Microtubule dynamics and tubulin interacting proteins

Beyond Cytotoxic Potency: Disposition Features Required to Design ADC Payload

Antibody-drug conjugates (ADCs) have demonstrated impressive clinical usefulness in treating several types of cancer, with the notion of widening of the therapeutic index of the cytotoxic payload through the minimization of the systemic toxicity. Therefore, choosing the most appropriate payload molecule is a particularly important part of the early design phase of ADC development, especially given the highly competitive environment ADCs find themselves in today. The focus of the current review is to describe critical attributes/considerations needed in the discovery and ultimately development of cytotoxic payloads in support of ADC design. In addition to potency, several key dispositional characteristics including solubility, permeability and bystander effect, pharmacokinetics, metabolism, and drug-drug interactions, are described as being an integral part of the integrated activities required in the design of clinically safe and useful ADC therapeutic agents.

Antibody-drug conjugates in urothelial carcinoma: scientometric analysis and clinical trials analysis

In 2020, bladder cancer, which commonly presents as urothelial carcinoma, became the 10th most common malignancy. For patients with metastatic urothelial carcinoma, the standard first-line treatment remains platinum-based chemotherapy, with immunotherapy serving as an alternative in cases of programmed death ligand 1 expression. However, treatment options become limited upon resistance to platinum and programmed death 1 or programmed death ligand 1 agents. Since the FDA's approval of Enfortumab Vedotin and Sacituzumab Govitecan, the therapeutic landscape has expanded, heralding a shift towards antibody-drug conjugates as potential first-line therapies. Our review employed a robust scientometric approach to assess 475 publications on antibody-drug conjugates in urothelial carcinoma, revealing a surge in related studies since 2018, predominantly led by U.S. institutions. Moreover, 89 clinical trials were examined, with 36 in Phase II and 13 in Phase III, exploring antibody-drug conjugates as both monotherapies and in combination with other agents. Promisingly, novel targets like HER-2 and EpCAM exhibit substantial therapeutic potential. These findings affirm the increasing significance of antibody-drug conjugates in urothelial carcinoma treatment, transitioning them from posterior-line to frontline therapies. Future research is poised to focus on new therapeutic targets, combination therapy optimization, treatment personalization, exploration of double antibody-coupled drugs, and strategies to overcome drug resistance.

Drug conjugates for the treatment of lung cancer: from drug discovery to clinical practice

A drug conjugate consists of a cytotoxic drug bound via a linker to a targeted ligand, allowing the targeted delivery of the drug to one or more tumor sites. This approach simultaneously reduces drug toxicity and increases efficacy, with a powerful combination of efficient killing and precise targeting. Antibody‒drug conjugates (ADCs) are the best-known type of drug conjugate, combining the specificity of antibodies with the cytotoxicity of chemotherapeutic drugs to reduce adverse reactions by preferentially targeting the payload to the tumor. The structure of ADCs has also provided inspiration for the development of additional drug conjugates. In recent years, drug conjugates such as ADCs, peptide‒drug conjugates (PDCs) and radionuclide drug conjugates (RDCs) have been approved by the Food and Drug Administration (FDA). The scope and application of drug conjugates have been expanding, including combination therapy and precise drug delivery, and a variety of new conjugation technology concepts have emerged. Additionally, new conjugation technology-based drugs have been developed in industry. In addition to chemotherapy, targeted therapy and immunotherapy, drug conjugate therapy has undergone continuous development and made significant progress in treating lung cancer in recent years, offering a promising strategy for the treatment of this disease. In this review, we discuss recent advances in the use of drug conjugates for lung cancer treatment, including structure-based drug design, mechanisms of action, clinical trials, and side effects. Furthermore, challenges, potential approaches and future prospects are presented.

Discovery of Novel Isoquinoline Analogues as Dual Tubulin Polymerization/V-ATPase Inhibitors with Immunogenic Cell Death Induction

Cancer immunotherapy has revolutionized clinical advances in a variety of cancers. Due to the low immunogenicity of the tumor, only a few patients can benefit from it. Specific microtubule inhibitors can effectively induce immunogenic cell death and improve immunogenicity of the tumor. A series of isoquinoline derivatives based on the natural products podophyllotoxin and diphyllin were designed and synthesized. Among them, F10 showed robust antiproliferation activity against four human cancer cell lines, and it was verified that F10 exerted antiproliferative activity by inhibiting tubulin and V-ATPase. Further studies indicated that F10 is able to induce immunogenic cell death in addition to apoptosis. Meanwhile, F10 inhibited tumor growth in an RM-1 homograft model with enhanced T lymphocyte infiltration. These results suggest that F10 may be a promising lead compound for the development of a new generation of microtubule drugs.

Recent Progress on Microtubule Degradation Agents

Targeted protein degradation (TPD) has emerged as the most promising approach for the specific knockdown of disease-associated proteins and is achieved by exploiting the cellular quality control machinery. TPD technologies are highly advantageous in overcoming drug resistance as they degrade the whole target protein. Microtubules play important roles in many cellular processes and are among the oldest and most well-established targets for tumor chemotherapy. However, the development of drug resistance, risk of hypersensitivity reactions, and intolerable toxicities severely restrict the clinical applications of microtubule-targeting agents (MTAs). Microtubule degradation agents (MDgAs) operate via completely different mechanisms compared with traditional MTAs and are capable of overcoming drug resistance. The emergence of MDgAs has expanded the scope of TPD and provided new avenues for the discovery of tubulin-targeted drugs. Herein, we summarized the development of MDgAs, and discussed their degradation mechanisms, mechanisms of action on the binding sites, potential opportunities, and challenges.

Single-cell transcriptome reveals cell division-regulated hub genes in the unicellular eukaryote Paramecium

The transition from growth to division during the cell cycle encompasses numerous conserved processes such as large-scale DNA replication and protein synthesis. In ciliate cells, asexual cell division is accompanied by additional cellular changes including amitotic nuclear division, extensive ciliogenesis, and trichocyst replication. However, the molecular mechanisms underlying these processes remain elusive. In this study, we present single-cell gene expression profiles of Paramecium cf. multimicronucleatum cells undergoing cell division. Our results reveal that the most up-regulated genes in dividing cells compared to growing cells are associated with 1) cell cycle signaling pathways including transcription, DNA replication, chromosome segregation and protein degradation; 2) microtubule proteins and tubulin glycylases which are essential for ciliogenesis, nuclei separation and structural differentiation signaling; and 3) trichocyst matrix proteins involved in trichocyst synthesis and reproduction. Furthermore, weighted gene co-expression network analysis identified hub genes that may play crucial roles during cell division. Our findings provide insights into cell cycle regulators, microtubules and trichocyst matrix proteins that may exert influence on this process in ciliates.

