Microtubule-binding agents: a dynamic field of cancer therapeutics

Microtubule-Targeting Combined with HDAC Inhibition Is a Novel Therapeutic Strategy for Diffuse Intrinsic Pontine Gliomas

Diffuse intrinsic pontine gliomas (DIPG) are an incurable childhood brain cancer for which novel treatments are needed. DIPGs are characterized by a mutation in the H3 histone (H3K27M), resulting in loss of H3K27 methylation and global gene dysregulation. TRX-E-009-1 is a novel anticancer agent with preclinical activity demonstrated against a range of cancers. We examined the antitumor activity of TRX-E-009-1 against DIPG neurosphere cultures and observed tumor-specific activity with IC50s ranging from 20 to 100 nmol/L, whereas no activity was observed against normal human astrocyte cells. TRX-E-009-1 exerted its anti-proliferative effect through the induction of apoptotic pathways, with marked increases in cleaved caspase 3 and cleaved PARP levels, while also restoring histone H3K27me3 methylation. Co-administration of TRX-E-009-1 and the histone deacetylase (HDAC) inhibitor SAHA extended survival in DIPG orthotopic animal models. This antitumor effect was further enhanced with irradiation. Our findings indicate that TRX-E-009-1, combined with HDAC inhibition, represents a novel, potent therapy for children with DIPG.

Design, synthesis and evaluation of dihydro-1H-indene derivatives as novel tubulin polymerisation inhibitors with anti-angiogenic and antitumor potency

Angiogenesis plays an important role in tumour generation and progression, which is used to supply nutrients and metastasis. Herein, a series of novel dihydro-1H-indene derivatives were designed and evaluated as tubulin polymerisation inhibitors by binding to colchicine site, exhibiting anti-angiogenic activities against new vessel forming. Through structure-activity relationships study, compound 12d was found to be the most potent derivative possessing the antiproliferative activity against four cancer lines with IC50 values among 0.028-0.087 µM. Compound 12d bound to colchicine site on tubulin and inhibited tubulin polymerisation in vitro. In addition, compound 12d induced cell cycle arrest at G2/M phase, stimulated cell apoptosis, inhibited tumour metastasis and angiogenesis. Finally, the results of in vivo assay suggested that compound 12d could prevent tumour generation, inhibit tumour proliferation and angiogenesis without obvious toxicity. Collectively, all these findings suggested that compound 12d is a novel tubulin polymerisation inhibitor deserving further research.

Ki67 and prostate specific antigen are prognostic in metastatic hormone naïve prostate cancer

BACKGROUND

For metastatic hormone naïve prostate cancer patients, androgen deprivation therapy (ADT) with escalation therapy including docetaxel and/or androgen targeting drugs is the standard therapy. However, de-escalation is preferable to avoid unnecessary side effects, especially from docetaxel, but markers to identify these patients are lacking. The purpose of the present study was to investigate the potential of PSA and Ki67 immunoreactive scores as prognostic and treatment-predictive markers.

MATERIAL AND METHODS

Prostate biopsies from 92 patients with metastatic hormone naïve PC (PSA > 80 ng/mL or clinical metastases) were immunohistochemically evaluated for PSA and Ki67. Gene expression analysis was performed with Clariom D microarrays to identify the phenotypic profile associated with the immunohistochemistry scores of biopsies. Cox regression analysis for progression free survival after ADT adjustment for age, ISUP, and serum PSA and Kaplan-Meier analyses were performed to assess prognostic values of Ki67, PSA, and the Ki67/PSA ratio.

RESULTS

The immunohistochemical score for PSA was the strongest prognostic factor for progression-free and overall survival after ADT. Consequently, the ratio between Ki67 and PSA displayed a stronger prognostic value than Ki67 itself. Further, mRNA expression data analysis showed an association between high Ki67/PSA ratio, cell-cycle regulation, and DNA damage repair. In an exploratory sub-analysis of 12 patients treated with early docetaxel as addition to ADT and matched controls, a high Ki67/PSA ratio showed potential to identify those who benefit from docetaxel.

CONCLUSION

PSA and Ki67 immunoreactive scores are prognostic in the metastatic hormone-sensitive setting, with PSA being superior. The combination of Ki67 and PSA did not give additional prognostic value. The results suggest immunohistochemical scoring of PSA to have potential to improve identification of patients responding well to ADT alone.

Guanidine-modified albumin-MMAE conjugates with enhanced endocytosis ability

Aiming to address the insufficient endocytosis ability of traditional albumin drug conjugates, this paper reports elegant guanidine modification to improve efficacy for the first time. A series of modified albumin drug conjugates were designed and synthesized with different structures, including guanidine (GA), biguanides (BGA) and phenyl (BA), and different quantities of modifications. Then, the endocytosis ability and in vitro/vivo potency of albumin drug conjugates were systematically studied. Finally, a preferred conjugate A4 was screened, which contained 15 BGA modifications. Conjugate A4 maintains spatial stability similar to that of the unmodified conjugate AVM and could significantly enhance endocytosis ability (p*** = 0.0009) compared with the unmodified conjugate AVM. Additionally, the in vitro potency of conjugate A4 (EC50 = 71.78 nmol in SKOV3 cells) was greatly enhanced (approximately 4 times) compared with that of the unmodified conjugate AVM (EC50 = 286.00 nmol in SKOV3 cells). The in vivo efficacy of conjugate A4 completely eliminated 50% of tumors at 33 mg/kg, which was significantly better than the efficacy of conjugate AVM at the same dose (P** = 0.0026). In addition, theranostic albumin drug conjugate A8 was designed to intuitively realize drug release and maintain antitumor activity similar to conjugate A4. In summary, the guanidine modification strategy could provide new ideas for the development of new generational albumin drug conjugates.

Modulation of taxane binding to tubulin curved and straight conformations by systematic 3'N modification provides for improved microtubule binding, persistent cytotoxicity and in vivo potency

The taxane class of microtubule stabilizers are some of the most effective and widely used chemotherapeutics. The anticancer activity of taxanes arises from their ability to induce tubulin assembly by selectively recognizing the curved (c-) conformation in unassembled tubulin as compared to the straight (s-) conformation in assembled tubulin. We first designed and synthesized a series of 3'N-modified taxanes bearing covalent groups. Instead of discovering covalent taxanes, we found a series of non-covalent taxanes 2, in which the 3'N side chain was found to be essential for cytotoxicity due to its role in locking tubulin in the s-conformation. A representative compound bearing an acrylamide moiety (2h) exhibited increased binding affinity to the unassembled tubulin c-conformation and less cytotoxicity than paclitaxel. Further exploration of chemical space around 2h afforded a new series 3, in which derivatives such as 3l bind more tightly to both the s- and c-conformations of tubulin compared to paclitaxel, leading to more efficient promotion of tubulin polymerization and a greater persistence of in vitro efficacy against breast cancer cells after drug washout. Although 3l also had improved in vivo potency as compared to paclitaxel, it was also associated with increased systemic toxicity that required localized, intratumoral injection to observe potent and prolonged antitumor efficacy.

Design, synthesis and bioevaluation of novel trifluoromethylquinoline derivatives as tubulin polymerization inhibitors

Aim: A series of novel trifluoromethylquinoline derivatives were designed, synthesized and evaluated for antitumor activities. Methodology: All compounds were evaluated for antiproliferative activity against four human cancer cell lines. Results: Among them, 5a, 5m, 5o and 6b exhibited remarkable antiproliferative activities against all the tested cell lines at nanomolar concentrations. Mechanism of action studies demonstrated that 6b targeted the colchicine binding site, potentially inhibiting tubulin polymerization, and further studies indicated that 6b could arrest LNCaP cells in the G2/M phase and induce cell apoptosis. Molecular docking confirmed that 6b could bind to the colchicine binding site. Conclusion: Results suggested that 6b could serve as a promising lead compound for the development of novel tubulin polymerization inhibitors and cancer therapy.

