Diazepam-based covalent modifiers of GPX4 induce ferroptosis in liver cancer cells

Developing new chemotherapeutics that are structurally and mechanistically unique is needed due to the rapid rise of the cancer incidence across the globe. Here, we report the identification of irreversible, thiol-reactive diazepam derivatives as GPX4 modifiers and nanomolar inducers of ferroptosis in liver cancer cells.

Mn(II) Polypyridyl Complexes: Precursors to High Valent Mn(V)=O Species and Inhibitors of Cancer Cell Proliferation

The reaction of [(L)MnII ]2+ (L = neutral polypyridine ligand framework) in the presence of mCPBA (mCPBA = m-Chloroperoxybenzoic acid) generates a putative MnV =O species at RT. The proposed MnV =O species is capable of performing the aromatic hydroxylation of Cl-benzoic acid derived from mCPBA to give [(L)MnIII (m-Cl-salicylate)]+ , which in the presence of excess mCPBA generates a metastable [(L)MnV (O)(m-Cl-salicylate)]+ , characterized by UV/Vis absorption, EPR, resonance Raman spectroscopy, and ESI-MS studies. The current study highlights the fact that [(L)MnIII (m-Cl-salicylate)]+ formation may not be a dead end for catalysis. Further, a plausible mechanism has been proposed for the formation of [(L)MnV (O)-m-Cl-salicylate)]+ from [(L)MnIII (m-Cl-salicylate)]+ . The characterized transient [(L)MnV (O)-m-Cl-salicylate)]+ reported in the current work exhibits high reactivity for oxygen atom transfer reactions, supported by the electrophilic character depicted from Hammett studies using a series of para-substituted thioanisoles. The unprecedented study starting from a non-heme neutral polypyridine ligand framework paves a path for mimicking the natural active site of photosystem II under ambient conditions. Finally, evaluating the intracellular effect of Mn(II) complexes revealed an enhanced intracellular ROS and mitochondrial dysfunction to prevent the proliferation of hepatocellular carcinoma and breast cancer cells.

Abstract P2-16-05: Targeting EZH2 to overcome chemoresistance in Triple Negative Breast Cancers Employing Combinatorial Approach

Objective: Triple Negative Breast Cancers (TNBC) are highly invasive and 46% of patients develop distant metastases, leading to higher mortality. Chemotherapy remains the most efficacious option, however, there is still a largely unmet need to identify novel therapeutic targets in TNBC to increase treatment options and improve patient outcomes, survival. Enhancer of zeste homologue 2 (EZH2), a member of the catalytic subunit of the polycomb repressive complex 2, is a histone methyltransferase and its canonical function is to methylate lysine 27 of histone 3. EZH2 is a potential driver of TNBC metastasis, and its high expression strongly associates with the TNBC phenotype as compared with other molecular subtypes of breast cancer. Despite the advancement in the discovery of inhibitors for EZH2 that attenuate its catalytic activity. Currently, several EZH2 inhibitors are under development and undergoing clinical trials and these compounds have been proved to be effective in the treatment of hematological malignancies, sarcomas and malignant rhabdoid tumors. However these inhibitors do not affect the intrinsic protein stability of EZH2, but typically competes with the cofactor S-adenosylmethionine (SAM) and binds to the SET domain of EZH2. Hence, the EZH2 inhibitors are only effective for some malignant blood tumors, and have poor efficacy for solid tumors, such as TNBC. Several studies have shown the involvement of neurotransmitter dopamine in proliferation, apoptosis, tumor angiogenesis, and drug resistance among different cancers, including the breast1. Dopamine D1 receptor activation in TNBC cell line induces apoptosis, autophagy and phosphorylation of eukaryotic translation initiation factor 2-alpha (eIF2a)2. Also, D1R agonists inhibits the invasion of breast cancer cell lines MDA-MB-231 and BT-20 and regress mammary tumors3. The oncogenic nature of EZH2 in driving aggressiveness in TNBC cells led us to simultaneously target dopamine D1 receptor and EZH2 to completely ablate tumor growth and metastasis. Methods: Schrodinger protein modeling software was employed for docking studies. TNBC cells MDA-MB-231 cells were treated with the EZH2 inhibitor GSK126 and/or D1R agonists A77636 and SKF38393 for assessing cell viability, migration. Immuno precipitation to investigate if the combination could disrupt the PRC2 complex in TNBC cells. To model tumor burden and the effects of combination therapy on tumor growth in vitro, we tested the combinatory effect of GSK126 and D1R agonists in a 3D culture system of MDA-MB-231 cells encapsulated in calcium-alginate microgels seeded from a microfluidic droplet generator. Cell death was determined by Yo-pro-Propidium Iodide staining. Result: In silico analysis confirmed that D1R agonists exhibited strong stabilization of protein structures upon binding to the EZH2 catalytic active site, albeit with slightly weaker affinity than GSK126. Combination treatment with GSK126 and dopamine agonists A77636 or SKF 38393 led to significant and synergistic inhibition of cell viability (p< 0.01), migration, invasion, and EZH2 activity (p< 0.01) in TNBC cells. In addition, MDA-MB-231 cells formed tumor spheroids that were subjected to the EZH2 inhibitor alongside dopamine agonists, indicating tumor reduction relative to single agent treatment in 3D culture (p < 0.0001). The combination also led to increased necrotic cell death (p < 0.05). Immunoprecipitation of EZH2 in the presence of GSK126 and SKF38393 and A77636 dissociated the physical interaction between EZH2, EED, and SUZ12 in MDA-MB-231 cells. Conclusion: Our data suggest that the combination of GSK126 and Dopamine D1 agonists synergistically inhibits TNBC proliferation by disrupting EZH2 functions leading to necrotic cell death. (This work is supported by DOD: W81XWH2010065, for Eswar Shankar). 1) PMID: 21531818 2) PMID: 29773888 3) PMID: 26477316

