Tubulin Polymerization Research Articles

EMIM] [OAc]: An Efficient Ionic Liquid Medium for the Synthesis of New 4-(furan/pyrrole/thiophene-2-yl)-3, 4-dihydro-1H-chromeno [4,3-d] pyrimidine-2,5-diones and Molecular Docking Studies

Abstract: An efficient synthesis of Chromeno[b]pyrimidine derivatives 4 has been achieved by treating 4-hydroxy-2H-chromen-2-one 1, furan-2-carbaldehyde / 1H-pyrrole-2-carbaldehyde/ thiophene-2- carbaldehyde 2, and urea/thiourea 3 at 65-70 °C for 90-120 min using 1-Ethyl-3-methylimidazolium acetate as ionic liquid and medium with good yields 86-90%. This synthetic method has numerous advantages, including high yields, a simple protocol, environmental friendliness, brief reaction times, and mild reaction conditions. Using a catalytically active ionic liquid as the medium eliminates the need for a catalyst and a solvent. In this study, the docking score of the synthesized compounds was found to be between -8 to -9 kcal/mol similar to the co-crystal. Additionally, the compounds maintained their amino acid interactions with Tyr 281 (coagulation protein; 6WV3) and Thr 179 (tubulin polymerization protein; 5LYJ.pdb).

Utidelone plus pembrolizumab as the fourth-line combination treatment in non-small cell lung cancer with EGFR mutation: a case report.

Utidelone is an ebomycin derivative chemotherapeutic drug, which can promote tubulin polymerization and stabilize microtubule structure, so as to induce apoptosis. The drug is an innovative drug independently developed by China with independent intellectual property rights. Phase II clinical trials for advanced breast cancer are being approved by National Medical Products Administration for the treatment of advanced breast cancer. However, there is no report on the application in non-small cell lung cancer (NSCLC) patients with the epidermal growth factor receptor (EGFR) mutation. This case is a patient with EGFR mutant stage IV NSCLC who has progressed after third-line targeted therapy. The fourth line was treated with utidelone combined with pabolizumab. The patient had progressed after targeted therapy with oxitinib, ametinib, and vometinib. Due to the patient's physical reasons, the traditional platinum drugs were not suitable, so the patient was treated with utidelone combined with pabolizumab. The curative effect was evaluated as SD after two cycles and progesterone receptor after four cycles. At present, it is still in the maintenance of reduction of utidelone combined with pabolizumab, and the tumor continues to shrink. Although peripheral neurotoxicity occurred during treatment, it improved after symptomatic treatment. The treatment of EGFR mutant stage IV NSCLC with utidelone combined with pabolizumab has good effect and mild adverse reactions.

Application of Chlorosulfonyl Isocyanate (CSI) in the Synthesis of Fused Tetracyclic Ketone Ring Systems.

Chlorosulfonyl isocyanate (CSI) is a complex reagent capable of facilitating numerous synthetic transformations, including lactam/lactone formation, sulfonylation, Friedel-Crafts-type acylations, and cycloadditions. Annulation reactions to form nitrogen-, oxygen-, and sulfur-bearing heterocycles have been observed with CSI; however, the application of CSI toward the generation of fused cyclic ketone ring systems has not been previously reported. A serendipitous discovery of the pertinence of CSI occurred during a structure-activity relationship campaign around our established lead benzosuberene-based molecule that functions as a potent inhibitor of tubulin polymerization. The benzylic olefin within this molecule represents a promising moiety for further functionalization. CSI was initially investigated as a reagent to effect transformation of this olefin to its corresponding β-lactam functionality, but instead resulted in an unexpected tetracyclic fused ring system in high yield (88%). This finding led to an exploration of the reactivity of CSI with various arenes. Benzosuberene analogues with varying functionalizations were synthesized and treated with CSI, with all examples resulting in a fused ring system except those bearing electron-withdrawing groups. Notably, simplified arene structures with fewer substituents were also observed to undergo cyclization under these conditions. This strategy represents a promising approach for the synthesis of appropriately functionalized tetracyclic ring systems.

