Plinabulin, an inhibitor of tubulin polymerization, targets KRAS signaling through disruption of endosomal recycling

Redefining bioactive small molecules from microbial metabolites as revolutionary anticancer agents

Cancer treatment remains a significant challenge due to issues such as acquired resistance to conventional therapies and the occurrence of adverse treatment-related toxicities. In recent years, researchers have turned their attention to the microbial world in search of novel and effective drugs to combat this devastating disease. Microbial derived secondary metabolites have proven to be a valuable source of biologically active compounds, which exhibit diverse functions and have demonstrated potential as treatments for various human diseases. The exploration of these compounds has provided valuable insights into their mechanisms of action against cancer cells. In-depth studies have been conducted on clinically established microbial metabolites, unraveling their anticancer properties, and shedding light on their therapeutic potential. This review aims to comprehensively examine the anticancer mechanisms of these established microbial metabolites. Additionally, it highlights the emerging therapies derived from these metabolites, offering a glimpse into the immense potential they hold for anticancer drug discovery. Furthermore, this review delves into approved treatments and major drug candidates currently undergoing clinical trials, focusing on specific molecular targets. It also addresses the challenges and issues encountered in the field of anticancer drug research and development. It also presents a comprehensive exposition of the contemporary panorama concerning microbial metabolites serving as a reservoir for anticancer agents, thereby illuminating their auspicious prospects and the prospect of forthcoming strides in the domain of cancer therapeutics.

Conformation and energy investigation of microtubule longitudinal dynamic instability induced by natural products

The natural products plinabulin, docetaxel, and vinblastine are microtubule targeting agents (MTAs). They have been used alone or in combination in cancer treatment. However, the exact nature of their effects on microtubule (MT) polymerization dynamics is poorly understood. To elucidate the longitudinal conformational and energetic changes during MT dynamics, a total of 140 ns molecular dynamic simulations combined with binding free energy calculations were performed on seven tubulin models. The results indicated that the drugs disrupted MT polymerization by altering both MT conformation and binding free energy of the neighboring tubulin subunits. The combination of plinabulin and docetaxel destabilized MT polymerization due to bending MT and weakening the polarity of tubulin polymerization. The new combination of docetaxel and vinblastine synergistically enhanced MT depolymerization and bending, while plinabulin and vinblastine had no synergistic inhibitory effects. The results were verified by the tubulin assembly assay. Our study obtained a comprehensive understanding of the action mechanisms of three natural drugs and their combinations on MT dynamic, provided theoretical guidance for new MTA combinations, and would promote the optimal use of MTA and contribute to developing new MTAs as anticancer agents.

The Chemotherapeutic Potentials of Compounds Isolated from the Plant, Marine, Fungus, and Microorganism: Their Mechanism of Action and Prospects

Research on natural products mainly focuses on developing a suitable drug to treat human disease. There has been a sharp increase in the development of drugs from natural products. Most of the drugs that are available are from the terrestrial origin. Marine natural products are less explored. Oceans are considered as a vast ecosystem with a wide variety of living organisms and natural products that are unexplored. Large numbers of antitumor drugs are from natural sources such as plants, marine, and microorganisms. 80% new chemical entities that were launched over the past 60 decades were from a natural source. In this article, the anticancer potential from the natural source such as plants, fungi, microorganisms, marine, and endophytes has been reviewed. Emphasis is given on the compound from the marine, plant, and of bacterial origin. Finally, we consider the future and how we might achieve better sustainability to alleviate human cancer suffering while having fewer side effects, more efficacies, and causing less harm than the present treatments.

Application of Feature-Based Molecular Networking for Comparative Metabolomics and Targeted Isolation of Stereoisomers from Algicolous Fungi