Citation Format: Eswar Shankar, Sridhar SNC, Xilal Y. Rima, Prem Kushwaha, Shiv Verma, Gautam K. Sarathy, Anagh kulkarni, Dharmaraja Allimuthu, Eduardo Reátegui, Sanjay Gupta, Bhuvaneswari Ramaswamy. Targeting EZH2 to overcome chemoresistance in Triple Negative Breast Cancers Employing Combinatorial Approach. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-16-05.

Nitroisobenzofuranone, a small molecule inhibitor of multidrug-resistant Staphylococcus aureus, targets peptidoglycan biosynthesis

Antimicrobial resistance (AMR) is a global health concern. Targetting AMR, we present an in situ lactonization mechanism generating 4-nitroisobenzofuran-1(3H)-one (IITK2020), an exclusive S. aureus inhibitor at 2-4 μg mL^-1 MIC including multidrug-resistant S. aureus clinical strains, that prevents peptidoglycan biosynthesis.

Enhancers of Human and Rodent Oligodendrocyte Formation Predominantly Induce Cholesterol Precursor Accumulation

Regeneration of myelin in the central nervous system is being pursued as a potential therapeutic approach for multiple sclerosis. Several labs have reported small molecules that promote oligodendrocyte formation and remyelination in vivo. Recently, we reported that many such molecules function by inhibiting a narrow window of enzymes in the cholesterol biosynthesis pathway. Here we describe a new high-throughput screen of 1,836 bioactive molecules and a thorough re-analysis of more than 60 molecules previously identified as promoting oligodendrocyte formation from human, rat, or mouse oligodendrocyte progenitor cells. These studies highlight that an overwhelming fraction of validated screening hits, including several molecules being evaluated clinically for remyelination, inhibit cholesterol pathway enzymes like emopamil-binding protein (EBP). To rationalize these findings, we suggest a model that relies on the high druggability of sterol-metabolizing enzymes and the ability of cationic amphiphiles to mimic the transition state of EBP. These studies further establish cholesterol pathway inhibition as a dominant mechanism among screening hits that enhance human, rat, or mouse oligodendrocyte formation.