NWD1 influences the extension of neuronal axons by regulating microtubule stability

Proteins belonging to the STAND (signal transduction ATPases with numerous domains) family have been implicated in crucial functions across various signal transduction pathways, encompassing both apoptosis and innate immune responses. In this study, we have identified NWD1, a member of the STAND superfamily, as a gene that regulates neurite outgrowth. This was confirmed by siRNA knockdown assay in E18 neurons. A zebrafish model was utilized to create NWD1 knockdown using the NgAgo-gDNA system, revealing the significant role of NWD1 in neurogenesis. We further revealed that NWD1 siRNA reduced the acetylated tubulin protein, and changed the ratio of soluble and polymerized tubulin. Moreover, we investigated the mechanism underlying the regulation of NWD1-mediated microtubule dynamics, and MAP1B may be a target gene. This research unveiled, for the first time, the potential role of NWD1 in regulating axon outgrowth through modulating the ratio of acetylated tubulin.

Discovery of novel quinazoline derivatives as tubulin polymerization inhibitors targeting the colchicine binding site with potential anti-colon cancer effects

Tubulin is a critical target for cancer therapy, with colchicine binding site inhibitors (CBSIs) being the most extensively researched. A series of quinazoline derivatives designed to target the colchicine binding site of tubulin were synthesized and evaluated for their biological activities. The antiproliferative effects of these compounds were tested against six human cancer cell lines, and compound Q19 demonstrated potent antiproliferative activity against the HT-29 cell line, with an IC50 value of 51 nM. Additionally, further investigation revealed that Q19 effectively inhibited microtubule polymerization by binding to the colchicine binding site on tubulin. Furthermore, compound Q19 arrested the HT-29 cell cycle at the G2/M phase, induced apoptosis in these cells, and disrupted angiogenesis. Finally, compound Q19 exhibited potent inhibitory effects on tumor growth in HT-29 xenografted mice while demonstrating minimal toxic side effects and acceptable pharmacokinetic properties. These findings suggested that Q19 hold promise as a potential candidate for colon cancer therapy targeting tubulin.

C-4 analogues of podophyllotoxin as tubulin inhibitors: synthesis, biological evaluation, and structure-activity relationship

The diversity of lignan small molecules derived from podophyllotoxin, a non-covalent tubulin inhibitor isolated from the Podophyllum family, has led to the clinical development of FDA-approved anticancer agents etoposide and teniposide. While these two compounds share the same tetracyclic core as podophyllotoxin, two subtle structural changes—4’ demethylation on the aromatic ring and stereospecific glycosylation at the C-4 hydroxyl—result in an alternate biological mechanism. Given the immense pharmacological importance of altering the C-4 position, we synthesised and evaluated a systematic library of diversified esters to establish a structure-activity relationship regarding modification at C-4 on the properties of podophyllotoxin. We determined the biological activity of these esters through cell viability assays, computer docking models, tubulin polymerisation assays, and cell cycle analysis. Altogether, we demonstrate that increasing steric hindrance at C-4 leads to a loss in potency against human cancer cells but has a significantly lesser impact on cell-free tubulin inhibition.

A potent Bioorganic azapodophyllotoxin derivative Suppresses tumor Progression in Triple negative breast Cancer: An Insight into its Inhibitory effect on tubulin polymerization and Disruptive effect on microtubule assembly

