Dual inhibitors of the pro-survival proteins Bcl-2 and Mcl-1 derived from natural compound meiogynin A

Targeted Penetrating Motif Engineering of BH3 Mimetic: Harnessing Non-Canonical Amino Acids for Coinhibition of MCL-1 and BCL-xL in Acute Myeloid Leukemia

Acute Myeloid Leukemia (AML) remains a formidable clinical challenge, predominantly due to the emergence of resistance to existing therapeutic regimens, including BCL-2 inhibitors like Venetoclax. Here, a novel approach is introduced by engineering BH3 mimetics utilizing non-canonical amino acids (ncAAs) to achieve dual inhibition of MCL-1 and BCL-xL. Through site saturation mutagenesis scanning, the I58(Chg) mutation is identified, significantly enhancing binding affinity with IC50 values of 2.77 nm for MCL-1 and 10.69 nm for BCL-xL, reflecting an increase of fourfold or more. The developed vMIP-II-TAT-I peptide, incorporating a CXCR4-targeted penetrating motif, demonstrated superior cellular uptake, with mean fluorescence intensity (MFI) 7.2-fold higher in CXCR4-positive AML cells and exhibited a high selectivity index (SI) for AML cells, with minimal impact on normal human hematopoietic stem cells (HSCs). When combined with Venetoclax, this peptide induced synergistic apoptosis, reducing tumor burden and prolonging survival in an AML mouse model, with median survival extended to 53 days from 37 days with Venetoclax alone. These findings reveal the therapeutic potential of dual inhibition in overcoming Venetoclax resistance and selectively targeting leukemic cells with reduced off-target effects, while laying the foundation for developing advanced BH3 mimetics with enhanced targeting, binding affinity, and efficacy for AML treatment.

Identification of new ClpC1-NTD binders for Mycobacterium tuberculosis drug development

MtbClpC1 is a promising drug target against tuberculosis. Recent studies have shown that several natural product antibiotics targeting the unfoldase N-terminal domain can impair MtbClpC1 function resulting in cell death. While the pharmacological properties of these natural product antibiotics prevent their use in the clinic, similar molecules binding to the same binding pockets can result in new drugs against Mtb. Here we demonstrate that we successfully used in silico screening to identify new ClpC1 N-terminal domain binders with micromolar affinity from a small compound library. In addition, we experimentally demonstrate that the new compounds bind to the same pockets used by the natural product antibiotics and inhibit ClpC1 function.

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.

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.

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.

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.

Molecular mechanism underlying the apoptotic modulation by ethanol extract of Pseudolarix kaempferi in mucoepidermoid carcinoma of the salivary glands

Background

Pseudolarix kaempferi is a traditional Chinese natural product that possesses the potential cytotoxic effects against cancer. However, the precise molecular mechanism underlying its cytotoxic effects has not yet been completely elucidated. Here, we clarify the mechanism via which the ethanol extract of P. kaempferi (EEPK) leads to cytotoxicity mediated by apoptosis in mucoepidermoid carcinoma (MEC) originating from the salivary glands.

Methods

We investigated the mechanism underlying the anticancer efficacy of EEPK in human MEC in vitro by assessing mitochondrial dysfunction, mRNA levels, and morphological changes in apoptotic cell nuclei as well as by using a cytotoxicity assay, flow cytometric analysis, and western blotting.

Results

EEPK inhibited the growth of two human MEC cells and stimulated the induction of caspase-mediated apoptosis that was accompanied by mitochondrial membrane depolarization. Compared with the vehicle control groups, EEPK decreased myeloid cell leukemia-1 (Mcl-1) expression in both cells whereas it significantly decreased B cell lymphoma-2 (Bcl-2) expression in MC3 cells only. The EEPK-induced altered Mcl-1 expression was caused by translational inhibition and proteasomal degradation. Additionally, EEPK significantly increased p-Bcl-2 (Ser⁷⁰) expression regardless of its total forms by facilitating the activation of the c-Jun N-terminal kinase (JNK) signaling pathway, which exhibited cell context dependency. Nevertheless, JNK activation following EEPK treatment was, at least in part, required for the proapoptotic efficacy of EEPK in both cells.

Conclusions

This study revealed that EEPK-induced alterations of Mcl-1 inhibition and JNK/Bcl-2 phosphorylation cause apoptosis and provided basic preclinical data for future clinical trials regarding therapy for patients with MEC.

