Development of Mcl-1 inhibitors for cancer therapy

Mixed Stereochemistry Macrocycle Acts as a Helix-Stabilizing Peptide N-Cap

Interactions between proteins and α-helical peptides have been the focus of drug discovery campaigns. However, the large interfaces formed between multiple turns of an α-helix and a binding protein represent a significant challenge to inhibitor discovery. Modified peptides featuring helix-stabilizing macrocycles have shown promise as inhibitors of these interactions. Here, we tested the ability of N-terminal to side-chain thioether-cyclized peptides to inhibit the α-helix binding protein Mcl-1, by screening a trillion-scale library. The enriched peptides were lariats featuring a small, four-amino-acid N-terminal macrocycle followed by a short linear sequence that resembled the natural α-helical Mcl-1 ligands. These "Heliats" (helical lariats) bound Mcl-1 with tens of nM affinity, and inhibited the interaction between Mcl-1 and a natural peptide ligand. Macrocyclization was found to stabilize α-helical structures and significantly contribute to affinity and potency. Yet, the 2nd and 3rd positions within the macrocycle were permissible to sequence variation, so that a minimal macrocyclic motif, of an N-acetylated d-phenylalanine at the 1st position thioether connected to a cysteine at the 4th, could be grafted into a range of peptides and stabilize helical conformations. We found that d-stereochemistry is more helix-stabilizing than l- at the 1st position in the motif, as the d-amino acid can utilize polyproline II torsional angles that allow for more optimal intrachain hydrogen bonding. This mixed stereochemistry macrocyclic N-cap is synthetically accessible, requiring only minor modifications to standard solid-phase peptide synthesis, and its compatibility with peptide screening can provide ready access to helix-focused peptide libraries for de novo inhibitor discovery.

Discovery of Phenylpyrazole Derivatives as a New Class of Selective Inhibitors of MCL-1 with Antitumor Activity

MCL-1, an antiapoptotic member of the BCL-2 family, is dysregulated and overexpressed in various tumors. In tumors with MCL-1 overexpression, selective inhibitors of MCL-1 are expected to overcome the drug resistance caused by BCL-2 inhibitors currently used in clinical treatment. Here, we employed docking-based virtual screening to identify an active hit, LC126, with binding affinity around 10 μM for MCL-1 and BCL-2. Under the guidance of structure-based design, we obtained a few selective inhibitors of MCL-1 after three rounds of structural optimization. The representative compound GQN-B37-E exhibited binding affinity for MCL-1 at the submicromolar range (K i = 0.6 μM) without apparent binding to BCL-2 or BCL-XL. 15N-heteronuclear single-quantum coherence NMR spectra suggested that this compound binds to the BH3-domain-binding pocket in the MCL-1 surface. Cellular assays revealed that GQN-B37-Me, the precursor of GQN-B37-E, is effective particularly on leukemia cells (such as H929 and MV-4-11) to induce caspase-dependent apoptosis. Its interaction with MCL-1 in cells was confirmed by coimmunoprecipitation. Administration of GQN-B37-Me to MV-4-11 xenograft mice at 50 mg/kg every 2 days for 20 days led to 43% tumor growth inhibition. GQN-B37-Me also exhibited reasonable in vitro stability in GSH and liver microsomes from several species. This new class of MCL-1 inhibitor may have potential to be further developed into a preclinical candidate for treating leukemia.

Targeting Myeloid Leukemia-1 in Cancer Therapy: Advances and Directions

As a tripartite cell death switch, B-cell lymphoma protein 2 (Bcl-2) family members precisely regulate the endogenous apoptosis pathway in response to various cell signal stresses through protein-protein interactions. Myeloid leukemia-1 (Mcl-1), a key anti-apoptotic Bcl-2 family member, is positioned downstream in the endogenous apoptotic pathway and plays a central role in regulating mitochondrial function. Mcl-1 is highly expressed in a variety of hematological malignancies and solid tumors, contributing to tumorigenesis, poor prognosis, and chemoresistance, making it an attractive target for cancer treatment. This Perspective aims to discuss the mechanism by which Mcl-1 regulates apoptosis and non-apoptotic functions in cancer cells and to outline the discovery and optimization process of potent Mcl-1 modulators. In addition, we summarize the structural characteristics of potent inhibitors that bind to Mcl-1 through multiple co-crystal structures and analyze the cardiotoxicity caused by current Mcl-1 inhibitors, providing prospects for rational targeting of Mcl-1.

Sacituzumab govitecan plus platinum-based chemotherapy mediates significant antitumor effects in triple-negative breast, urinary bladder, and small-cell lung carcinomas

Sacituzumab govitecan (SG) is an antibody-drug conjugate composed of an anti-Trop-2-directed antibody conjugated with the topoisomerase I inhibitory drug, SN-38, via a proprietary hydrolysable linker. SG has received United States Food and Drug Administration (FDA) approval to treat metastatic triple-negative breast cancer (TNBC), unresectable locally advanced or metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer, and accelerated approval for metastatic urothelial cancer. We investigated the utility of combining SG with platinum-based chemotherapeutics in TNBC, urinary bladder carcinoma (UBC), and small-cell lung carcinoma (SCLC). SG plus carboplatin or cisplatin produced additive growth-inhibitory effects in vitro that trended towards synergy. Immunoblot analysis of cell lysates suggests perturbation of the cell-cycle and a shift towards pro-apoptotic signaling evidenced by an increased Bax to Bcl-2 ratio and down-regulation of two anti-apoptotic proteins, Mcl-1 and survivin. Significant antitumor effects were observed with SG plus carboplatin in mice bearing TNBC or SCLC tumors compared to all controls (P < 0.0062 and P < 0.0017, respectively) and with SG plus cisplatin in UBC and SCLC tumor-bearing animals (P < 0.0362 and P < 0.0001, respectively). These combinations were well tolerated by the animals. Combining SG with platinum-based chemotherapeutics demonstrates the benefit in these indications and warrants further clinical investigation.

Development of Potent Mcl-1 Inhibitors: Structural Investigations on Macrocycles Originating from a DNA-Encoded Chemical Library Screen

Evasion of apoptosis is critical for the development and growth of tumors. The pro-survival protein myeloid cell leukemia 1 (Mcl-1) is an antiapoptotic member of the Bcl-2 family, associated with tumor aggressiveness, poor survival, and drug resistance. Development of Mcl-1 inhibitors implies blocking of protein-protein interactions, generally requiring a lengthy optimization process of large, complex molecules. Herein, we describe the use of DNA-encoded chemical library synthesis and screening to directly generate complex, yet conformationally privileged macrocyclic hits that serve as Mcl-1 inhibitors. By applying a conceptual combination of conformational analysis and structure-based design in combination with a robust synthetic platform allowing rapid analoging, we optimized in vitro potency of a lead series into the low nanomolar regime. Additionally, we demonstrate fine-tuning of the physicochemical properties of the macrocyclic compounds, resulting in the identification of lead candidates 57/59 with a balanced profile, which are suitable for future development toward therapeutic use.