Triple negative breast cancer (TNBC) has long been a challenging disease owing to its high aggressive behaviour, poor prognosis and its limited treatment options. The growing demand of new therapeutics against TNBC enables us to examine the therapeutic efficiency of an emerging class of anticancer compounds, azapodophyllotoxin derivative (HTDQ), a nitrogen analogue of podophyllotoxin, using different biochemical, spectroscopic and computational approaches. The anticancer activities of HTDQ are studied by performing MTT assay in a dose depended manner on Triple negative breast cancer cells using MDA–MB-468 and MDA-MB-231 cell lines with IC50 value 937 nM and 1.13 µM respectively while demonstrating minimal effect on normal epithelial cells. The efficacy of HTDQ was further tested in 3D tumour spheroids formed by the human TNBC cell line MDA-MB468 and also the murine MMTV positive TNBC cell line 4 T1. The shrinkage that observed in the tumor spheroid clearly indicates that HTDQ remarkably decreases the growth of tumor spheroid thereby affirming its cytotoxicity. The 2D cell viability assay shows significant morphological alteration that possibly caused by the cytoskeleton disturbances. Hence the binding interaction of HTDQ with cytoskeleton protein tubulin, its effect on tubulin polymerisation as well as depolymerisation of preformed microtubules along with the conformational alternation in the protein itself have been investigated in detail. Moreover, the apoptotic effects of HTDQ have been examined using a range of apoptotic markers. HTDQ-treated cancer cells showed increased expression of cleaved PARP-1 and pro-caspase-3, suggesting activation of the apoptosis process. HTDQ also upregulated pro-apoptotic Bax expression while inhibiting anti-apoptotic Bcl2 expression, supporting its ability to induce apoptosis in cancer cells. Hence the consolidated biochemical and spectroscopic research described herein may provide enormous information to use azapodophyllotoxin as promising anticancer therapeutics for TNBC cells.

The novel herbicide icafolin‐methyl is a plant‐specific inhibitor of tubulin polymerization

AbstractBACKGROUNDWithout controlling weeds, it is estimated that about one third of global crop yields would be lost. Herbicides remain the most effective solution for weed control, but they face multiple challenges, such as the emergence and growth of resistant weed populations. Consequently, there is an urgent need for either herbicides with new modes of action or at least novel chemistries within established modes of action, with outstanding efficacy but without showing cross‐resistance to the herbicides present in the prospective markets.RESULTSIcafolin‐methyl is a novel herbicide with a unique biological profile. It is hydrolyzed in planta to the carboxylic acid icafolin. After post‐emergence application icafolin‐methyl and icafolin both show high efficacy against the most relevant competitive weeds in cold and warm season cropping systems at low application rates, including resistant black‐grass and rye‐grass biotypes. Biochemical and genetic evidence is provided that icafolin‐methyl and icafolin inhibit plant tubulin polymerization probably by binding to ß‐tubulins.CONCLUSIONIcafolin‐methyl is a novel non‐selective herbicide with an established mode of action, but with a superior potency and spectrum, specifically after foliar application. This makes icafolin‐methyl fundamentally different from existing tubulin polymerization inhibiting herbicides. It complements the farmers weed control toolbox, particularly with respect to resistance management. © 2024 Society of Chemical Industry.

Discovery and biological evaluation of 6-aryl-4-(3,4,5-trimethoxyphenyl)quinoline derivatives with promising antitumor activities as novel colchicine-binding site inhibitors

Tubulin, as the fundamental unit of microtubules, is a crucial target in the investigation of anticarcinogens. The synthesis and assessment of small-molecule tubulin polymerization inhibitors remains a promising avenue for the development of novel cancer therapeutics. Through an analysis of reported colchicine-binding site inhibitors (CBSIs) and tubulin binding models, a set of 6-aryl-4-(3,4,5-trimethoxyphenyl)quinoline derivatives were meticulously crafted as potential CBSIs. Notably, compound 14u exhibited potent anti-proliferative efficacy, displaying IC50 values ranging from 0.03 to 0.18 μM against three human cancer cell lines (Huh7, MCF-7, and SGC-7901). Mechanistic investigations revealed that compound 14u could disrupt tubulin polymerization, dismantle the microtubule architecture, arrest the cell cycle at G2/M phase, and induce apoptosis in cancer cells. Furthermore, compound 14u demonstrated significant inhibition of tumor proliferation in vivo with no discernible toxicity in the Huh7 orthotopic tumor model mice. Additionally, physicochemical property predictions indicated that compound 14u adhered well to Lipinski's rule of five. These findings collectively suggest that compound 14u holds promise as an antitumor agent targeting the colchicine-binding site on tubulin and warrants further investigation.