The ARSACS disease protein sacsin controls lysosomal positioning and reformation by regulating microtubule dynamics

Autosomal recessive spastic ataxia of Charlevoix-Saguenay is a fatal brain disorder featuring cerebellar neurodegeneration leading to spasticity and ataxia. This disease is caused by mutations in the SACS gene that encodes sacsin, a massive 4579-amino acid protein with multiple modular domains. However, molecular details of the function of sacsin are not clear. Here, using live cell imaging and biochemistry, we demonstrate that sacsin binds to microtubules and regulates microtubule dynamics. Loss of sacsin function in various cell types, including knockdown and KO primary neurons and patient fibroblasts, leads to alterations in lysosomal transport, positioning, function, and reformation following autophagy. Each of these phenotypic changes is consistent with altered microtubule dynamics. We further show the effects of sacsin are mediated at least in part through interactions with JIP3, an adapter for microtubule motors. These data reveal a new function for sacsin that explains its previously reported roles and phenotypes.

Antibody drug conjugate: the "biological missile" for targeted cancer therapy

Antibody–drug conjugate (ADC) is typically composed of a monoclonal antibody (mAbs) covalently attached to a cytotoxic drug via a chemical linker. It combines both the advantages of highly specific targeting ability and highly potent killing effect to achieve accurate and efficient elimination of cancer cells, which has become one of the hotspots for the research and development of anticancer drugs. Since the first ADC, Mylotarg^® (gemtuzumab ozogamicin), was approved in 2000 by the US Food and Drug Administration (FDA), there have been 14 ADCs received market approval so far worldwide. Moreover, over 100 ADC candidates have been investigated in clinical stages at present. This kind of new anti-cancer drugs, known as “biological missiles”, is leading a new era of targeted cancer therapy. Herein, we conducted a review of the history and general mechanism of action of ADCs, and then briefly discussed the molecular aspects of key components of ADCs and the mechanisms by which these key factors influence the activities of ADCs. Moreover, we also reviewed the approved ADCs and other promising candidates in phase-3 clinical trials and discuss the current challenges and future perspectives for the development of next generations, which provide insights for the research and development of novel cancer therapeutics using ADCs.

Structure-Based Design and Synthesis of N-Substituted 3-Amino-β-Carboline Derivatives as Potent αβ-Tubulin Degradation Agents

So far, relatively few small molecules have been reported to promote tubulin degradation. Our previous studies have found that compound 2, a noncovalent colchicine-site ligand, was capable of promoting αβ-tubulin degradation. To further improve its antiproliferative activity, 66 derivatives or analogues of 2 were designed and synthesized based on 2-tubulin cocrystal structure. Among them, 12b displayed nanomolar potency against a variety of tumor cells, including paclitaxel- and adriamycin-resistant cell lines. 12b binds to the colchicine site and promotes αβ-tubulin degradation in a concentration-dependent manner via the ubiquitin-proteasome pathway. The X-ray crystal structure revealed that 12b binds in a similar manner as 2, but there is a slight conformation change of the B ring, which resulted in better interaction of 12b with surrounding residues. 12b effectively suppressed tumor growth at an i.v. dose of 40 mg/kg (3 times a week) on both A2780S (paclitaxel-sensitive) and A2780T (paclitaxel-resistant) ovarian xenograft models, with respective TGIs of 92.42 and 79.75% without obvious side effects, supporting its potential utility as a tumor-therapeutic compound.

Dermal Fibroblast Migration and Proliferation Upon Wounding or Lipopolysaccharide Exposure is Mediated by Stathmin

The dermal fibroblast is a crucial executor involved in wound healing, and lipopolysaccharide is a key factor in initiating the migration and proliferation of the dermal fibroblasts, followed by wound healing. However, the underlying molecular mechanism is still unknown. In this study, we demonstrated that stathmin increased concomitantly with p38/MAPK pathway activation by lipopolysaccharide stimulation of the human dermal fibroblast (HDF), which induced microtubule (MT) depolymerization followed by increased HDF migration and proliferation. In contrast, the application of taxol, the small interfering RNA transfection of stathmin, or the application of the p38/MAPK inhibitor SB203580 suppressed MT depolymerization and HDF migration and proliferation. Additionally, the overexpression of a MKK6(Glu) mutant, which constitutively activated p38/MAPK, resulted in MT depolymerization and, subsequently, promoted HDF migration and proliferation. Our data reveal a crucial role of stathmin in HDF migration and proliferation. These findings will provide new targets and strategies for clinical interventions in wound healing.

K-fiber bundles in the mitotic spindle are mechanically reinforced by Kif15

The mitotic spindle, a self-constructed microtubule-based machine, segregates chromosomes during cell division. In mammalian cells, microtubule bundles called kinetochore fibers (k-fibers) connect chromosomes to the spindle poles. Chromosome segregation thus depends on the mechanical integrity of k-fibers. Here we investigate the physical and molecular basis of k-fiber bundle cohesion. We detach k-fibers from poles by laser ablation-based cutting, thus revealing the contribution of pole-localized forces to k-fiber cohesion. We then measure the physical response of the remaining kinetochore-bound segments of the k-fibers. We observe that microtubules within ablated k-fibers often splay apart from their minus-ends. Furthermore, we find that minus-end clustering forces induced by ablation seem at least partially responsible for k-fiber splaying. We also investigate the role of the k-fiber-binding kinesin-12 Kif15. We find that pharmacological inhibition of Kif15-microtubule binding reduces the mechanical integrity of k-fibers. In contrast, inhibition of its motor activity but not its microtubule binding ability, i.e., locking Kif15 into a rigor state, does not greatly affect splaying. Altogether, the data suggest that forces holding k-fibers together are of similar magnitude to other spindle forces, and that Kif15, acting as a microtubule cross-linker, helps fortify and repair k-fibers. This feature of Kif15 may help support robust k-fiber function and prevent chromosome segregation errors.

