Stabilizing versus destabilizing the microtubules: a double-edge sword for an effective cancer treatment option?

Molecular Dynamics and Machine Learning reveal distinguishing mechanisms of Competitive Ligands to perturb α,β-Tubulin

The mechanisms of action of ligands competing for the Colchicine Binding Site (CBS) of the α,β-Tubulin are non-standard compared to the commonly witnessed ligand-induced inhibition of proteins. This is because their potencies are not solely judged by the binding affinity itself, but also by their capacity to bias the conformational states of the dimer. Regarding the latter requirement, it is observed that ligands competing for the same pocket that binds colchicine exhibit divergence in potential clinical outcomes. Molecular dynamics-based ∼5.2 µs sampling of α,β-Tubulin complexed with four different ligands has revealed that each ligand has its customized way of influencing the complex. Primarily, it is the proportion of twisting and/or bending characteristic of modes of the intrinsic dynamics which is revealed to be 'fundamental' to tune this variation in the mechanism. The milder influence of 'bending' makes a ligand (TUB092), better classifiable under the group of vascular disrupting agents (VDAs), which are phenotypically effective on cytoskeletons; whereas a stronger impact of 'bending' makes the classical ligand Colchicine (COL) a better Anti-Mitotic agent (AMA). Two other ligands BAL27862 (2RR) and Nocodazole (NZO) fall in the intermediate zone as they fail to explicitly induce bending modes. Random Forest Classification method and K-means Clustering is applied to reveal the efficiency of Machine Learning methods in classifying the Tubulin conformations according to their ligand-specific perturbations and to highlight the significance of specific amino acid residues, mostly positioned in the α-β and β-β interfaces involved in the mechanism. These key residues responsible to yield discriminative actions of the ligands are likely to be highly useful in future endeavours to design more precise inhibitors.

Fused Imidazopyrazine-Based Tubulin Polymerization Inhibitors Inhibit Neuroblastoma Cell Function

Targeting the colchicine binding site on tubulin is a promising approach for cancer treatment to overcome the limitations of current tubulin polymerization inhibitors. New classes of colchicine binding site inhibitors (CBSIs) are continually being uncovered; however, balancing metabolic stability and cellular potency remains an issue that needs to be resolved. Therefore, we designed and synthesized a series of novel fused imidazopyridine and -pyrazine CBSIs and evaluated their cellular activity, metabolic stability, and tubulin-binding properties. Evidence shows that the imidazo[1,2-a]pyrazine series are effective against neuroblastoma cell lines marked by MYCN amplification. Further assessment shows that a combination of an imidazo[1,2-a]pyrazine core with a trimethoxyphenyl ring D results in the highest cellular activity and binding characteristics compared with a dichloromethoxyphenyl or difluoromethoxyphenyl ring D. However, the metabolic stability of compounds with a dichloromethoxyphenyl or difluoromethoxyphenyl ring D is significantly higher than that of those containing a trimethoxyphenyl ring D, suggesting that improved metabolic stability is achieved with a moderate impact on potency.

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.

Design, synthesis and anti-tumor evaluation of plinabulin derivatives as potential agents targeting β-tubulin

Plinabulin is a promising microtubule destabilizing agent in phase 3 clinical stage for treating non-small cell lung cancer. However, the high toxicity and the poor water solubility of plinabulin limited its use and more plinabulin derivatives need to be explored. Here, two series of 29 plinabulin derivatives were designed, synthesized and evaluated for their anti-tumor effect against three types of cancer cell lines. Most of derivatives exerted obvious inhibition to the proliferation of the cell lines tested. Among them, compound 11c exerted stronger efficiency than plinabulin, and the reason might be the additional hydrogen bond between the nitrogen atom of the indole ring in compound 11c and Gln134 of β-tubulin. Immunofluorescence assay showed that compound 11c at 10 nM significantly disrupted tubulin structure. Compound 11c also significantly induced G2/M cell cycle arrest and apoptosis in dose dependent manner. These results suggest that compound 11c might be a potential candidate for cancer treatment as antimicrotubule agent.

Cancer chemotherapy and beyond: Current status, drug candidates, associated risks and progress in targeted therapeutics

Cancer is an abnormal state of cells where they undergo uncontrolled proliferation and produce aggressive malignancies that causes millions of deaths every year. With the new understanding of the molecular mechanism(s) of disease progression, our knowledge about the disease is snowballing, leading to the evolution of many new therapeutic regimes and their successive trials. In the past few decades, various combinations of therapies have been proposed and are presently employed in the treatment of diverse cancers. Targeted drug therapy, immunotherapy, and personalized medicines are now largely being employed, which were not common a few years back. The field of cancer discoveries and therapeutics are evolving fast as cancer type-specific biomarkers are progressively being identified and several types of cancers are nowadays undergoing systematic therapies, extending patients' disease-free survival thereafter. Although growing evidence shows that a systematic and targeted approach could be the future of cancer medicine, chemotherapy remains a largely opted therapeutic option despite its known side effects on the patient's physical and psychological health. Chemotherapeutic agents/pharmaceuticals served a great purpose over the past few decades and have remained the frontline choice for advanced-stage malignancies where surgery and/or radiation therapy cannot be prescribed due to specific reasons. The present report succinctly reviews the existing and contemporary advancements in chemotherapy and assesses the status of the enrolled drugs/pharmaceuticals; it also comprehensively discusses the emerging role of specific/targeted therapeutic strategies that are presently being employed to achieve better clinical success/survival rate in cancer patients.

Therapeutic potential of marine peptides in malignant melanoma

Malignant melanoma is the most dangerous type of skin cancer. It is becoming more common globally and is increasingly resistant to treatment options. Despite extensive research into its pathophysiology, there are still no proven cures for metastatic melanoma. Unfortunately, current treatments are frequently ineffective and costly, and have several adverse effects. Natural substances have been extensively researched for their anti-MM capabilities. Chemoprevention and adjuvant therapy with natural products is an emerging strategy to prevent, cure or treat melanoma. Numerous prospective drugs are found in aquatic species, providing a plentiful supply of lead cytotoxic chemicals for cancer treatment. Anticancer peptides are less harmful to healthy cells and cure cancer through several different methods, such as altered cell viability, apoptosis, angiogenesis/metastasis suppression, microtubule balance disturbances and targeting lipid composition of the cancer cell membrane. This review addresses marine peptides as effective and safe treatments for MM and details their molecular mechanisms of action.

Marine Cyanobacterial Peptides in Neuroblastoma: Search for Better Therapeutic Options

Neuroblastoma is the most prevalent extracranial solid tumor in pediatric patients, originating from sympathetic nervous system cells. Metastasis can be observed in approximately 70% of individuals after diagnosis, and the prognosis is poor. The current care methods used, which include surgical removal as well as radio and chemotherapy, are largely unsuccessful, with high mortality and relapse rates. Therefore, attempts have been made to incorporate natural compounds as new alternative treatments. Marine cyanobacteria are a key source of physiologically active metabolites, which have recently received attention owing to their anticancer potential. This review addresses cyanobacterial peptides' anticancer efficacy against neuroblastoma. Numerous prospective studies have been carried out with marine peptides for pharmaceutical development including in research for anticancer potential. Marine peptides possess several advantages over proteins or antibodies, including small size, simple manufacturing, cell membrane crossing capabilities, minimal drug-drug interactions, minimal changes in blood-brain barrier (BBB) integrity, selective targeting, chemical and biological diversities, and effects on liver and kidney functions. We discussed the significance of cyanobacterial peptides in generating cytotoxic effects and their potential to prevent cancer cell proliferation via apoptosis, the activation of caspases, cell cycle arrest, sodium channel blocking, autophagy, and anti-metastasis behavior.