Seaweed endophytic (algicolous) fungi are talented producers of bioactive natural products. We have previously isolated two strains of the endophytic fungus, Pyrenochaetopsis sp. FVE-001 and FVE-087, from the thalli of the brown alga Fucus vesiculosus. Initial chemical studies yielded four new decalinoylspirotetramic acid derivatives with antimelanoma activity, namely pyrenosetins A-C (1-3) from Pyrenochaetopsis sp. strain FVE-001, and pyrenosetin D (4) from strain FVE-087. In this study, we applied a comparative metabolomics study employing HRMS/MS based feature-based molecular networking (FB MN) on both Pyrenochaetopsis strains. A higher chemical capacity in production of decalin derivatives was observed in Pyrenochaetopsis sp. FVE-087. Notably, several decalins showed different retention times despite the same MS data and MS/MS fragmentation pattern with the previously isolated pyrenosetins, indicating they may be their stereoisomers. FB MN-based targeted isolation studies coupled with antimelanoma activity testing on the strain FVE-087 afforded two new stereoisomers, pyrenosetins E (5) and F (6). Extensive NMR spectroscopy including DFT computational studies, HR-ESIMS, and Mosher's ester method were used in the structure elucidation of compounds 5 and 6. The 3'R,5'R stereochemistry determined for compound 6 was identical to that previously reported for pyrenosetin C (3), whose stereochemistry was revised as 3'S,5'R in this study. Pyrenosetin E (5) inhibited the growth of human malignant melanoma cells (A-375) with an IC50 value of 40.9 μM, while 6 was inactive. This study points out significant variations in the chemical repertoire of two closely related fungal strains and the versatility of FB MN in identification and targeted isolation of stereoisomers. It also confirms that the little-known fungal genus Pyrenochaetopsis is a prolific source of complex decalinoylspirotetramic acid derivatives.

Biomaterials from the sea: Future building blocks for biomedical applications

Marine resources have tremendous potential for developing high-value biomaterials. The last decade has seen an increasing number of biomaterials that originate from marine organisms. This field is rapidly evolving. Marine biomaterials experience several periods of discovery and development ranging from coralline bone graft to polysaccharide-based biomaterials. The latter are represented by chitin and chitosan, marine-derived collagen, and composites of different organisms of marine origin. The diversity of marine natural products, their properties and applications are discussed thoroughly in the present review. These materials are easily available and possess excellent biocompatibility, biodegradability and potent bioactive characteristics. Important applications of marine biomaterials include medical applications, antimicrobial agents, drug delivery agents, anticoagulants, rehabilitation of diseases such as cardiovascular diseases, bone diseases and diabetes, as well as comestible, cosmetic and industrial applications.

Potential role of marine species-derived bioactive agents in the management of SARS-CoV-2 infection

COVID-19, caused by the SARS-CoV-2 outbreak, has resulted in a massive global health crisis. Bioactive molecules extracted or synthesized using starting material obtained from marine species, including griffithsin, plitidepsin and fingolimod are in clinical trials to evaluate their anti-SARS-CoV-2 and anti-HIV efficacies. The current review highlights the anti-SARS-CoV-2 potential of marine-derived phytochemicals explored using in silico, in vitro and in vivo models. The current literature suggests that these molecules have the potential to bind with various key drug targets of SARS-CoV-2. In addition, many of these agents have anti-inflammatory and immunomodulatory potentials and thus could play a role in the attenuation of COVID-19 complications. Overall, these agents may play a role in the management of COVID-19, but further preclinical and clinical studies are still required to establish their role in the mitigation of the current viral pandemic.

Molecular Networking-Guided Isolation of New Etzionin-Type Diketopiperazine Hydroxamates from the Persian Gulf Sponge Cliona celata

The Persian Gulf is a unique and biologically diverse marine environment dominated by invertebrates. In continuation of our research interest in the chemistry and biological activity of marine sponges from the Persian Gulf, we selected the excavating sponge Cliona celata for detailed metabolome analyses, in vitro bioactivity screening, and chemical isolation studies. A UPLC-MS/MS (MS²) molecular-networking-based dereplication strategy allowed annotation and structural prediction of various diketopiperazines (DKPs) and etzionin-type diketopiperazine hydroxamates (DKPHs) in the crude sponge extract. The molecular-networking-guided isolation approach applied to the crude extract afforded the DKPH etzionin (1) and its two new derivatives, clioetzionin A (2) and clioetzionin B (3). Another new modified DKP (4) was identified by MS/MS analyses but could not be isolated in sufficient quantities to confirm its structure. The chemical characterization of the purified DKPHs 1–3 was performed by a combination of 1D and 2D NMR spectroscopy, HRMS, HRMS/MS, and [α]_D analyses. Compounds 1 and 2 exhibited broad antibacterial, antifungal, and anticancer activities, with IC₅₀ values ranging from 19.6 to 159.1 µM. This is the first study investigating the chemical constituents of a C. celata specimen from the Persian Gulf. It is also the first report of full spectroscopic data of etzionin based on extensive spectroscopic analyses.