Graphic abstract

Design, synthesis and biological evaluation of dual Bcl-2/Mcl-1 inhibitors bearing 2-(1H-indol-4-yl)benzoic acid scaffold

The anti-apoptotic protein inhibitors of the B cell lymphoma 2 (Bcl-2) family have been developed as new anticancer therapies. Numerous studies illustrated the great potential in the development of dual Bcl-2/myeloid cell leukemia 1 (Mcl-1) inhibitors. Herein, we reported a series of Bcl-2/Mcl-1 inhibitors that optimized from a hit compound 1 via structure-based rational design. The biological evaluation suggested that most compounds exhibited potent binding affinities at submicromolar to both Bcl-2 and Mcl-1 without any Bcl-xL binding affinities, especially compound 9o, with a K_i value of 0.07 μM to Mcl-1 and 0.66 μM to Bcl-2, that has great potential for developing dual inhibitors targeting Bcl-2 and Mcl-1.

Targeting MCL-1 in cancer: current status and perspectives

Myeloid leukemia 1 (MCL-1) is an antiapoptotic protein of the BCL-2 family that prevents apoptosis by binding to the pro-apoptotic BCL-2 proteins. Overexpression of MCL-1 is frequently observed in many tumor types and is closely associated with tumorigenesis, poor prognosis and drug resistance. The central role of MCL-1 in regulating the mitochondrial apoptotic pathway makes it an attractive target for cancer therapy. Significant progress has been made with regard to MCL-1 inhibitors, some of which have entered clinical trials. Here, we discuss the mechanism by which MCL-1 regulates cancer cell apoptosis and review the progress related to MCL-1 small molecule inhibitors and their role in cancer therapy.

Drimane Derivatives as the First Examples of Covalent BH3 Mimetics that Target MCL-1

Drimane sesquiterpenoid dialdehydes are natural compounds with antiproliferative properties. Nevertheless, their mode of action has not yet been discovered. Herein, we demonstrate that various drimanes are potent inhibitors of MCL-1 and BCL-xL, two proteins of the BCL-2 family that are overexpressed in various cancers, including lymphoid malignancies. Subtle changes in their structure significantly modified their activity on the target proteins. The two most active compounds are MCL-1 selective and bind in the BH3 binding groove of the protein. Complementary studies by NMR spectroscopy and mass spectrometry analyses, but also synthesis, showed that they covalently inhibit MCL-1 though the formation of a pyrrole adduct. In addition, cytotoxic assays revealed that these two compounds show a cytotoxic selectivity for BL2, a MCL-1/BCL-xL-dependent cell line and induce apoptosis.

Development of Mcl-1 inhibitors for cancer therapy

The myeloid leukemia cell differentiation protein (Mcl-1) is an anti-apoptotic protein of the B-cell lymphoma 2 (Bcl-2) family, which regulates cellular apoptosis. Mcl-1 expression plays a key role in survival of cancer cells and therefore serves as a promising target in cancer therapy. Besides, its importance as a cancer target, various peptides and small-molecule inhibitors have been successfully designed and synthesized, yet no Mcl-1 inhibitor is approved for clinical use. However, recent development on the understanding of Mcl-1's role in key cellular processes in cancer and an upsurge of reports highlighting its association in various anticancer drug resistance supports the view that Mcl-1 is a key target in various cancers, especially hematological cancers. This review compiles structures of a variety of inhibitors of Mcl-1 reported to date. These include inhibitors based on a diverse range of heterocycles (e.g. indole, imidazole, thiophene, nicotinic acid, piperazine, triazine, thiazole, isoindoline), oligomers (terphenyl, quaterpyridine), polyphenol, phenalene, anthranilic acid, anthraquinone, macrocycles, natural products, and metal-based complexes. In addition, an effort has been made to summarize the structure activity relationships, based on a variety of assays, of some important classes of Mcl-1 inhibitors, giving affinities and selectivities for Mcl-1 compared to other Bcl-2 family members. A focus has been placed on categorizing the inhibitors based on their core frameworks (scaffolds) to appeal to the chemical biologist or medicinal chemist.

LncRNA CDKN2B-AS1 relieved inflammation of ulcerative colitis via sponging miR-16 and miR-195

BACKGROUND

This study was aimed to explore the differential expression of lncRNA CDKN2B-AS1-miR-195-5p/miR-16-5p axis in ulcerative colitis (UC) and its role in regulating UC pathogenesis.