Long noncoding RNA H19: functions and mechanisms in regulating programmed cell death in cancer

Long noncoding RNAs (lncRNAs) are a group of noncoding RNAs with transcript lengths of >200 nucleotides. Mounting evidence suggests that lncRNAs are closely associated with tumorigenesis. LncRNA H19 (H19) was the first lncRNA to function as an oncogene in many malignant tumors. Apart from the established role of H19 in promoting cell growth, proliferation, invasion, migration, epithelial-mesenchymal transition (EMT), and metastasis, it has been recently discovered that H19 also inhibits programmed cell death (PCD) of cancer cells. In this review, we summarize the mechanisms by which H19 regulates PCD in cancer cells through various signaling pathways, molecular mechanisms, and epigenetic modifications. H19 regulates PCD through the Wnt/β-catenin pathway and the PI3K-Akt-mTOR pathway. It also acts as a competitive endogenous RNA (ceRNA) in PCD regulation. The interaction between H19 and RNA-binding proteins (RBP) regulates apoptosis in cancer. Moreover, epigenetic modifications, including DNA and RNA methylation and histone modifications, are also involved in H19-associated PCD regulation. In conclusion, we summarize the role of H19 signaling via PCD in cancer chemoresistance, highlighting the promising research significance of H19 as a therapeutic target. We hope that our study will contribute to a broader understanding of H19 in cancer development and treatment.

Targeting BCL2 pathways in CLL: a story of resistance and ingenuity

Chronic lymphocytic leukemia (CLL) is common amongst leukemic malignancies, prompting dedicated investigation throughout the years. Over the last decade, the treatment for CLL has significantly advanced with agents targeting B-cell lymphoma 2 (BCL2), Bruton's tyrosine kinase, and CD20. Single agents or combinations of these targets have proven efficacy. Unfortunately, resistance to one or multiple of the new treatment targets develops. Our review investigates various mechanisms of resistance to BCL2 inhibitors, including mutations in BCL2, alterations in the Bcl protein pathway, epigenetic modifications, genetic heterogeneity, Richter transformation, and alterations in oxidative phosphorylation. Additionally, the review will discuss potential avenues to overcome this resistance with novel agents such as bispecific antibodies, Bruton's tyrosine kinase (BTK) degraders, non-covalent BTK inhibitors, and chimeric antigen receptor T (CART).

Small molecules targeting protein-protein interactions for cancer therapy

Protein-protein interactions (PPIs) are fundamental to many biological processes that play an important role in the occurrence and development of a variety of diseases. Targeting the interaction between tumour-related proteins with emerging small molecule drugs has become an attractive approach for treatment of human diseases, especially tumours. Encouragingly, selective PPI-based therapeutic agents have been rapidly advancing over the past decade, providing promising perspectives for novel therapies for patients with cancer. In this review we comprehensively clarify the discovery and development of small molecule modulators of PPIs from multiple aspects, focusing on PPIs in disease, drug design and discovery strategies, structure-activity relationships, inherent dilemmas, and future directions.

Imidazoles as Serotonin Receptor Modulators for Treatment of Depression: Structural Insights and Structure-Activity Relationship Studies

Serotoninergic signaling is identified as a crucial player in psychiatric disorders (notably depression), presenting it as a significant therapeutic target for treating such conditions. Inhibitors of serotoninergic signaling (especially selective serotonin reuptake inhibitors (SSRI) or serotonin and norepinephrine reuptake inhibitors (SNRI)) are prominently selected as first-line therapy for the treatment of depression, which benefits via increasing low serotonin levels and norepinephrine by blocking serotonin/norepinephrine reuptake and thereby increasing activity. While developing newer heterocyclic scaffolds to target/modulate the serotonergic systems, imidazole-bearing pharmacophores have emerged. The imidazole-derived pharmacophore already demonstrated unique structural characteristics and an electron-rich environment, ultimately resulting in a diverse range of bioactivities. Therefore, the current manuscript discloses such a specific modification and structural activity relationship (SAR) of attempted derivatization in terms of the serotonergic efficacy of the resultant inhibitor. We also featured a landscape of imidazole-based development, focusing on SAR studies against the serotoninergic system to target depression. This study covers the recent advancements in synthetic methodologies for imidazole derivatives and the development of new molecules having antidepressant activity via modulating serotonergic systems, along with their SAR studies. The focus of the study is to provide structural insights into imidazole-based derivatives as serotonergic system modulators for the treatment of depression.

Targeting MCL-1 protein to treat cancer: opportunities and challenges

Evading apoptosis has been linked to tumor development and chemoresistance. One mechanism for this evasion is the overexpression of prosurvival B-cell lymphoma-2 (BCL-2) family proteins, which gives cancer cells a survival advantage. Mcl-1, a member of the BCL-2 family, is among the most frequently amplified genes in cancer. Targeting myeloid cell leukemia-1 (MCL-1) protein is a successful strategy to induce apoptosis and overcome tumor resistance to chemotherapy and targeted therapy. Various strategies to inhibit the antiapoptotic activity of MCL-1 protein, including transcription, translation, and the degradation of MCL-1 protein, have been tested. Neutralizing MCL-1's function by targeting its interactions with other proteins via BCL-2 interacting mediator (BIM)S2A has been shown to be an equally effective approach. Encouraged by the design of venetoclax and its efficacy in chronic lymphocytic leukemia, scientists have developed other BCL-2 homology (BH3) mimetics-particularly MCL-1 inhibitors (MCL-1i)-that are currently in clinical trials for various cancers. While extensive reviews of MCL-1i are available, critical analyses focusing on the challenges of MCL-1i and their optimization are lacking. In this review, we discuss the current knowledge regarding clinically relevant MCL-1i and focus on predictive biomarkers of response, mechanisms of resistance, major issues associated with use of MCL-1i, and the future use of and maximization of the benefits from these agents.

Chamaecyparis lawsoniana Leaf Essential Oil as a Potential Anticancer Agent: Experimental and Computational Studies

Cancer remains one of the leading causes of death worldwide, affected by several factors including oxidative stress; and although conventional synthetic medicines have been used to treat cancer, they often result in various side effects. Consequently, there is a growing need for newer, safer and more effective alternatives, such as natural plant products. Essential oils (EOs) are one such alternative, offering a wide range of bioactivities, including antibacterial, antiviral, antioxidant, and anticancer properties. Accordingly, the objective of the present study was to investigate the chemical composition, as well as the antioxidant and anticancer properties of the leaf essential oil of Chamaecyparis lawsoniana (CLLEO) belonging to the Cupressaceae family. Totally, 59 constituents were identified by gas chromatography-mass spectrometry (GC-MS) analysis. cis-Abienol, trans-ferruginol, α-cadinol, δ-muurolene and α-pinene were the major components. The in vitro cytotoxicity study against human breast (MCF-7), colon (HCT-116), lung (A-549), hepatocellular (HepG-2) carcinoma cells using MTT assay indicated a promising cytotoxic activity against all the tested cancer cells, particularly HepG-2, with significant selectivity indices. CLLEO exhibited weak antioxidant activity according to the DPPH, ABTS and FRAP assays. In silico docking of these constituents against the epidermal growth factor receptor (EGFR), the myeloid cell leukemia-1 (Mcl-1) and caspase-8 using Molecular Operating Environment (MOE) software demonstrated good binding affinities of the components with the active site of these targets. These findings suggested using CLLEO, or its individual components, as a potentially viable therapeutic option for managing cancerous conditions.

