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Microtubules are pivotal in diverse cellular functions encompassing cell signaling, morphology, intracellular trafficking, and cell mitosis/division. They are validated targets for disease treatment, notably hematological cancers and solid tumors. Microtubule‐targeting agents (MTAs) exert their effects by modulating microtubule dynamics, impeding cell proliferation, and promoting cell death. Recent advances in structural biology have unveiled novel perspectives for investigating multiple binding sites and mechanisms of action used by MTAs. In this review, we first provide an overview of the intricate structure and dynamics of microtubules. Then we explore the seven binding sites and the three primary strategies (stabilization, destabilization, and degradation) harnessed by MTAs. Furthermore, we introduce the emerging domain of microtubule‐targeting degraders, exemplified by PROteolysis TArgeting Chimeras and small‐molecule degraders, which enable precise degradation of specific microtubule‐associated proteins implicated in cancer pathogenesis. Additionally, we discuss the promising realm of precision‐targeted approaches, including antibody–drug conjugates and the utilization of photopharmacology in MTAs. Lastly, we provide a comprehensive overview of the clinical applications of microtubule‐targeting therapies, assessing their efficacy and current challenges. We aim to provide a global picture of MTAs development as well as insights into the microtubule‐targeting drug discovery for cancer treatment.

Microtubule‐targeting agents represent one of the most successful classes of anticancer agents. However, the development of drug resistance and the appearance of adverse effects hamper their clinical implementation. Novel microtubule‐targeting agents without such limitations are urgently needed. By employing a gene expression‐based drug repositioning strategy, this study identifies VU‐0365114, originally synthesized as a positive allosteric modulator of human muscarinic acetylcholine receptor M5 (M5 mAChR), as a novel type of tubulin inhibitor by destabilizing microtubules. VU‐0365114 exhibits a broad‐spectrum in vitro anticancer activity, especially in colorectal cancer cells. A tumor xenograft study in nude mice shows that VU‐0365114 slowed the in vivo colorectal tumor growth. The anticancer activity of VU‐0365114 is not related to its original target, M5 mAChR. In addition, VU‐0365114 does not serve as a substrate of multidrug resistance (MDR) proteins, and thus, it can overcome MDR. Furthermore, a kinome analysis shows that VU‐0365114 did not exhibit other significant off‐target effects. Taken together, our study suggests that VU‐0365114 primarily targets microtubules, offering potential for repurposing in cancer treatment, although more studies are needed before further drug development. Microtubule‐targeting agents combat cancer, but resistance and adverse effects hinder their use. Employing gene expression‐based repositioning, we identified VU‐0365114 as a microtubule‐destabilizing agent. It shows broad‐spectrum anticancer activity, particularly in colorectal cancer cells. VU‐0365114 overcomes multidrug resistance (MDR) and lacks significant off‐target effects. Repurposing VU‐0365114 holds promise for cancer treatment and resistance reversal.

ABSTRACT v‐Src oncogene causes cell transformation through its strong tyrosine kinase activity. We have revealed that v‐Src‐mediated cell transformation occurs at a low frequency and it is attributed to mitotic abnormalities‐mediated chromosome instability. v‐Src directly phosphorylates Tyr‐15 of cyclin‐dependent kinase 1 (CDK1), thereby causing mitotic slippage and reduction in Eg5 inhibitor cytotoxicity. However, it is not clear whether v‐Src modifies cytotoxicities of the other anticancer drugs targeting cell division. In this study, we found that v‐Src restores cancer cell viability reduced by various microtubule‐targeting agents (MTAs), although v‐Src does not alter cytotoxicity of DNA‐damaging anticancer drugs. v‐Src causes mitotic slippage of MTAs‐treated cells, consequently generating proliferating tetraploid cells. We further demonstrate that v‐Src also restores cell viability reduced by a polo‐like kinase 1 (PLK1) inhibitor. Interestingly, treatment with Aurora kinase inhibitor strongly induces cell death when cells express v‐Src. These results suggest that the v‐Src modifies cytotoxicities of anticancer drugs targeting cell division. Highly activated Src‐induced resistance to MTAs through mitotic slippage might have a risk to enhance the malignancy of cancer cells through the increase in chromosome instability upon chemotherapy using MTAs.