Depsipeptides Targeting Tumor Cells: Milestones from In Vitro to Clinical Trials

Cancer is currently considered one of the most threatening diseases worldwide. Diet could be one of the factors that can be enhanced to comprehensively address a cancer patient's condition. Unfortunately, most molecules capable of targeting cancer cells are found in uncommon food sources. Among them, depsipeptides have emerged as one of the most reliable choices for cancer treatment. These cyclic amino acid oligomers, with one or more subunits replaced by a hydroxylated carboxylic acid resulting in one lactone bond in a core ring, have broadly proven their cancer-targeting efficacy, some even reaching clinical trials and being commercialized as "anticancer" drugs. This review aimed to describe these depsipeptides, their reported amino acid sequences, determined structure, and the specific mechanism by which they target tumor cells including apoptosis, oncosis, and elastase inhibition, among others. Furthermore, we have delved into state-of-the-art in vivo and clinical trials, current methods for purification and synthesis, and the recognized disadvantages of these molecules. The information collated in this review can help researchers decide whether these molecules should be incorporated into functional foods in the near future.

KC-180-2 Exerts Anti-SCLC Effects via Dual Inhibition of Tubulin Polymerization and Src Signaling

In this study, a series of N-benzyl-2-(5-phenylpyridin-2-yl) acetamide-based derivatives were successfully designed and synthesized as anti-cancer agents. KC-180-2 was screened as a potentially leading compound with dual mechanisms of action: Src signaling and tubulin polymerization inhibition. It efficiently suppressed the proliferation of five cancer cell lines (MDA-MB-231, H446, SKOV-3, HepG2, and HT29), with IC₅₀ values ranging from 5 to 188 nM, especially small-cell lung cancer (SCLC) cells (IC₅₀, 5 nM). Correspondingly, it exerted a significant therapeutic effect on the H446 small-cell lung cancer xenograft model, significantly reducing the volume of tumors without obvious toxicity. Mechanistically, this compound significantly inhibited the polymerization of purified tubulin in vitro, inducing G2/M cell cycle arrest and binding to the kinase catalytic domain of the Src protein, which reduced the phosphorylation of Src. Thus, KC-180-2 is a potential lead compound for the further development of a new anti-tumor drug against SCLC.

Early Pharmacological Profiling of Antiproliferative Compounds by Live Cell Imaging

Natural products represent an excellent source of unprecedented anticancer compounds. However, the identification of the mechanism of action remains a major challenge. Several techniques and methodologies have been considered, but with limited success. In this work, we explored the combination of live cell imaging and machine learning techniques as a promising tool to depict in a fast and affordable test the mode of action of natural compounds with antiproliferative activity. To develop the model, we selected the non-small cell lung cancer cell line SW1573, which was exposed to the known antimitotic drugs paclitaxel, colchicine and vinblastine. The novelty of our methodology focuses on two main features with the highest relevance, (a) meaningful phenotypic metrics, and (b) fast Fourier transform (FFT) of the time series of the phenotypic parameters into their corresponding amplitudes and phases. The resulting algorithm was able to cluster the microtubule disruptors, and meanwhile showed a negative correlation between paclitaxel and the other treatments. The FFT approach was able to group the samples as efficiently as checking by eye. This methodology could easily scale to group a large amount of data without visual supervision.

Combination of microtubule targeting agents with other antineoplastics for cancer treatment

Microtubule targeting agents (MTAs) have attracted extensive attention for cancer treatment. However, their clinical efficacies are limited by intolerable toxicities, inadequate efficacy and acquired multidrug resistance. The combination of MTAs with other antineoplastics has become an efficient strategy to lower the toxicities, overcome resistance and improve the efficacies for cancer treatment. In this article, we review the combinations of MTAs with some other anticancer drugs, such as cytotoxic agents, kinases inhibitors, histone deacetylase inhibitors, immune checkpoints inhibitors, to overcome these obstacles. We strongly believe that this review will provide helpful information for combination therapy based on MTAs.

Therapeutic Potential of Marine Peptides in Prostate Cancer: Mechanistic Insights

Prostate cancer (PCa) is the leading cause of cancer death in men, and its treatment is commonly associated with severe adverse effects. Thus, new treatment modalities are required. In this context, natural compounds have been widely explored for their anti-PCa properties. Aquatic organisms contain numerous potential medications. Anticancer peptides are less toxic to normal cells and provide an efficacious treatment approach via multiple mechanisms, including altered cell viability, apoptosis, cell migration/invasion, suppression of angiogenesis and microtubule balance disturbances. This review sheds light on marine peptides as efficacious and safe therapeutic agents for PCa.

A comprehensive insight into the antineoplastic activities and molecular mechanisms of deoxypodophyllotoxin: Recent trends, challenges, and future outlook

Lignans constitute an important group of polyphenols, which have been demonstrated to potently suppress cancer cell proliferation. Numerous in vitro and in vivo studies indicate that deoxypodophyllotoxin as a natural lignan possesses potent anticancer activities against various types of human cancer. The purpose of current review is to provide the reader with the latest findings in understanding the anticancer effects and molecular mechanisms of deoxypodophyllotoxin. This review comprehensively describes the influence of deoxypodophyllotoxin on signaling cascades and molecular targets implicated in cancer cell proliferation and invasion. A number of various signaling molecules and pathways, including apoptosis, necroptosis, cell cycle, angiogenesis, vascular disruption, ROS, MMPs, glycolysis, and microtubules as well as NF-κB, PI3K/Akt/mTOR, and MAPK cascades have been reported to be responsible for the anticancer activities of deoxypodophyllotoxin. The results of present review suggest that the cyclolignan deoxypodophyllotoxin can be developed as a novel and potent anticancer agent, especially as an alternative option for treatment of resistant tumors to chemotherapy.

Synthesis and Biological Evaluation of Highly Active 7-Anilino Triazolopyrimidines as Potent Antimicrotubule Agents

Two different series of fifty-two compounds, based on 3′,4′,5′-trimethoxyaniline (7a–ad) and variably substituted anilines (8a–v) at the 7-position of the 2-substituted-[1,2,4]triazolo [1,5-a]pyrimidine nucleus, had moderate to potent antiproliferative activity against A549, MDA-MB-231, HeLa, HT-29 and Jurkat cancer cell lines. All derivatives with a common 3-phenylpropylamino moiety at the 2-position of the triazolopyrimidine scaffold and different halogen-substituted anilines at its 7-position, corresponding to 4′-fluoroaniline (8q), 4′-fluoro-3′-chloroaniline (8r), 4′-chloroaniline (8s) and 4′-bromoaniline (8u), displayed the greatest antiproliferative activity with mean IC50′s of 83, 101, 91 and 83 nM, respectively. These four compounds inhibited tubulin polymerization about 2-fold more potently than combretastatin A-4 (CA-4), and their activities as inhibitors of [3H]colchicine binding to tubulin were similar to that of CA-4. These data underlined that the 3′,4′,5′-trimethoxyanilino moiety at the 7-position of the [1,2,4]triazolo [1,5-a]pyrimidine system, which characterized compounds 7a–ad, was not essential for maintaining potent antiproliferative and antitubulin activities. Compounds 8q and 8r had high selectivity against cancer cells, and their interaction with tubulin led to the accumulation of HeLa cells in the G2/M phase of the cell cycle and to apoptotic cell death through the mitochondrial pathway. Finally, compound 8q significantly inhibited HeLa cell growth in zebrafish embryos.