New Multi-Targeted Antiproliferative Agents: Design and Synthesis of IC261-Based Oxindoles as Potential Tubulin, CK1 and EGFR Inhibitors

A series of 3-benzylideneindolin-2-one compounds was designed and synthesized based on combretastatin A-4 and compound IC261, a dual casein kinase (CK1)/tubulin polymerization inhibitor, taking into consideration the pharmacophore required for EGFR-tyrosine kinase inhibition. The new molecular entities provoked significant growth inhibition against PC-3, MCF-7 and COLO-205 at a 10 μM dose. Compounds 6-chloro-3-(2,4,6-trimethoxybenzylidene) indolin-2-one, 4b, and 5-methoxy-3-(2,4,6-trimethoxybenzylidene)indolin-2-one, 4e, showed potent activity against the colon cancer COLO-205 cell line with an IC50 value of 0.2 and 0.3 μM. A mechanistic study demonstrated 4b's efficacy in inhibiting microtubule assembly (IC50 = 1.66 ± 0.08 μM) with potential binding to the colchicine binding site (docking study). With an IC50 of 1.92 ± 0.09 μg/mL, 4b inhibited CK1 almost as well as IC261. Additionally, 4b and 4e were effective inhibitors of EGFR-TK with IC50s of 0.19 μg/mL and 0.40 μg/mL compared to Gifitinib (IC50 = 0.05 μg/mL). Apoptosis was induced in COLO-205 cells treated with 4b, with apoptotic markers dysregulated. Caspase 3 levels were elevated to more than three-fold, while Cytochrome C levels were doubled. The cell cycle was arrested in the pre-G1 phase with extensive cellular accumulation in the pre-G1 phase, confirming apoptosis induction. Levels of cell cycle regulating proteins BAX and Bcl-2 were also defective. The binding interaction patterns of these compounds at the colchicine binding site of tubulin and the Gifitinib binding site of EGFR were verified by molecular docking, which adequately matched the reported experimental result. Hence, 4b and 4e are considered promising potent multitarget agents against colon cancer that require optimization.

Novel function of N-acetyltransferase for microtubule stability and JNK signaling in Drosophila organ development

Regulation of microtubule stability is crucial for the maintenance of cell structure and function. While the acetylation of α-tubulin lysine 40 by acetylase has been implicated in the regulation of microtubule stability, the in vivo functions of N-terminal acetyltransferases (NATs) involved in the acetylation of N-terminal amino acids are not well known. Here, we identify an N-terminal acetyltransferase, Mnat9, that regulates cell signaling and microtubule stability in Drosophila Loss of Mnat9 causes severe developmental defects in multiple tissues. In the wing imaginal disc, Mnat9 RNAi leads to the ectopic activation of c-Jun N-terminal kinase (JNK) signaling and apoptotic cell death. These defects are suppressed by reducing the level of JNK signaling. Overexpression of Mnat9 can also inhibit JNK signaling. Mnat9 colocalizes with mitotic spindles, and its loss results in various spindle defects during mitosis in the syncytial embryo. Furthermore, overexpression of Mnat9 enhances microtubule stability. Mnat9 is physically associated with microtubules and shows a catalytic activity in acetylating N-terminal peptides of α- and β-tubulin in vitro. Cell death and tissue loss in Mnat9-depleted wing discs are restored by reducing the severing protein Spastin, suggesting that Mnat9 protects microtubules from its severing activity. Remarkably, Mnat9 mutated in the acetyl-CoA binding site is as functional as its wild-type form. We also find that human NAT9 can rescue Mnat9 RNAi phenotypes in flies, indicating their functional conservation. Taken together, we propose that Mnat9 is required for microtubule stability and regulation of JNK signaling to promote cell survival in developing Drosophila organs.

OMA1520 and OMA1774, novel 1,2,4-triazole bearing analogs of combretastatin A-4, inhibit hepatocellular carcinoma: Histological and immunohistochemical studies

Combretastatin A-4 (CA-4) received significant interest as a potential anticancer agent in recent years. Several CA-4 analogs were synthesized and investigated to enhance the activity or solve the in vivo decreased activity of CA-4.

AIM

The present study aims to investigate the chemotherapeutic and the antiproliferative effects of the mono and the dual therapy of the newly synthesized CA-4 analogs OMA1520 and OMA1774 against hepatocellularcarcinoma (HCC) induced in male adult rats by N-methylnitrosourea (MNU).

METHODS

50 male rats were divided into 5 groups of 10 animals in each group. Group I: normal healthy control; group II: MNU treated group, group III: MNU animals treated by OMA1520, group IV: MNU animals treated by OMA1774, and group V: MNU animals treated by both OMA1520 and OMA1774. The rats were assessed for liver cancer progression or inhibition by evaluating the histopathological, immunohistochemical, biochemical, and antioxidant enzyme status.

RESULTS

The present work indicated that OMA1520 and OMA1774 possessed substantial chemotherapeutic efficiency against HCC. The histological and immunohistochemical examinations of liver tissues confirmed the biochemical sera data. Also, they diminished the cytotoxic effects of MNU and restored the normal histological hepatic architecture. Both analogs restored the normal levels of liver enzymes and functions and revealed potential antioxidant effects. OMA1520 and OMA1774 reduced the inflammatory and tumor markers' elevated expressions in serum.

CONCLUSION

Substantial evidence in our results suggests that both CA-4 analogs could be possible alternative anticancer agents, and their co-administration provides a synergistic activity.

Discovery of novel indole-1,2,4-triazole derivatives as tubulin polymerization inhibitors

A series of novel indole-1,2,4-triazole derivatives have been designed, synthesized, and evaluated as potential tubulin polymerization inhibitors. The top hit 12, bearing the 3,4,5-trimethoxyphenyl moiety, exhibited substantial anti-proliferative activity against HepG2, HeLa, MCF-7, and A549 cells in vitro with IC₅₀ values of 0.23 ± 0.08 μM, 0.15 ± 0.18 μM, 0.38 ± 0.12 μM, and 0.30 ± 0.13 μM, respectively. It also inhibited tubulin polymerization with the IC₅₀ value of 2.1 ± 0.12 μM, which was comparable with that of the positive controls. Furthermore, compound 12 regulated the expression of cell cycle-related proteins (Cyclin B1, Cdc25c, and Cdc2) and apoptosis-related proteins (Bcl-2, Bcl-x, and Mcl-1). Mechanistically, compound 12 could arrest cell cycle at the G2/M phase, thus induce an increase of apoptotic cell death. In addition, molecular docking hinted the possible interaction mode of compound 12 into the colchicine binding site of tubulin heterodimers. According to the applications of microtubule-targeting agents in both direct and synergistic cancer therapies, we hope this work might be of significance for future researches.