AMG176, an MCL-1 inhibitor, is active in pre-clinical models of aggressive B-cell lymphomas

Upregulation of the anti-apoptotic protein MCL-1 has been implicated in chemotherapy resistance and poor clinical outcomes in B-cell lymphoma (BCL). We report the activity of AMG176, a direct, selective MCL-1 inhibitor, in preclinical models of BCL. A panel of cell lines representing diffuse large B-cell lymphoma (DLBCL), double-hit lymphoma (DHL) and Burkitt's lymphoma (BL) was selected. AMG176 induced apoptotic cell death in a dose- and time-dependent manner in all BCL cell lines. Baseline MCL-1 expression was not predictive of response. AMG176 exhibited impressive synergy with venetoclax and chemotherapeutic agents, less so with proteasomal inhibitors, and antagonism with anti-CD20 monoclonal antibodies. The activity of AMG176 could not be confirmed in murine models of BCL. Combination therapy targeting MCL-1 and BCL-2 may provide an alternative therapeutic approach in BCL, however optimal patient selection will remain the key to obtaining high response rates and tolerability.

Going beyond Binary: Rapid Identification of Protein-Protein Interaction Modulators Using a Multifragment Kinetic Target-Guided Synthesis Approach

Kinetic target-guided synthesis (KTGS) is a powerful screening approach that enables identification of small molecule modulators for biomolecules. While many KTGS variants have emerged, a majority of the examples suffer from limited throughput and a poor signal/noise ratio, hampering reliable hit detection. Herein, we present our optimized multifragment KTGS screening strategy that tackles these limitations. This approach utilizes selected reaction monitoring liquid chromatography tandem mass spectrometry for hit detection, enabling the incubation of 190 fragment combinations per screening well. Consequentially, our fragment library was expanded from 81 possible combinations to 1710, representing the largest KTGS screening library assembled to date. The expanded library was screened against Mcl-1, leading to the discovery of 24 inhibitors. This work unveils the true potential of KTGS with respect to the rapid and reliable identification of hits, further highlighting its utility as a complement to the existing repertoire of screening methods used in drug discovery.

Therapeutic advancements in targeting BCL-2 family proteins by epigenetic regulators, natural, and synthetic agents in cancer

Cancer is amongst the deadliest and most disruptive disorders, having a much higher death rate than other diseases worldwide. Human cancer rates continue to rise, thereby posing the most significant concerns for medical health professionals. In the last two decades, researchers have gone past several milestones in tackling cancer while gaining insight into the role of apoptosis in cancer or targeting various biomarker tools for prognosis and diagnosis. Apoptosis which is still a topic full of complexities, can be controlled considerably by B-cell lymphoma 2 (BCL-2) and its family members. Therefore, targeting proteins of this family to prevent tumorigenesis, is essential to focus on the pharmacological features of the anti-apoptotic and pro-apoptotic members, which will help to develop and manage this disorder. This review deals with the advancements of various epigenetic regulators to target BCL-2 family proteins, including the mechanism of several microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Similarly, a rise in natural and synthetic molecules' research over the last two decades has allowed us to acquire insights into understanding and managing the transcriptional alterations that have led to apoptosis and treating various neoplastic diseases. Furthermore, several inhibitors targeting anti-apoptotic proteins and inducers or activators targeting pro-apoptotic proteins in preclinical and clinical stages have been summarized. Overall, agonistic and antagonistic mechanisms of BCL-2 family proteins conciliated by epigenetic regulators, natural and synthetic agents have proven to be an excellent choice in developing cancer therapeutics.

Simultaneous Inhibition of Ceramide Hydrolysis and Glycosylation Synergizes to Corrupt Mitochondrial Respiration and Signal Caspase Driven Cell Death in Drug-Resistant Acute Myeloid Leukemia

Acute myelogenous leukemia (AML), the most prevalent acute and aggressive leukemia diagnosed in adults, often recurs as a difficult-to-treat, chemotherapy-resistant disease. Because chemotherapy resistance is a major obstacle to successful treatment, novel therapeutic intervention is needed. Upregulated ceramide clearance via accelerated hydrolysis and glycosylation has been shown to be an element in chemotherapy-resistant AML, a problem considering the crucial role ceramide plays in eliciting apoptosis. Herein we employed agents that block ceramide clearance to determine if such a "reset" would be of therapeutic benefit. SACLAC was utilized to limit ceramide hydrolysis, and D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-threo-PDMP) was used to block the glycosylation route. The SACLAC D-threo-PDMP inhibitor combination was synergistically cytotoxic in drug-resistant, P-glycoprotein-expressing (P-gp) AML but not in wt, P-gp-poor cells. Interestingly, P-gp antagonists that can limit ceramide glycosylation via depression of glucosylceramide transit also synergized with SACLAC, suggesting a paradoxical role for P-gp in the implementation of cell death. Mechanistically, cell death was accompanied by a complete drop in ceramide glycosylation, concomitant, striking increases in all molecular species of ceramide, diminished sphingosine 1-phosphate levels, resounding declines in mitochondrial respiratory kinetics, altered Akt, pGSK-3β, and Mcl-1 expression, and caspase activation. Although ceramide was generated in wt cells upon inhibitor exposure, mitochondrial respiration was not corrupted, suggestive of mitochondrial vulnerability in the drug-resistant phenotype, a potential therapeutic avenue. The inhibitor regimen showed efficacy in an in vivo model and in primary AML cells from patients. These results support the implementation of SL enzyme targeting to limit ceramide clearance as a therapeutic strategy in chemotherapy-resistant AML, inclusive of a novel indication for the use of P-gp antagonists.

Cytotoxic and apoptotic effects of some (R)-carvone-isoxazoline derivatives on human fibrosarcoma and carcinoma cells: experimental evaluation for cytotoxicity, molecular docking and molecular dynamics studies

This study aimed to analyze the cytotoxic and apoptotic effects of isoxazoline derivatives with monoterpene scaffold 9a-e in HT-1080 fibrosarcoma, MCF-7, and MDA-MB-231 breast carcinoma, and A-549 lung carcinoma. The cytotoxic effects data revealed that compounds 9a-e generally induced significant cell growth inhibition in all cell lines, with IC₅₀ ranging from 10 to 30 µM. However, for compounds 9c and 9e, the IC₅₀ reached a value of 100 µM in HT-1080 cells. Compounds 9a, 9b, and 9d could induce apoptosis in HT-1080 cells as demonstrated by Annexin-V labeling and Caspase-3/7 activity. The apoptotic effect was accompanied by cell cycle arrest in the S phase. Molecular docking and molecular dynamics confirmed the empirical assay results and confirmed the stability of the complex with the inhibition of the anti-apoptotic protein, leading to cancer cell death. Overall, these data suggest that the proposed isoxazoline derivatives may be potential candidates for further investigation to evaluate their efficacy and optimal use in cancer treatment.Communicated by Ramaswamy H. Sarma.