Unveiling the anti-cancer potentiality of phthalimide-based Analogues targeting tubulin polymerization in MCF-7 cancerous Cells: Rational design, chemical Synthesis, and Biological-coupled Computational investigation

The present study deals with an anti-cancer investigation of an array of phthalimide-1,2,3-triazole molecular conjugates with various sulfonamide fragments against human breast MCF-7 and prostate PC3 cancer cell lines. The targeted 1,2,3-triazole derivatives 4a-l and 6a-c were synthesized from focused phthalimide-based alkyne precursors using a facile click synthesis approach and were thoroughly characterized using several spectroscopic techniques (IR, 1H, 13C NMR, and elemental analysis). The hybrid click adducts 4b, 4 h, and 6c displayed cytotoxic potency (IC50 values of 1.49, 1.07, and 0.56 μM, respectively) against MCF-7 cells. On the contrary, none of the synthesized compounds showed apparent cytotoxic efficacy for PC3 cells (IC50 ranging from 9.87- >100 μM). As a part of the mechanism analysis, compound 6c demonstrated a potent inhibitory effect (78.3 % inhibition) of tubulin polymerization in vitro with an IC50 value of 6.53 µM. In addition, biological assays showed that compound 6c could prompt apoptotic cell death and induce G2/M cell cycle arrest in MCF-7 cells. Accordingly, compound 6c can be further developed as an anti-breast cancer agent through apoptosis-induction.

Design, Synthesis, and In Vitro Cytotoxic Studies of Some Novel Arylidene-Hydrazinyl-Thiazoles as Anticancer and Apoptosis-Inducing Agents.

Cancer, defined by uncontrolled cell growth, poses a significant global health challenge, necessitating the development of new anticancer drugs crucial to address drug resistance, side effects, and the need for combination therapies. The study presents the design, synthesis, and anticancer screening of a series of novel functionalized arylidene-hydrazinyl-thiazoles against various human cancer cell lines. The environmentally benign synthetic protocol involves the visible-light prompted, NBS-mediated domino reaction of thiosemicarbazide, heteroaryl aldehydes, and unsymmetrical 1,3-diketones. The regioselective organic transformation delivered the single regioisomeric product, characterized unambiguously through detailed 2D NMR spectral studies. In vitro cytotoxic studies revealed that the synthesized derivatives exhibited excellent cytotoxic potential against BxPC-3, MOLT-4, and MCF-7 cancer cell lines. Notably, compounds 4m, 4n, and 4r showed significant cytotoxicity, reducing cell survival to 23.85-26.45% for BxPC-3, 30.08-33.30% for MOLT-4, and 44.40-47.63% for MCF-7 at a concentration of 10 μM. These compounds profoundly induced apoptosis, evidenced by increased caspase-3/7 activity, loss of mitochondrial membrane potential, and modulation of Bcl2 and Bax gene expression. Additionally, these compounds caused robust cell cycle arrest at the G2/M phase by inhibiting tubulin polymerization, indicating their multifaceted impact on cancer cells.

Insights into medicinal attributes of imidazo[1,2-a]pyridine derivatives as anticancer agents.