The Dis1/Stu2/XMAP215 Family Gene FgStu2 Is Involved in Vegetative Growth, Morphology, Sexual and Asexual Reproduction, Pathogenicity and DON Production of Fusarium graminearum

The conserved Dis1/Stu2/XMAP215 microtubule association proteins (MAPs) family plays an important role in microtubule dynamics, nucleation, and kinetochore-microtubule attachments. However, function of Dis1/Stu2/XMAP215 homolog in plant pathogenic fungi has not been determined. Here, we identified and investigated the Dis1/Stu2/XMAP215 homolog (FGSG_10528) in Fusarium graminearum (FgStu2p). Co-localization experiment and co-immunoprecipitation (Co-IP) assay demonstrated that FgStu2p is a microtubule associated protein. Besides, FgStu2 could also interact with Fgγ-tubulin and presumed FgNdc80, which suggested that the FgStu2 gene might associate with microtubule nucleation and kinetochore-microtubule attachments like Dis1/Stu2/XMAP215 homologs in other species. Moreover, the FgStu2 promoter replacement mutants (FgStu2-Si mutants) produced twisted hyphae and decreased growth rate. Microscope examination further showed that the microtubule polymerization was reduced in FgStu2-Si mutants, which could account for the aberrant morphology. Although the microtubule polymerization was affected in FgStu2-Si mutants, the FgStu2-Si mutants didn't show highly increased sensitivity to anti-microtubule fungicide carbendazim (methyl benzimidazol-2-ylcarbamate [MBC]). In addition, the FgStu2-Si mutants exhibited curved conidia, decreased number of conidial production, blocked ability of perithecia production, decreased pathogenicity and deoxynivalenol (DON) production. Taken together, these results indicate that the FgStu2 gene plays a crucial role in vegetative growth, morphology, sexual reproduction, asexual reproduction, virulence and deoxynivalenol (DON) production of F. graminearum, which brings new insights into the functions of Dis1/Stu2/XMAP215 homolog in plant pathogenic fungi.

MAP4 as a New Candidate in Cardiovascular Disease

Microtubule and mitochondrial dysfunction have been implicated in the pathogenesis of cardiovascular diseases (CVDs), including cardiac hypertrophy, fibrosis, heart failure, and hypoxic/ischemic related heart dysfunction. Microtubule dynamics instability leads to disrupted cell homeostasis and cell shape, decreased cell survival, and aberrant cell division and cell cycle, while mitochondrial dysfunction contributes to abnormal metabolism and calcium flux, increased cell death, oxidative stress, and inflammation, both of which causing cell and tissue dysfunction followed by CVDs. A cytosolic skeleton protein, microtubule-associated protein 4 (MAP4), belonging to the family of microtubule-associated proteins (MAPs), is widely expressed in non-neural cells and possesses an important role in microtubule dynamics. Increased MAP4 phosphorylation results in microtubule instability. In addition, MAP4 also expresses in mitochondria and reveals a crucial role in maintaining mitochondrial homeostasis. Phosphorylated MAP4 promotes mitochondrial apoptosis, followed by cardiac injury. The aim of the present review is to highlight the novel role of MAP4 as a potential candidate in multiple cardiovascular pathologies.

Synthesis, Anti-proliferative Evaluation, and Molecular Docking Studies of 3-(alkylthio)-5,6-diaryl-1,2,4-triazines as Tubulin Polymerization Inhibitors

Background:

The role of microtubules in cell division and signaling, intercellular transport, and mitosis has been well known. Hence, they have been targeted for several anti-cancer drugs.

Methods:

A series of 3-(alkylthio)-5,6-diphenyl-1,2,4-triazines were prepared and evaluated for their cytotoxic activities in vitro against three human cancer cell lines; human colon carcinoma cells HT-29, human breast adenocarcinoma cell line MCF-7, human Caucasian gastric adenocarcinoma cell line AGS as well as fibroblast cell line NIH-3T3 by MTT assay. Docking simulation was performed to insert these compounds into the crystal structure of tubulin at the colchicine binding site to determine a probable binding model. Compound 5d as the most active compound was selected for studying of microtubule disruption.

Results:

Compound 5d showed potent cytotoxic activity against all cell lines. The molecular modeling study revealed that some derivatives of triazine strongly bind to colchicine binding site. The tubulin polymerization assay kit showed that the cytotoxic activity of 5d may be related to inhibition of tubulin polymerization.

Conclusion:

The cytotoxicity and molecular modeling study of the synthesized compounds with their inhibition activity in tubulin polymerization demonstrate the potential of triazine derivatives for development of new anti-cancer agents.

Sea Urchin Extracellular Proteins Design a Complex Protein Corona on Titanium Dioxide Nanoparticle Surface Influencing Immune Cell Behavior

Extensive exploitation of titanium dioxide nanoparticles (TiO₂NPs) augments rapid release into the marine environment. When in contact with the body fluids of marine invertebrates, TiO₂NPs undergo a transformation and adhere various organic molecules that shape a complex protein corona prior to contacting cells and tissues. To elucidate the potential extracellular signals that may be involved in the particle recognition by immune cells of the sea urchin Paracentrotus lividus, we investigated the behavior of TiO₂NPs in contact with extracellular proteins in vitro. Our findings indicate that TiO₂NPs are able to interact with sea urchin proteins in both cell-free and cell-conditioned media. The two-dimensional proteome analysis of the protein corona bound to TiO₂NP revealed that negatively charged proteins bound preferentially to the particles. The main constituents shaping the sea urchin cell-conditioned TiO₂NP protein corona were proteins involved in cellular adhesion (Pl-toposome, Pl-galectin-8, Pl-nectin) and cytoskeletal organization (actin and tubulin). Immune cells (phagocytes) aggregated TiO₂NPs on the outer cell surface and within well-organized vesicles without eliciting harmful effects on the biological activities of the cells. Cells showed an active metabolism, no oxidative stress or caspase activation. These results provide a new level of understanding of the extracellular proteins involved in the immune-TiO₂NP recognition and interaction in vitro, confirming that primary immune cell cultures from P. lividus can be an optional model for swift and efficient immune-toxicological investigations.

Potent combretastatin A-4 analogs containing 1,2,4-triazole: Synthesis, antiproliferative, anti-tubulin activity, and docking study

A series of cis restricted 1,2,4-triazole analogs of combretastatin A-4 (CA-4) were designed and synthesized. The antiproliferative activity of these compounds was measured on hepatocellular carcinoma HepG2, leukemia HL-60, and breast cancer MCF-7 cell lines. The obtained results showed a substantial ability of the synthesized anilides to inhibit tumor growth. On HepG2 cells, 5o and 5r showed potent IC₅₀ values of 0.10 and 0.04 μM, respectively. While on HL-60 cells, the IC₅₀ values were 0.004 and 0.01 μM for 5b and 5i, respectively. The inhibitory activity of tubulin polymerization was evaluated on HepG2 cells. The anilide 5r showed a remarkable tubulin inhibition compared to CA-4. Moreover, flow cytometry studies showed that HepG2 cells treated with the most potent compounds 5b and 5r were arrested in the G2/M phase of the cell cycle. This effect was accompanied by cellular apoptosis and activation of caspase-3. Molecular modeling showed several hydrogen bonding and van der Waals interactions with several important amino acids inside the colchicine binding site of tubulin.