Targeting Mcl-1 Degradation by Bergenin Inhibits Tumorigenesis of Colorectal Cancer Cells

Myeloid leukemia 1 (Mcl-1) is frequently overexpressed in human malignancies and emerged as a promising drug target. In this study, we verified the inhibitory effect of bergenin on colorectal cancer cells both in vivo and in vitro. In an in vitro setting, bergenin significantly reduced the viability and colony formation and promoted apoptosis of CRC cells dose-dependently. Bergenin decreased the activity of Akt/GSK3β signaling and enhanced the interaction between FBW7 and Mcl-1, which eventually induced Mcl-1 ubiquitination and degradation. Using the HA-Ub K48R mutant, we demonstrated that bergenin promotes Mcl-1 K48-linked polyubiquitination and degradation. In vivo studies showed that bergenin significantly reduced tumor size and weight without toxicity to vital organs in mice. Overall, our results support the role of bergenin in inhibiting CRC cells via inducing Mcl-1 destruction, suggesting that targeting Mcl-1 ubiquitination could be an alternative strategy for antitumor therapy.

Discovery of N-sulfonylated aminosalicylic acids as dual MCL-1/BCL-xL inhibitors

The anti-apoptotic protein MCL-1, which is overexpressed in multiple cancers, is presently a focus for the development of targeted drugs in oncology. We previously discovered inhibitors of MCL-1 based on 1-sulfonylated 1,2,3,4-tetrahydroquinoline-6-carboxylic acids ("1,6-THQs"). However, with the nitrogen atom constrained in the bicyclic ring, we were unable to modify the alkyl portion of the tertiary sulfonamide functionality. Moreover, the introduction of additional functional groups onto the benzene ring portion of the THQ bicycle would not be trivial. Therefore, we elected to deconstruct the piperidine-type ring of the 6-carboxy-THQ lead to create a new 4-aminobenzoic acid scaffold. Given its simplicity, this permitted us to introduce diversity at the sulfonamide nitrogen, as well as vary the positions and substituents of the benzene ring. One of our most potent MCL-1 inhibitors, 6e-OH, exhibited a K i of 0.778 μM. Heteronuclear single quantum coherence experiments suggested 6e-OH bound in the canonical BH3-binding groove, with significant perturbations of R263, which forms a salt bridge with MCL-1's pro-apoptotic binding partners, as well as residues in the p2 pocket. Selectivity studies indicated that our compounds are dual inhibitors of MCL-1 and BCL-xL, with 17cd the most potent dual inhibitor: K i = 0.629 μM (MCL-1), 1.67 μM (BCL-xL). Whilst selective inhibitors may be more desirable in certain instances, polypharmacological agents whose additional target(s) address other pathways associated with the disease state, or serve to counter resistance mechanisms to the primary target, may prove particularly effective therapeutics. Since selective MCL-1 inhibition may be thwarted by overexpression of sister anti-apoptotic proteins, including BCL-xL and BCL-2, we believe our work lays a solid foundation towards the development of multi-targeting anti-cancer drugs.

Indene-Derived Hydrazides Targeting Acetylcholinesterase Enzyme in Alzheimer's: Design, Synthesis, and Biological Evaluation

As acetylcholinesterase (AChE) plays a crucial role in advancing Alzheimer's disease (AD), its inhibition is a promising approach for treating AD. Sulindac is an NSAID of the aryl alkanoic acid class, consisting of a indene moiety, which showed neuroprotective behavior in recent studies. In this study, newer Indene analogs were synthesized and evaluated for their in vitro AChE inhibition. Additionally, compared with donepezil as the standard drug, these Indene analogs were accessed for their cell line-based toxicity study on SH-SY5Y cell line. The molecule SD-30, having hydrogen bond donor (HBD) at para-position, showed maximum AChE inhibition potential (IC₅₀ 13.86 ± 0.163 µM) in the indene series. Further, the SD-30 showed maximum BuChE inhibition potential (IC₅₀ = 48.55 ± 0.136 µM) with a selectivity ratio of 3.50 and reasonable antioxidant properties compared to ascorbic acid (using DPPH assay). SD-30 (at a dose level: of 10 µM, 20 µM) effectively inhibited AChE-induced Aβ aggregation and showed no significant toxicity up to 30 mM against SH-SY5Y cell lines.

Estrogen Receptor-α Targeting: PROTACs, SNIPERs, Peptide-PROTACs, Antibody Conjugated PROTACs and SNIPERs

Targeting selective estrogen subtype receptors through typical medicinal chemistry approaches is based on occupancy-driven pharmacology. In occupancy-driven pharmacology, molecules are developed in order to inhibit the protein of interest (POI), and their popularity is based on their virtue of faster kinetics. However, such approaches have intrinsic flaws, such as pico-to-nanomolar range binding affinity and continuous dosage after a time interval for sustained inhibition of POI. These shortcomings were addressed by event-driven pharmacology-based approaches, which degrade the POI rather than inhibit it. One such example is PROTACs (Proteolysis targeting chimeras), which has become one of the highly successful strategies of event-driven pharmacology (pharmacology that does the degradation of POI and diminishes its functions). The selective targeting of estrogen receptor subtypes is always challenging for chemical biologists and medicinal chemists. Specifically, estrogen receptor α (ER-α) is expressed in nearly 70% of breast cancer and commonly overexpressed in ovarian, prostate, colon, and endometrial cancer. Therefore, conventional hormonal therapies are most prescribed to patients with ER + cancers. However, on prolonged use, resistance commonly developed against these therapies, which led to selective estrogen receptor degrader (SERD) becoming the first-line drug for metastatic ER + breast cancer. The SERD success shows that removing cellular ER-α is a promising approach to overcoming endocrine resistance. Depending on the mechanism of degradation of ER-α, various types of strategies of developed.

Natural Products as Mcl-1 Inhibitors: A Comparative Study of Experimental and Computational Modelling Data

The human myeloid leukemia cell differentiation protein (hMcl-1) is an anti-apoptotic multi-partner protein, belonging to the B-cell lymphoma-2 (Bcl-2) family of proteins. Studies have linked hMcl-1 alleviated expression with resistance to hemopoietic chemotherapeutics, which makes it a key drug target in blood cancers. However, most of the developed small- to medium-sized hMcl-1 inhibitors have typical off-target activity towards other members of the Bcl-2 family. To improve the hMcl-1 inhibitor design, especially exploring a suitable scaffold with pharmacophoric features, we focused on natural hMcl-1 inhibitors. To date, seven classes of natural compounds have been isolated, which display a low micromolar affinity for hMcl-1 and have limited biophysical studies. We screened hMcl-1 co-crystal structures, and identified nine co-crystal structures of hMcl-1 protein, which were later evaluated by multiple receptor conformations (which indicates that the differences between hMcl-1 in crystal structures are low (RMSD values between 0.52 and 1.13 Å, average RMSD of 0.638–0.888 Å, with a standard deviation of 0.102–0.185Å)), and multiple ligand conformations (which led to the selection of the PDB structure, 3WIX (RMSD value = 0.879 Å, standard deviation 0.116 Å), to accommodate various Mcl-1 ligands from a range of co-crystal PDB files) methods. Later, the three adopted docking methods were assessed for their ability to reproduce the conformation bound to the crystal as well as predict trends in Ki values based on calculated RMSD and docking energies. Iterative docking and clustering of the docked pose within ≤1.0 Å was used to evaluate the reproducibility of the adopted docking methods and compared with their experimentally determined hMcl-1 affinity data.