METHODS

One hundred and eighty-seven UC patients and one hundred and fifty-two healthy volunteers were recruited, and their blood samples were collected. Inflammatory cytokines in serum were determined with ELISA, and lncRNA CDKN2B-AS1, miR-195-5p and miR-16-5p levels were detected with RT-PCR. Then pcDNA3.1-CDKN2B-AS1, si-CDKN2B-AS1, miR-195-5p mimic, miR-195-5p inhibitor, miR-16-5p mimic and miR-16-5p inhibitor were transfected into HT29 cells, and proliferation and apoptosis of the cells were assessed. Dual-luciferase reporter gene assay was implemented to identify the sponging relationship between lncRNA CDKN2B-AS1 and miR-195-5p/miR-16-5p.

RESULTS

CDKN2B-AS1 level was negatively correlated with levels of inflammatory cytokines, including TNF-α, IL-6 and sIL-2R, yet miR-16-5p and miR-195-5p levels were negatively correlated with the CDKN2B-AS1 level. The CDKN2B-AS1 combined with miR-16-5p and miR-195-5p also achieved an optimum efficacy in differentiating between light and medium UC, light and severe UC, as well as medium and heavy UC. Furthermore, pcDNA3.1-CDKN2B-AS1 depressed expressions of IFN-γ, IL-8, IL-1β and TNF-α in HT29 cells (P < 0.05), and strengthened proliferation of the cells (P < 0.05). CDKN2B-AS1 also sponged and regulated miR-16-5p and miR-195-5p in HT29 cells, and miR-16-5p and miR-195-5p could reverse the effect of CDKN2B-AS1 on inflammatory cytokine production, barrier function and apoptosis of HT29 cells (P < 0.05).

CONCLUSION

LncRNA CDKN2B-AS1 regulated inflammation of UC by sponging miR-195-5p and miR-16-5p, providing an alternative for diagnosis and treatment of UC.

Single and dual target inhibitors based on Bcl-2: Promising anti-tumor agents for cancer therapy

B-cell lymphoma-2 (Bcl-2) proteins family is an essential checkpoint in apoptosis. Extensive evidences suggested that overexpression of anti-apoptotic Bcl-2 proteins can be observed in multiple cancer cell lines and primary tumor biopsy samples, which is an important reason for tumor cells to evade apoptosis and further acquire drug resistance for chemotherapy. Hence, down-regulation of anti-apoptotic Bcl-2 proteins is effective for the treatment of cancers. In view that Bcl-2 inhibitors and some other anti-tumor agents, such as HDAC inhibitors and Mdm2 inhibitors, exert synergy effects in tumor cells, it is pointed out that dual-targeting therapies based on these targets are regarded as rational strategies to enhance the effectiveness of single target agents for cancer treatment. This review briefly introduces the apoptosis, the structure of Bcl-2 family proteins, and focuses on the current status and recent advances of Bcl-2 inhibitors and the corresponding SARs of them. Moreover, we discuss the synergisms between Bcl-2 and other anti-tumor targets, and summarize the current dual-target agents.

Inhibition of Anti-Apoptotic Bcl-2 Proteins in Preclinical and Clinical Studies: Current Overview in Cancer

The dynamic interplay between pro-death and pro-survival Bcl-2 family proteins is responsible for a cell’s fate. Due to the recognized relevance of this family in cancer progression and response to therapy, different efforts have made in recent years in order to develop small molecules able to target anti-apoptotic proteins such as Bcl-2, Bcl-xL and Mcl-1. The limitations of the first Bcl-2 family targeted drugs, regarding on-target and off-target toxicities, have been overcome with the development of venetoclax (ABT-199), the first BH3 mimetic inhibitor approved by the FDA. The purpose of this review is to discuss the state-of-the-art in the development of drugs targeting Bcl-2 anti-apoptotic proteins and to highlight the potential of their application as single agents or in combination for improving anti-cancer therapy, focusing in particular on solid tumors.

Pro-apoptotic carboxamide analogues of natural fislatifolic acid targeting Mcl-1 and Bcl-2

A library of 26 novel carboxamides deriving from natural fislatifolic acid has been prepared. The synthetic strategy involved a bio-inspired Diels-Alder cycloaddition, followed by functionalisations of the carbonyl moiety. All the compounds were evaluated on Bcl-xL, Mcl-1 and Bcl-2 proteins. In this series of cyclohexenyl chalcone analogues, six compounds behaved as dual Bcl-xL/Mcl-1 inhibitors in micromolar range and one exhibited sub-micromolar affinities toward Mcl-1 and Bcl-2. The most potent compounds evaluated on A549 and MCF7 cancer cell lines showed moderate cytotoxicities.