Design, synthesis and biological evaluation of novel vicinal diaryl-substituted 1H-Pyrazole analogues of combretastatin A-4 as highly potent tubulin polymerization inhibitors

A series of 3-(3',4',5'-trimethoxyphenyl)-4-substituted 1H-pyrazole and their related 3-aryl-4-(3',4',5'-trimethoxyphenyl)-1-H-pyrazole regioisomeric derivatives, prepared as cis-rigidified combretastatin A-4 (CA-4) analogues, were synthesized and evaluated for their in vitro antiproliferative against six different cancer cell lines and, for selected highly active compounds, inhibitory effects on tubulin polymerization, cell cycle effects and in vivo potency. We retained the 3',4',5'-trimethoxyphenyl moiety as ring A throughout the present investigation, and a structure-activity relationship (SAR) information was obtained by adding electron-withdrawing (OCF₃, CF₃) or electron-releasing (alkyl and alkoxy) groups on the second aryl ring, corresponding to the B-ring of CA-4, either at the 3- or 4-position of the pyrazole nucleus. In addition, the B-ring was replaced with a benzo[b]thien-2-yl moiety. For many of the compounds, their activity was greater than, or comparable with, that of CA-4. Maximal activity was observed with the two regioisomeric derivatives characterized by the presence of a 4-ethoxyphenyl and a 3',4',5'-trimethoxyphenyl group at the C-3 and C-4 positions, and vice versa, of the 1H-pyrazole ring. The data showed that the 3',4',5'-trimethoxyphenyl moiety can be moved from the 3- to the 4-position of the 1H-pyrazole ring without significantly affecting antiproliferative activity. The most active derivatives bound to the colchicine site of tubulin and inhibited tubulin polymerization at submicromolar concentrations. In vivo experiments, on an orthotopic murine mammary tumor, revealed that 4c inhibited tumor growth even at low concentrations (5 mg/kg) compared to CA-4P (30 mg/kg).

Imidazopyridine linked triazoles as tubulin inhibitors, effectively triggering apoptosis in lung cancer cell line

A library of new imidazopyridine linked triazole hybrid conjugates (8a-r) were designed, synthesized and evaluated for their cytotoxicity against four cancer cell lines namely, human lung (A549), human prostate (DU-145), human colon (HCT-116) and breast (MDA-MB 231) cancer. These conjugates exhibited good to moderate activity against the tested human cancer cell lines. Two of the conjugates (8g and 8j) showed significant antitumor activity against human lung cancer cell line (A549) with IC₅₀ values of 0.51 µM and 0.63 µM respectively. Flow cytometry analysis revealed that these conjugates arrested the cell cycle at G₂/M phase in human lung cancer cell line (A549). Immune-histochemistry and tubulin polymerization assay suggest inhibition of tubulin. Hoechst staining, annexin V and DNA fragmentation by tunnel assay suggested that these compounds induce cell death by apoptosis. Overall, the current study demonstrates that the synthesis of imidazopyridine linked triazole conjugates as promising anticancer agents causing G₂/M arrest and apoptotic-inducing ability.

Synthesis and biological evaluation of imidazo[2,1-b]thiazole-benzimidazole conjugates as microtubule-targeting agents

A series of imidazo[2,1-b]thiazole-benzimidazole conjugates were synthesized and evaluated for their antiproliferative activity against four human cancer cell lines i.e.; HeLa (cervical), A549 (lung), MCF-7 (breast) and DU-145 (prostate) along with normal HEK-293 cell line. Amongst them, conjugate 6d displayed significant cytotoxicity against human lung cancer cell line, A549 with IC₅₀ value 1.08 µM. Further, cell cycle analysis revealed that this compound arrested the cell cycle at G2/M phase in A549 cells. Furthermore, the tubulin polymerization assay results suggest that this conjugate (6d) exhibits significant inhibitory effect on the tubulin assembly with an IC50 value of 1.68 µM. Moreover, the apoptotic inducing properties of compound 6d was confirmed by Hoechst staining, measurement of mitochondrial membrane potential (ΔΨm) and annexin V-FITC assay. Further, molecular docking studies revealed that compound 6d occupied the colchicine binding site.

Cold sensing in grapevine-Which signals are upstream of the microtubular "thermometer"

Plants can acquire freezing tolerance in response to cold but non-freezing temperatures. To efficiently activate this cold acclimation, low temperature has to be sensed and processed swiftly, a process that is linked with a transient elimination of microtubules. Here, we address cold-induced microtubules elimination in a grapevine cell line stably expressing a green fluorescent protein fusion of Arabidopsis TuB6, which allows to follow their response in vivo and to quantify this response by quantitative image analysis. We use time-course studies with several specific pharmacological inhibitors and activators to dissect the signalling events acting upstream of microtubules elimination. We find that microtubules disappear within 30 min after the onset of cold stress. We provide evidence for roles of calcium influx, membrane rigidification, and activation of NAD(P)H oxidase as factors in signal susception and amplification. We further conclude that a G-protein in concert with a phospholipase D convey the signal towards microtubules, whereas calmodulin seems to be not involved. Moreover, activation of jasmonate pathway in response to cold is required for an efficient microtubule response. We summarize our findings in a working model on a complex signalling hub at the membrane-cytoskeleton interphase that assembles the susception, perception and early transduction of cold signals.

Dynamics of microtubules: highlights of recent computational and experimental investigations

Microtubules are found in most eukaryotic cells, with homologs in eubacteria and archea, and they have functional roles in mitosis, cell motility, intracellular transport, and the maintenance of cell shape. Numerous efforts have been expended over the last two decades to characterize the interactions between microtubules and the wide variety of microtubule associated proteins that control their dynamic behavior in cells resulting in microtubules being assembled and disassembled where and when they are required by the cell. We present the main findings regarding microtubule polymerization and depolymerization and review recent work about the molecular motors that modulate microtubule dynamics by inducing either microtubule depolymerization or severing. We also discuss the main experimental and computational approaches used to quantify the thermodynamics and mechanics of microtubule filaments.

Microtubules-associated Rac regulation of endothelial barrier: a role of Asef in acute lung injury

The endothelial barrier function regulated by the cytoskeletal reorganizations has been implicated in the pathogenesis of multiple lung diseases including asthma, sepsis, edema, and acute respiratory distress syndrome. The extensive studies have established that activation of small GTPase Rac is a key mechanism in endothelial barrier protection but the role of microtubules-associated Rac in the endothelial functions remains poorly understood. With the emerging evidences that microtubules disassembly also plays a critical role in actin cytoskeleton remodeling leading to endothelial permeability, the knowledge on microtubules-mediated regulation of endothelial barrier is imperative to better understand the etiology of lung injuries as well as to develop novel therapeutics against these disorders. In this regard, our recent studies have revealed some novel aspects of microtubules-mediated regulation of endothelial barrier functions and unraveled a putative role of Rac-specific guanine nucleotide exchange factor Asef in mediating the barrier protective effects of hepatocyte growth factor. In this review, we will discuss the role of this novel Rac activator Asef in endothelial barrier protection and its regulation by microtubules.