Cancer ranks among the most life-threatening diseases worldwide and is continuously affecting all age groups. Consequently, many research studies are being carried out to develop new cancer treatments, but many of them experience resistance and cause severe toxicity to the patients. Therefore, there is a continuous need to design novel anticancer agents that are target-based, have a higher potency, and have minimal toxicity. The imidazo[1,2-a]pyridine (IP) pharmacophore has been found to be a prominent moiety in the field of medicinal chemistry due to its vast biological properties. Also, it holds immense potential for combating cancer with minimal side effects, depending on the substitution patterns of the core structure. IPs exhibit significant capability in regulating various cellular pathways, offering possibilities for targeted anticancer effects. The present review summarizes the anticancer profile of numerous IP derivatives synthesized and developed by various researchers from 2016 till now, as inhibitors of phosphoinositide-3-kinase/mammalian target of rapamycin (PI3K/mTOR), protein kinase B/mammalian target of rapamycin (Akt/mTOR), aldehyde dehydrogenase (ALDH), and tubulin polymerization. This review provides a comprehensive analysis of the anticancer activity afforded by the discussed IP compounds, emphasizing the structure-activity-relationships (SARs). The aim is also to underscore the potential therapeutic future of the IP moiety as a potent partial structure for upcoming cancer drug development and to aid researchers in the field of rational drug design.

Synthesis of New Thiazole-Privileged Chalcones as Tubulin Polymerization Inhibitors with Potential Anticancer Activities.

A series of novel thiazole-based chalcones were evaluated for their anticancer activity as potential tubulin polymerization inhibitors. In vitro anticancer screening for the thiazole derivatives 2a-2p exhibited broad-spectrum antitumor activity against various cancer cell lines particularly Ovar-3 and MDA-MB-468 cells with a GI50 range from 1.55 to 2.95 μΜ, respectively. Compound 2e demonstrated significant inhibition of tubulin polymerization, with an IC50 value of 7.78 μM compared to Combretastatin-A4 (CA-4), with an IC50 value of 4.93 μM. Molecular docking studies of compounds 2e, 2g, and 2h into tubulin further supported these findings, revealing that they bind effectively to the colchicine binding site, mirroring key interactions exhibited by CA-4. Computational predictions suggested favorable oral bioavailability and drug-likeness for these compounds, highlighting their potential for further development as chemotherapeutic agents.

Cellular Uptake of Phase-Separating Peptide Coacervates.

Peptide coacervates self-assembling via liquid-liquid phase separation are appealing intracellular delivery vehicles of macromolecular therapeutics (proteins, DNA, mRNA) owing to their non-cytotoxicity, high encapsulation capacity, and efficient cellular uptake. However, the mechanisms by which these viscoelastic droplets cross the cellular membranes remain unknown. Here, using multimodal imaging, data analytics, and biochemical inhibition assays, identify the key steps by which droplets enter the cell. find that the uptake follows a non-canonical pathway and instead integrates essential features of macropinocytosis and phagocytosis, namely active remodeling of the actin cytoskeleton and appearance of filopodia-like protrusions. Experiments using giant unilamellar vesicles show that the coacervates attach to the bounding membrane in a charge- and cholesterol-dependent manner but do not breach the lipid bilayer barrier. Cell uptake in the presence of small molecule inhibitors - interfering with actin and tubulin polymerization - confirm the active role of cytoskeleton remodeling, most prominently evident in electron microscopy imaging. These findings suggest a peculiar internalization mechanism for viscoelastic, glassy coacervate droplets combining features of non-specific uptake of fluids by macropinocytosis and particulate uptake of phagocytosis. The broad implications of this study will enable to enhance the efficacy and utility of coacervate-based strategies for intracellular delivery of macromolecular therapeutics.