Development of tubulin polymerization inhibitors as anticancer agents

INTRODUCTION

Microtubules are intracellular, filamentous, polymeric structures that extend throughout the cytoplasm, composed of α-tubulin and β-tubulin subunits. They regulate many cellular functions including cell polarity, cell shape, mitosis, intracellular transport, cell signaling, gene expression, cell integrity, and are associated with tumorigenesis. Inhibition of tubulin polymerization within tumor cells represents a crucial focus in the pursuit of developing anticancer treatments.

AREAS COVERED

This review focuses on the natural product and their synthetic congeners as tubulin inhibitors along with their site of interaction on tubulin. This review also covers the developed novel tubulin inhibitors and important patents focusing on the development of tubulin inhibition for cancer treatment reported from 2018 to 2023. The scientific and patent literature has been searched on PubMed, Espacenet, ScienceDirect, and Patent Guru from 2018-2023.

EXPERT OPINION

Tubulin is one of the promising targets explored extensively for drug discovery. Compounds binding in the colchicine site could be given importance because they can elude resistance mediated by the P-glycoprotein efflux pump and no colchicine site binding inhibitor is approved by FDA so far. The research on the development of antibody drug conjugates (ADCs) for tubluin polymerization inhibition could be significant strategy for cancer treatment.

Understanding the promising role of antibody drug conjugates in breast and ovarian cancer

A nascent category of anticancer therapeutic drugs called antibody-drug conjugates (ADCs) relate selectivity of aimed therapy using chemotherapeutic medicines with high cytotoxic power. Progressive linker technology led to the advancement of more efficacious and safer treatments. It offers neoteric as well as encouraging therapeutic strategies for treating cancer. ADCs selectively administer a medication by targeting antigens which are abundantly articulated on the membrane surface of tumor cells. Tumor-specific antigens are differently expressed in breast and ovarian cancers and can be utilized to direct ADCs. Compared to conventional chemotherapeutic drugs, this approach enables optimal tumor targeting while minimizing systemic damage. A cleavable linker improves the ADCs because it allows the toxic payload to be distributed to nearby cells that do not express the target protein, operating on assorted tumors with dissimilar cell aggregation. Presently fifteen ADCs are being studied in breast and ovarian carcinoma preclinically, and assortment of few have already undergone promising early-phase clinical trial testing. Furthermore, Phase I and II studies are investigating a wide variety of ADCs, and preliminary findings are encouraging. An expanding sum of ADCs will probably become feasible therapeutic choices as solo agents or in conjunction with chemotherapeutic agents. This review accentuates the most recent preclinical findings, pharmacodynamics, and upcoming applications of ADCs in breast and ovarian carcinoma.

Unlocking Colchicine's Untapped Potential: A Paradigm Shift in Hepatocellular Carcinoma Prevention

Background: Liver cancer and notably hepatocellular carcinoma (HCC), results in significantly high mortality rates worldwide. Chronic hepatitis and fatty liver, recognized precursors, underscore the imperative need for effective preventive strategies. This study explores colchicine, traditionally acknowledged for its anti-inflammatory properties and investigates its potential in liver cancer prevention. Methods: Utilizing the iHi Data Platform of China Medical University Hospital, Taiwan, this study analyzed two decades of medical data, incorporating 10,353 patients each in the Colchicine and Non-Colchicine cohorts, to investigate the association between colchicine use and liver cancer risk. Results: The study identified that colchicine users exhibited a 19% reduction in liver cancer risk, with a multivariable-adjusted odds ratio of 0.81 after accounting for confounding variables. Additionally, the influence of gender and comorbidities like diabetes mellitus on liver cancer risk was identified, corroborating the existing literature. A notable finding was that the prolonged use of colchicine was associated with improved outcomes, indicating a potential dose-response relationship. Conclusions: This study proposes a potential new role for colchicine in liver cancer prevention, extending beyond its established anti-inflammatory applications. While the findings are promising, further research is essential to validate these results. This research may serve as a foundation for future studies, aiming to further explore colchicine's role via clinical trials and in-depth investigations, potentially impacting preventive strategies for liver cancer.

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.

Design, Synthesis, and Biological Evaluation of SSE1806, a Microtubule Destabilizer That Overcomes Multidrug Resistance

Microtubules are dynamic structures that form spindle fibers during cell division; pharmacological inhibition of microtubule dynamics arrests cells in mitosis, leading to apoptosis, and they have been extensively used to treat various cancers. However, the efficacy of such drugs is often limited by multidrug resistance. This study synthesized and evaluated 30 novel derivatives of podophyllotoxin, a natural antimitotic compound, for their antiproliferative activities. Compound SSE1806 exhibited the most potent antiproliferative activity with GI50 values ranging from 1.29 ± 0.01 to 21.15 ± 2.1 μM in cancer cell lines of different origins; it directly inhibited microtubule polymerization, causing aberrant mitosis and G2/M arrest. Prolonged treatment with SSE1806 increased p53 expression, induced cell death in monolayer cultures, and reduced the growth of mouse- and patient-derived human colon cancer organoids. Importantly, SSE1806 overcame multidrug resistance in a cell line overexpressing MDR-1. Thus, SSE1806 represents a potential anticancer agent that can overcome multidrug resistance.

Design, synthesis and biological evaluation of tetrahydroquinoxaline sulfonamide derivatives as colchicine binding site inhibitors

Colchicine binding site inhibitors (CBSIs) are potential microtubule targeting agents (MTAs), which can overcome multidrug resistance, improve aqueous solubility and reduce toxicity faced by most MTAs. Novel tetrahydroquinoxaline sulfonamide derivatives were designed, synthesized and evaluated for their antiproliferative activities. The MTT assay results demonstrated that some derivatives exhibited moderate to strong inhibitory activities against HT-29 cell line. Among them, compound I-7 was the most active compound. Moreover, I-7 inhibited tubulin polymerization, disturbed microtubule network, disrupted the formation of mitotic spindle and arrested cell cycle at G2/M phase. However, I-7 didn't induce cell apoptosis. Furthermore, the prediction of ADME demonstrated that I-7 showed favorable physiochemical and pharmacokinetic properties. And the detailed molecular docking confirmed I-7 targeted the site of colchicine through hydrogen and hydrophobic interactions.

Special Issue "Novel Anti-Proliferative Agents"

Cancer is a disease that can affect any organ and spread to other nearby or distant organs [...].