Screening Reveals Sterol Derivatives with Pro-Differentiation, Pro-Survival, or Potent Cytotoxic Effects on Oligodendrocyte Progenitor Cells

Inducing the formation of new oligodendrocytes from oligodendrocyte progenitor cells (OPCs) represents a potential approach to repairing the loss of myelin observed in multiple sclerosis and other diseases. Recently, we demonstrated that accumulation of specific cholesterol precursors, 8,9-unsaturated sterols, is a dominant mechanism by which dozens of small molecules enhance oligodendrocyte formation. Here, we evaluated a library of 56 sterols and steroids to evaluate whether other classes of bioactive sterol derivatives may also influence mouse oligodendrocyte precursor cell (OPC) differentiation or survival. From this library, we identified U-73343 as a potent enhancer of oligodendrocyte formation that induces 8,9-unsaturated sterol accumulation by inhibition of the cholesterol biosynthesis enzyme sterol 14-reductase. In contrast, we found that mouse OPCs are remarkably vulnerable to treatment with the glycosterol OSW-1, an oxysterol-binding protein (OSBP) modulator that induces Golgi stress and OPC death in the low picomolar range. A subsequent small-molecule suppressor screen identified mTOR signaling as a key effector pathway mediating OSW-1's cytotoxic effects in mouse OPCs. Finally, evaluation of a panel of ER and Golgi stress-inducing small molecules revealed that mouse OPCs are highly sensitive to these perturbations, more so than closely related neural progenitor cells. Together, these studies highlight the wide-ranging influence of sterols and steroids on OPC cell fate, with 8,9-unsaturated sterols positively enhancing differentiation to oligodendrocytes and OSW-1 able to induce lethal Golgi stress with remarkable potency.

Modulation of lanosterol synthase drives 24,25-epoxysterol synthesis and oligodendrocyte formation

Small molecules that promote the formation of new myelinating oligodendrocytes from oligodendrocyte progenitor cells (OPCs) are potential therapeutics for demyelinating diseases. We recently established inhibition of specific cholesterol biosynthesis enzymes and resulting accumulation of 8,9-unsaturated sterols as a unifying mechanism through which many such molecules act. To identify more potent sterol enhancers of oligodendrocyte formation, we synthesized a collection of 8,9-unsaturated sterol derivatives and found that 24,25-epoxylanosterol potently promoted oligodendrocyte formation. In OPCs, 24,25-epoxylanosterol was metabolized to 24,25-epoxycholesterol via the epoxycholesterol shunt pathway. Increasing flux through the epoxycholesterol shunt using genetic manipulation or small-molecule inhibition of lanosterol synthase (LSS) increased endogenous 24,25-epoxycholesterol levels and OPC differentiation. Notably, exogenously supplied 24,25-epoxycholesterol promoted oligodendrocyte formation despite lacking an 8,9-unsaturation. This work highlights epoxycholesterol shunt usage, controlled by inhibitors of LSS, as a target to promote oligodendrocyte formation. Additionally, sterols beyond the 8,9-unsaturated sterols, including 24,25-epoxycholesterol, drive oligodendrocyte formation.

Diverse Chemical Scaffolds Enhance Oligodendrocyte Formation by Inhibiting CYP51, TM7SF2, or EBP

Small molecules that promote oligodendrocyte formation have been identified in "drug repurposing" screens to nominate candidate therapeutics for diseases in which myelin is lost, including multiple sclerosis. We recently reported that many such molecules enhance oligodendrocyte formation not by their canonical targets but by inhibiting a narrow range of enzymes in cholesterol biosynthesis. Here we identify enhancers of oligodendrocyte formation obtained by screening a structurally diverse library of 10,000 small molecules. Identification of the cellular targets of these validated hits revealed a majority inhibited the cholesterol biosynthesis enzymes CYP51, TM7SF2, or EBP. In addition, evaluation of analogs led to identification of CW3388, a potent EBP-inhibiting enhancer of oligodendrocyte formation poised for further optimization.