Analysis of Plant-Plant Interactions Reveals the Presence of Potent Antileukemic Compounds

A method to identify anticancer compounds in plants was proposed based on the hypothesis that these compounds are primarily present in plants to provide them with an ecological advantage over neighboring plants and other competitors. According to this view, identifying plants that contain compounds that inhibit or interfere with the development of other plant species may facilitate the discovery of novel anticancer agents. The method was developed and tested using Magnolia grandiflora, Gynoxys verrucosa, Picradeniopsis oppositifolia, and Hedyosmum racemosum, which are plant species known to possess compounds with cytotoxic activities. Plant extracts were screened for growth inhibitory activity, and then a thin-layer chromatography bioautography assay was conducted. This located the major antileukemic compounds 1, 2, 4, and 5 in the extracts. Once the active compounds were located, they were extracted and purified, and their structures were determined. The growth inhibitory activity of the purified compounds showed a significant correlation with their antileukemic activity. The proposed approach is rapid, inexpensive, and can easily be implemented in areas of the world with high biodiversity but with less access to advanced facilities and biological assays.

Microtubule Organization Is Essential for Maintaining Cellular Morphology and Function

Microtubules (MTs) are highly dynamic polymers essential for a wide range of cellular physiologies, such as acting as directional railways for intracellular transport and position, guiding chromosome segregation during cell division, and controlling cell polarity and morphogenesis. Evidence has established that maintaining microtubule (MT) stability in neurons is vital for fundamental cellular and developmental processes, such as neurodevelopment, degeneration, and regeneration. To fulfill these diverse functions, the nervous system employs an arsenal of microtubule-associated proteins (MAPs) to control MT organization and function. Subsequent studies have identified that the disruption of MT function in neurons is one of the most prevalent and important pathological features of traumatic nerve damage and neurodegenerative diseases and that this disruption manifests as a reduction in MT polymerization and concomitant deregulation of the MT cytoskeleton, as well as downregulation of microtubule-associated protein (MAP) expression. A variety of MT-targeting agents that reverse this pathological condition, which is regarded as a therapeutic opportunity to intervene the onset and development of these nervous system abnormalities, is currently under development. Here, we provide an overview of the MT-intrinsic organization process and how MAPs interact with the MT cytoskeleton to promote MT polymerization, stabilization, and bundling. We also highlight recent advances in MT-targeting therapeutic agents applied to various neurological disorders. Together, these findings increase our current understanding of the function and regulation of MT organization in nerve growth and regeneration.

Glycogen Synthase Kinase 3β Involvement in Neuroinflammation and Neurodegenerative Diseases

BACKGROUND

GSK-3β activity has been strictly related to neuroinflammation and neurodegeneration. Alzheimer's disease is the most studied neurodegenerative disease, but GSK-3β seems to be involved in almost all neurodegenerative diseases including Parkinson's disease, amyotrophic lateral sclerosis, frontotemporal dementia, Huntington's disease and the autoimmune disease multiple sclerosis.

OBJECTIVE

The aim of this review is to help researchers both working on this research topic or not to have a comprehensive overview on GSK-3β in the context of neuroinflammation and neurodegeneration.

METHOD

Literature has been searched using PubMed and SciFinder databases by inserting specific keywords. A total of more than 500 articles have been discussed.

RESULTS

First of all, the structure and regulation of the kinase were briefly discussed and then, specific GSK-3β implications in neuroinflammation and neurodegenerative diseases were illustrated also with the help of figures, to conclude with a comprehensive overview on the most important GSK-3β and multitarget inhibitors. For all discussed compounds, the structure and IC50 values at the target kinase have been reported.

CONCLUSION

GSK-3β is involved in several signaling pathways both in neurons as well as in glial cells and immune cells. The fine regulation and interconnection of all these pathways are at the base of the rationale use of GSK-3β inhibitors in neuroinflammation and neurodegeneration. In fact, some compounds are now under clinical trials. Despite this, pharmacodynamic and ADME/Tox profiles of the compounds were often not fully characterized and this is deleterious in such a complex system.

Therapeutic potential of marine peptides in cervical and ovarian cancers

Cervical and ovarian cancers contribute significantly to female morbidity and mortality worldwide. The current standard of treatment, including surgical removal, radiation therapy, and chemotherapy, offers poor outcomes. There are many side effects to traditional chemotherapeutic agents and treatment-resistant types, and often the immune response is depressed. As a result, traditional approaches have evolved to include new alternative remedies, such as natural compounds. Aquatic species provide a rich supply of possible drugs. The potential anti-cancer peptides are less toxic to normal cells and can attenuate multiple drug resistance by providing an efficacious treatment approach. The physiological effects of marine peptides are described in this review focusing on various pathways, such as apoptosis, microtubule balance disturbances, suppression of angiogenesis, cell migration/invasion, and cell viability. The review also highlights the potential role of marine peptides as safe and efficacious therapeutic agent for the treatment of cervical and ovarian cancers.

Phase I/IIa Trial of BMS-986148, an Anti-mesothelin Antibody-drug Conjugate, Alone or in Combination with Nivolumab in Patients with Advanced Solid Tumors

PURPOSE

To assess the safety and tolerability of BMS-986148, a mesothelin-directed antibody-drug conjugate (ADC) ± nivolumab, in patients with selected tumors.

PATIENTS AND METHODS

In an international phase I/IIa study [NCT02341625 (CA008-002)], patients received BMS-986148 monotherapy (0.1-1.6 mg/kg intravenously (i.v.) every 3 weeks or 0.4 or 0.6 mg/kg i.v. once weekly; n = 96) or BMS-986148 0.8 mg/kg + nivolumab 360 mg i.v. every 3 weeks (n = 30). The primary endpoint was safety and tolerability.

RESULTS

In CA008-002, the most common (≥ 10%) treatment-related adverse events (TRAEs) included increased aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase. Grade 3/4 TRAEs occurred in 42 patients (49%) receiving BMS-986148 every 3 weeks monotherapy, three (25%) receiving BMS-986148 once-weekly monotherapy, and 10 (33%) receiving BMS-986148 + nivolumab every 3 weeks. Overall, 17 of 126 patients (13%) discontinued because of a TRAE. The MTD of BMS-986148 was 1.2 mg/kg i.v. every 3 weeks. The safety profile of BMS-986148 + nivolumab was similar to that of BMS-986148 monotherapy (0.8 mg/kg). Active ADC exposures increased in a dose-proportional manner with both dosing regimens (every 3 weeks and once weekly). Preliminary clinical activity was observed with BMS-986148 ± nivolumab. No association between mesothelin expression and response was detected.

CONCLUSIONS

BMS-986148 ± nivolumab demonstrated a clinically manageable safety profile and preliminary evidence of clinical activity, supporting additional studies combining directed cytotoxic therapies with checkpoint inhibitors as potential multimodal therapeutic strategies in patients with advanced solid tumors.

Cardiovascular safety profile of taxanes and vinca alkaloids: 30 years FDA registry experience

OBJECTIVE

Antimicrotubular agents are among the most commonly used classes of chemotherapeutic agents, but the risk of cardiovascular adverse events (CVAEs) remains unclear. Our objective was to study the CVAEs associated with antimicrotubular agents.