Biological evaluation of [4-(4-aminophenyl)-1-(4-fluorophenyl)-1H-pyrrol-3-yl](3,4,5-trimethoxyphenyl)methanone as potential antineoplastic agent in 2D and 3D breast cancer models

Targeting tubulin polymerization and depolymerization represents a promising approach to treat solid tumors. In this study, we investigated the molecular mechanisms underlying the anticancer effects of a structurally novel tubulin inhibitor, [4-(4-aminophenyl)-1-(4-fluorophenyl)-1H-pyrrol-3-yl](3,4,5-trimethoxyphenyl)methanone (ARDAP), in two- and three-dimensional MCF-7 breast cancer models. At sub-cytotoxic concentrations, ARDAP showed a marked decrease in cell proliferation, colony formation, and ATP intracellular content in MCF-7 cells, by acting through a cytostatic mechanism. Additionally, drug exposure caused blockage of the epithelial-to-mesenchymal transition (EMT). In 3D cell culture, ARDAP negatively affected tumor spheroid growth, with inhibition of spheroid formation and reduction of ATP concentration levels. Notably, ARDAP exposure promoted the differentiation of MCF-7 cells by inducing: (i) expression decrease of Oct4 and Sox2 stemness markers, both in 2D and 3D models, and (ii) downregulation of the stem cell surface marker CD133 in 2D cell cultures. Interestingly, treated MCF7 cells displayed a major sensitivity to cytotoxic effects of the conventional chemotherapeutic drug doxorubicin. In addition, although exhibiting growth inhibitory effects against breast cancer cells, ARDAP showed insignificant harm to MCF10A healthy cells. Collectively, our results highlight the potential of ARDAP to emerge as a new chemotherapeutic agent or adjuvant compound in chemotherapeutic treatments.

Antibody-drug conjugates: Recent advances in payloads

Antibody‒drug conjugates (ADCs), which combine the advantages of monoclonal antibodies with precise targeting and payloads with efficient killing, show great clinical therapeutic value. The ADCs' payloads play a key role in determining the efficacy of ADC drugs and thus have attracted great attention in the field. An ideal ADC payload should possess sufficient toxicity, low immunogenicity, high stability, and modifiable functional groups. Common ADC payloads include tubulin inhibitors and DNA damaging agents, with tubulin inhibitors accounting for more than half of the ADC drugs in clinical development. However, due to clinical limitations of traditional ADC payloads, such as inadequate efficacy and the development of acquired drug resistance, novel highly efficient payloads with diverse targets and reduced side effects are being developed. This perspective summarizes the recent research advances of traditional and novel ADC payloads with main focuses on the structure-activity relationship studies, co-crystal structures, and designing strategies, and further discusses the future research directions of ADC payloads. This review also aims to provide valuable references and future directions for the development of novel ADC payloads that will have high efficacy, low toxicity, adequate stability, and abilities to overcome drug resistance.

Tubulin degradation: Principles, agents, and applications

The microtubule system plays an important role in the mitosis and growth of eukaryotic cells, and it is considered as an appealing and highly successful molecular target for cancer treatment. In fact, microtubule targeting agents, such as paclitaxel and vinblastine, have been approved by FDA for tumor therapy, which have achieved significant therapeutic effects and sales performance. At present, microtubule targeting agents mainly include microtubule-destabilizing agents, microtubule-stabilizing agents, and a few tubulin degradation agents. Although there are few reports about tubulin degradation agents at present, tubulin degradation agents show great potential in overcoming multidrug resistance and reducing neurotoxicity. In addition, some natural drugs could specifically degrade tubulin in tumor cells, but have no effect in normal cells, thus showing a good biosafety profile. Therefore, tubulin degradation agents might exhibit a better application. Currently, some small molecules have been designed to promote tubulin degradation with potent antiproliferative activities, showing the potential for cancer treatment. In this work, we reviewed the reports on tubulin degradation, and focused on the degradation mechanism and important functional groups of chemically synthesized compounds, hoping to provide help for the degradation design of tubulin.

On the Simulation of Thermal Isomerization of Molecular Photoswitches in Biological Systems

Molecular photoswitches offer precise, reversible photocontrol over biomolecular functions and are promising light-regulated drug candidates with minimal side effects. Quantifying thermal isomerization rates of photoswitches in their target biomolecules is essential for fine-tuning their light-controlled drug activity. However, the effects of protein binding on isomerization kinetics remain poorly understood, and simulations are crucial for filling this gap. Challenges in the simulation include describing multireference electronic structures near transition states, disentangling competing reaction pathways, and sampling protein-ligand interactions. To overcome these challenges, we used multiscale simulations to characterize the thermal isomerization of photostatins (PSTs), which are light-regulated microtubule inhibitors for potential cancer phototherapy. We employed a new ab initio multireference electronic structure method in a quantum mechanics/molecular mechanics setting and combined it with enhanced sampling techniques to characterize the cis to trans free-energy profiles of three PSTs in a vacuum, aqueous solution, and tubulin dimer. The significant advantage of our novel approach is the efficient treatment of the multireference character in PSTs' electronic wavefunction throughout the conformational sampling of protein-ligand interactions along their isomerization pathways. We also benchmarked our calculations using high-level ab initio multireference electronic structure methods and explored the competing isomerization pathways. Notably, calculations in a vacuum and implicit solvent models cannot predict the order of the PSTs' thermal half-lives in the aqueous solution observed in the experiment. Only by explicitly treating the solvent molecules can the correct order of isomerization kinetics be reproduced. Protein binding perturbs free-energy barriers due to hydrogen bonding between PSTs and nearby polar residues. Our work generates comprehensive, high-quality benchmark data and offers guidance for selecting computational methods to study the thermal isomerization of photoswitches. Ab initio multireference free-energy calculations in explicit molecular environments are crucial for predicting the effects of substituents on the thermal half-lives of photoswitches in biological systems.

Laxiflorin B covalently binds the tubulin colchicine-binding site to inhibit triple negative breast cancer proliferation and induce apoptosis

Laxiflorin B is a natural ent-kaurane diterpenoid that can be isolated from the leaves of the Isodon eriocalyx var. laxiflora, a perennial shrub native to parts of China. While this compound has potent cytotoxic activity against various tumor cells, the anti-tumor targets and molecular mechanisms of Laxiflorin B are unclear. Here, we show that Laxiflorin B exhibits strong antiproliferative and proapoptotic effects on triple-negative breast cancer (TNBC) cells. At the mechanistic level, we show that β-tubulin (TUBB) is a cellular target of Laxiflorin B. By covalently binding the Cys239 and C354 residues of the TUBB colchicine-binding site, Laxiflorin B disturbs microtubule integrity and structure in vitro and in vivo. Cytotoxicity analyses also showed that the α, β-unsaturated carbonyl in the D ring of Laxiflorin B is responsible for mediating its covalent binding and anti-tumor activity. To assess the therapeutic effects of Laxiflorin B, we synthesized a Laxiflorin B-ALA pro-drug and delivered it by intraperitoneal injection (10 mg/kg) into a 4T1 orthotopic tumor mouse model. Drug treatment had anti-tumor effects without inducing notable weight loss or organ dysfunction. We conclude that Laxiflorin B is a promising colchicine binding site inhibitor that might be exploited in the context of TNBC treatment in the future.

2-Methoxyestradiol as an Antiproliferative Agent for Long-Term Estrogen-Deprived Breast Cancer Cells

To identify effective treatment modalities for breast cancer with acquired resistance, we first compared the responsiveness of estrogen receptor-positive breast cancer MCF-7 cells and long-term estrogen-deprived (LTED) cells (a cell model of endocrine therapy-resistant breast cancer) derived from MCF-7 cells to G-1 and 2-methoxyestradiol (2-MeO-E2), which are microtubule-destabilizing agents and agonists of the G protein-coupled estrogen receptor 1 (GPER1). The expression of GPER1 in LTED cells was low (~0.44-fold), and LTED cells displayed approximately 1.5-fold faster proliferation than MCF-7 cells. Although G-1 induced comparable antiproliferative effects on both MCF-7 and LTED cells (IC50 values of >10 µM), 2-MeO-E2 exerted antiproliferative effects selective for LTED cells with an IC50 value of 0.93 μM (vs. 6.79 μM for MCF-7 cells) and induced G2/M cell cycle arrest. Moreover, we detected higher amounts of β-tubulin proteins in LTED cells than in MCF-7 cells. Among the β-tubulin (TUBB) isotype genes, the highest expression of TUBB2B (~3.2-fold) was detected in LTED cells compared to that in MCF-7 cells. Additionally, siTUBB2B restores 2-MeO-E2-mediated inhibition of LTED cell proliferation. Other microtubule-targeting agents, i.e., paclitaxel, nocodazole, and colchicine, were not selective for LTED cells. Therefore, 2-MeO-E2 can be an antiproliferative agent to suppress LTED cell proliferation.