Accumulation of 8,9-unsaturated sterols drives oligodendrocyte formation and remyelination

Regeneration of myelin is mediated by oligodendrocyte progenitor cells (OPCs), an abundant stem cell population in the CNS and the principal source of new myelinating oligodendrocytes. Loss of myelin-producing oligodendrocytes in the central nervous system (CNS) underlies a number of neurological diseases, including multiple sclerosis (MS) and diverse genetic diseases^1–3. Using high throughput chemical screening approaches, we and others have identified small molecules that stimulate oligodendrocyte formation from OPCs and functionally enhance remyelination in vivo^4–10. Here we show a broad range of these pro-myelinating small molecules function not through their canonical targets but by directly inhibiting CYP51 (cytochrome P450, family 51), TM7SF2, or EBP (emopamil binding protein), a narrow range of enzymes within the cholesterol biosynthesis pathway. Subsequent accumulation of the 8,9-unsaturated sterol substrates of these enzymes is a key mechanistic node that promotes oligodendrocyte formation, as 8,9-unsaturated sterols are effective when supplied to OPCs in purified form while analogous sterols lacking this structural feature have no effect. Collectively, our results define a unifying sterol-based mechanism-of-action for most known small-molecule enhancers of oligodendrocyte formation and highlight specific targets to propel the development of optimal remyelinating therapeutics.

Novel chloroacetamido compound CWR-J02 is an anti-inflammatory glutaredoxin-1 inhibitor

Glutaredoxin (Grx1) is a ubiquitously expressed thiol-disulfide oxidoreductase that specifically catalyzes reduction of S-glutathionylated substrates. Grx1 is known to be a key regulator of pro-inflammatory signaling, and Grx1 silencing inhibits inflammation in inflammatory disease models. Therefore, we anticipate that inhibition of Grx1 could be an anti-inflammatory therapeutic strategy. We used a rapid screening approach to test 504 novel electrophilic compounds for inhibition of Grx1, which has a highly reactive active-site cysteine residue (pKa 3.5). From this chemical library a chloroacetamido compound, CWR-J02, was identified as a potential lead compound to be characterized. CWR-J02 inhibited isolated Grx1 with an IC₅₀ value of 32 μM in the presence of 1 mM glutathione. Mass spectrometric analysis documented preferential adduction of CWR-J02 to the active site Cys-22 of Grx1, and molecular dynamics simulation identified a potential non-covalent binding site. Treatment of the BV2 microglial cell line with CWR-J02 led to inhibition of intracellular Grx1 activity with an IC₅₀ value (37 μM). CWR-J02 treatment decreased lipopolysaccharide-induced inflammatory gene transcription in the microglial cells in a parallel concentration-dependent manner, documenting the anti-inflammatory potential of CWR-J02. Exploiting the alkyne moiety of CWR-J02, we used click chemistry to link biotin azide to CWR-J02-adducted proteins, isolating them with streptavidin beads. Tandem mass spectrometric analysis identified many CWR-J02-reactive proteins, including Grx1 and several mediators of inflammatory activation. Taken together, these data identify CWR-J02 as an intracellularly effective Grx1 inhibitor that may elicit its anti-inflammatory action in a synergistic manner by also disabling other pro-inflammatory mediators. The CWR-J02 molecule provides a starting point for developing more selective Grx1 inhibitors and anti-inflammatory agents for therapeutic development.

2-Chloropropionamide As a Low-Reactivity Electrophile for Irreversible Small-Molecule Probe Identification

Resurgent interest in covalent target engagement in drug discovery has demonstrated that small molecules containing weakly reactive electrophiles can be safe and effective therapies. Several recently FDA-approved drugs feature an acrylamide functionality to selectively engage cysteine side chains of kinases (Ibrutinib, Afatinib, and Neratinib). Additional electrophilic functionalities whose reactivity is compatible with highly selective target engagement and in vivo application could open new avenues in covalent small molecule discovery. Here, we report the synthesis and evaluation of a library of small molecules containing the 2-chloropropionamide functionality, which we demonstrate is less reactive than typical acrylamide electrophiles. Although many library members do not appear to label proteins in cells, we identified S-CW3554 as selectively labeling protein disulfide isomerase and inhibiting its enzymatic activity. Subsequent profiling of the library against five diverse cancer cell lines showed unique cytotoxicity for S-CW3554 in cells derived from multiple myeloma, a cancer recently reported to be sensitive to PDI inhibition. Our novel PDI inhibitor highlights the potential of 2-chloropropionamides as weak and stereochemically tunable electrophiles for covalent drug discovery.