Kinesin family member 20B (KIF20B, also known as MPHOSPH1) is a kinesin protein that plays a critical role in cytokinesis. Previously, we and others have demonstrated the oncogenic role of KIF20B in several cancers; however, the exact mechanisms underlying its tumorigenic effects remain unclear. Herein, we showed overexpression of KIF20B in human hepatocellular carcinoma (HCC) and reported a negative correlation between KIF20B level and prognosis of patients. Mechanistically, reducing KIF20B blockades mitotic exit of HCC cells at telophase in a spindle assembly checkpoint independent way. Importantly, reducing KIF20B acts synergistically with three microtubule‐associated agents (MTA) to p53‐ or p14ARF‐dependently suppress p53‐wt or p53‐null HCC cells. In addition to taxol, reducing KIF20B also enhanced the toxicity of two chemotherapeutic drugs, hydroxycamptothecin and mitomycin C. In conclusion, we found a novel mechanism in that blocking cytokinesis by KIF20B inhibition increases the efficacy of MTA; our results thus suggested a dual‐mitotic suppression approach against HCC by combining MTA with KIF20B inhibition, which simultaneously blocks mitosis at both metaphase and telophase. We found a novel mechanism in that blocking cytokinesis by MPHOSPH1 inhibition increases the efficacy of MTA. Based on this finding, we proposed and validated an effective dual‐mitotic suppression strategy against HCC by combining antimitotic drugs with cytokinesis inhibition, which blocks mitosis at both metaphase and telophase. Moreover, our work raised the possibility that proteins essential for cytokinesis may be considered as potential targets for cancer therapy, especially against SAC‐insensitive cancers.

It is over 50 years since the discovery of microtubules, and they have become one of the most important drug targets for anti-cancer therapies. Microtubules are predominantly composed of the protein tubulin, which contains a number of different binding sites for small-molecule drugs. There is continued interest in drug development for compounds targeting the colchicine-binding site of tubulin, termed colchicine-binding site inhibitors (CBSIs). This review highlights CBSIs discovered through diverse sources: from natural compounds, rational design, serendipitously and via high-throughput screening. We provide an update on CBSIs reported in the past three years and discuss the clinical status of CBSIs. It is likely that efforts will continue to develop CBSIs for a diverse set of cancers, and this review provides a timely update on recent developments.

Cancer, one of the leading illnesses, accounts for about 10 million deaths worldwide. The treatment of cancer includes surgery, chemotherapy, radiation therapy, and drug therapy, along with others, which not only put a tremendous economic effect on patients but also develop drug resistance in patients with time. A significant number of cancer cases can be prevented/treated by implementing evidence-based preventive strategies. Plant-based drugs have evolved as promising preventive chemo options both in developing and developed nations. The secondary plant metabolites such as alkaloids have proven efficacy and acceptability for cancer treatment. Apropos, this review deals with a spectrum of promising alkaloids such as colchicine, vinblastine, vincristine, vindesine, vinorelbine, and vincamine within different domains of comprehensive information on these molecules such as their medical applications (contemporary/traditional), mechanism of antitumor action, and potential scale-up biotechnological studies on an in-vitro scale. The comprehensive information provided in the review will be a valuable resource to develop an effective, affordable, and cost effective cancer management program using these alkaloids.

Plants are an important source of chemically diverse natural products that target microtubules, one of the most successful targets in cancer therapy. Colchicine, paclitaxel, and vinca alkaloids are the earliest plant-derived microtubule-targeting agents (MTAs), and paclitaxel and vinca alkaloids are currently important drugs used in the treatment of cancer. Several additional plant-derived compounds that act on microtubules with improved anticancer activity are at varying stages of development. Here, we move beyond the well-discussed paclitaxel and vinca alkaloids to present other promising plant-derived MTAs with potential for development as anticancer agents. Various biological and biochemical aspects are discussed. We hope that the review will provide guidance for further exploration and identification of more effective, novel MTAs derived from plant sources.