METHODS

The Food and Drug Administration's Adverse Event Reporting System was used to study CVAEs in adults from 1990 to 2020. Reported single-agent (only taxane or vinca alkaloid) CVAEs were compared with combination therapy (with at least one of the four major cardiotoxic drugs: anthracycline, HER2Neu inhibitors, tyrosine kinase inhibitors and checkpoint inhibitors) using adjusted polytomous logistic regression.

RESULTS

Over 30 years, 134 398 adverse events were reported, of which 18 426 (13.4%) were CVAEs, with 74.1% due to taxanes and 25.9% due to vinca alkaloids. In 30 years, there has been a reduction in the proportion of reported CVAEs for taxanes from 15% to 11.8% (Cochran-Armitage P-trends <0.001) with no significant change in the proportion of reported CVAEs for vinca alkaloids (9.2%-11.7%; P-trends=0.06). The proportion of reported CVAEs was lower in both taxane and vinca alkaloid monotherapy versus combination therapy (reporting OR=0.50 and 0.55, respectively). Anthracyclines and HER2Neu inhibitor combinations with taxanes or vinca alkaloids primarily drove the higher burden of combination CVAEs. Hypertension requiring hospitalisation and heart failure was significantly lower in monotherapy versus combination antimicrotubular agent therapy.

CONCLUSIONS

Antimicrotubular agents are associated with CVAEs, especially in combination chemotherapy regimens. Based on this study, we suggest routine cardiovascular assessment of patients with cancer before initiating antimicrotubular agents in combination therapy.

Microtubule Integrity Is Associated with the Functional Activity of Mitochondria in HEK293

Mitochondria move along the microtubule network and produce bioenergy in the cell. However, there is no report of a relationship between bioenergetic activity of mitochondria and microtubule stability in mammalian cells. This study aimed to investigate this relationship. We treated HEK293 cells with microtubule stabilizers (Taxol and Epothilone D) or a microtubule disturber (vinorelbine), and performed live-cell imaging to determine whether mitochondrial morphology and bioenergetic activity depend on the microtubule status. Treatment with microtubule stabilizers enhanced the staining intensity of microtubules, significantly increased ATP production and the spare respiratory capacity, dramatically increased mitochondrial fusion, and promoted dynamic movement of mitochondria. By contrast, bioenergetic activity of mitochondria was significantly decreased in cells treated with the microtubule disturber. Our data suggest that microtubule stability promotes mitochondrial functional activity. In conclusion, a microtubule stabilizer can possibly recover mitochondrial functional activity in cells with unstable microtubules.

Mechanisms of influence of the microtubule over-stabilizing ligands on the structure and intrinsic dynamics of α,β-Tubulin

The intervention into the cell cycle progression by administering microtubule over-stabilizing ligands that arrest the mitotic cell division by preventing spindle dissociation, is a promising strategy to fight against cancers. The building blocks of the microtubules and the spindles, i.e. the α,β-tubulin dimer, upon binding of such ligands, stay more comfortably in the microtubular multimeric form; the phenomenon of which is the key to the said over-stabilization. Using two such over-stabilizing ligands, Taxol and Taxotere, the present work reports the collective changes that these ligands induce on the structure and dynamics of the α,β-tubulin dimer which could be reconciled as the molecular basis of the over-stabilization of the microtubules; the trends have been found to be statistically significant across all independent calculations on them. The ligand binding increases the coherence between the residue communities of the two opposite faces of the β-subunit, which in a periodic arrangement in microtubule are knwon to form intermolecular contact with each other. This is likely to create an indirect cooperativity between those structural regions and this is a consequence of the reshuffling of the internal network of interactions upon ligand binding. Such reorganizations are also complemented by the increased contributions of the softer modes of the intrinsic dynamics more, which is likely to increase the plasticity of the system favourable for making structural adjustments in a multimer. Further, the ligands are able to compensate the drawback of lacking one phosphate group in protein-GDP interactions compared to the same for protein-GTP and this is in agreement with the hints form the earlier reports. The findings form a mechanistic basis of the enhanced capacity of the α,β-tubulin dimer to get more favourably accommodated into the microtubule superstructure upon binding either of Taxol and Taxotere.

The Design, Synthesis, and Biological Activities of Pyrrole-Based Carboxamides: The Novel Tubulin Inhibitors Targeting the Colchicine-Binding Site

Microtubule targeting agents (MTAs) that interfere with the dynamic state of the mitotic spindle are well-known and effective chemotherapeutic agents. These agents interrupt the microtubule network via polymerization or depolymerization, halting the cell cycle progression and leading to apoptosis. We report two novel pyrrole-based carboxamides (CAs) (CA-61 and -84) as the compounds exhibiting potent anti-cancer properties against a broad spectrum of epithelial cancer cell lines, including breast, lung, and prostate cancer. The anti-cancer activity of CAs is due to their ability to interfere with the microtubules network and inhibit tubulin polymerization. Molecular docking demonstrated an efficient binding between these ligands and the colchicine-binding site on the tubulin. CA-61 formed two hydrogen bond interactions with THR 179 (B) and THR 353 (B), whereas two hydrogen bonds with LYS 254 (B) and 1 with ASN 101 (A) were identified for CA-84. The binding energy for CA-84 and CA-61 was −9.910 kcal/mol and −9.390 kcal/mol. A tubulin polymerization assay revealed a strong inhibition of tubulin polymerization induced by CA-61 and -84. The immunofluorescence data revealed the disruption of the tubulin assembly in CA-treated cancer cells. As an outcome of the tubulin inhibition, these compounds halted the cell cycle progression in the G2/M phase, leading to the accumulation of the mitotic cells, and further induced apoptosis. Lastly, the in vivo study indicated that CAs significantly inhibited the HCC1806 breast cancer xenograft tumor growth in a nude mouse model. Collectively, we identified the novel CAs as potent MTAs, inhibiting tubulin polymerization via binding to the colchicine-binding site, disrupting the microtubule network, and exhibiting potent pro-apoptotic activities against the epithelial cancer cell lines both in vitro and in vivo.

X-ray Crystallography-Guided Design, Antitumor Efficacy, and QSAR Analysis of Metabolically Stable Cyclopenta-Pyrimidinyl Dihydroquinoxalinone as a Potent Tubulin Polymerization Inhibitor

Small molecules that interact with the colchicine binding site in tubulin have demonstrated therapeutic efficacy in treating cancers. We report the design, syntheses, and antitumor efficacies of new analogues of pyridopyrimidine and hydroquinoxalinone compounds with improved drug-like characteristics. Eight analogues, 5j, 5k, 5l, 5m, 5n, 5r, 5t, and 5u, showed significant improvement in metabolic stability and demonstrated strong antiproliferative potency in a panel of human cancer cell lines, including melanoma, lung cancer, and breast cancer. We report crystal structures of tubulin in complex with five representative compounds, 5j, 5k, 5l, 5m, and 5t, providing direct confirmation for their binding to the colchicine site in tubulin. A quantitative structure-activity relationship analysis of the synthesized analogues showed strong ability to predict potency. In vivo, 5m (4 mg/kg) and 5t (5 mg/kg) significantly inhibited tumor growth as well as melanoma spontaneous metastasis into the lung and liver against a highly paclitaxel-resistant A375/TxR xenograft model.