Development of Marine-Derived Compounds for Cancer Therapy

Cancer has always been a threat to human health with its high morbidity and mortality rates. Traditional therapy, including surgery, chemotherapy and radiotherapy, plays a key role in cancer treatment. However, it is not able to prevent tumor recurrence, drug resistance and treatment side effects, which makes it a very attractive challenge to search for new effective and specific anticancer drugs. Nature is a valuable source of multiple pharmaceuticals, and most of the anticancer drugs are natural products or derived from them. Marine-derived compounds, such as nucleotides, proteins, peptides and amides, have also shed light on cancer therapy, and they are receiving a fast-growing interest due to their bioactive properties. Their mechanisms contain anti-angiogenic, anti-proliferative and anti-metastasis activities; cell cycle arrest; and induction of apoptosis. This review provides an overview on the development of marine-derived compounds with anticancer properties, both their applications and mechanisms, and discovered technologies.

The Role of Microtubules in Pancreatic Cancer: Therapeutic Progress

Pancreatic cancer has an extremely low prognosis, which is attributable to its high aggressiveness, invasiveness, late diagnosis, and lack of effective therapies. Among all the drugs joining the fight against this type of cancer, microtubule-targeting agents are considered to be the most promising. They inhibit cancer cells although through different mechanisms such as blocking cell division, apoptosis induction, etc. Hereby, we review the functions of microtubule cytoskeletal proteins in tumor cells and comprehensively examine the effects of microtubule-targeting agents on pancreatic carcinoma.

Plinabulin, a Distinct Microtubule-Targeting Chemotherapy, Promotes M1-Like Macrophage Polarization and Anti-tumor Immunity

Reprogramming tumor infiltrating myeloid cells to elicit pro-inflammatory responses is an exciting therapeutic maneouver to improve anti-tumor responses. We recently demonstrated that a distinct microtubule-targeting drug, plinabulin—a clinical-stage novel agent—modulates dendritic cell maturation and enhances anti-tumor immunity. Here, we investigated the effects of plinabulin on macrophage polarization in vitro and in vivo. Plinabulin monotherapy induced significant tumor growth inhibition in mice bearing subcutaneous MC38 colon cancer. Importantly, the regressing tumors were characterized by an increase in M1-like/M2-like tumor-associated macrophages (TAM) ratio. The efficacy of plinabulin remained unaltered in T cell-deficient Rag2^−/− mice, suggesting an important role of macrophages in driving the drug's anti-tumor effect. Exposure of murine and healthy human macrophages to plinabulin induced polarization toward the M1 phenotype, including increased expression of co-stimulatory molecules CD80, CD86 and pro-inflammatory cytokines IL-1β, IL-6, and IL-12. M2-associated immunosuppressive cytokines IL-10 and IL-4 were reduced. This pro-inflammatory M1-like skewing of TAMs in response to plinabulin was dependent on the JNK pathway. Functionally, plinabulin-polarized human M1 macrophages directly killed HuT 78 tumor cells in vitro. Importantly, plinabulin induced a functional M1-like polarization of tumor infiltrating macrophages in murine tumors as well as in tumor samples from ovarian cancer patients, by preferentially triggering M1 proliferation. Our study uncovers a novel immunomodulatory effect of plinabulin in directly triggering M1 polarization and proliferation as well as promoting TAM anti-tumoral effector functions.

Antimicrobial and Antioxidant Polyketides from a Deep-Sea-Derived Fungus Aspergillus versicolor SH0105

Fifteen polyketides, including four new compounds, isoversiol F (1), decumbenone D (2), palitantin B (7), and 1,3-di-O-methyl-norsolorinic acid (8), along with 11 known compounds (3-6 and 9-15), were isolated from the deep-sea-derived fungus Aspergillus versicolor SH0105. Their structures and absolute configurations were determined by comprehensive spectroscopic data, including 1D and 2D NMR, HRESIMS, and ECD calculations, and it is the first time to determine the absolute configuration of known decumbenone A (6). All of these compounds were evaluated for their antimicrobial activities against four human pathogenic microbes and five fouling bacterial strains. The results indicated that 3,7-dihydroxy-1,9-dimethyldibenzofuran (14) displayed obvious inhibitory activity against Staphylococcus aureus (ATCC 27154) with the MIC value of 13.7 μM. In addition, the antioxidant assays of the isolated compounds revealed that aspermutarubrol/violaceol-I (15) exhibited significant 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity with the IC50 value of 34.1 μM, and displayed strong reduction of Fe3+ with the ferric reducing antioxidant power (FRAP) value of 9.0 mM under the concentration of 3.1 μg/mL, which were more potent than ascorbic acid.

Combinational immunotherapy based on immune checkpoints inhibitors in small cell lung cancer: is this the beginning to reverse the refractory situation?

