Biology subjects

Houtman, R.

Publications and source records attributed to Houtman, R..

7 recordsLinked to original sources

bioRxiv2025

Distinct 2-phenyl-imidazo pyridine derivatives drive ER degradation and selectively impair proliferation of ER+ breast cancer cells via the aryl hydrocarbon receptor

X15695 is a 2-phenyl-imidazo[1, 2] pyridine derivative identified as an orally active, selective oestrogen receptor (ER) degrader that inhibits the proliferation of ER+ breast cancer cells. Here, we show that X15695 is an aryl hydrocarbon receptor (AHR) ligand that stabilises the AHR more efficiently than its classical ligand, indirubin. X15695 enables AHR to form a complex with the ER, promoting its proteasomal degradation. In the presence of oestradiol, X15695 outperforms the standard of care drug fulvestrant in suppressing the growth of ER+ breast cancer cells, either expressing the wild-type or clinically relevant ER mutant forms (Y537S and D538G), and of patient-derived xenograft organoids established from ER+ tumours. Using computational techniques, we discovered that a low pKa value resulting from electron-withdrawing substituents in the 2-phenyl-imidazo[1, 2] pyridine compounds is a key feature that identify them as potent AHR ligands, leading to the potential discovery of additional derivatives for future therapeutic development.

cancer biology↗

bioRxiv2023

Antagonism and selective modulation of the human glucocorticoid receptor both reduce recruitment of p300/CBP and the Mediator complex

Exogenous glucocorticoids are frequently used to treat inflammatory disorders and as adjuncts for treatment of solid cancers. However, their use is associated with severe side effects and therapy resistance. Novel glucocorticoid receptor (GR) ligands with a patient-validated reduced side effect profile have not yet reached the clinic. GR is a member of the nuclear receptor family of transcription factors and heavily relies on interactions with coregulator proteins for its transcriptional activity. To elucidate the role of the GR interactome in the differential transcriptional activity of GR following treatment with agonists, antagonists, or lead selective GR agonists and modulators (SEGRAMs), we generated comprehensive interactome maps by high-confidence proximity proteomics in lung epithelial carcinoma cells. We found that the GR antagonist RU486 and the SEGRAM Dagrocorat both reduced GR interaction with CREB-binding protein (CBP)/p300 and the Mediator complex when compared to the full GR agonist Dexamethasone. Our data offer new insights into the role of differential coregulator recruitment in shaping ligand-specific GR-mediated transcriptional responses. In BriefGlucocorticoids are commonly prescribed for the treatment of inflammatory disorders but are associated with severe side effects. Novel glucocorticoid receptor (GR) ligands with strong anti-inflammatory effects but reduced side effects are still sought after. Despite decades-long GR research, there is still an incomplete understanding of the molecular mechanisms driving context-specific GR activity. Using proximity labeling proteomics, we identified CREB-binding protein (CBP), p300 and the Mediator complex as potential crucial GR coregulators driving ligand-induced changes in GRs transcriptional activity. HighlightsO_LIGlucocorticoids (GCs), potent anti-inflammatory agents, can elicit side effects C_LIO_LIMore selective GCs, causing less side effects, are currently still unavailable C_LIO_LILack of fundamental insights on context-specific actions of the GC receptor (GR) C_LIO_LIWe mapped ligand-specific GR interactomes using proximity labeling proteomics C_LIO_LIp300/CBP and Mediator undergo ligand-dependent changes in interaction with GR C_LI

molecular biology↗

bioRxiv2020

Tapping into a phospholipid-LRH-1 axis yields a powerful anti-inflammatory agent with in vivo activity against colitis

Phospholipids are ligands for nuclear hormone receptors (NRs) and regulate transcriptional programs relevant to normal physiology and disease. Here, we demonstrate that mimicking phospholipid-NR interactions greatly improves agonists of liver receptor homolog-1 (LRH-1), a promising therapeutic target for diabetes and colitis. Conventional LRH-1 modulators partially occupy the binding pocket, leaving vacant a region important for phospholipid binding and allostery. Therefore, we constructed a set of hybrid molecules with elements of natural phospholipids appended to a synthetic LRH-1 agonist. The phospholipid-mimicking group improves binding affinity, increases LRH-1 transcriptional activity, promotes coregulator recruitment, and interacts with the targeted LRH-1 residues in crystal structures. The best new agonist markedly improves colonic histopathology and disease-related weight loss in a humanized LRH-1 murine T-cell transfer model of colitis. This is the first evidence of in vivo efficacy for an LRH-1 modulator in colitis, a leap forward in agonist development.

biochemistry↗

bioRxiv2020

Dual-Mechanism Estrogen Receptor Inhibitors Reveal an Ensemble of Binding Modes for Robust Breast Cancer Antagonism