Discovery of chiral 1,4-diarylazetidin-2-one-based hydroxamic acid derivatives as novel tubulin polymerization inhibitors with histone deacetylase inhibitory activity

Tubulin and histone deacetylase have been clinically proven as promising targets for cancer therapy. Herein, we describe the design and synthesis of chiral 1,4-diarylazetidin-2-one-based hydroxamic acids as novel tubulin/HDAC dual inhibitors. Among them, compound 12a was validated to effectively disrupt tubulin polymerization, and exhibited potent HDAC1/8 inhibitory activities. Meanwhile, 12a showed good antiproliferative activities against four tumor cell lines. Further studies showed 12a works through blocking cellular cycle, inducing apoptosis and inhibiting colony formation. In addition, 12a has suitable physicochemical properties and high liver microsomal metabolic stability. Importantly, compound 12a was found to exhibit significant antitumor efficacy in vivo, thus warranting it as a promising tubulin/HDAC dual inhibitor for further development.

Antiproliferative and Antimetastatic Properties of 16-Azidomethyl Substituted 3-O-Benzyl Estrone Analogs

Four diastereomers of 16-azidomethyl substituted 3-O-benzyl estradiol (1-4) and their two estrone analogs (16AABE and 16BABE) were tested for their antiproliferative properties against human gynecological cancer cell lines. The estrones were selected for additional experiments based on their outstanding cell growth-inhibiting activities. Both compounds increased hypodiploid populations of breast cancer cells, and 16AABE elicited cell cycle disturbance as evidenced by flow cytometry. The two analogs substantially increased the rate of tubulin polymerization in vitro. 16AABE and 16BABE inhibited breast cancer cells' migration and invasive ability, as evidenced by wound healing and Boyden chamber assays. Since both estrone analogs exerted remarkable estrogenic activities, as documented by a luciferase reporter gene assay, they can be considered as promising drug candidates for hormone-independent malignancies.

Isothiocyanates as Tubulin Polymerization Inhibitors-Synthesis and Structure-Activity Relationship Studies

Among the various substances that interfere with the microtubule formation process, isothiocyanates (ITCs) are the group of compounds for which the binding mode and mechanism of action have not yet been explained. To better understand the structure-activity relationship of tubulin-isothiocyanate interactions, we designed and synthesized a series of sixteen known and novel, structurally diverse ITCs, including amino acid ester-derived isothiocyanates, bis-isothiocyanates, analogs of benzyl isothiocyanate, and phosphorus analogs of sulforaphane. All synthesized compounds and selected natural isothiocyanates (BITC, PEITC, AITC, and SFN) were tested in vitro to evaluate their antiproliferative activity, tubulin polymerization inhibition potential, and influence on cell cycle progression. The antiproliferative activity of most of the newly tested compounds exceeded the action of natural isothiocyanates, with four structures being more potent as tubulin polymerization inhibitors than BITC. As a confirmation of anti-tubulin activity, the correlation between polymerization inhibition and cell cycle arrest in the G2/M phase was observed for the most active compounds. In light of the biological results indicating significant differences in the impact of structurally diverse isothiocyanate on tubulin polymerization, in silico analysis was conducted to analyze the possible mode of isothiocyanate-tubulin binding and to show how it can influence the polymerization reaction.

Design, Synthesis, and Evaluation of Biological Activity of Ferrocene-Ispinesib Hybrids: Impact of a Ferrocenyl Group on the Antiproliferative and Kinesin Spindle Protein Inhibitory Activity

With the aim to combine more than one biologically-active component in a single molecule, derivatives of ispinesib and its (S) analogue were prepared that featured ferrocenyl moieties or bulky organic substituents. Inspired by the strong kinesin spindle protein (KSP) inhibitory activity of ispinesib, the compounds were investigated for their antiproliferative activity. Among these compounds, several derivatives demonstrated significantly higher antiproliferative activity than ispinesib with nanomolar IC50 values against cell lines. Further evaluation indicated that the antiproliferative activity is not directly correlated with their KSP inhibitory activity while docking suggested that several of the derivatives may bind in a manner similar to ispinesib. In order to investigate the mode of action further, cell cycle analysis and reactive oxygen species formation were investigated. The improved antiproliferative activity of the most active compounds may be assigned to synergic effects of various factors such as KSP inhibitory activity due to the ispinesib core and ability to generate ROS and induce mitotic arrest.

New insights into the anticancer therapeutic potential of maytansine and its derivatives

Maytansine is a pharmacologically active 19-membered ansamacrolide derived from various medicinal plants and microorganisms. Among the most studied pharmacological activities of maytansine over the past few decades are anticancer and anti-bacterial effects. The anticancer mechanism of action is primarily mediated through interaction with the tubulin thereby inhibiting the assembly of microtubules. This ultimately leads to decreased stability of microtubule dynamics and cause cell cycle arrest, resulting in apoptosis. Despite its potent pharmacological effects, the therapeutic applications of maytansine in clinical medicine are quite limited due to its non-selective cytotoxicity. To overcome these limitations, several derivatives have been designed and developed mostly by modifying the parent structural skeleton of maytansine. These structural derivatives exhibit improved pharmacological activities as compared to maytansine. The present review provides a valuable insight into maytansine and its synthetic derivatives as anticancer agents.

Effect of Colchicine Binding Site Inhibitors on the Tubulin Intersubunit Interaction

Microtubules are dynamic, non-covalent polymers consisting of α- and β-tubulin subunits that are involved in a wide range of intracellular processes. The polymerization and dynamics of microtubules are regulated by many factors, including small molecules that interact with different sites on the tubulin dimer. Colchicine binding site inhibitors (CBSIs) destabilize microtubules and inhibit tubulin polymerization, leading to cell cycle arrest. Because of their therapeutic potential, the molecular mechanism of CBSI function is an area of active research. Nevertheless, important details of this mechanism have yet to be resolved. In this study, we use atomistic molecular dynamics simulations to show that the binding of CBSIs to the tubulin heterodimer leads to the weakening of tubulin intersubunit interaction. Using atomistic molecular dynamics simulations and binding free energy calculations, we show that CBSIs act as protein-protein interaction inhibitors and destabilize interlinkage between α and β subunits, which is crucial for longitudinal contacts in the microtubule lattice. Our results offer new insight into the mechanisms of microtubule polymerization inhibition by colchicine and its analogs.

Antibody-drug conjugates come of age in oncology

Antibody-drug conjugates (ADCs) combine the specificity of monoclonal antibodies with the potency of highly cytotoxic agents, potentially reducing the severity of side effects by preferentially targeting their payload to the tumour site. ADCs are being increasingly used in combination with other agents, including as first-line cancer therapies. As the technology to produce these complex therapeutics has matured, many more ADCs have been approved or are in late-phase clinical trials. The diversification of antigenic targets as well as bioactive payloads is rapidly broadening the scope of tumour indications for ADCs. Moreover, novel vector protein formats as well as warheads targeting the tumour microenvironment are expected to improve the intratumour distribution or activation of ADCs, and consequently their anticancer activity for difficult-to-treat tumour types. However, toxicity remains a key issue in the development of these agents, and better understanding and management of ADC-related toxicities will be essential for further optimization. This Review provides a broad overview of the recent advances and challenges in ADC development for cancer treatment.