Therapeutic potential of the novel Bcl-2/Bcl-XL dual inhibitor, APG1252, alone or in combination against non-small cell lung cancer

Targeting the induction of apoptosis is a promising cancer therapeutic strategy with some clinical success. This study focused on evaluating the therapeutic efficacy of the novel Bcl-2/Bcl-X_L dual inhibitor, APG1252-M1 (also named APG-1244; an in vivo active metabolite of APG1252 or pelcitoclax), as a single agent or in combination, against non-small cell lung cancer (NSCLC) cells. APG1252-M1 effectively decreased the survival of some NSCLC cell lines expressing low levels of Mcl-1 and induced apoptosis. Overexpression of ectopic Mcl-1 in the sensitive cells substantially compromised APG1252-M1's cell-killing effects, whereas inhibition of Mcl-1 greatly sensitized insensitive cell lines to APG1252-M1, indicating the critical role of Mcl-1 levels in impacting cell response to APG1252-M1. Moreover, APG1252-M1, when combined with the third generation epidermal growth factor receptor (EGFR) inhibitor, osimertinib, synergistically decreased the survival of EGFR-mutant NSCLC cell lines including those resistant to osimertinib with enhanced induction of apoptosis and abrogated emergence of acquired resistance to osimertinib. Importantly, the combination was effective in inhibiting the growth of osimertinib-resistant tumors in vivo. Collectively, these results demonstrate the efficacy of APG1252 alone or in combination against human NSCLC cells.

Recent applications of covalent chemistries in protein-protein interaction inhibitors

Protein-protein interactions (PPIs) are large, often featureless domains whose modulations by small-molecules are challenging. Whilst there are some notable successes, such as the BCL-2 inhibitor venetoclax, the requirement for larger ligands to achieve the desired level of potency and selectivity may result in poor "drug-like" properties. Covalent chemistry is presently enjoying a renaissance. In particular, targeted covalent inhibition (TCI), in which a weakly electrophilic "warhead" is installed onto a protein ligand scaffold, is a powerful strategy to develop potent inhibitors of PPIs that are smaller/more drug-like yet have enhanced affinities by virtue of the reinforcing effect on the existing non-covalent interactions by the resulting protein-ligand covalent bond. Furthermore, the covalent bond delivers sustained inhibition, which may translate into significantly reduced therapeutic dosing. Herein, we discuss recent applications of a spectrum of TCIs, as well as covalent screening strategies, in the discovery of more effective inhibitors of PPIs using the HDM2 and BCL-2 protein families as case studies.

Chitosan Nanoparticle Encapsulation of Antibacterial Essential Oils

Chitosan is the most suitable encapsulation polymer because of its natural abundance, biodegradability, and surface functional groups in the form of free NH₂ groups. The presence of NH₂ groups allows for the facile grafting of functionalized molecules onto the chitosan surface, resulting in multifunctional materialistic applications. Quaternization of chitosan's free amino is one of the typical chemical modifications commonly achieved under acidic conditions. This quaternization improves its ionic character, making it ready for ionic-ionic surface modification. Although the cationic nature of chitosan alone exhibits antibacterial activity because of its interaction with negatively-charged bacterial membranes, the nanoscale size of chitosan further amplifies its antibiofilm activity. Additionally, the researcher used chitosan nanoparticles as polymeric materials to encapsulate antibiofilm agents (such as antibiotics and natural phytochemicals), serving as an excellent strategy to combat biofilm-based secondary infections. This paper provided a summary of available carbohydrate-based biopolymers as antibiofilm materials. Furthermore, the paper focuses on chitosan nanoparticle-based encapsulation of basil essential oil (Ocimum basilicum), mandarin essential oil (Citrus reticulata), Carum copticum essential oil ("Ajwain"), dill plant seed essential oil (Anethum graveolens), peppermint oil (Mentha piperita), green tea oil (Camellia sinensis), cardamom essential oil, clove essential oil (Eugenia caryophyllata), cumin seed essential oil (Cuminum cyminum), lemongrass essential oil (Cymbopogon commutatus), summer savory essential oil (Satureja hortensis), thyme essential oil, cinnamomum essential oil (Cinnamomum zeylanicum), and nettle essential oil (Urtica dioica). Additionally, chitosan nanoparticles are used for the encapsulation of the major essential components carvacrol and cinnamaldehyde, the encapsulation of an oil-in-water nanoemulsion of eucalyptus oil (Eucalyptus globulus), the encapsulation of a mandarin essential oil nanoemulsion, and the electrospinning nanofiber of collagen hydrolysate-chitosan with lemon balm (Melissa officinalis) and dill (Anethum graveolens) essential oil.

Identification of bicyclic compounds that act as dual inhibitors of Bcl-2 and Mcl-1

Elevated expression of anti-apoptotic proteins, such as Bcl-2 and Mcl-1 contributes to poor prognosis and resistance to current treatment modalities in multiple cancers. Here, we report the design, synthesis and characterization of benzimidazole chalcone and flavonoid scaffold-derived bicyclic compounds targeting both Bcl-2 and Mcl-1 by optimizing the structural differences in the binding sites of both these proteins. Initial docking screen of Bcl-2 and Mcl-1 with pro-apoptotic protein Bim revealed possible hits with optimal binding energies. All the optimized bicyclic compounds were screened for their in vitro cytotoxic activity against two oral cancer cell lines (AW8507 and AW13516) which express high levels of Bcl-2 and Mcl-1. Compound 4d from the benzimidazole chalcone series and compound 6d from the flavonoid series exhibited significant cytotoxic activity (IC₅₀ 7.12 μM and 17.18 μM, respectively) against AW13516 cell line. Time Resolved-Fluorescence Resonance Energy Transfer (TR-FRET) analysis further demonstrated that compound 4d and compound 6d could effectively inhibit the Bcl-2 and Mcl-1 proteins by displacing their BH3 binding partners. Both compounds exhibited potent activation of canonical pathway of apoptosis evident from appearance of cleaved Caspase-3 and PARP. Further, treatment of oral cancer cells with the inhibitors induced dissociation of the BH3 only protein Bim from Mcl-1 and Bak from Bcl-2 but failed to release Bax from Bcl-xL thereby confirming the nature of compounds as BH3-mimetics selectively targeting Bcl-2 and Mcl-1. Our study thus identifies bicyclic compounds as promising candidates for anti-apoptotic Bcl-2/Mcl-1 dual inhibitors with a potential for further development.

Development of a series of novel Mcl-1 inhibitors bearing an indole carboxylic acid moiety

The B cell lymphoma protein 2 (Bcl-2) family proteins regulate cell apoptosis by participating in the endogenous apoptosis pathway. As an important anti-apoptotic protein, Myeloid cell leukemia 1 (Mcl-1) is overexpressed in a variety of tumor cells, and targeting this protein has been a promising strategy for cancer therapy. Herein, based on the 1H-indole-5-carboxylic acid structure previously discovered, we have developed a series of novel compounds with increased affinities and selectivity toward Mcl-1 through structure-based drug design. Among those compounds, 26 exerted relatively better affinity and selectivity for Mcl-1 with moderate inhibition in HL-60 cells. Mechanism studies showed that compound 26 could induce cancer cells apoptosis in an Mcl-1-dependent manner. It also exhibited good microsomal and plasma stability with acceptable pharmacokinetics profiles. Furthermore, treatment with target compound in a 4T1 xenograft mouse model significantly suppressed the tumor growth. Overall, the small molecule described herein represents a promising Mcl-1 inhibitor for further study.

