support or Funding Information NINDS IRP This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .