Mohamed O. Radwan

Liver X receptors (LXRα/β) are members of the nuclear receptor superfamily that have garnered attention over the last two decades. LXRα/β regulate myriad biological functions, including metabolism, cholesterol homeostasis, and immune responses, suggesting they may be effective drug targets for a range of diseases. Kuwanon G, a botanical-origin flavonoid, has previously been shown to regulate LXR-driven biological pathways, but the exact target of this compound has not been fully demonstrated. We conducted LXRα/β radioligand-binding and co-transfection reporter assays, as well as direct examination of LXRα/β target gene expression in HepG2 cells. Kuwanon G displayed potent LXRα binding activity as well as agonist activity in cell-based assays. Based on the activity of kuwanon G, we also examined other kuwanons with relevant structures (kuwanon C and kuwanon K). While kuwanon C showed insignificant activity in the radioligand binding assay, kuwanon K, a constitutional isomer of kuwanon G, displayed high-affinity binding to LXRα/β, but intriguingly, kuwanon K functioned as an LXRα/β inverse agonist in the cotransfection and gene expression assays. This study provides critical structural insights into the chemical diversity that drives agonism vs inverse agonism as essential knowledge for opportunities in LXRα/β ligands from botanical sources.

Background: Inhibition of histone deacetylase is a highly sought-after objective in the fight against cancer. Thus, the development of innovative HDAC inhibitors with significantly higher potency than SAHA against specific cancer cell types represents complex and demanding work. Method: The utilization of the underexplored and privileged scaffold 4-chlorothieno[2,3-b]pyridine as a cap tethering diverse aliphatic and aromatic linkers, followed by the screening of both cellular and enzymatic activities, is undertaken in this study. Results: Compounds 7a and 9a demonstrated impressive mean GI₅₀ values of 2.15 µM and 1.89 µM, respectively. Both compounds reduced caspase-3 levels in RPMI-8226 cells, suggesting induction of apoptosis. Compound 7a showed remarkable IC₅₀ values of 0.37 µM, 0.58 µM, and 0.70 µM against HDACs 1, 4, and 6, respectively, consistent with the cellular assay. Additionally, compound 7a exhibited a selectivity index of 11 for RPMI-8226 cells over PBMCs, reflecting its high selectivity and potential safety. Moreover, ADMET prediction tools indicated that compounds 7a and 9b may have more favorable pharmacokinetic properties than the gold-standard HDAC inhibitor, SAHA. Conclusions: Further study and exploration of the derivatives of compounds 7a and 9a can lead to further advancement in the development of potent HDAC inhibitor anticancer drugs.

Drug repurposing, rebranding an existing drug for a new therapeutic indication, is deemed a beneficial approach for a quick and cost-effective drug discovery process by skipping preclinical, Phase 1 trials and pharmacokinetic studies. Several psychotropic drugs, including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), were studied for their potential application in different diseases, especially in cancer therapy. Fluoxetine (FLX) is one of the most prescribed psychotropic agents from the SSRIs class for the treatment of several neuropsychiatric disorders with a favorable safety profile. FLX exhibited different oncolytic effects via mechanisms distinct from its main serotonergic activity. Taking advantage of its ability to rapidly penetrate the blood–brain barrier, FLX could be particularly useful in brain tumors. This was proved by different in vitro and in vivo experiments using FLX as a monotherapy or combination with temozolomide (TMZ) or radiotherapy. In this review of the literature, we summarize the potential pleiotropic oncolytic roles of FLX against different cancers, highlighting the multifaceted activities of FLX and its ability to interrupt cancer proliferation via several molecular mechanisms and even surmount multidrug resistance (MDR). We elaborated on the successful synergistic combinations such as FXR/temozolomide and FXR/raloxifene for the treatment of glioblastoma and breast cancer, respectively. We showcased beneficial pharmaceutical trials to load FLX onto carriers to enhance its safety and efficacy on cancer cells. This is the first review article extensively summarizing all previous FLX repurposing studies for the management of cancer.

Pancreatic cancer (PC) is considered one of the most challenging and formidable malig-nancies to treat because it is usually diagnosed at terminal stage, thus it is characterized with a poor prognosis with 5% of patients living over 5 years. The late diagnosis leads to a lower suc-cess rate of resectability, hence chemotherapy or chemoradiotherapy are the only hopes for most PC patients. However, the available drug combinations for PC treatment did not provide satisfactory clinical outcomes. There is a pressing and urgent need to discover new chemothera-peutics which fight PC with tolerable side effects and less liability for resistance. Pentacyclic triterpenes (PTs) are privileged structures with a multitude of biological activities mitigating several ailments, particularly in neoplasm field. They are characterized by a high therapeutic window and their activity can be highly enhanced through structural modifications. Indeed, several parent PTs such as oleanolic acid, ursolic acid, lupeol, betulinic acid, and celastrol proved effective against different PC phenotypes inhibiting their proliferation, invasion, and metastasis mainly via KRAS modulation. Some PTs worked as adjuvant chemosensitizers in gemcitabine-resistant or TRAIL-resistant cells. Owing to their potential in PC treatment, we pre-sent this review article summarizing PC pathogenesis and the promising role of PTs in the man-agement of PC when used either solely or in combination with other chemotherapies such as gemcitabine and 5-Fluorouracil.

Drug repurposing, rebranding an existing drug for a new therapeutic indication, is deemed a beneficial approach for a quick and cost-effective drug discovery process by skipping preclinical, Phase 1 trials and pharmacokinetic studies. Several psychotropic drugs including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antide-pressants (TCAs) were studied for their potential application in different diseases es-pecially in cancer therapy. Fluoxetine (FLX) is one of the most prescribed psychotropic agents from SSRIs class for the treatment of several neuropsychiatric disorders with a favourable safety profile. FLX exhibited different oncolytic effects via mechanisms dis-tinct from its main serotonergic activity. Taking advantage of its ability to rapidly pen-etrate the blood-brain barrier, FLX could be particularly useful in brain tumors. This was proved by different in vitro and in vivo experiments using FLX as a monotherapy or combination with temozolomide (TMZ) or radiotherapy. In this review of literature, we summarize the potential pleiotropic oncolytic roles of FLX against different cancers highlighting the multifaceted activities of FLX and its ability to interrupt cancer prolif-eration via several molecular mechanisms and even surmount multidrug resistance (MDR). We elaborated on the successful synergistic combinations such as FXR/temozolomide and FXR/raloxifene for the treatment of glioblastoma and breast cancer, respectively. We showcased beneficial pharmaceutical trials to load FLX on car-riers to enhance its safety and efficacy on cancer cells. This is the first review article ex-tensively summarizing all previous FLX repurposing studies for the management of cancer.

Multiple myeloma (MM) is an incurable hematological malignancy with increasing incidence and mortality rates with a worldwide incidence of 160,000 cases per year. The current approved treatments including bortezomib have serious side effects and ultimately develop resistance. Inadequate vitamin D (VD) levels are frequent in MM patients and its supplementation has an antiproliferative effect on different MM phenotypes. However, the risk of hypercalcemia restricts VD application in cancer therapy, hence we pursued truncated VD analogues with anticancer effect accompanied with no calcemic activity. Previously, we have revealed a truncated VD2 C/D rings derivative against cervical cancer, lung cancer and MM. Herein, we generate its SAR study by introducing more derivatives and testing then against different MM cells including bortezomib sensitive and resistant phenotypes. Compound VDF4 exhibited remarkable toxicity against all tested cells with less effect on normal blood cells reflecting its potential high selectivity. VDF-4 IC₅₀ value against KMS-12-PE, KMS-11, and KMS-11/BTZ is 19.1±1.0, 19.8±2.5, and 23.3±1.9 respectively. Notably, KMS-11/BTZ was not sensitive to VD2. Furthermore, it demonstrated moderate activity against other leukemic cells including Jurkat and M8166 cells. Although its mechanism of action is not fully understood, VDF-4 stands out as a promising lead compound that warrants further investigations.

Tumor necrosis factor receptor-associated factors (TRAFs) are a protein family with a wide variety of roles and binding partners. Among them, TRAF6, a ubiquitin ligase, possesses unique receptor binding specificity and shows diverse functions in immune system regulation, cellular signaling, central nervous system, and tumor formation. TRAF6 consists of an N-terminal Really Interesting New Gene (RING) domain, multiple zinc fingers, and a C-terminal TRAF domain. TRAF6 is an important therapeutic target for various disorders and structural studies of this protein are crucial for the development of next-generation therapeutics. Here, we presented a TRAF6 N-terminal structure determined at the Turkish light source “Turkish DeLight” to be 3.2 Å resolution at cryogenic temperature (PDB ID: 8HZ2). This structure offers insight into the domain organization and zinc-binding, which are critical for protein function. Since the RING domain and the zinc fingers are key targets for TRAF6 therapeutics, structural insights are crucial for future research. Separately, we rationally designed numerous new compounds and performed molecular docking studies using this template (PDB ID:8HZ2). According to the results, 10 new compounds formed key interactions with essential residues and zinc ion in the N-terminal region of TRAF6. Molecular dynamic (MD) simulations were performed for 300 ns to evaluate the stability of three docked complexes (compounds 256, 322, and 489). Compounds 256 and 489 was found to possess favorable bindings with TRAF6. These new compounds also showed moderate to good pharmacokinetic profiles, making them potential future drug candidates as TRAF6 inhibitors.

Nuclear receptors (NRs) form a family of druggable transcription factors that are regulated by ligand binding to orchestrate multifaceted physiological functions, including reproduction, immunity, metabolism, and growth. NRs represent attractive and valid targets for the management and treatment of a vast array of ailments. Pentacyclic triterpenes (PTs) are ubiquitously distributed natural products in medicinal and aromatic plants, of which ursolic acid (UA) is an extensively studied member, due to its diverse bio-pertinent activities against different cancers, inflammation, aging, obesity, diabetes, dyslipidemia, and liver injury. In fact, PTs share a common lipophilic structure that resembles NRs’ endogenous ligands. Herein, we present a review of the literature on UA’s effect on NRs, showcasing the resulting health benefits and potential therapeutic outcomes. De facto, UA exhibited numerous pharmacodynamic effects on PPAR, LXR, FXR, and PXR, resulting in remarkable anti-inflammatory, anti-hyperlipidemic, and hepatoprotective properties, by lowering lipid accumulation in hepatocytes and mitigating non-alcoholic steatohepatitis (NASH) and its subsequent liver fibrosis. Furthermore, UA reversed valproate and rifampicin-induced hepatic lipid accumulation. Additionally, UA showed great promise for the treatment of autoimmune inflammatory diseases such as multiple sclerosis and autoimmune arthritis by antagonizing RORγ. UA exhibited antiproliferative effects against skin, prostate, and breast cancers, partially via PPARα and RORγ pathways. Herein, for the first time, we explore and provide insights into UA bioactivity with respect to NR modulation.