Mcl-1 levels critically impact the sensitivities of human colorectal cancer cells to APG-1252-M1, a novel Bcl-2/Bcl-XL dual inhibitor that induces Bax-dependent apoptosis

New treatment options, such as targeted therapies, are urgently needed for the treatment of colorectal cancer (CRC), the third leading cause of cancer-related deaths worldwide. The current study focuses on demonstrating the therapeutic efficacies of APG-1252-M1 (an active form of the prodrug, APG-1252 or pelcitoclax), a highly potent Bcl-2/Bcl-X_L dual inhibitor in clinical trials, against CRC and understanding the underlying mechanisms. APG-1252-M1 effectively decreased the survival of CRC cell lines, particularly those expressing relatively low levels of Mcl-1, with the induction of apoptosis. High levels of Mcl-1 were significantly correlated with decreased sensitivity of CRC cell lines to APG-1252-M1. When combined with an Mcl-1 inhibitor, APG-1252-M1 synergistically decreased the survival and induced apoptosis of APG-1252-M1-insensitive cell lines with high levels of Mcl-1. This combination further decreased the survival and enhanced apoptosis even in sensitive cell lines with relatively low levels of Mcl-1, whereas enforced expression of ectopic Mcl-1 in these cells abrogated APG-1252-M1’s effects on decreasing cell survival and inducing apoptosis, which could be reversed by Mcl-1 inhibition. APG-1252-M1 rapidly induced cytochrome C and Smac release from mitochondria with caspase-3 and PARP cleavage. Deficiency of Bax in CRC cells abolished APG-1252-M1’s ability to induce apoptosis, indicating that APG-1252-M1 induces Bax-dependent apoptosis. The current study thus demonstrates the potential of APG-1252-M1 as a monotherapy in the treatment of CRC, particularly those with low Mcl-1 expression, or in combination with an Mcl-1 inhibitor, warranting further evaluation in vivo and in the clinic.

Strategies to Reduce the On-Target Platelet Toxicity of Bcl-xL Inhibitors: PROTACs, SNIPERs and Prodrug-Based Approaches

Apoptosis is a highly regulated cellular process. Aberration in apoptosis is a common characteristic of various disorders. Therefore, proteins involved in apoptosis are prime targets in multiple therapies. Bcl-xL is an antiapoptotic protein. Compared to other antiapoptotic proteins, the expression of Bcl-xL is common in solid tumors and, to an extent, in some leukemias and lymphomas. The overexpression of Bcl-xL is also linked to survival and chemoresistance in cancer and senescent cells. Therefore, Bcl-xL is a promising anticancer and senolytic target. Various nanomolar range Bcl-xL inhibitors have been developed. ABT-263 was successfully identified as a Bcl-xL /Bcl-2 dual inhibitor. But it failed in the clinical trial (phase-II) because of its on-target platelet toxicity, which also implies an essential role of Bcl-xL protein in the survival of human platelets. Classical Bcl-xL inhibitor designs utilize occupancy-driven pharmacology with typical shortcomings (such as dose-dependent off-target and on-target platelet toxicities). Hence, event-driven pharmacology-based approaches, such as proteolysis targeting chimeras (PROTACs) and SNIPERs (specific non-genetic IAP-based protein erasers) have been developed. The development of Bcl-xL based PROTACs was expected, as 600 E3-ligases are available in humans, while some (such as cereblon (CRBN), von Hippel-Lindau (VHL)) are relatively less expressed in platelets. Therefore, E3 ligase ligand-based Bcl-xL PROTACs (CRBN: XZ424, XZ739; VHL: DT2216, PZ703b, 753b) showed a significant improvement in platelet therapeutic index than their parent molecules (ABT-263: DT2216, PZ703b, 753b, XZ739, PZ15227; A1155463: XZ424). Other than their distinctive pharmacology, PROTACs are molecularly large, which limits their cell permeability and plays a role in improving their cell selectivity. We also discuss prodrug-based approaches, such as antibody-drug conjugates (ABBV-155), phosphate prodrugs (APG-1252), dendrimer conjugate (AZD0466), and glycosylated conjugates (Nav-Gal). Studies of in-vitro, in-vivo, structure-activity relationships, biophysical characterization, and status of preclinical/clinical inhibitors derived from these strategies are also discussed in the review.

Brain-Targeted Codelivery of Bcl-2/Bcl-xl and Mcl-1 Inhibitors by Biomimetic Nanoparticles for Orthotopic Glioblastoma Therapy

Glioblastoma (GBM) is among the most treatment-resistant solid tumors and often recurrs after resection. One of the mechanisms through which GBM escapes various treatment modalities is the overexpression of anti-apoptotic Bcl-2 family proteins (e.g., Bcl-2, Bcl-xl, and Mcl-1) in tumor cells. Small-molecule inhibitors such as ABT-263 (ABT), which can promote mitochondrial-mediated cell apoptosis by selectively inhibiting the function of Bcl-2 and Bcl-xl, have been proven to be promising anticancer agents in clinical trials. However, the therapeutic prospects of ABT for GBM treatment are hampered by its limited blood-brain barrier (BBB) penetration, dose-dependent thrombocytopenia, and the drug resistance driven by Mcl-1, which is overexpressed in GBM cells and further upregulated upon treatment with ABT. Herein, we reported that the Mcl-1-specific inhibitor A-1210477 (A12) can act synergistically with ABT to induce potent cell apoptosis in U87 MG cells, drug-resistant U251 cells, and patient-derived GBM cancer stem cells. We further designed a biomimetic nanomedicine, based on the apolipoprotein E (ApoE) peptide-decorated red blood cell membrane and pH-sensitive dextran nanoparticles, for the brain-targeted delivery of ABT and A12. The synergistic anti-GBM effect was retained after encapsulation in the nanomedicine. Additionally, the obtained nanomedicine possessed good biocompatibility, exhibited efficient BBB penetration, and could effectively suppress tumor growth and prolong the survival time of mice bearing orthotopic GBM xenografts without inducing detectable adverse effects.