Design, Synthesis, in Silico Molecular Docking and ADMET Studies of Indole‐Sulfonamide Derivatives as Tubulin Polymerization Inhibiting Agents

Design, Synthesis, in Silico Molecular Docking and ADMET Studies of Indole‐Sulfonamide Derivatives as Tubulin Polymerization Inhibiting Agents

Discovery of novel thiophene[3,2-d]pyrimidine-based tubulin inhibitors with enhanced antitumor efficacy for combined use with anti-pd-l1 immunotherapy in melanoma

Herein, we designed and synthesized a series of novel 2-methylthieno [3,2-d]pyrimidine analogues as tubulin inhibitors with antiproliferative activities at low nanomolar levels. Among them, compound DPP-21 displayed the most potent anti-proliferative activity against six cancer cell lines with an average IC50 of ∼6.23 nM, better than that of colchicine (IC50 = 9.26 nM). DPP-21 exerted its anti-cancer activity by suppressing the polymerization of tubulin with an IC50 of 2.4 μM. Furthermore, the crystal structure of DPP-21 in complex with tubulin was solved by X-ray crystallography to 2.94 Å resolution, confirming the direct binding of DPP-21 to the colchicine site. Moreover, DPP-21 arrested the cell cycle in the G2/M phase of mitosis, subsequently inducing tumor cell apoptosis. Additionally, DPP-21 was able to effectively inhibit the migration of cancer cells. Besides, DPP-21 exhibited significant in vivo anti-tumor efficacy in a B16–F10 melanoma tumor model with a TGI of 63.3 % (7 mg/kg) by intraperitoneal (i.p.) injection. Notably, the combination of DPP-21 with NP-19 (a PD-L1-targeting small molecule inhibitor reported by our group before) demonstrated enhanced anti-cancer efficacy in vivo. These results suggest that DPP-21 is a promising lead compound deserving further investigation as a potential anti-cancer agent.

Exploring the anticancer potential of new 3-cyanopyridine derivatives bearing N-acylhydrazone motif: Synthesis, DFT calculations, cytotoxic evaluation, molecular modeling, and antioxidant properties.

3-Cyanopyridine derivatives are known for exhibiting excellent anticancer activity due to their strong capability to inhibit various biological targets, including Pim-1 kinase, survivin, and tubulin polymerization. On the other hand, N-acylhydrazones (NAH) are known to be a very versatile motif in medicinal chemistry and drug design. Based on these data, we report in this paper, the synthesis of novel 3-cyanopyridines incorporating N-acyl hydrazine scaffold, the evaluation of their cytotoxicity on the breast (MCF-7) and ovarian (A-2780) cancer cell lines and their antioxidant properties. Excluding 4a and 4d, all tested molecules exhibited high cytotoxicity against A-2780, with IC50 values ranging from 1.14 to 1.76 µM. Conversely, only four molecules 3d, 4b, 4c, and 4d demonstrated cytotoxicity against MCF-7, with IC50 values ranging from 1.14 to 3.38 µM. On the other hand, all the tested molecules exhibited a moderate antioxidant capacity in both the DPPH and metal chelation assays. Docking and molecular dynamics studies revealed that 2d, 3d, and 4d are potential inhibitors of tubulin and the œstrogen receptor, which may explain their high cytotoxicity. These results are promising to study these newly synthesized 3-cyanopyridine-N-acylhydrazones in depth for use as potential anticancer candidates.

Scaffold overlay of flavonoid-inspired molecules: Discovery of 2,3-diaryl-pyridopyrimidin-4-imine/ones as dual hTopo-II and tubulin targeting anticancer agents