First-in-Class Colchicine-Based Visible Light Photoswitchable Microtubule Dynamics Disrupting Agent

Compounds that disrupt microtubule dynamics, such as colchicine, paclitaxel, or Vinca alkaloids, have been broadly used in biological studies and have found application in clinical anticancer medications. However, their main disadvantage is the lack of specificity towards cancerous cells, leading to severe side effects. In this paper, we report the first synthesis of 12 new visible light photoswitchable colchicine-based microtubule inhibitors AzoCols. Among the obtained compounds, two photoswitches showed light-dependent cytotoxicity in cancerous cell lines (HCT116 and MCF-7). The most promising compound displayed a nearly twofold increase in potency. Moreover, dissimilar inhibition of purified tubulin polymerisation in cell-free assay and light-dependent disruption of microtubule organisation visualised by immunofluorescence imaging sheds light on the mechanism of action as microtubule photoswitchable destabilisers. The presented results provide a foundation towards the synthesis and development of a novel class of photoswitchable colchicine-based microtubule polymerisation inhibitors.

RNAseq Analysis of Novel 1,3,4-Oxadiazole Chalcogen Analogues Reveals Anti-Tubulin Properties on Cancer Cell Lines

1,3,4-Oxadiazole derivatives are among the most studied anticancer drugs. Previous studies have analyzed the action of different 1,3,4-oxadiazole derivatives and their effects on cancer cells. This study investigated the characterization of two new compounds named 6 and 14 on HeLa and PC-3 cancer cell lines. Based on the previously obtained IC₅₀, cell cycle effects were monitored by flow cytometry. RNA sequencing (RNAseq) was performed to identify differentially expressed genes, followed by functional annotation using gene ontology (GO), KEGG signaling pathway enrichment, and protein-protein interaction (PPI) network analyses. The tubulin polymerization assay was used to analyze the interaction of both compounds with tubulin. The results showed that 6 and 14 strongly inhibited the proliferation of cancer cells by arresting them in the G2/M phase of the cell cycle. Transcriptome analysis showed that exposure of HeLa and PC-3 cells to the compounds caused a marked reprograming of gene expression. Functional enrichment analysis indicated that differentially expressed genes were significantly enriched throughout the cell cycle and cancer-related biological processes. Furthermore, PPI network, hub gene, and CMap analyses revealed that compounds 14 and 6 shared target genes with established microtubule inhibitors, indicating points of similarity between the two molecules and microtubule inhibitors in terms of the mechanism of action. They were also able to influence the polymerization process of tubulin, suggesting the potential of these new compounds to be used as efficient chemotherapeutic agents.

Mechanism of ribosome-associated mRNA degradation during tubulin autoregulation

Microtubules play crucial roles in cellular architecture, intracellular transport, and mitosis. The availability of free tubulin subunits affects polymerization dynamics and microtubule function. When cells sense excess free tubulin, they trigger degradation of the encoding mRNAs, which requires recognition of the nascent polypeptide by the tubulin-specific ribosome-binding factor TTC5. How TTC5 initiates the decay of tubulin mRNAs is unknown. Here, our biochemical and structural analysis reveals that TTC5 recruits the poorly studied protein SCAPER to the ribosome. SCAPER, in turn, engages the CCR4-NOT deadenylase complex through its CNOT11 subunit to trigger tubulin mRNA decay. SCAPER mutants that cause intellectual disability and retinitis pigmentosa in humans are impaired in CCR4-NOT recruitment, tubulin mRNA degradation, and microtubule-dependent chromosome segregation. Our findings demonstrate how recognition of a nascent polypeptide on the ribosome is physically linked to mRNA decay factors via a relay of protein-protein interactions, providing a paradigm for specificity in cytoplasmic gene regulation.

Novel Tetrazole Derivatives Targeting Tubulin Endowed with Antiproliferative Activity against Glioblastoma Cells

Increasing awareness of the structure of microtubules has made tubulin a relevant target for the research of novel chemotherapies. Furthermore, the particularly high sensitivity of glioblastoma multiforme (GBM) cells to microtubule disruption could open new doors in the search for new anti-GBM treatments. However, the difficulties in developing potent anti-tubulin drugs endowed with improved pharmacokinetic properties necessitates the expansion of medicinal chemistry campaigns. The application of an ensemble pharmacophore screening methodology helped to optimize this process, leading to the development of a new tetrazole-based tubulin inhibitor. Considering this scaffold, we have synthesized a new family of tetrazole derivatives that achieved remarkable antimitotic effects against a broad panel of cancer cells, especially against GBM cells, showing high selectivity in comparison with non-tumor cells. The compounds also exerted high aqueous solubility and were demonstrated to not be substrates of efflux pumps, thus overcoming the main limitations that are usually associated with tubulin binding agents. Tubulin polymerization assays, immunofluorescence experiments, and flow cytometry studies demonstrated that the compounds target tubulin and arrest cells at the G2/M phase followed by induction of apoptosis. The docking experiments agreed with the proposed interactions at the colchicine site and explained the structure-activity relationships.

Research progress of STAT3-based dual inhibitors for cancer therapy

Signal transducer and activator of transcription 3 (STAT3), a transcription factor, regulates gene levels that are associated with cell survival, cell cycle, and immune reaction. It is correlated with the grade of malignancy and the development of various cancers and targeting STAT3 protein is a potentially promising therapeutic strategy for tumors. Over the past 20 years, various compounds have been found to directly inhibit STAT3 activity via different strategies. However, numerous difficulties exist in the development of STAT3 inhibitors, such as serious toxic effects, poor therapeutic effects, and intrinsic and acquired drug resistance. STAT3 inhibitors synergistically suppress cancer development with additional anti-tumor drugs, such as indoleamine 2,3-dioxygenase 1 inhibitors (IDO1i), histone deacetylase inhibitors (HDACi), DNA inhibitors, pro-tumorigenic cytokine inhibitors (PTCi), NF-κB inhibitors, and tubulin inhibitors. Therefore, individual molecule- based dual-target inhibitors can be the candidate alternative or complementary treatment to overcome the disadvantages of just STAT3 or other targets as a monotherapy. In this review, we discuss the theoretical basis for formulating STAT3-based dual-target inhibitors and also summarize their structure-activity relationships (SARs).

Potent and Selective Benzothiazole-Based Antimitotics with Improved Water Solubility: Design, Synthesis, and Evaluation as Novel Anticancer Agents

The design of colchicine site ligands on tubulin has proven to be a successful strategy to develop potent antiproliferative drugs against cancer cells. However, the structural requirements of the binding site endow the ligands with low aqueous solubility. In this work, the benzothiazole scaffold is used to design, synthesize, and evaluate a new family of colchicine site ligands exhibiting high water solubility. The compounds exerted antiproliferative activity against several human cancer cell lines, due to tubulin polymerization inhibition, showing high selectivity toward cancer cells in comparison with non-tumoral HEK-293 cells, as evidenced by MTT and LDH assays. The most potent derivatives, containing a pyridine moiety and ethylurea or formamide functionalities, displayed IC₅₀ values in the nanomolar range even in the difficult-to-treat glioblastoma cells. Flow cytometry experiments on HeLa, MCF7, and U87MG cells showed that they arrest the cell cycle at the G2/M phases at an early time point (24 h), followed by apoptotic cell death 72 h after the treatment. Tubulin binding was confirmed by microtubule network disruption observed via confocal microscopy. Docking studies support favorable interaction of the synthesized ligands at the colchicine binding site. These results validate the proposed strategy to develop potent anticancer colchicine ligands with improved water solubility.