Stimuli-responsive, dual-function prodrug encapsulated in hyaluronic acid micelles to overcome doxorubicin resistance

Multidrug resistance (MDR) is the main challenge faced by cancer chemotherapy. Drug-conjugate offers a promising strategy for breast cancer therapy. In this regard, we developed a DNVM multifunctional drug delivery system by crosslinking doxorubicin (DOX) and vitamin E succinate (VES) with a pH-sensitive hydrazone bond and then encapsulated the DOX-NN-VES prodrug into pH-sensitive hyaluronic acid-2-(octadecyloxy)-1,3-dioxan-5-amine (HOD) micelles. DOX resistant MCF-7/ADR cell were adopted as a model to study the capability and mechanism of MDR reversal. DNVM exhibited much higher cytotoxicity and cell uptake efficiency compared with that of acid-insensitive DOX-VES loaded HOD micelles (DVSM) and DOX loaded HOD micelles (DOXM), indicating the better capacity of DNVM for the reversal of MDR. Moreover, DNVM prevented drug efflux more effectively, inhibited the expression of P-gp, induced excessive production of reactive oxygen species and affected the expression of apoptosis-related proteins. In vivo experiments showed that DNVM significantly inhibited the tumor growth with no obvious changes in the body weight of MCF-7/ADR cells-bearing nude mice. The results suggested that the "double gain" DNVM can synergistically enhance the efficacy of chemotherapeutics for DOX resistant tumor cells and has the potential to overcome tumor MDR. STATEMENT OF SIGNIFICANCE: A dual-functional pH-sensitive doxorubicin - vitamin E succinate prodrug was developed and loaded into tumor microenvironment-sensitive hyaluronic acid-2-(octadecyloxy)-1,3-dioxan-5-amine micelle system (DNVM) for sequencing stimuli-release and overcoming doxorubicin resistance. The "double gain" DNVM can synergistically enhance the efficacy of chemotherapeutics for doxorubicin resistant tumor cells and has the potential to overcome tumor multiple drug resistance.

Overcoming acquired resistance to third-generation EGFR inhibitors by targeting activation of intrinsic apoptotic pathway through Mcl-1 inhibition, Bax activation, or both

Treatment of EGFR-mutant non-small cell lung cancer (NSCLC) with mutation-selective third-generation EGFR-tyrosine kinase inhibitors (EGFR-TKIs) such as osimertinib has achieved remarkable success in the clinic. However, the immediate challenge is the emergence of acquired resistance, limiting the long-term remission of patients. This study suggests a novel strategy to overcome acquired resistance to osimertinib and other third-generation EGFR-TKIs through directly targeting the intrinsic apoptotic pathway. We found that osimertinib, when combined with Mcl-1 inhibition or Bax activation, synergistically decreased the survival of different osimertinib-resistant cell lines, enhanced the induction of intrinsic apoptosis, and inhibited the growth of osimertinib-resistant tumor in vivo. Interestingly, the triple-combination of osimertinib with Mcl-1 inhibition and Bax activation exhibited the most potent activity in decreasing the survival and inducing apoptosis of osimertinib-resistant cells and in suppressing the growth of osimertinib-resistant tumors. These effects were associated with increased activation of the intrinsic apoptotic pathway evidenced by augmented mitochondrial cytochrome C and Smac release. Hence, this study convincingly demonstrates a novel strategy for overcoming acquired resistance to osimertinib and other 3rd generation EGFR-TKIs by targeting activation of the intrinsic apoptotic pathway through Mcl-1 inhibition, Bax activation or both, warranting further clinical validation of this strategy.

Neutralizing Anti-IL-17A Antibody Demonstrates Preclinical Activity Enhanced by Vinblastine in Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm characterised by the accumulation into granulomas of apoptosis-resistant pathological dendritic cells (LCH-DCs). LCH outcome ranges from self-resolving to fatal. Having previously shown that, (i) monocyte-derived DCs (Mo-DCs) from LCH patients differentiate into abnormal and pro-inflammatory IL-17A-producing DCs, and (ii) recombinant IL-17A induces survival and chemoresistance of healthy Mo-DCs, we investigated the link between IL-17A and resistance to apoptosis of LCH-DCs. In LCH granulomas, we uncovered the strong expression of BCL2A1 (alias BFL1), an anti-apoptotic BCL2 family member. In vitro, intracellular IL-17A expression was correlated with BCL2A1 expression and survival of Mo-DCs from LCH patients. Based on the chemotherapeutic drugs routinely used as first or second line LCH therapy, we treated these cells with vinblastine, or cytarabine and cladribine. Our preclinical results indicate that high doses of these drugs decreased the expression of Mcl-1, the main anti-apoptotic BCL2 family member for myeloid cells, and killed Mo-DCs from LCH patients ex vivo, without affecting BCL2A1 expression. Conversely, neutralizing anti-IL-17A antibodies decreased BCL2A1 expression, the downregulation of which lowered the survival rate of Mo-DCs from LCH patients. Interestingly, the in vitro combination of low-dose vinblastine with neutralizing anti-IL-17A antibodies killed Mo-DCs from LCH patients. In conclusion, we show that BCL2A1 expression induced by IL-17A links the inflammatory environment to the unusual pro-survival gene activation in LCH-DCs. Finally, these preclinical data support that targeting both Mcl-1 and BCL2A1 with low-dose vinblastine and anti-IL-17A biotherapy may represent a synergistic combination for managing recurrent or severe forms of LCH.

Design, synthesis and biological evaluation of hydantoin derivatives as Mcl-1 selective inhibitors

As a member of Bcl-2 protein family, myeloid cell leukemia-1 (Mcl-1) plays a critical role in cell apoptosis and has become a promising anti-cancer drug target. Herein, we designed and synthesized a series of hydantoin derivatives as novel Mcl-1 inhibitors based on our previously developed lead compound. Among them, compound M23 and M24 exhibited good binding affinities against Mcl-1 with K_i values of 0.49 μM and 0.33 μM respectively. Especially, compound M23 exhibited good selectivity over Bcl-xL, whereas compound M24 possessed good selectivity over both Bcl-2 and Bcl-xL. Furthermore, we also investigated the effects of these new Mcl-1 inhibitors on cell proliferation, apoptosis and mitochondrial membrane potential, as well as the stability in plasma.

Synthesis and biological evaluation of FJ-809, a compound originally described as MIM1 and an inhibitor of the anti-apoptotic protein Mcl-1

The development of inhibitors of anti-apoptotic proteins, such as Mcl-1, is currently a very active area in the field of cancer research.

Sulfonamide derivatives as potential anti-cancer agents and their SARs elucidation

Currently, the arise of drug resistance and undesirable off-target effects of anti-cancer agents are major challenges for cancer treatment, which energizes medicinal chemists to develop more anti-cancer agents with high efficiency and low toxicity continuously. Sulfonamide derivatives are a class of promising compounds with diverse biological activities including anti-cancer, and parts of them have been marketed for cancer therapy, such as Belinostat, ABT-199 and Amsacrine. In this review, we summed up the recent advances of sulfonamide derivatives as potential anti-cancer agents based on the anti-cancer targets, such as aromatase, carbonic anhydrase (CA), anti-apoptotic B-cell lymphoma-2 (Bcl-2) proteins, topoisomerase and phosphatidylinositol 3-kinase (PI3K), and elucidated the corresponding structure-activity relationships (SARs) of most sulfonamide derivatives. We hope this review could provide a clear insight for medicinal chemists in the rational design of more potent and bio-target specific anti-cancer agents.