Small cell lung cancer (SCLC), a particular neuroendocrine tumor, occupies 13% of lung cancers, with the highest mortality among cancers. Immune checkpoints inhibitors (ICIs) based on programmed cell death protein-1 (PD-1)/programmed cell death one ligand (PD-L1) inhibitors and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors have been one of the most favorable therapies in SCLC. Simultaneously, not all the patients respond to ICIs due to the lack of biomarkers to predict the immunotherapeutic effect. Multiple combinational approaches are under exploration, including the integrated or successive assessment of additional immunotherapeutic agents, chemotherapy, radiotherapy, and targeted therapy with ICIs. The current review offers a general view of the rationale for clinical studies exploring the experimental result of combinational immunotherapy based on ICIs, with both available results and ongoing trials. Moreover, the development of more predictive biomarkers, specific clinical trial designs, enhancement of the efficacy, and decreasing the financial toxicity will become the trend of future research and clinical applications of ICIs. Understanding the evolving immuno-oncology is increasingly relevant and crucial to solve those problems and define therapeutic strategies and potential target populations of combinational immunotherapy. Ultimately, emerging combinational immunotherapy will transform SCLC into a chronic disease to help patients survive from tumors.

The Endosomal Recycling Pathway-At the Crossroads of the Cell

The endosomal recycling pathway lies at the heart of the membrane trafficking machinery in the cell. It plays a central role in determining the composition of the plasma membrane and is thus critical for normal cellular homeostasis. However, defective endosomal recycling has been linked to a wide range of diseases, including cancer and some of the most common neurological disorders. It is also frequently subverted by many diverse human pathogens in order to successfully infect cells. Despite its importance, endosomal recycling remains relatively understudied in comparison to the endocytic and secretory transport pathways. A greater understanding of the molecular mechanisms that support transport through the endosomal recycling pathway will provide deeper insights into the pathophysiology of disease and will likely identify new approaches for their detection and treatment. This review will provide an overview of the normal physiological role of the endosomal recycling pathway, describe the consequences when it malfunctions, and discuss potential strategies for modulating its activity.

Targeting and extending the eukaryotic druggable genome with natural products: cytoskeletal targets of natural products

Covering: 2014-2019We review recent progress on natural products that target cytoskeletal components, including microtubules, actin, intermediate filaments, and septins and highlight their demonstrated and potential utility in the treatment of human disease. The anticancer efficacy of microtubule targeted agents identified from plants, microbes, and marine organisms is well documented. We highlight new microtubule targeted agents currently in clinical evaluations for the treatment of drug resistant cancers and the accumulating evidence that the anticancer efficacy of these agents is not solely due to their antimitotic effects. Indeed, the effects of microtubule targeted agents on interphase microtubules are leading to their potential for more mechanistically guided use in cancers as well as neurological disease. The discussion of these agents as more targeted drugs also prompts a reevaluation of our thinking about natural products that target other components of the cytoskeleton. For instance, actin active natural products are largely considered chemical probes and non-selective toxins. However, studies utilizing these probes have uncovered aspects of actin biology that can be more specifically targeted to potentially treat cancer, neurological disorders, and infectious disease. Compounds that target intermediate filaments and septins are understudied, but their continued discovery and mechanistic evaluations have implications for numerous therapeutic indications.

Pyrenosetins A-C, New Decalinoylspirotetramic Acid Derivatives Isolated by Bioactivity-Based Molecular Networking from the Seaweed-Derived Fungus Pyrenochaetopsis sp. FVE-001

Marine algae represent a prolific source of filamentous fungi for bioprospecting. In continuation of our search for new anticancer leads from fungi derived from the brown alga Fucus vesiculosus, an endophytic Pyrenochaetopsis sp. FVE-001 was selected for an in-depth chemical analysis. The crude fungal extract inhibited several cancer cell lines in vitro, and the highest anticancer activity was tracked to its CHCl3-soluble portion. A bioactivity-based molecular networking approach was applied to C18-SPE fractions of the CHCl3 subextract to predict the bioactivity scores of metabolites in the fractions and to aid targeted purification of anticancer metabolites. This approach led to a rapid isolation of three new decalinoylspirotetramic acid derivatives, pyrenosetins A-C (1-3) and the known decalin tetramic acid phomasetin (4). The structures of the compounds were elucidated by extensive NMR, HR-ESIMS, FT-IR spectroscopy, [α]D and Mosher's ester method. Compounds 1 and 2 showed high anticancer activity against malignant melanoma cell line A-375 (IC50 values 2.8 and 6.3 μM, respectively), in line with the bioactivity predictions. This is the first study focusing on secondary metabolites of a marine-derived Pyrenochaetopsis sp. and the second investigation performed on the member of the genus Pyrenochaetopsis.