Combination Therapy as a Promising Way to Fight Oral Cancer

Oral cancer is a highly aggressive tumor with invasive properties that can lead to metastasis and high mortality rates. Conventional treatment strategies, such as surgery, chemotherapy, and radiation therapy, alone or in combination, are associated with significant side effects. Currently, combination therapy has become the standard practice for the treatment of locally advanced oral cancer, emerging as an effective approach in improving outcomes. In this review, we present an in-depth analysis of the current advancements in combination therapies for oral cancer. The review explores the current therapeutic options and highlights the limitations of monotherapy approaches. It then focuses on combinatorial approaches that target microtubules, as well as various signaling pathway components implicated in oral cancer progression, namely, DNA repair players, the epidermal growth factor receptor, cyclin-dependent kinases, epigenetic readers, and immune checkpoint proteins. The review discusses the rationale behind combining different agents and examines the preclinical and clinical evidence supporting the effectiveness of these combinations, emphasizing their ability to enhance treatment response and overcome drug resistance. Challenges and limitations associated with combination therapy are discussed, including potential toxicity and the need for personalized treatment approaches. A future perspective is also provided to highlight the existing challenges and possible resolutions toward the clinical translation of current oral cancer therapies.

Not all benzimidazole derivatives are microtubule destabilizing agents

In recent years, microtubule-targeting agents (MTAs) have gained considerable interest in developing novel small-molecule anticancer drugs. MTAs demonstrate anticancer activity either as microtubule-stabilizing agents (paclitaxel) or microtubule-destabilizing agents (nocodazole). FDA-approved drugs containing a benzimidazole ring (nocodazole, albendazole, mebendazole, etc.) are well-known microtubule-destabilizing agents. Thus, most recent research on benzimidazole scaffold-based MTAs focuses on developing microtubule-destabilizing agents. However, there is no report on the benzimidazole scaffold-based microtubule-stabilizing agent. Here, we present the benzimidazole derivatives NI-11 and NI-18 that showed a profound anticancer activity as microtubule-stabilization agents. About twenty benzimidazole analogues were synthesized with excellent yield (80.0% ∼ 98.0%) and tested for their anticancer activity using two cancer cell lines (A549, MCF-7) and one normal cell line (MRC-5). NI-11 showed IC₅₀ values of 2.90, 7.17, and 16.9 µM in A549, MCF-7, and MRC-5 cell lines. NI-18 showed IC₅₀ values of 2.33, 6.10, and 12.1 µM in A549, MCF-7, and MRC-5 cell lines. Thus, NI-11 and NI-18 demonstrated selectivity indexes of 5.81 and 5.20, respectively, which are much higher than the currently available anticancer agents. NI-11 and NI-18 inhibited the cancer cell motility and migration, induced the early phase apoptosis. Both of these comounds were found to show an upregulation of DeY-α-tubulin and downregulation of Ac-α-tubulin expressions in cancer cells. Eventhough the reported benzimidazole scaffold-based commercially available drugs are known to be microtubule-destabilizing agents, the analogues NI-11 and NI-18 were found to have microtubule-stabilizing activity. The in vitro tubulin polymerization assay and the immunofluorescence assay results indicate that the NI-11 and NI-18 exhibit anticancer activity by stabilizing the microtubule network.

Fluoroindole chalcone analogues targeting the colchicine binding site of tubulin for colorectal oncotherapy

Colorectal cancer (CRC) is a common malignancy of the gastrointestinal tract with high morbidity and mortality. Our previous studies have demonstrated that indole-chalcone-based compounds targeting tubulin displayed potential cytotoxicity to CRC cells. Herein, three new series of derivatives were systematically designed and synthesized to explore their structure-activity relationship (SAR) against CRC based on prior research. Among them, a representative fluorine-containing analog (FC116) exerted superior efficacy on HCT116 (IC₅₀ = 4.52 nM) and CT26 (IC₅₀ = 18.69 nM) cell lines, and HCT116-xenograft mice with tumor growth inhibition rate of 65.96% (3 mg/kg). Of note, FC116 could also suppress the growth of organoid models (IC₅₀ = 1.8-2.5 nM) and showed adenoma number inhibition rate of 76.25% at the dose of 3 mg/kg in APC^min/+ mice. In terms of mechanism, FC116 could induce endoplasmic reticulum (ER) stress to produce excess reactive oxygen species (ROS), leading to mitochondrial damage to promote the apoptosis of CRC cells by targeting microtubules. Our results support that indole-chalcone compounds are promising tubulin inhibitors and highlight the potential of FC116 to combat CRC.

Synthesis and bioevaluation of novel stilbene-based derivatives as tubulin/HDAC dual-target inhibitors with potent antitumor activities in vitro and in vivo

A series of novel stilbene-based derivatives were designed and synthesized as tubulin/HDAC dual-target inhibitors. Among forty-three target compounds, compound II-19k not only exhibited considerable antiproliferative activity in the hematological cell line K562 with IC₅₀ value of 0.003 μM, but also effectively inhibited the growth of various solid tumor cell lines with IC₅₀ values ranging from 0.005 to 0.036 μM. The mechanism studies demonstrated that II-19k could inhibit microtubules and HDACs at the cellular level, block cell cycle arrest at G2 phase, induce cell apoptosis, and reduce solid tumor cells metastasis. What's more, the vascular disrupting effects of compound II-19k were more pronounced than the combined administration of parent compound 8 and HDAC inhibitor SAHA. The in vivo antitumor assay of II-19k also showed the superiority of dual-target inhibition of tubulin and HDAC. II-19k significantly suppressed the tumor volume and effectively reduced tumor weight by 73.12% without apparent toxicity. Overall, the promising bioactivities of II-19k make it valuable for further development as an antitumor agent.

Indolyl-chalcone derivatives trigger apoptosis in cisplatin-resistant mesothelioma cells through aberrant tubulin polymerization and deregulation of microtubule-associated proteins

Introduction

Malignant pleural mesothelioma (MPM) is a neoplasm with dismal prognosis and notorious resistance to the standard therapeutics cisplatin and pemetrexed. Chalcone derivatives are efficacious anti-cancer agents with minimal toxicity and have, therefore, gained pharmaceutical interest. Here, we investigated the efficacy of CIT-026 and CIT-223, two indolyl-chalcones (CITs), to inhibit growth and viability of MPM cells and defined the mechanism by which the compounds induce cell death.

Methods

The effects of CIT-026 and CIT-223 were analyzed in five MPM cell lines, using viability, immunofluorescence, real-time cell death monitoring, and tubulin polymerization assays, along with siRNA knockdown. Phospho-kinase arrays and immunoblotting were used to identify signaling molecules that contribute to cell death.

Results

CIT-026 and CIT-223 were toxic in all cell lines at sub-micromolar concentrations, in particular in MPM cells resistant to cisplatin and pemetrexed, while normal fibroblasts were only modestly affected. Both CITs targeted tubulin polymerization via (1) direct interaction with tubulin and (2) phosphorylation of microtubule regulators STMN1, CRMP2 and WNK1. Formation of aberrant tubulin fibers caused abnormal spindle morphology, mitotic arrest and apoptosis. CIT activity was not reduced in CRMP2-negative and STMN1-silenced MPM cells, indicating that direct tubulin targeting is sufficient for toxic effects of CITs.