Design, synthesis and biological evaluation of imidazopyridine-propenone conjugates as potent tubulin inhibitors

A library of imidazopyridine-propenone conjugates (8a-8u) were synthesized and evaluated for their antitumor activity against four human cancer cell lines, namely, prostate (DU-145), lung (A549), cervical (Hela) and breast (MCF-7) cancer cell lines. These conjugates showed good to moderate activity against the tested cell lines. Among them, two conjugates (8m and 8q) showed significant antiproliferative activity against the human lung cancer cell line (A549) with IC₅₀ values of 0.86 μM and 0.93 μM, respectively. Flow cytometry analysis revealed that these compounds arrested the cell cycle at the G₂/M phase in the human lung cancer cell line (A549), inhibiting tubulin polymerization leading to apoptosis. Further, Hoechst staining, decrease in mitochondrial membrane potential and Annexin V-FITC assay suggested that the cell death was due to apoptosis induction. Overall, the present investigation demonstrated that the synthesized imidazopyridine-propenone conjugates are promising tubulin inhibitors and apoptotic inducers.

Live Imaging to Study Microtubule Dynamic Instability in Taxane-resistant Breast Cancers

Taxanes such as docetaxel belong to a group of microtubule-targeting agents (MTAs) that are commonly relied upon to treat cancer. However, taxane resistance in cancerous cells drastically reduces the effectiveness of the drugs' long-term usage. Accumulated evidence suggests that the mechanisms underlying taxane resistance include both general mechanisms, such as the development of multidrug resistance due to the overexpression of drug-efflux proteins, and taxane-specific mechanisms, such as those that involve microtubule dynamics. Because taxanes target cell microtubules, measuring microtubule dynamic instability is an important step in determining the mechanisms of taxane resistance and provides insight into how to overcome this resistance. In the experiment, an in vivo method was used to measure microtubule dynamic instability. GFP-tagged α-tubulin was expressed and incorporated into microtubules in MCF-7 cells, allowing for the recording of the microtubule dynamics by time lapse using a sensitive camera. The results showed that, as opposed to the non-resistant parental MCF-7CC cells, the microtubule dynamics of docetaxel-resistant MCF-7TXT cells are insensitive to docetaxel treatment, which causes the resistance to docetaxel-induced mitotic arrest and apoptosis. This paper will outline this in vivo method of measuring microtubule dynamic instability.

Synthesis and biological evaluation of novel indole derivatives containing sulfonamide scaffold as potential tubulin inhibitor

Microtubule-targeted drugs play a critical role in various types of cancer therapy worldwide.

Down-regulation of Stathmin Is Required for the Phenotypic Changes and Classical Activation of Macrophages

Macrophages are important cells of innate immunity with specialized capacity for recognition and elimination of pathogens and presentation of antigens to lymphocytes for adaptive immunity. Macrophages become activated upon exposure to pro-inflammatory cytokines and pathogenic stimuli. Classical activation of macrophages with interferon-γ (IFNγ) and lipopolysaccharide (LPS) triggers a wide range of signaling events and morphological changes to induce the immune response. Our previous microtubule (MT) proteomic work revealed that the stathmin association with MTs is considerably reduced in activated macrophages, which contain significantly more stabilized MTs. Here, we show that there is a global decrease in stathmin levels, an MT catastrophe protein, in activated macrophages using both immunoblotting and immunofluorescent microscopy. This is an LPS-specific response that induces proteasome-mediated degradation of stathmin. We explored the functions of stathmin down-regulation in activated macrophages by generating a stable cell line overexpressing stathmin-GFP. We show that stathmin-GFP overexpression impacts MT stability, impairs cell spreading, and reduces activation-associated phenotypes. Furthermore, overexpressing stathmin reduces complement receptor 3-mediated phagocytosis and cellular activation, implicating a pivotal inhibitory role for stathmin in classically activated macrophages.

Synthesis and biological evaluation of imidazo[1,5-a]pyridine-benzimidazole hybrids as inhibitors of both tubulin polymerization and PI3K/Akt pathway

A series of imidazo[1,5-a]pyridine-benzimidazole hybrids (5a–aa) were prepared and evaluated for their cytotoxic activity against a panel of sixty human tumor cell lines. Among them compounds 5d and 5l showed significant cytotoxic activity with GI50 values ranging from 1.06 to 14.9 μM and 0.43 to 7.73 μM, respectively. Flow cytometric analysis revealed that these compounds arrest the cell cycle at G2/M phase and induced cell death by apoptosis. The tubulin polymerization assay (IC50 of 5d is 3.25 μM and 5l is 1.71 μM) and immunofluorescence analysis showed that these compounds effectively inhibited the microtubule assembly in human breast cancer cells (MCF-7). Further, the apoptotic effects of compounds were confirmed by Hoechst staining, mitochondrial membrane potential, cytochrome c release, ROS generation, caspase 9 activation and DNA fragmentation analysis. After treatment with these compounds for 48 h, p-PTEN and p-AKT levels were markedly decreased. Moreover, these compounds did not significantly inhibit the normal human embryonic kidney cells, HEK-293. The molecular docking simulations predicted the binding interactions of 5d and 5l with colchicine binding site of the tubulin, which is in compliance with the antiproliferative activity data.

In vivo TCR Signaling in CD4(+) T Cells Imprints a Cell-Intrinsic, Transient Low-Motility Pattern Independent of Chemokine Receptor Expression Levels, or Microtubular Network, Integrin, and Protein Kinase C Activity

Intravital imaging has revealed that T cells change their migratory behavior during physiological activation inside lymphoid tissue. Yet, it remains less well investigated how the intrinsic migratory capacity of activated T cells is regulated by chemokine receptor levels or other regulatory elements. Here, we used an adjuvant-driven inflammation model to examine how motility patterns corresponded with CCR7, CXCR4, and CXCR5 expression levels on ovalbumin-specific DO11.10 CD4⁺ T cells in draining lymph nodes. We found that while CCR7 and CXCR4 surface levels remained essentially unaltered during the first 48–72 h after activation of CD4⁺ T cells, their in vitro chemokinetic and directed migratory capacity to the respective ligands, CCL19, CCL21, and CXCL12, was substantially reduced during this time window. Activated T cells recovered from this temporary decrease in motility on day 6 post immunization, coinciding with increased migration to the CXCR5 ligand CXCL13. The transiently impaired CD4⁺ T cell motility pattern correlated with increased LFA-1 expression and augmented phosphorylation of the microtubule regulator Stathmin on day 3 post immunization, yet neither microtubule destabilization nor integrin blocking could reverse TCR-imprinted unresponsiveness. Furthermore, protein kinase C (PKC) inhibition did not restore chemotactic activity, ruling out PKC-mediated receptor desensitization as mechanism for reduced migration in activated T cells. Thus, we identify a cell-intrinsic, chemokine receptor level-uncoupled decrease in motility in CD4⁺ T cells shortly after activation, coinciding with clonal expansion. The transiently reduced ability to react to chemokinetic and chemotactic stimuli may contribute to the sequestering of activated CD4⁺ T cells in reactive peripheral lymph nodes, allowing for integration of costimulatory signals required for full activation.