Therapeutic potential of marine peptides in glioblastoma: Mechanistic insights

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in humans. It is characterized by excessive cell growth and accelerated intrusion of normal brain tissue along with a poor prognosis. The current standard of treatment, including surgical removal, radiation therapy, and chemotherapy, is largely ineffective, with high mortality and recurrence rates. As a result, traditional approaches have evolved to include new alternative remedies, such as natural compounds. Aquatic species provide a rich supply of possible drugs. The physiological effects of marine peptides in glioblastoma are mediated by a range of pathways, including apoptosis, microtubule balance disturbances, suppression of angiogenesis, cell migration/invasion, and cell viability; autophagy and metabolic enzymes downregulation. Herein, we address the efficacy of marine peptides as putative safe therapeutic agents for glioblastoma coupled with detail molecular mechanisms.

Marine peptides in breast cancer: Therapeutic and mechanistic understanding

Breast cancer is the most prevalent invasive form of cancer in females and posing a great challenge for overcoming disease burden. The growth in global cancer deaths mandates the discovery of new efficacious natural anti-tumor treatments. In this regard, aquatic species offer a rich supply of possible drugs. Studies have shown that several marine peptides damage cancer cells by a broad range of pathways, including apoptosis, microtubule balance disturbances, and suppression of angiogenesis. Traditional chemotherapeutic agents are characterized by a plethora of side effects, including immune response suppression. The discovery of novel putative anti-cancer peptides with lesser toxicity is therefore necessary and timely, especially those able to thwart multi drug resistance (MDR). This review addresses marine anti-cancer peptides for the treatment of breast cancer.

Coumarin Interferes with Polar Auxin Transport Altering Microtubule Cortical Array Organization in Arabidopsis thaliana (L.) Heynh. Root Apical Meristem

Coumarin is a phytotoxic natural compound able to affect plant growth and development. Previous studies have demonstrated that this molecule at low concentrations (100 µM) can reduce primary root growth and stimulate lateral root formation, suggesting an auxin-like activity. In the present study, we evaluated coumarin’s effects (used at lateral root-stimulating concentrations) on the root apical meristem and polar auxin transport to identify its potential mode of action through a confocal microscopy approach. To achieve this goal, we used several Arabidopsis thaliana GFP transgenic lines (for polar auxin transport evaluation), immunolabeling techniques (for imaging cortical microtubules), and GC-MS analysis (for auxin quantification). The results highlighted that coumarin induced cyclin B accumulation, which altered the microtubule cortical array organization and, consequently, the root apical meristem architecture. Such alterations reduced the basipetal transport of auxin to the apical root apical meristem, inducing its accumulation in the maturation zone and stimulating lateral root formation.

Inhibition of microtubule assembly and cytotoxic effect of graphene oxide on human colorectal carcinoma cell HCT116

Nanomaterials, such as graphene oxide (GO), are increasingly being investigated for their suitability in biomedical applications. Tubulin is the key molecule for the formation of microtubules crucial for cellular function and proliferation, and as such an appealing target for developing anticancer drug. Here we employ biophysical techniques to study the effect of GO on tubulin structure and how the changes affect the tubulin/microtubule assembly. GO disrupts the structural integrity of the protein, with consequent retardation of tubulin polymerization. Investigating the anticancer potential of GO, we found that it is more toxic to human colon cancer cells (HCT116), as compared to human embryonic kidney epithelial cells (HEK293). Immunocytochemistry indicated the disruption of microtubule assembly in HCT116 cells. GO arrested cells in the S phase with increased accumulation in Sub-G1 population of cell cycle, inducing apoptosis by generating reactive oxygen species (ROS) in a dose- and time-dependent manner. GO inhibited microtubule formation by intervening into the polymerization of tubulin heterodimers both in vitro and ex vivo, resulting in growth arrest at the S phase and ROS induced apoptosis of HCT116 colorectal carcinoma cells. There was no significant harm to the HEK293 kidney epithelial cells used as control. Our report of pristine GO causing ROS-induced apoptosis of cancer cells and inhibition of tubulin-microtubule assembly can be of interest in cancer therapeutics and nanomedicine.

Targeting protein-protein interaction interfaces in COVID-19 drug discovery

To date, the COVID-19 pandemic has claimed over 1 million human lives, infected another 50 million individuals and wreaked havoc on the global economy. The crisis has spurred the ongoing development of drugs targeting its etiological agent, the SARS-CoV-2. Targeting relevant protein-protein interaction interfaces (PPIIs) is a viable paradigm for the design of antiviral drugs and enriches the targetable chemical space by providing alternative targets for drug discovery. In this review, we will provide a comprehensive overview of the theory, methods and applications of PPII-targeted drug development towards COVID-19 based on recent literature. We will also highlight novel developments, such as the successful use of non-native protein-protein interactions as targets for antiviral drug screening. We hope that this review may serve as an entry point for those interested in applying PPIIs towards COVID-19 drug discovery and speed up drug development against the pandemic.

The Frequent Sampling of Wound Scratch Assay Reveals the "Opportunity" Window for Quantitative Evaluation of Cell Motility-Impeding Drugs

Wound healing assay performed with automated microscopy is widely used in drug testing, cancer cell analysis, and similar approaches. It is easy to perform, and the results are reproducible. However, it is usually used as a semi-quantitative approach because of inefficient image segmentation in transmitted light microscopy. Recently, several algorithms for wound healing quantification were suggested, but none of them was tested on a large dataset. In the current study, we develop a pipeline allowing to achieve correct segmentation of the wound edges in >95% of pictures and extended statistical data processing to eliminate errors of cell culture artifacts. Using this tool, we collected data on wound healing dynamics of 10 cell lines with 10 min time resolution. We determine that the overall kinetics of wound healing is non-linear; however, all cell lines demonstrate linear wound closure dynamics in a 6-h window between the fifth and 12th hours after scratching. We next analyzed microtubule-inhibiting drugs’, nocodazole, vinorelbine, and Taxol, action on the kinetics of wound healing in the drug concentration-dependent way. Within this time window, the measurements of velocity of the cell edge allow the detection of statistically significant data when changes did not exceed 10–15%. All cell lines show decrease in the wound healing velocity at millimolar concentrations of microtubule inhibitors. However, dose-dependent response was cell line specific and drug specific. Cell motility was completely inhibited (edge velocity decreased 100%), while in others, it decreased only slightly (not more than 50%). Nanomolar doses (10–100 nM) of microtubule inhibitors in some cases even elevated cell motility. We speculate that anti-microtubule drugs might have specific effects on cell motility not related to the inhibition of the dynamic instability of microtubules.