The paradigm that microtubule-targeting agents (MTAs) cause cell death via mitotic arrest applies to rapidly dividing cells but cannot explain MTA activity in slowly growing human cancers. Many preferred cancer regimens combine a MTA with a DNA-damaging agent (DDA). We hypothesized that MTAs synergize with DDAs by interfering with trafficking of DNA repair proteins on interphase microtubules. We investigated nine proteins involved in DNA repair: ATM, ATR, DNA-PK, Rad50, Mre11, p95/NBS1, p53, 53BP1, and p63. The proteins were sequestered in the cytoplasm by vincristine and paclitaxel but not by an aurora kinase inhibitor, colocalized with tubulin by confocal microscopy and coimmunoprecipitated with the microtubule motor dynein. Furthermore, adding MTAs to radiation, doxorubicin, or etoposide led to more sustained γ-H2AX levels. We conclude DNA damage-repair proteins traffic on microtubules and addition of MTAs sequesters them in the cytoplasm, explaining why MTA/DDA combinations are common anticancer regimens. Significance Drugs targeting microtubules are among the most active anticancer agents. In vitro and in preclinical models, these agents are said to interfere with mitosis. However human tumors divide too slowly for this paradigm to apply, evidenced by the failure of over a dozen well-designed antimitotic agents targeting the aurora kinases and kinesin spindle protein that had minimal antitumor activity but caused severe bone marrow suppression. We have proposed that microtubule-targeting agents interfere with the trafficking of critical proteins in interphase microtubules. If true, then one must identify critical proteins whose traffic on microtubules is impacted. We identify nine DNA repair proteins that traffic on microtubules, explaining why combinations of a microtubule-targeting agent and a DNA-damaging agent are frequently used in cancer therapy.

Significance Microtubules are dynamic protein filaments assembled from tubulin subunits, which play a key role for cell division. Ligands that target microtubules and affect their dynamics belong to the most successful classes of chemotherapeutic drugs against cancer by inhibiting cell proliferation. Here we have analyzed three structurally unrelated drugs that destabilize microtubules, using X-ray crystallography. The data reveal a new tubulin-binding site for these drugs, which renders their mechanism of action distinct from that of other types of microtubule assembly inhibitors. Similar key interactions with tubulin are observed for all three ligands, thus defining a common pharmacophore. Our results offer an opportunity for the rational design of potent tubulin modulators for the development of more efficient cancer therapies. The recent success of antibody–drug conjugates (ADCs) in the treatment of cancer has led to a revived interest in microtubule-destabilizing agents. Here, we determined the high-resolution crystal structure of the complex between tubulin and maytansine, which is part of an ADC that is approved by the US Food and Drug Administration (FDA) for the treatment of advanced breast cancer. We found that the drug binds to a site on β-tubulin that is distinct from the vinca domain and that blocks the formation of longitudinal tubulin interactions in microtubules. We also solved crystal structures of tubulin in complex with both a variant of rhizoxin and the phase 1 drug PM060184. Consistent with biochemical and mutagenesis data, we found that the two compounds bound to the same site as maytansine and that the structures revealed a common pharmacophore for the three ligands. Our results delineate a distinct molecular mechanism of action for the inhibition of microtubule assembly by clinically relevant agents. They further provide a structural basis for the rational design of potent microtubule-destabilizing agents, thus opening opportunities for the development of next-generation ADCs for the treatment of cancer.

Microtubules (MTs), highly dynamic structures composed of α- and β-tubulin heterodimers, are involved in cell movement and intracellular traffic and are essential for cell division. Within the cell, MTs are not uniform as they can be composed of different tubulin isotypes that are post-translationally modified and interact with different microtubule-associated proteins (MAPs). These diverse intrinsic factors influence the dynamics of MTs. Extrinsic factors such as microtubule-targeting agents (MTAs) can also affect MT dynamics. MTAs can be divided into two main categories: microtubule-stabilizing agents (MSAs) and microtubule-destabilizing agents (MDAs). Thus, the MT skeleton is an important target for anticancer therapy. This review discusses factors that determine the microtubule dynamics in normal and cancer cells and describes microtubule–MTA interactions, highlighting the importance of tubulin isoform diversity and post-translational modifications in MTA responses and the consequences of such a phenomenon, including drug resistance development.