Effect of HSA coated iron oxide labeling on human umbilical cord derived mesenchymal stem cells

Human umbilical cord derived mesenchymal stem cells (hUC-MSCs) are known for self-renewal and differentiation into cells of various lineages like bone, cartilage and fat. They have been used in biomedical applications to treat degenerative disorders. However, to exploit the therapeutic potential of stem cells, there is a requirement of sensitive non-invasive imaging techniques which will offer the ability to track transplanted cells, bio-distribution, proliferation and differentiation. In this study, we have analyzed the efficacy of human serum albumin coated iron oxide nanoparticles (HSA-IONPs) on the differentiation of hUC-MSCs. The colloidal stability of the HSA-IONPs was tested over a long period of time (≥20 months) and the optimized concentration of HSA-IONPs for labeling the stem cells was 60 μg ml(-1). Detailed in vitro assays have been performed to ascertain the effect of the nanoparticles (NPs) on stem cells. Lactate dehydrogenase (LDH) assay showed minimum release of LDH depicting the least disruptions in cellular membrane. At the same time, mitochondrial impairment of the cells was also not observed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Flow cytometry analysis revealed lesser generation of reactive oxygen species in HSA-IONPs labeled hUC-MSCs in comparison to bare and commercial IONPs. Transmission electron microscopy showed endocytic engulfment of the NPs by the hUC-MSCs. During the process, the gross morphologies of the actin cytoskeleton were found to be intact as shown by immunofluorescence microscopy. Also, the engulfment of the HSA-IONPs did not show any detrimental effect on the differentiation potential of the stem cells into adipocytes, osteocytes and chondrocytes, thereby confirming that the inherent properties of stem cells were maintained.

Microtubule severing by katanin p60 AAA+ ATPase requires the C-terminal acidic tails of both α- and β-tubulins and basic amino acid residues in the AAA+ ring pore

The microtubule (MT) network is highly dynamic and undergoes dramatic reorganizations during the cell cycle. Dimers of α- and β-tubulins rapidly polymerize to and depolymerize from the end of MT fibrils in an intrinsic GTP-dependent manner. MT severing by ATP-driven enzymes such as katanin and spastin contributes significantly to microtubule dynamics, and it has been shown that katanin p60, a AAA+ family protein, has ATPase and MT-severing activities. The mechanism of MT severing by katanin p60 is poorly understood, and the residues in katanin p60 and tubulins important for severing activity were therefore explored in this study. MT-severing activity, but not ATPase activity, was inhibited by mutations of the conserved aromatic residue and the flanking basic residues in the pore region of the katanin p60 hexameric ring. When the acidic residue-rich C-terminal unstructured segment of either α- or β-tubulin was removed, polymerized MTs were resistant to katanin p60 treatment. Interactions between katanin p60 and the mutant MTs, on the other hand, were unaffected. Taken together, these findings led us to propose that the interactions between the positively charged residues of katanin p60 and the acidic tails of both tubulins are essential for efficient severing of MTs.

P38/MAPK contributes to endothelial barrier dysfunction via MAP4 phosphorylation-dependent microtubule disassembly in inflammation-induced acute lung injury

Excessive activation of inflammation and the accompanying lung vascular endothelial barrier disruption are primary pathogenic features of acute lung injury (ALI). Microtubule-associated protein 4 (MAP4), a tubulin assembly-promoting protein, is important for maintaining the microtubule (MT) cytoskeleton and cell-cell junctional structures. However, both the involvement and exact mechanism of MAP4 in the development of endothelial barrier disruption in ALI remains unknown. In this study, lipopolysaccharide (LPS) and tumour necrosis factor-α (TNF-α) were applied to human pulmonary microvascular endothelial cells (HPMECs) to mimic the endothelial damage during inflammation in vitro. We demonstrated that the MAP4 (Ser696 and Ser787) phosphorylation increased concomitantly with the p38/MAPK pathway activation by the LPS and TNF-α stimulation of HPMECs, which induced MT disassembly followed by hyperpermeability. Moreover, the application of taxol, the overexpression of a MAP4 (Ala) mutant, or the application of the p38/MAPK inhibitor SB203580 inhibited the MT disruption and the intracellular junction dysfunction. In contrast, MKK6 (Glu), which constitutively activated p38/MAPK, resulted in microtubule depolymerisation and, subsequently, hyperpermeability. Our findings reveal a novel role of MAP4 in endothelial barrier dysfunction.

RhoGTPases as key players in mammalian cell adaptation to microgravity

A growing number of studies are revealing that cells reorganize their cytoskeleton when exposed to conditions of microgravity. Most, if not all, of the structural changes observed on flown cells can be explained by modulation of RhoGTPases, which are mechanosensitive switches responsible for cytoskeletal dynamics control. This review identifies general principles defining cell sensitivity to gravitational stresses. We discuss what is known about changes in cell shape, nucleus, and focal adhesions and try to establish the relationship with specific RhoGTPase activities. We conclude by considering the potential relevance of live imaging of RhoGTPase activity or cytoskeletal structures in order to enhance our understanding of cell adaptation to microgravity-related conditions.

Synthesis, biological evaluation and mechanism study of a class of cyclic combretastatin A-4 analogues as novel antitumour agents

In the search for novel antitumor agents, a series of cyclic CA-4 analogues bearing amide group, A–B or B–C ring condensation, and CC or CN bond in the B ring were designed, synthesized and identified as microtubule inhibitors.

Synthesis of 2-anilinopyridine–arylpropenone conjugates as tubulin inhibitors and apoptotic inducers

2-Anilinopyridine–arylpropenone conjugates as novel tubulin inhibitors and apoptotic inducers.