2-APCAs, the Novel Microtubule Targeting Agents Active Against Distinct Cancer Cell Lines

Microtubules are known as the most attractive molecular targets for anti-cancer drugs. However, the number of serious limitations of the microtubule targeting agents (MTAs) including poor bioavailability, adverse effects (e.g., systemic and neural toxicity), and acquired resistance after initiation of MTA-based therapy remain the driving forces to develop the novel therapeutic agents effectively targeting microtubules and exhibiting potent anti-tumor activities. Here, we report the discovery of 2-amino-pyrrole-carboxamides (2-APCAs), a novel class of MTA, which effectively inhibited the growth of the broad spectrum of cancer cell lines in vitro, including various types of breast, prostate, and non-small lung cancer (NSLC), soft tissue sarcomas (STS) (e.g., leio-, rhabdomyo-, and fibrosarcomas), osteosarcomas and gastrointestinal stromal tumors (GISTs). Importantly, 2-APCAs were also effective in cancer cell lines exhibiting resistance to certain chemotherapeutic agents, including MTAs and topoisomerase II inhibitors. The anti-proliferative effect of 2-APCAs was due to their ability to interfere with the polymerization of tubulin and thereby leading to the accumulation of tumor cells in the M-phase. As an outcome of the mitotic arrest, cancer cells underwent apoptotic cell death which was evidenced by increased expression of cleaved forms of the poly-ADP-ribose polymerase (PARP) and caspase-3 and the increased numbers of Annexin V-positive cells, as well. Among the compounds exhibiting the potent anti-cancer activities against the various cancer cell lines indicated above, 2-APCA-III was found the most active. Importantly, its cytotoxic activities correlated with its highest potency to interfere with the dynamics of tubulin polymerization and inducement of cell cycle arrest in the G2/M phase. Interestingly, the cytotoxic and tubulin polymerization activities of 2-APCAs correlated with the stability of the «tubulin-2-АРСА» complexes, illustrating the "tubulin-2-APCA-III" complex as the most stable. Molecular docking showed that the binding site for 2-АРСА-III is located in α tubulin by forming a hydrogen bond with Leu23. Of note, single-cell electrophoresis (Comet assay) data illustrated the low genotoxic activities of 2-APCAs when compared to certain anti-cancer chemotherapeutic agents. Taken together, our study describes the novel MTAs with potent anti-proliferative and pro-apoptotic activities, thereby illustrating them as a scaffold for the development of successful chemotherapeutic anti-cancer agent targeting microtubules.

Furan-2-carboxamide derivative, a novel microtubule stabilizing agent induces mitotic arrest and potentiates apoptosis in cancer cells

The vital role played by microtubules in the cell division process, marks them as a potential druggable target to decimate cancer. A novel furan-2-carboxamide based small molecule, is a selective microtubule stabilizing agent (MSA) with IC₅₀ ranging from 4 µM to 8 µM in different cancer cell lines. Inhibition of tubulin polymerization or stabilization of tubulin polymers abrogates chromosomal segregation during cell division, results in cell cycle arrest and leads to cell death due to the delayed repair mechanism. A novel furan-2-carboxamide based small molecule exhibited potent anti-proliferative and anti-metastatic property In-Vitro against the panel of cancer cells. Annexin V-FITC/PI, double staining reveals potent cytotoxic effect of SH09 against HeLa cells. FACS analysis displays induction of G2/M arrest and accumulation of subG1 population of cells upon treatment with SH09. Molecular docking study unveils SH09 binding affinity to the Taxol binding pocket of tubulin proteins and MM-GBSA also confirms strong binding energies of SH09 with tubulin proteins.

Mechanisms of Taxane Resistance

The taxane family of chemotherapy drugs has been used to treat a variety of mostly epithelial-derived tumors and remain the first-line treatment for some cancers. Despite the improved survival time and reduction of tumor size observed in some patients, many have no response to the drugs or develop resistance over time. Taxane resistance is multi-faceted and involves multiple pathways in proliferation, apoptosis, metabolism, and the transport of foreign substances. In this review, we dive deeper into hypothesized resistance mechanisms from research during the last decade, with a focus on the cancer types that use taxanes as first-line treatment but frequently develop resistance to them. Furthermore, we will discuss current clinical inhibitors and those yet to be approved that target key pathways or proteins and aim to reverse resistance in combination with taxanes or individually. Lastly, we will highlight taxane response biomarkers, specific genes with monitored expression and correlated with response to taxanes, mentioning those currently being used and those that should be adopted. The future directions of taxanes involve more personalized approaches to treatment by tailoring drug-inhibitor combinations or alternatives depending on levels of resistance biomarkers. We hope that this review will identify gaps in knowledge surrounding taxane resistance that future research or clinical trials can overcome.

Thermosensitive Betulinic Acid-Loaded Magnetoliposomes: A Promising Antitumor Potential for Highly Aggressive Human Breast Adenocarcinoma Cells Under Hyperthermic Conditions

PURPOSE

Breast cancer presents one of the highest rates of prevalence around the world. Despite this, the current breast cancer therapy is characterized by significant side effects and high risk of recurrence. The present work aimed to develop a new therapeutic strategy that may improve the current breast cancer therapy by developing a heat-sensitive liposomal nano-platform suitable to incorporate both anti-tumor betulinic acid (BA) compound and magnetic iron nanoparticles (MIONPs), in order to address both remote drug release and hyperthermia-inducing features. To address the above-mentioned biomedical purposes, the nanocarrier must possess specific features such as specific phase transition temperature, diameter below 200 nm, superparamagnetic properties and heating capacity. Moreover, the anti-tumor activity of the developed nanocarrier should significantly affect human breast adenocarcinoma cells.

METHODS

BA-loaded magnetoliposomes and corresponding controls (BA-free liposomes and liposomes containing no magnetic payload) were obtained through the thin-layer hydration method. The quality and stability of the multifunctional platforms were physico-chemically analysed by the means of RAMAN, scanning electron microscopy-EDAX, dynamic light scattering, zeta potential and DSC analysis. Besides this, the magnetic characterization of magnetoliposomes was performed in terms of superparamagnetic behaviour and heating capacity. The biological profile of the platforms and controls was screened through multiple in vitro methods, such as MTT, LDH and scratch assays, together with immunofluorescence staining. In addition, CAM assay was performed in order to assess a possible anti-angiogenic activity induced by the test samples.

RESULTS

The physico-chemical analysis revealed that BA-loaded magnetoliposomes present suitable characteristics for the purpose of this study, showing biocompatible phase transition temperature, a diameter of 198 nm, superparamagnetic features and heating capacity. In vitro results showed that hyperthermia induces enhanced anti-tumor activity when breast adenocarcinoma MDA-MB-231 cells were exposed to BA-loaded magnetoliposomes, while a low cytotoxic rate was exhibited by the non-tumorigenic breast epithelial MCF 10A cells. Moreover, the in ovo angiogenesis assay endorsed the efficacy of this multifunctional platform as a good strategy for breast cancer therapy, under hyperthermal conditions. Regarding the possible mechanism of action of this multifunctional nano-platform, the immunocytochemistry of the MCF7 and MDA-MB-231 breast carcinoma cells revealed a microtubule assembly modulatory activity, under hyperthermal conditions.

CONCLUSION

Collectively, these findings indicate that BA-loaded magnetoliposomes, under hyperthermal conditions, might serve as a promising strategy for breast adenocarcinoma treatment.

CPPF, A Novel Microtubule Targeting Anticancer Agent, Inhibits the Growth of a Wide Variety of Cancers

In the past, several microtubule targeting agents (MTAs) have been developed into successful anticancer drugs. However, the usage of these drugs has been limited by the acquisition of drug resistance in many cancers. Therefore, there is a constant demand for the development of new therapeutic drugs. Here we report the discovery of 5-5 (3-cchlorophenyl)-N-(3-pyridinyl)-2-furamide (CPPF), a novel microtubule targeting anticancer agent. Using both 2D and 3D culture systems, we showed that CPPF was able to suppress the proliferation of diverse cancer cell lines. In addition, CPPF was able to inhibit the growth of multidrug-resistant cell lines that are resistant to other MTAs, such as paclitaxel and colchicine. Our results showed that CPPF inhibited growth by depolymerizing microtubules leading to mitotic arrest and apoptosis. We also confirmed CPPF anticancer effects in vivo using both a mouse xenograft and a two-step skin cancer mouse model. Using established zebrafish models, we showed that CPPF has low toxicity in vivo. Overall, our study proves that CPPF has the potential to become a successful anticancer chemotherapeutic drug.