Discussion

CIT-026 and CIT-223 are highly effective inducers of tumor cell apoptosis by disrupting microtubule assembly, with only modest effects on non-malignant cells. CITs are potent anti-tumor agents against MPM cells, in particular cells resistant to standard therapeutics, and thus warrant further evaluation as potential small-molecule therapeutics in MPM.

Synthesis, Modeling, and Biological Evaluation of Anti-Tubulin Indole-Substituted Furanones

Due to the central role of tubulin in various cellular functions, it is a validated target for anti-cancer therapeutics. However, many of the current tubulin inhibitors are derived from complex natural products and suffer from multidrug resistance, low solubility, toxicity issues, and/or the lack of multi-cancer efficacy. As such, there is a continued need for the discovery and development of new anti-tubulin drugs to enter the pipeline. Herein we report on a group of indole-substituted furanones that were prepared and tested for anti-cancer activity. Molecular docking studies showed positive correlations between favorable binding in the colchicine binding site (CBS) of tubulin and anti-proliferative activity, and the most potent compound was found to inhibit tubulin polymerization. These compounds represent a promising new structural motif in the search for small heterocyclic CBS cancer inhibitors.

Computational analysis of drug resistance of taxanes bound to human β-tubulin mutant (D26E)

The single-point mutation D26E in human β-tubulin is associated with drug resistance seen with two anti-mitotic taxanes (paclitaxel and docetaxel) when used to treat cancers. The molecular mechanism of this resistance remains elusive. However, docetaxel and a third-generation taxane, cabazitaxel, are thought to overcome this resistance. Here, structural models of both the wildtype (WT) and D26E mutant (MT) human β-tubulin were constructed based on the crystal structure of pig β-tubulin in complex with docetaxel (PDB ID: 1TUB). The three taxanes were docked into the WT and MT β-tubulin, and the resulting complexes were submitted to three independent runs of 200 ns molecular dynamic simulations, which were then averaged. MM/GBSA calculations revealed the binding energy of paclitaxel with WT and MT β-Tubulin to be -101.5 ± 8.4 and -90.4 ± 8.9 kcal/mol, respectively. The binding energy of docetaxel was estimated to be -104.7 ± 7.0 kcal/mol with the WT and -103.8 ± 5.5 kcal/mol with the MT β-tubulin. Interestingly, cabazitaxel was found to have a binding energy of -122.8 ± 10.8 kcal/mol against the WT and -106.2 ± 7.0 kcal/mol against the MT β-tubulin. These results show that paclitaxel and docetaxel bound to the MT less strongly than the WT, suggesting possible drug resistance. Similarly, cabazitaxel displayed a greater binding propensity against WT and MT β-tubulin than the other two taxanes. Furthermore, the dynamic cross-correlation matrices (DCCM) analysis suggests that the single-point mutation D26E induces a subtle dynamical difference in the ligand-binding domain. Overall, the present study revealed how the single-point mutation D26E may reduce the binding affinity of the taxanes, however, the effect of the mutation does not significantly affect the binding of cabazitaxel.

Sandwich-Structured Implants to Obstruct Multipath Energy Supply and Trigger Self-Enhanced Hypoxia-Initiated Chemotherapy Against Postsurgical Tumor Recurrence and Metastasis

As a currently common strategy to treat cancer, surgical resection may cause tumor recurrence and metastasis due to residual postoperative tumors. Herein, an implantable sandwich-structured dual-drug depot is developed to trigger a self-intensified starvation therapy and hypoxia-induced chemotherapy sequentially. The two outer layers are 3D-printed using a calcium-crosslinked mixture ink containing soy protein isolate, polyvinyl alcohol, sodium alginate, and combretastatin A4 phosphate (CA4P). The inner layer is one patch of poly (lactic-co-glycolic acid)-based electrospun fibers loaded with tirapazamine (TPZ). The preferentially released CA4P destroys the preexisting blood vessels and prevents neovascularization, which obstructs the external energy supply to cancer cells but aggravates hypoxic condition. The subsequently released TPZ is bioreduced to cytotoxic benzotriazinyl under hypoxia, further damaging DNA, generating reactive oxygen species, disrupting mitochondria, and downregulating hypoxia-inducible factor 1α, vascular endothelial growth factor, and matrix metalloproteinase 9. Together these processes induce apoptosis, block the intracellular energy supply, counteract the disadvantage of CA4P in favoring intratumor angiogenesis, and suppress tumor metastasis. The in vivo and in vitro results and the transcriptome analysis demonstrate that the postsurgical adjuvant treatment with the dual-drug-loaded sandwich-like implants efficiently inhibits tumor recurrence and metastasis, showing great potential for clinical translation.

Discovery of novel N-aryl-2-trifluoromethyl-quinazoline-4-amine derivatives as the inhibitors of tubulin polymerization in leukemia cells

A series of new N-aryl-2-trifluoromethylquinazoline-4-amine analogs were designed and synthesized based on structure optimization of quinazoline by introducing a trifluoromethyl group into 2-position. The structures of the twenty-four newly synthesized compounds were confirmed by ¹H NMR, ¹³C NMR and ESI-MS. The in vitro anti-cancer activity against chronic myeloid leukemia cells (K562), erythroleukemia cells (HEL), human prostate cancer cells (LNCaP), and cervical cancer cells (HeLa) of the target compounds was evaluated. Among them, compounds 15d, 15f, 15h, and 15i showed the significantly (P < 0.01) stronger growth inhibitory activity on K562 than those of the positive controls of paclitaxel and colchicine, while compounds 15a, 15d, 15e, and 15h displayed significantly stronger growth inhibitory activity on HEL than those of the positive controls. However, all the target compounds exhibited weaker growth inhibition activity against K562 and HeLa than those of the positive controls. The selectivity ratio of compounds 15h, 15d, and 15i were significantly higher than those of other active compounds, indicating that these three compounds had the lower hepatotoxicity. Several compounds displayed strong inhibition against leukemia cells. They inhibited tubulin polymerization, disrupted cellular microtubule networks by targeting the colchicine site, and promoted cell cycle arrest of leukemia cells at G2/M phase and cell apoptosis, as well as inhibiting angiogenesis. In summary, our research provided that novel synthesized N-aryl-2-trifluoromethyl-quinazoline-4-amine active derivatives as the inhibitors of tubulin polymerization in leukemia cells, which might be a valuable lead compounds for anti-leukemia agents.

Discovery of a novel Coumarin-Dihydroquinoxalone derivative MY-673 as a tubulin polymerization inhibitor capable of inhibiting the ERK pathway with potent anti-gastric cancer activities

As a class of microtubule targeting agents, colchicine binding site inhibitors (CBSIs) are considered as promising drug candidates for cancer therapy. However, due to adverse reactions, there are currently no CBSIs approved by FDA for cancer treatment. Therefore, extensive efforts are still encouraged to find novel CBSIs with different chemical structures and better anticancer efficacies. In this work, we designed and synthesized a new coumarin-dihydroquinoxalone derivative, MY-673, and evaluated its anticancer potency in vitro and in vivo. We confirmed that MY-673 was a potent CBSI that it not only inhibited tubulin polymerization, but also exhibited significant inhibitory potency on the growth of 13 cancer cells with IC₅₀ values from 11.7 nM to 395.9 nM. Based on the results of kinase panel screening, MY-673 could inhibit ERK (extracellular regulated protein kinases) pathways-related kinases. We further confirmed that MY-673 could inhibit ERK signaling pathway in MGC-803 and HGC-27 cells, and then affected the expression level of SMAD4 protein in TGF-β (transforming growth factor β) /SMAD (small mother against decapentaplegic) signaling pathway using the western blotting assay. In addition, compound MY-673 could effectively inhibit cell proliferation, migration and induce cell apoptosis. We also further confirmed the in vivo efficacy of MY-673 in inhibiting tumor growth using the MGC-803 xenograft tumor model. At 20 mg/kg, the TGI rate was 85.9%, and it did not cause obvious toxicity to the main organs of mice. Together, the results we report here indicated that MY-673 was a promising CBSI for cancer treatment, which was capable of inhibiting the ERK pathway with potent antiproliferative activities in vitro and in vivo.