Almost half of all medicines approved by the U.S. Food and Drug Administration have been found to be developed based on inspiration from natural products (NPs). Here, we report a novel strategy of scaffold overlaying of scaffold-hopped analogs of bioactive flavones and isoflavones and installation of drug-privileged motifs, which has led to discovery of anticancer agents that surpass the functional efficiency of the original NPs. The analogs, 2,3-diaryl-pyridopyrimidin-4-imine/ones were efficiently synthesized by an approach of a nitrile-stabilized quaternary ammonium ylide as masked synthon and Pd-catalyzed activation–arylation methods. Compared to the NPs, these NP-analogs exhibited differentiated functions; dual inhibition of human topoisomerase-II (hTopo-II) enzyme and tubulin polymerization, and pronounced antiproliferative effect against various cancer cell lines, including numerous drug-resistant cancer cells. The most active compound 5l displayed significant inhibition of migration ability of cancer cells and blocked G1/S phase transition in cell cycle. Compound 5l caused pronounced effect in expression patterns of various key cell cycle regulatory proteins; up-regulation of apoptotic proteins, Bax, Caspase 3 and p53, and down-regulation of apoptosis-inhibiting proteins, BcL-xL, Cyclin D1, Cyclin E1 and NF-κB, which indicates high efficiency of the molecule 5l in apoptosis-signal axis interfering potential. Cheminformatics analysis revealed that 2,3-diaryl-pyridopyrimidin-4-imine/ones occupy a distinctive drug-relevant chemical space that is seldom represented by natural products and good physicochemical, ADMET and pharmacokinetic-relevant profile. Together, the anticancer potential of the investigated analogs was found to be much more efficient compared to the original natural products and two anticancer drugs, Etoposide (hTopo-II inhibitor) and 5-Flurouracile (5-FU).

Benzimidazole‐Containing Compounds as Anticancer Agents

AbstractCancer is the second leading cause of death today and remains a threat to human health. The advent of multi‐drug resistance and adverse effects make the current first‐line anti‐cancer medicines inadequate, despite the fact that numerous efforts have been made in the field of cancer therapy and significant progress has been made in the diagnosis and treatment of cancer. Consequently, the development of novel anticancer drugs with high activity and minimal toxicity is imperative. The benzimidazole ring has attracted the attention of medicinal chemists due to its medicinal and pharmacological properties. The heterocyclic pharmacophore of benzimidazole is a crucial scaffold for developing pharmaceuticals and drugs. In this review, we summarized the recent progress of benzimidazole as a privileged scaffold for the discovery of anti‐cancer agents based on biological targets, such as VEGFR (Vascular Endothelial Growth Factor), PI3 K inhibitors (Phosphoinositide 3‐kinase), EGFR kinase inhibitors (Epidermal Growth Factor Receptor), PARPs (Poly ADP‐ribose polymerases), Tubulin Polymerization, HAT/HDAC (histone acetylase/histone deacetylase), SphK1 (Sphingosine kinase‐1 inhibitors), aromatase, carbonic anhydrase, and topoisomerase inhibitors. The last 5 years of literature have been reviewed and relevant studies have been summarized in this review.

Thiostrepton induces spindle abnormalities and enhances Taxol cytotoxicity in MDA-MB-231 cells

BackgroundThiostrepton (TST) is a known inhibitor of the transcription factor Forkhead box M1 (FoxM1) and inducer of heat shock response (HSR) and autophagy. TST thus may be one potential candidate of anticancer drugs for combination chemotherapy.Methods and ResultsImmunofluorescence staining of mitotic spindles and flow cytometry analysis revealed that TST induces mitotic spindle abnormalities, mitotic arrest, and apoptotic cell death in the MDA-MB-231 triple-negative breast cancer cell line. Interestingly, overexpression or depletion of FoxM1 in MDA-MB-231 cells did not affect TST induction of spindle abnormalities; however, TST-induced spindle defects were enhanced by inhibition of HSP70 or autophagy. Moreover, TST exhibited low affinity for tubulin and only slightly inhibited in vitro tubulin polymerization, but it severely impeded tubulin polymerization and destabilized microtubules in arrested mitotic MDA-MB-231 cells. Additionally, TST significantly enhanced Taxol cytotoxicity. TST also caused cytotoxicity and spindle abnormalities in a Taxol-resistant cell line, MDA-MB-231-T4R.ConclusionsThese results suggest that, in addition to inhibiting FoxM1, TST may induce proteotoxicity and autophagy to disrupt cellular tubulin polymerization, and this mechanism might account for its antimitotic effects, enhancement of Taxol anticancer effects, and ability to overcome Taxol resistance in MDA-MB-231 cells. These data further imply that TST may be useful to improve the therapeutic efficacy of Taxol.