Natural disesquiterpenoids: an update

This review highlights the progress on the isolation, bioactivity, biogenesis and total synthesis of dimeric sesquiterpenoids since 2010.

1,2,3-Triazole-containing hybrids as potential anticancer agents: Current developments, action mechanisms and structure-activity relationships

Anticancer agents are critical for the cancer treatment, but side effects and the drug resistance associated with the currently used anticancer agents create an urgent need to explore novel drugs with low side effects and high efficacy. 1,2,3-Triazole is privileged building block in the discovery of new anticancer agents, and some of its derivatives have already been applied in clinics or under clinical trials for fighting against cancers. Hybrid molecules occupy an important position in cancer control, and hybridization of 1,2,3-triazole framework with other anticancer pharmacophores may provide valuable therapeutic intervention for the treatment of cancer, especially drug-resistant cancer. This review emphasizes the recent advances in 1,2,3-triazole-containing hybrids with anticancer potential, covering articles published between 2015 and 2019, and the structure-activity relationships, together with mechanisms of action are also discussed.

Discovery of Inhibitors of Aurora/PLK Targets as Anticancer Agents

Aurora and polo-like kinases control the G2/M phase in cell mitosis, which are both considered as crucial targets for cancer cell proliferations. Here, naphthalene-based Aurora/PLK coinhibitors as leading compounds were designed through in silico approach, and a total of 36 derivatives were synthesized. One candidate (AAPK-25) was selected under in vitro cell based high throughput screening with an IC50 value = 0.4 μM to human colon cancer cell HCT-116. A kinome scan assay showed that AAPK-25 was remarkably selective to both Aurora and PLK families. The relevant genome pathways were also depicted by microarray based gene expression analysis. Furthermore, validated from a set of in vitro and in vivo studies, AAPK-25 significantly inhibited the development of the colon cancer growth and prolonged the median survival time at the end of the administration (p < 0.05). To sum up, AAPK-25 has a great potential to be developed for a chemotherapeutic agent in clinical use.

1,2,3-Triazole-containing hybrids as leads in medicinal chemistry: A recent overview

The 1,2,3-triazole ring is a major pharmacophore system among nitrogen-containing heterocycles. These five-membered heterocyclic motifs with three nitrogen heteroatoms can be prepared easily using 'click' chemistry with copper- or ruthenium-catalysed azide-alkyne cycloaddition reactions. Recently, the 'linker' property of 1,2,3-triazoles was demonstrated, and a novel class of 1,2,3-triazole-containing hybrids and conjugates was synthesised and evaluated as lead compounds for diverse biological targets. These lead compounds have been demonstrated as anticancer, antimicrobial, anti-tubercular, antiviral, antidiabetic, antimalarial, anti-leishmanial, and neuroprotective agents. The present review summarises advances in lead compounds of 1,2,3-triazole-containing hybrids, conjugates, and their related heterocycles in medicinal chemistry published in 2018. This review will be useful to scientists in research fields of organic synthesis, medicinal chemistry, phytochemistry, and pharmacology.

Rhodium(iii) complexes with isoquinoline derivatives as potential anticancer agents: in vitro and in vivo activity studies

Two rhodium complexes Rh1 and Rh2 with isoquinoline derivatives were synthesized and characterized.

Bioactive heterocycles containing a 3,4,5-trimethoxyphenyl fragment exerting potent antiproliferative activity through microtubule destabilization

Novel bioactive heterocycles containing a 3,4,5-trimethoxyphenyl fragment as antiproliferative agents by targeting tubulin were synthesized and their preliminary structure activity relationships (SARs) were explored. Among all these chemical agents, 2-(Benzo[d]oxazol-2-ylthio)-N-(4-methoxybenzyl)-N-(3,4,5-trimethoxyphenyl)acetamide (4d) exhibited the potent antiproliferative activity against MGC-803 cells with an IC₅₀ value of 0.45 μM by induction of G2/M pahse arrest and cell apoptosis. In addition, 4d could change the membrane potential (ΔΨ) of the mitochondria against MGC-803 cells. Importantly, 4d acted as a novel tubulin polymerization inhibitor binding to colchicine site with an IC₅₀ value of 3.35 μM.