Efforts to improve estrogen receptor-a (ER)-targeted therapies in breast cancer have relied upon a single mechanism, with ligands having a single side chain on the ligand core that extends outward to determine antagonism of breast cancer growth. Here, we describe inhibitors with two ER-targeting moieties, one of which uses an alternate structural mechanism to generate full antagonism, freeing the side chain to independently determine other critical properties of the ligands. By combining two molecular targeting approaches into a single ER ligand, we have generated antiestrogens that function through new mechanisms and structural paradigms to achieve antagonism. These dual-mechanism ER inhibitors (DMERIs) cause alternate, non-canonical structural perturbations of the receptor ligand-binding domain (LBD) to drive antagonism of proliferation in ER-positive breast cancer cells and in allele-specific resistance models. Solution structural and coregulator peptide binding analyses with DMERIs highlight marked differences from current standard-of-care, single-mechanism antiestrogens. These findings uncover an enhanced flexibility of the ER LBD through which it can access non-consensus conformational modes in response to DMERI binding, broadly and effectively suppressing ER activity. Significance StatementTo address the unmet clinical need for effectively suppressing estrogen receptor (ER) activity with both de novo resistance and in advanced ER-positive breast cancers that are resistant to standard-of-care antiestrogens, we have developed dual-mechanism ER inhibitors (DMERIs) that employ two distinct ER targeting moieties. These DMERI elicited non-canonical structural perturbations of the receptor ligand-binding domain and stabilized multiple antagonist sub-states within the dimer to generate highly efficacious antagonism of proliferation in ER-positive breast cancer cells and in allele-specific resistance models. This work reveals new conformational modes by which the activity of ER can be effectively suppressed to block breast cancer proliferation.

cancer biology↗

bioRxiv2020

Chemical Systems Biology Reveals Mechanisms of Dissociated Glucocorticoid Receptor Signaling

Glucocorticoids display remarkable anti-inflammatory activity, but their use is limited by on-target adverse effects including insulin resistance and skeletal muscle atrophy. We used a chemical systems biology approach, Ligand Class Analysis (LCA), to examine ligands designed to modulate glucocorticoid receptor activity through distinct structural mechanisms. These ligands displayed diverse activity profiles, providing the variance required to identify target genes and coregulator interactions that were highly predictive of their effects on myocyte glucose disposal and protein balance. Their anti-inflammatory effects were linked to glucose disposal but not muscle atrophy. This approach also predicted selective modulation in vivo, identifying compounds that were muscle sparing or anabolic for protein balance and mitochondrial potential. LCA defined the mechanistic links between the ligand-receptor interface and ligand-driven physiological outcomes, a general approach that can be applied to any ligand-regulated allosteric signaling system.

pharmacology and toxicology↗

bioRxiv2020

Development of a new class of liver receptor homolog-1 (LRH-1) agonists by photoredox conjugate addition

LRH-1 is a nuclear receptor that regulates lipid metabolism and homeostasis, making it an attractive target for the treatment of diabetes and non-alcoholic fatty liver disease. Building on recent structural information about ligand binding from our labs, we have designed a series of new LRH-1 agonists that further engage LRH-1 through added polar interactions. While the current synthetic approach to this scaffold has, in large part, allowed for decoration of the agonist core, significant variation of the bridgehead substituent is mechanistically precluded. We have developed a new synthetic approach to overcome this limitation, identified that bridgehead substitution is necessary for LRH-1 activation, and described an alternative class of bridgehead substituents for effective LRH-1 agonist development. We determined the crystal structure of LRH-1 bound to a bridgehead-modified compound, revealing a promising opportunity to target novel regions of the ligand-binding pocket to alter LRH-1 target gene expression.

biochemistry↗

bioRxiv2018

The SERM/SERD Bazedoxifene Disrupts ESR1 Helix 12 to Overcome Acquired Hormone Resistance in Breast Cancer Cells

Acquired resistance to endocrine therapy remains a significant clinical burden for breast cancer patients. Somatic mutations in the ESR1 (estrogen receptor alpha (ER) gene ligand-binding domain (LBD) represent a recognized mechanism of acquired resistance. Antiestrogens with improved efficacy versus tamoxifen might overcome the resistant phenotype in ER+ breast cancers. Bazedoxifene (BZA) is a potent antiestrogen that is clinically approved for use in hormone replacement therapies. We find BZA possesses improved inhibitory potency against the Y537S and D538G ER mutants compared to tamoxifen and has additional inhibitory activity in combination with the CDK4/6 inhibitor palbociclib. In addition, comprehensive biophysical and structural biology studies show that BZAs selective estrogen receptor degrading (SERD) properties that override the stabilizing effects of the Y537S and D538G ER mutations.\n\nSignificanceBazedoxifene (BZA) is a potent orally available antiestrogen that is clinically approved for use in hormone replacement therapy (DUAVEE). We explore the efficacy of BZA to inhibit activating somatic mutants of ER that can arise in metastatic breast cancers after prolonged exposure to aromatase inhibitors or tamoxifen therapy. Breast cancer cell line, biophysical, and structural data show that BZA disrupts helix 12 of the ER ligand binding domain to achieve improved potency against Y537S and D538G somatic mutants compared to 4-hydroxytamoxifen.

cancer biology↗