Design and synthesis of aminostilbene-arylpropenones as tubulin polymerization inhibitors

A series of aminostilbene-arylpropenones were designed and synthesized by Michael addition and were investigated for their cytotoxic activity against various human cancer cell lines. Some of the investigated compounds exhibited significant antiproliferative activity against a panel of 60 human cancer cell lines of the US National Cancer Institute, with 50 % growth inhibition (GI50) values in the range from < 0.01 to 19.9 μM. One of the compounds showed a broad spectrum of antiproliferative efficacy on most of the cell lines, with a GI50 value of < 0.01 μM. All of the synthesized compounds displayed cytotoxicity against A549 (non-small-cell lung cancer), HeLa (cervical carcinoma), MCF-7 (breast cancer), and HCT116 (colon carcinoma) with 50 % inhibitory concentration (IC50) values ranging from 0.011 to 8.56 μM. A cell cycle assay revealed that these compounds arrested the G2/M phase of the cell cycle. Two compounds exhibited strong inhibitory effects on tubulin assembly with IC50 values of 0.71 and 0.79 μM. Moreover, dot-blot analysis of cyclin B1 demonstrated that some of the congeners strongly induced cyclin B1 protein levels. Molecular docking studies indicated that these compounds occupy the colchicine binding site of tubulin.

Stathmin destabilizing microtubule dynamics promotes malignant potential in cancer cells by epithelial-mesenchymal transition

BACKGROUND

Stathmin is a ubiquitous cytosolic regulatory phosphoprotein and is overexpressed in different human malignancies. The main physiological function of stathmin is to interfere with microtubule dynamics by promoting depolymerization of microtubules or by preventing polymerization of tubulin heterodimers. Stathmin plays important roles in regulating many cellular functions as a result of its microtubule-destabilizing activity. Currently, the critical roles of stathmin in cancer cells, as well as in lymphocytes have been valued. This review discusses stathmin and microtubule dynamics in cancer development, and hypothesizes their possible relationship with epithelial-mesenchymal transition (EMT).

DATA SOURCES

A PubMed search using such terms as "stathmin", "microtubule dynamics", "epithelial-mesenchymal transition", "EMT", "malignant potential" and "cancer" was performed to identify relevant studies published in English. More than 100 related articles were reviewed.

RESULTS

The literature clearly documented the relationship between stathmin and its microtubule-destabilizing activity of cancer development. However, the particular mechanism is poorly understood. Microtubule disruption is essential for EMT, which is a crucial process during cancer development. As a microtubule-destabilizing protein, stathmin may promote malignant potential in cancer cells by initiating EMT.

CONCLUSIONS

We propose that there is a stathmin-microtubule dynamics-EMT (S-M-E) axis during cancer development. By this axis, stathmin together with its microtubule-destabilizing activity contributes to EMT, which stimulates the malignant potential in cancer cells.

The Leishmania donovani chaperone cyclophilin 40 is essential for intracellular infection independent of its stage-specific phosphorylation status

During its life cycle, the protozoan pathogen Leishmania donovani is exposed to contrasting environments inside insect vector and vertebrate host, to which the parasite must adapt for extra- and intracellular survival. Combining null mutant analysis with phosphorylation site-specific mutagenesis and functional complementation we genetically tested the requirement of the L. donovani chaperone cyclophilin 40 (LdCyP40) for infection. Targeted replacement of LdCyP40 had no effect on parasite viability, axenic amastigote differentiation, and resistance to various forms of environmental stress in culture, suggesting important functional redundancy to other parasite chaperones. However, ultrastructural analyses and video microscopy of cyp40-/- promastigotes uncovered important defects in cell shape, organization of the subpellicular tubulin network and motility at stationary growth phase. More importantly, cyp40-/- parasites were unable to establish intracellular infection in murine macrophages and were eliminated during the first 24 h post infection. Surprisingly, cyp40-/- infectivity was restored in complemented parasites expressing a CyP40 mutant of the unique S274 phosphorylation site. Together our data reveal non-redundant CyP40 functions in parasite cytoskeletal remodelling relevant for the development of infectious parasites in vitro independent of its phosphorylation status, and provide a framework for the genetic analysis of Leishmania-specific phosphorylation sites and their role in regulating parasite protein function.

Synthesis and evaluation of N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)nicotinamides as potential anticancer agents that inhibit tubulin polymerization

A series of N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)nicotinamides (4) was synthesized and tested for their anticancer activity against a panel of 60 human cancer cell lines. Some of the representative compounds such as 4a, 4b, 4f, 4g, 4i and 4t were selected for the five dose study and amongst them 4g and 4i displayed significant anticancer activity with GI50 values ranging from 0.25 to 8.34 and 1.42 to 5.86μM, respectively. Cell cycle analysis revealed that these compounds induced cell cycle arrest at G2/M phase in MCF-7 cells. The most active compound in this series 4g also inhibited tubulin polymerization with IC50 value 1.93μM superior to that of E7010. Moreover, assay to investigate the effect on caspase-9, Hoechst staining and DNA fragmentation analysis suggested that these compounds induced cell death by apoptosis. Docking experiments showed that they interact and bind efficiently with tubulin protein. Overall, the results demonstrate that N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)nicotinamide scaffold possess anticancer property by inhibiting the tubulin polymerization.

Mechanics of severing for large microtubule complexes revealed by coarse-grained simulations

We investigate the mechanical behavior of microtubule (MT) protofilaments under the action of bending forces, ramped up linearly in time, to provide insight into the severing of MTs by microtubule associated proteins (MAPs). We used the self-organized polymer model which employs a coarse-grained description of the protein chain and ran Brownian dynamics simulations accelerated on graphics processing units that allow us to follow the dynamics of a MT system on experimental timescales. Our study focused on the role played in the MT depolymerization dynamics by the inter-tubulin contacts a protofilament experiences when embedded in the MT lattice, and the number of binding sites of MAPs on MTs. We found that proteins inducing breaking of MTs must have at least three attachment points on any tubulin dimer from an isolated protofilament. In contrast, two points of contact would suffice when dimers are located in an intact MT lattice, in accord with experimental findings on MT severing proteins. Our results show that confinement of a protofilament in the MT lattice leads to a drastic reduction in the energy required for the removal of tubulin dimers, due to the drastic reduction in entropy. We further showed that there are differences in the energetic requirements based on the location of the dimer to be removed by severing. Comparing the energy of tubulin dimers removal revealed by our simulations with the amount of energy resulting from one ATP hydrolysis, which is the source of energy for all MAPs, we provided strong evidence for the experimental finding that severing proteins do not bind uniformly along the MT wall.

Synthesis and evaluation of a series of quinolinyl trans-cyanostilbene analogs as anticancer agents

2-Quinolyl- and 3-quinolyl-cyanocombretastatin analogs exhibit potent growth inhibition against a panel of 60 human cancer cell lines.