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A Novel Radioligand Reveals Tissue Specific Pharmacological Modulation of Glucocorticoid Receptor Expression with Positron Emission Tomography.

ABSTRACT: The complexity of glucocorticoid receptor (GR) signaling cannot be measured with direct tissue analysis in living subjects, which has stifled our understanding of GR's role in human physiology or disease and impeded the development of selective GR modulators. Herein, we report ¹⁸F-5-(4-fluorobenzyl)-10-methoxy-2,2,4-trimethyl-2,5-dihydro-1H-chromeno[3,4-f]quinoline (¹⁸F-YJH08), a radioligand that enables noninvasive measurements of tissue autonomous GR expression levels in vivo with positron emission tomography (PET). YJH08 potently binds GR (K_i ∼ 0.4 nM) with ∼100-fold selectivity compared to nuclear hormone receptors in the same subfamily. ¹⁸F-YJH08 was prepared via Cu(OTf)₂(py)₄-mediated radiofluorination of an arylboronic acid pinacol ester with ∼12% decay corrected radiochemical yield from the starting ¹⁸F-fluoride ion. We applied treatment with the tissue-wide GR agonist dexamethasone and adrenalectomy and generated an adipocyte specific GR knockout mouse to show that ¹⁸F-YJH08 specifically binds GR in normal mouse tissues, including those for which aberrant GR expression is thought to drive severe diseases (e.g., brain, adipose tissue, kidneys). Remarkably, ¹⁸F-YJH08 PET also revealed that JG231, a potent and bioavailable HSP70 inhibitor, selectively degrades GR only in the adipose tissue of mice, a finding that foreshadows how GR targeted PET might be integrated into drug discovery to screen for selective GR modulation at the tissue level, beyond the historical screening that was performed at the transcriptional level. In summary, ¹⁸F-YJH08 enables a quantitative assessment of GR expression levels in real time among multiple tissues simultaneously, and this technology is a first step toward unraveling the daunting complexity of GR signaling and rationally engineering tissue specific therapeutic modulators in vivo.

SUBMITTER: Huang Y

PROVIDER: S-EPMC8031368 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Fluorine-18-fluoro-2-deoxy-D-glucose (FDG) is widely used as positron-emission-tomography (PET) radiotracer for the detection and staging of human cancer. Tumor uptake of FDG varies substantially between different cancer types and between patients with the same tumor type. The molecular basis for this heterogeneity is unknown. Using cancer cell lines and primary human tumors of distinct histologic origins, we here show that increased FDG uptake is universally associated with coordinate upregulation of genes within the glycolysis, pentose-phosphate, and other related metabolic pathways. In primary human breast cancers, this FDG signature shows significant overlap with established breast cancer signatures for the “basal-like” disease subtype and “poor prognosis”. FDG high breast cancer showed significantly more gene copy number alterations genome wide than FDG low cancers. About 50 % of primary breast cancers with high FDG uptake and FDG gene expression signature show DNA copy gain encompassing the c-myc gene locus and express gene sets regulated by the transcription factor MYC. Our data shows that FDG-PET marks a distinct subset of “basal-like” human breast cancer which is characterized by MYC and prognostically unfavorable gene expression signatures, suggesting that FDG-PET imaging may be useful to risk-stratify patients with locally advanced breast cancer. Our general strategy to identify molecular determinants of FDG-retention through a genome-wide approach consisted of FDG uptake measurements in cancer cell lines and primary human tumors, the selection of samples with particularly high versus low FDG-retention, and subsequent pathway-based analysis of RNA expression data collected from these samples. Cell line RNA was extracted from a 10 cm plate seeded simultaneously and at the same density as the wells for FDG-uptake assays. For primary human tumor samples, RNA was extracted from macrodissected frozen tumor tissue. All cell line RNA samples and the astrocytoma RNA aliquots were hybridized to Affymetrix U133 Plus 2.0 arrays. All primary breast cancer RNA samples were hybridized to Affymetrix U133A arrays.

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A Novel Radioligand Reveals Tissue Specific Pharmacological Modulation of Glucocorticoid Receptor Expression with Positron Emission Tomography.

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