Thermomagnetic resonance affects cancer growth and motility

The fight against a multifaceted incurable disease such as cancer requires a multidisciplinary approach to overcome the multitude of molecular defects at its origin. Here, a new thermophysical biochemical approach has been suggested and associated with the use of electromagnetic fields to control the growth of cancer cells. In particular, thermodynamic analysis of the heat transfer is developed in correlation with cellular parameters such as the volume/area ratio. We propose that the electromagnetic wave, at the specific frequency calculated as the characteristic response time of any cell type to the external thermal perturbation, can affect resonant intracellular molecular oscillations. The biochemical model hypothesizes that microtubules are stabilized, and the impact is predicted on cell growth, migration and mitochondrial activity. Experimental validation of the theoretical results shows that the thermodynamic analysis allows the application of the specific electromagnetic field able to decrease cancer cell invasion and proliferation.

Synthesis and Cytotoxicity Studies of Stilbene Long-Chain Fatty Acid Conjugates

A series of 16 conjugates of the tubulin polymerization inhibitor combretastatin A4 (CA-4) and other functionally related stilbene with four 18-carbon fatty acids, namely, stearic, oleic, linoleic, and linolenic acids, have been synthesized in good yields. These new derivatives have been evaluated against the KB-3-1 (human epidermoid carcinoma), NCI-H460 (human lung cancer), HEK293 (human embryonic kidney), and MCF-7 (human breast adenocarcinoma) cell lines for antiproliferative activity, with the exhibited cytotoxic activities comparable with those of CA-4 and colchicine. Compounds 22 and 23, CA-4 conjugates of linoleic and linolenic acids, respectively, were determined to have exhibited the most active in vitro assays, with compound 23 exhibiting very similar activity to the parent compound against the NCI-H460 cell line. Our studies further delineated the structurally required Z-geometry of the stilbene moiety and that conjugation of the less active E-stilbenes with the most active fatty acid had minimal or no improvement in their respective activities.

Mechanism-Based Rational Discovery and In Vitro Evaluation of Novel Microtubule Stabilizing Agents with Non-Taxol-Competitive Activity

Microtubules (MT) are cytoskeletal polymers of αβ-tubulin dimers that play a critical role in many cellular functions. Diverse antimitotic drugs bind to MT and disrupt their dynamics acting as MT stabilizing or destabilizing agents. The occurrence of undesired side effects and drug resistance encourages the search for novel MT binding agents with chemically diverse structures and different interaction profiles compared to known active compounds. This work reports the rational discovery of seven novel MT stabilizers using a combination of molecular modeling methods and in vitro experimental assays. Virtual screening, similarity filtering, and molecular mechanics generalized Born surface area (MM/GBSA) binding free energy refinement were employed to select seven potential candidates with high predicted affinity toward the non-taxoid site for MT stabilizers on β-tubulin. MD simulations of 150 ns on reduced MT models suggest that candidate compounds strengthen the longitudinal interactions between tubulin dimers across protofilaments, which is a primary molecular mechanism of action for known MT stabilizers. In vitro MT polymerization assays confirmed that all candidates promote MT assembly at concentrations of >50 mM and exhibit noncompetitive MT polymerization profiles when cotreating with Taxol. Preliminary HeLa cell viability assays revealed a moderate cytotoxic effect for the compounds under study at 100 μM concentration. These results support the validity of our rational discovery strategy and the use of molecular modeling methods to pursue the search and optimization of new MT targeting agents.

Interplay between Convective and Viscoelastic Forces Controls the Morphology of In Vitro Paclitaxel-Stabilized Microtubules

Microtubules (MTs) are self-assembling, high-aspect-ratio tubular nanostructures formed from the polymerization of tubulin protein. MTs are capable of globally assembling into optically birefringent morphologies, but there is disagreement on the mechanisms driving this behavior. We investigated the temporal evolution of paclitaxel (PTX)-stabilized MT solutions under a range of in vitro conditions. Significant morphological differences were observed in the polymerized PTX-MT solutions as a consequence of varying the orientation of the reaction vessel (vertical vs. horizontal), the type of heating source (hot plate vs. incubator), the incubation time, and the concentration of PTX (high vs. low). The most robust birefringent patterns were found only in vertically oriented cuvettes that were heated asymmetrically on a hot plate, suggesting dependence upon a convective flow, which we confirmed with a combination of optical and thermal imaging. Higher concentrations of PTX led to denser PTX-MT domain formation and brighter birefringence, due to more complete polymerization. Combining our experimental observations, we conclude that birefringent patterns arise principally through a combination of convective and viscoelastic forces, and we identify the sequence of dynamical stages through which they evolve.

Microtubule disruption changes endothelial cell mechanics and adhesion

The interest in studying the mechanical and adhesive properties of cells has increased in recent years. The cytoskeleton is known to play a key role in cell mechanics. However, the role of the microtubules in shaping cell mechanics is not yet well understood. We have employed Atomic Force Microscopy (AFM) together with confocal fluorescence microscopy to determine the role of microtubules in cytomechanics of Human Umbilical Vein Endothelial Cells (HUVECs). Additionally, the time variation of the adhesion between tip and cell surface was studied. The disruption of microtubules by exposing the cells to two colchicine concentrations was monitored as a function of time. Already, after 30 min of incubation the cells stiffened, their relaxation times increased (lower fluidity) and the adhesion between tip and cell decreased. This was accompanied by cytoskeletal rearrangements, a reduction in cell area and changes in cell shape. Over the whole experimental time, different behavior for the two used concentrations was found while for the control the values remained stable. This study underlines the role of microtubules in shaping endothelial cell mechanics.

Help or hindrance: how do microtubule-based forces contribute to genome damage and repair?

Forces generated by molecular motors and the cytoskeleton move the nucleus and genome during many cellular processes, including cell migration and division. How these forces impact the genome, and whether cells regulate cytoskeletal forces to preserve genome integrity is unclear. We recently demonstrated that, in budding yeast, mutants that stabilize the microtubule cytoskeleton cause excessive movement of the mitotic spindle and nucleus. We found that increased nuclear movement results in DNA damage and increased time to repair the damage through homology-directed repair. Our results indicate that nuclear movement impairs DNA repair through increased tension on chromosomes and nuclear deformation. However, the previous studies have shown genome mobility, driven by cytoskeleton-based forces, aids in homology-directed DNA repair. This sets up an apparent paradox, where genome mobility may prevent or promote DNA repair. Hence, this review explores how the genome is affected by nuclear movement and how genome mobility could aid or hinder homology-directed repair.