Tumor Suppressor FBXW7 and Its Regulation of DNA Damage Response and Repair

The proper DNA damage response (DDR) and repair are the central molecular mechanisms for the maintenance of cellular homeostasis and genomic integrity. The abnormality in this process is frequently observed in human cancers, and is an important contributing factor to cancer development. FBXW7 is an F-box protein serving as the substrate recognition component of SCF (SKP1-CUL1-F-box protein) E3 ubiquitin ligase. By selectively targeting many oncoproteins for proteasome-mediated degradation, FBXW7 acts as a typical tumor suppressor. Recent studies have demonstrated that FBXW7 also plays critical roles in the process of DDR and repair. In this review, we first briefly introduce the processes of protein ubiquitylation by SCF^FBXW7 and DDR/repair, then provide an overview of the molecular characteristics of FBXW7. We next discuss how FBXW7 regulates the process of DDR and repair, and its translational implication. Finally, we propose few future perspectives to further elucidate the role of FBXW7 in regulation of a variety of biological processes and tumorigenesis, and to design a number of approaches for FBXW7 reactivation in a subset of human cancers for potential anticancer therapy.

Structural revision of the Mcl-1 inhibitor MIM1: synthesis and biological studies on ovarian cancer cells with evaluation of designed analogues

In the area of cancer research, the development of new and potent inhibitors of anti-apoptotic proteins is a very active and promising topic. The small molecule MIM1 has been reported earlier as one of the first selective inhibitors of the anti-apoptotic protein Mcl-1. In the present paper, we first revised the structure of this molecule based on extensive physicochemical analyses. Then we designed and synthesized a focused library of analogues for the corrected structure of MIM1. Next, these molecules were subjected to a panel of in cellulo biological studies, allowing the identification of dual Bcl-xL/Mcl-1 inhibitors, as well as selective Mcl-1 inhibitors. These results have been complemented by fluorescence polarization assays with the Mcl-1 protein. Preliminary structure-activity relationships were discussed and extensive molecular modelling studies allowed us to propose a rationale for the biological activity of this series of new inhibitors, in particular for the selectivity of inhibition of Mcl-1 versus Bcl-xL.

Kidney cancer biomarkers and targets for therapeutics: survivin (BIRC5), XIAP, MCL-1, HIF1α, HIF2α, NRF2, MDM2, MDM4, p53, KRAS and AKT in renal cell carcinoma

The incidence of renal cell carcinoma (RCC) is increasing worldwide with an approximate 20% mortality rate. The challenge in RCC is the therapy-resistance. Cancer resistance to treatment employs multiple mechanisms due to cancer heterogeneity with multiple genetic and epigenetic alterations. These changes include aberrant overexpression of (1) anticancer cell death proteins (e.g., survivin/BIRC5), (2) DNA repair regulators (e.g., ERCC6) and (3) efflux pump proteins (e.g., ABCG2/BCRP); mutations and/or deregulation of key (4) oncogenes (e.g., MDM2, KRAS) and/or (5) tumor suppressor genes (e.g., TP5/p53); and (6) deregulation of redox-sensitive regulators (e.g., HIF, NRF2). Foci of tumor cells that have these genetic alterations and/or deregulation possess survival advantages and are selected for survival during treatment. We will review the significance of survivin (BIRC5), XIAP, MCL-1, HIF1α, HIF2α, NRF2, MDM2, MDM4, TP5/p53, KRAS and AKT in treatment resistance as the potential therapeutic biomarkers and/or targets in RCC in parallel with our analized RCC-relevant TCGA genetic results from each of these gene/protein molecules. We then present our data to show the anticancer drug FL118 modulation of these protein targets and RCC cell/tumor growth. Finally, we include additional data to show a promising FL118 analogue (FL496) for treating the specialized type 2 papillary RCC.

Myeloid cell leukemia 1 (MCL-1): Structural characteristics and application in cancer therapy

Apoptosis, a major hallmark of cancer cells, regulates cellular fate and homeostasis. BCL-2 (B-cell CLL/Lymphoma 2) protein family is popularly known to mediate the intrinsic mode of apoptosis, of which MCL-1 is a crucial member. Myeloid cell leukemia 1 (MCL-1) is an anti-apoptotic oncoprotein and one of the most investigated members of the BCL-2 family. It is commonly known to be genetically altered, aberrantly overexpressed, and primarily associated with drug resistance in various human cancers. Recent advancements in the development of selective MCL-1 inhibitors and evaluating their effectiveness in cancer treatment establish its popularity as a molecular target. The overall aim is the selective induction of apoptosis in cancer cells by using a single or combination of BCL-2 family inhibitors. Delineating the precise molecular mechanisms associated with MCL-1-mediated cancer progression will certainly improve the efficacy of clinical interventions aimed at MCL-1 and hence patient survival. This review is structured to highlight the structural characteristics of MCL-1, its specific interactions with NOXA, MCL-1-regulatory microRNAs, and at the same time focus on the emerging therapeutic strategies targeting our protein of interest (MCL-1), alone or in combination with other treatments.

Structure-Based Optimization of 3-Phenyl-N-(2-(3-phenylureido)ethyl)thiophene-2-sulfonamide Derivatives as Selective Mcl-1 Inhibitors

Selective Mcl-1 inhibitors may overcome the drug resistance caused by current anti-apoptotic Bcl-2 protein inhibitors in tumors with Mcl-1 overexpression. Based on previously discovered compounds with a 3-phenylthiophene-2-sulfonamide core moiety, in this work, we have obtained new compounds with improved binding affinity and/or selectivity under the guidance of structure-based design. The most potent compounds achieved sub-micromolar binding affinities to Mcl-1 (K_i ∼ 0.4 μM) and good cytotoxicity (IC₅₀ < 10 μM) on several tumor cells. ¹⁵N-heteronuclear single-quantum coherence NMR spectra suggested that these compounds bound to the BH3-binding groove on Mcl-1. Several cellular assays revealed that FWJ-D4 as well as its precursor FWJ-D5 effectively induced caspase-dependent apoptosis, and their target engagement at Mcl-1 was confirmed by co-immunoprecipitation experiments. Treatment with FWJ-D5 at 50 mg/kg every 2 days on an RS4;11 xenograft mouse model for 22 days led to 75% reduction in tumor volume without body weight loss.

LCT-3d Induces Oxidative Stress-Mediated Apoptosis by Upregulating Death Receptor 5 in Gastric Cancer Cells

Gastric cancer is a global health problem. In this study, we investigate the role of a novel Indole derivative, named LCT-3d, in inhibiting the growth of gastric cancer cells by MTT assay. The Western blotting results showed that LCT-3d modulated the mitochondrial-related proteins and Cleaved-Caspases 3/9, to induce cell apoptosis. The up-regulation of Death receptor 5 (DR5) in MGC803 cells was observed with LCT-3d treatment. Knockdown of DR5 on MGC803 cells partially reversed the LCT-3d-induced mitochondrial apoptosis. The level of Reactive Oxygen Species (ROS) in MGC803 cells was increased with LCT-3d treatment and could be blocked with the pretreatment of the ROS inhibitor N-Acetylcysteine (NAC). The results demonstrate that the elevating ROS can up-regulate the expression of DR5, resulting in apoptosis via mitochondrial pathway. Although the nuclear factor erythroid-2 related factor 2 (Nrf2) pathway served an important role in protecting gastric cancer cells against the injury of ROS, it can’t reverse LCT-3d-induced cell apoptosis. Taken together, our study showed that LCT-3d induced apoptosis via DR5-mediated mitochondrial apoptotic pathway in gastric cancer cells. LCT-3d could be a novel lead compound for development of anti-cancer activity in gastric cancer.