Reorganization of paclitaxel-stabilized microtubule arrays at mitotic entry: roles of depolymerizing kinesins and severing proteins

Paclitaxel is a widely used anti-cancer treatment that disrupts cell cycle progression by blocking cells in mitosis. The block at mitosis, with spindles assembled from short microtubules, is surprising given paclitaxel’s microtubule stabilizing activity and the need to depolymerize long interphase microtubules prior to spindle formation. Cells must antagonize paclitaxel’s microtubule stabilizing activity during a brief window of time at the transition from interphase to mitosis, allowing microtubule reorganization into a mitotic spindle, although the mechanism underlying microtubule depolymerization in the presence of paclitaxel has not been examined. Here we test the hypothesis that microtubule severing and/or depolymerizing proteins active at mitotic entry are necessary to clear the interphase array in paclitaxel-treated cells and allow subsequent formation of mitotic spindles formed of short microtubules. A549 and LLC-PK1 cells treated with 30nM paclitaxel approximately 4 h prior to mitotic entry successfully progress through the G2/M transition by clearing the interphase microtubule array from the cell interior outward to the cell periphery, a spatial pattern of reorganization that differs from that of cells possessing dynamic microtubules. Depletion of kinesin-8s, KIF18A and/or KIF18B obstructed interphase microtubule clearing at mitotic entry in paclitaxel-treated cells, with KIF18B making the larger contribution. Of the severing proteins, depletion of spastin, but not katanin, reduced microtubule loss as cells entered mitosis in the presence of paclitaxel. These results support a model in which KIF18A, KIF18B, and spastin promote interphase microtubule array disassembly at mitotic entry and can overcome paclitaxel-induced microtubule stability specifically at the G2/M transition.

Synthesis and in Vitro Bioactivity of Polyunsaturated Fatty Acid Conjugates of Combretastatin A-4

Combretastatin A-4 (CA-4) (1) is a plant-derived anticancer agent binding to the tubulin colchicine site. Polyunsaturated fatty acids (PUFAs) are readily taken up by cancer cells and have been used to improve cell targeting. In the present study, four CA-4-PUFA conjugates were synthesized by coupling combretastatin A-4 (1) with several polyunsaturated fatty acids. The conjugates (2a-d) were characterized using spectroscopic methods. Their cytotoxicity was evaluated against human breast cancer cells (MCF-7), and the inhibition of tubulin polymerization was determined in vitro. All conjugates influenced tubulin polymerization, with the arachidonic acid conjugate (2c) displaying cytotoxicity similar in potency to the natural product CA-4 (1).

Indibulin dampens microtubule dynamics and produces synergistic antiproliferative effect with vinblastine in MCF-7 cells: Implications in cancer chemotherapy

Indibulin, a synthetic inhibitor of tubulin assembly, has shown promising anticancer activity with a minimal neurotoxicity in preclinical animal studies and in Phase I clinical trials for cancer chemotherapy. Using time-lapse confocal microscopy, we show that indibulin dampens the dynamic instability of individual microtubules in live breast cancer cells. Indibulin treatment also perturbed the localization of end-binding proteins at the growing microtubule ends in MCF-7 cells. Indibulin reduced inter-kinetochoric tension, produced aberrant spindles, activated mitotic checkpoint proteins Mad2 and BubR1, and induced mitotic arrest in MCF-7 cells. Indibulin-treated MCF-7 cells underwent apoptosis-mediated cell death. Further, the combination of indibulin with an anticancer drug vinblastine was found to exert synergistic cytotoxic effects on MCF-7 cells. Interestingly, indibulin displayed a stronger effect on the undifferentiated neuroblastoma (SH-SY5Y) cells than the differentiated neuronal cells. Unlike indibulin, vinblastine and colchicine produced similar depolymerizing effects on microtubules in both differentiated and undifferentiated SH-SY5Y cells. The data indicated a possibility that indibulin may reduce chemotherapy-induced peripheral neuropathy in cancer patients.

Design, synthesis and biological evaluation of chromenopyrimidines as potential cytotoxic agents

Aim: The design and synthesis of chromenopyrimidines as microtubule destabilizing agents. Materials & methods: Novel chromenopyrimidines and chromenotriazolopyrimidines were prepared and evaluated for their cytotoxicity against MCF-7 cell line. The most potent compound was tested for its possible effect on tubulin inhibition, cell cycle distribution, apoptosis initiation and caspase-3 activation. Results: All the prepared compounds showed potent cytotoxic activity. Compound 13 was the most prominent (IC50 = 0.13 μM on tumor cell line MCF-7 and 14.06 μM on mammary epithelial cell line MCF-10A). Compound 13 inhibited tubulin polymerization (IC50 = 8.39 μM), caused cell cycle arrest at G2/M phase (fivefold more than control) and cellular apoptosis. Compound 13 increased the level of active caspase-3, 12-fold compared with control.

Antitumor activity of the microtubule inhibitor MBRI-001 against human hepatocellular carcinoma as monotherapy or in combination with sorafenib

PURPOSE

MBRI-001 is a novel synthetic derivative of plinabulin. In this study, our purpose is to investigate the inhibition effects of MBRI-001 on human hepatocellular carcinoma as monotherapy or in combination with sorafenib.

METHODS

HCCLM3 and Bel-7402 cell lines were used for activity evaluation in vitro. The anti-proliferative activity of MBRI-001 was assessed by MTT assay. The morphological change of microtubules was determined by immunofluorescence assay. The cell cycle was measured by flow cytometer. The expression of cyclin B1 (CCNB1) was analyzed by RT-qPCR and western blotting assays. The antitumor activities in vivo were evaluated with human HCC xenograft mice model.

RESULTS

Our data demonstrated that MBRI-001 had better anti-proliferative activities than that of plinabulin against HCCLM3 and Bel-7402 cell lines. MBRI-001 inhibited the formation of microtubules and induced G2/M arrest with the downregulation of CCNB1. In vivo orthotopic mice model demonstrated that MBRI-001 significantly inhibited the growth of HCCLM3 with the apoptosis and necrosis observed in tumor. The combination treatment of MBRI-001 with sorafenib in subcutaneous mice model exhibited a higher antitumor inhibition rate at 72.0%, in comparison with MBRI-001 or sorafenib as monotherapy at 40.7% or 47.7%, respectively.

CONCLUSION

MBRI-001 had better inhibition effects on microtubules and human hepatocellular carcinoma than that of plinabulin. The combination treatment of MBRI-001 and sorafenib exhibited a higher antitumor effect, which could provide a new strategy to treat HCC in the future.

The comparison of outcomes from tyrosine kinase inhibitor monotherapy in second- or third-line for advanced non-small-cell lung cancer patients with wild-type or unknown EGFR status

BACKGROUND

Second-line treatment for advanced non-small-cell lung cancer (NSCLC) patients includes monotherapy with a third-generation cytotoxic drug (CT) or a tyrosine kinase inhibitor (TKI). These options are the actual standard for EGFR wild-type (WT) status, as patients with EGFR mutations achieve greater benefit by the use of TKI in first-line treatment. Some clinical trials and meta-analyses investigated the comparison between CT and TKI in second-line, but data are conflicting.

METHODS

We designed a retrospective trial to gather information about TKI sensitivity in comparison with CT. We selected from clinical records patients treated with at least 1 line of CT and at least 1 line of TKI. We collected data about age, sex, performance status, comorbidity, smoking status, histotype, metastatic sites, EGFR status, treatment schedule, better response and time-to-progression (TTP) for each line of treatment and overall survival (OS).

RESULTS

93 patients met selection criteria. Mean age 66,7 (range: 46-84). M/F ratio is 3:1. 39 EGFR-WT and 54 EGFR-UK. All patients received erlotinib or gefitinib as second-line treatment or erlotinib as third-line treatment. No TTP differences were observed for both second-line (HR:0,91; p = 0,6333) and third-line (HR:1.1; p = 0,6951) treatment (TKI vs CT). A trend of a benefit in OS in favor of 3rd-line TKI (HR:0,68; p = 0,11).

CONCLUSIONS

This study explores the role of TKIs in EGFR non-mutated NSCLC patients. OS analysis highlights a trend to a benefit in patients who received TKI in third-line, even if this result is statistically non-significant. Further analysis are needed to find an explanation for this observation.