Mechanisms of chromosomal instability (CIN) tolerance in aggressive tumors: surviving the genomic chaos

Chromosomal instability (CIN) is a pervasive feature of human cancers involved in tumor initiation and progression and which is found elevated in metastatic stages. CIN can provide survival and adaptation advantages to human cancers. However, too much of a good thing may come at a high cost for tumor cells as excessive degree of CIN-induced chromosomal aberrations can be detrimental for cancer cell survival and proliferation. Thus, aggressive tumors adapt to cope with ongoing CIN and most likely develop unique susceptibilities that can be their Achilles' heel. Determining the differences between the tumor-promoting and tumor-suppressing effects of CIN at the molecular level has become one of the most exciting and challenging aspects in cancer biology. In this review, we summarized the state of knowledge regarding the mechanisms reported to contribute to the adaptation and perpetuation of aggressive tumor cells carrying CIN. The use of genomics, molecular biology, and imaging techniques is significantly enhancing the understanding of the intricate mechanisms involved in the generation of and adaptation to CIN in experimental models and patients, which were not possible to observe decades ago. The current and future research opportunities provided by these advanced techniques will facilitate the repositioning of CIN exploitation as a feasible therapeutic opportunity and valuable biomarker for several types of human cancers.

Design, Synthesis, and Biological Evaluation of Pyrimidine Dihydroquinoxalinone Derivatives as Tubulin Colchicine Site-Binding Agents That Displayed Potent Anticancer Activity Both In Vitro and In Vivo

Polymerization of tubulin dimers to form microtubules is one of the key events in cell proliferation. The inhibition of this event has long been recognized as a potential treatment option for various types of cancer. Compound 1e was previously developed by our team as a potent inhibitor of tubulin polymerization that binds to the colchicine site. To further improve the potency and therapeutic properties of compound 1e, we hypothesized based on the X-ray crystal structure that modification of the pyrimidine dihydroquinoxalinone scaffold with additional hetero-atom (N, O, and S) substituents could allow the resulting new compounds to bind more tightly to the colchicine site and display greater efficacy in cancer therapy. We therefore synthesized a series of new pyrimidine dihydroquinoxalinone derivatives, compounds 10, 12b-c, 12e, 12h, and 12j-l, and evaluated their cytotoxicity and relative ability to inhibit proliferation, resulting in the discovery of new tubulin-polymerization inhibitors. Among these, the most potent new inhibitor was compound 12k, which exhibited high cytotoxic activity in vitro, a longer half-life than the parental compound in liver microsomes (IC50 = 0.2 nM, t 1/2 = >300 min), and significant potency against a wide range of cancer cell lines including those from melanoma and breast, pancreatic, and prostate cancers. High-resolution X-ray crystal structures of the best compounds in this scaffold series, 12e, 12j, and 12k, confirmed their direct binding to the colchicine site of tubulin and revealed their detailed molecular interactions. Further evaluation of 12k in vivo using a highly taxane-resistant prostate cancer xenograft model, PC-3/TxR, demonstrated the strong tumor growth inhibition at the low dose of 2.5 mg/kg (i.v., twice per week). Collectively, these results strongly support further preclinical evaluations of 12k as a potential candidate for development.

Overcoming Cancer Multi-drug Resistance (MDR): Reasons, mechanisms, nanotherapeutic solutions, and challenges

Multi-drug resistance (MDR) in cancer cells, either intrinsic or acquired through various mechanisms, significantly hinders the therapeutic efficacy of drugs. Typically, the reduced therapeutic performance of various drugs is predominantly due to the inherent over expression of ATP-binding cassette (ABC) transporter proteins on the cell membrane, resulting in the deprived uptake of drugs, augmenting drug detoxification, and DNA repair. In addition to various physiological abnormalities and extensive blood flow, MDR cancer phenotypes exhibit improved apoptotic threshold and drug efflux efficiency. These severe consequences have substantially directed researchers in the fabrication of various advanced therapeutic strategies, such as co-delivery of drugs along with various generations of MDR inhibitors, augmented dosage regimens and frequency of administration, as well as combinatorial treatment options, among others. In this review, we emphasize different reasons and mechanisms responsible for MDR in cancer, including but not limited to the known drug efflux mechanisms mediated by permeability glycoprotein (P-gp) and other pumps, reduced drug uptake, altered DNA repair, and drug targets, among others. Further, an emphasis on specific cancers that share pathogenesis in executing MDR and effluxed drugs in common is provided. Then, the aspects related to various nanomaterials-based supramolecular programmable designs (organic- and inorganic-based materials), as well as physical approaches (light- and ultrasound-based therapies), are discussed, highlighting the unsolved issues and future advancements. Finally, we summarize the review with interesting perspectives and future trends, exploring further opportunities to overcome MDR.

Dual Ruthenium-Catalyzed Alkene Isomerization-Hydrogen Auto-Transfer Unlocks Skipped Dienes as Pronucleophiles for Enantioselective Alcohol C-H Allylation

The first use of 1,4-pentadiene and 1,5-hexadiene as allylmetal pronucleophiles in regio-, anti-diastereo-, and enantioselective carbonyl addition from alcohol proelectrophiles is described. As corroborated by deuterium labeling experiments, primary alcohol dehydrogenation delivers a ruthenium hydride that affects alkene isomerization to furnish a conjugated diene, followed by transfer hydrogenative carbonyl addition. Hydrometalation appears to be assisted by the formation of a fluxional olefin-chelated homoallylic alkylruthenium complex II, which exists in equilibrium with its pentacoordinate η1 form to enable β-hydride elimination. This effect confers remarkable chemoselectivity: while 1,4-pentadiene and 1,5-hexadiene are competent pronucleophiles, higher 1,n-dienes are not, and the olefinic functional groups of the products remain intact under conditions in which the 1,4- and 1,5-dienes isomerize. A survey of halide counterions reveals iodide-bound ruthenium-JOSIPHOS catalysts are uniquely effective in these processes. This method was used to prepare a previously reported C1-C7 substructure of (-)-pironetin in 4 vs 12 steps.

Investigation of the Antineoplastic Effects of 2-(4-Chlorophenyl)-13α-Estrone Sulfamate against the HPV16-Positive Human Invasive Cervical Carcinoma Cell Line SiHa

Cervical carcinoma is one of the most frequent malignant gynecological cancers in women of reproductive age. Because of the poor tolerability of currently available chemotherapeutic agents, efforts have been focused on developing innovative molecules, including steroids, that exert antineoplastic effects with a better safety profile. In addition to their endocrine properties, certain estrogens exhibit additional biological activities, such as antiangiogenic and anticancer effects. Based on previous studies, the antineoplastic properties of 13α-estrone sulfamate derivatives (13AES1-3) were investigated, and the mechanism of action for the most promising compound 13AES3 was explored. Based on their effects on the viability of different human adherent gynecological cancer cells, the SiHa cervical cell line was used for mechanistic experiments. The most active analog 13AES3 was shown to exert considerable proapoptotic effects, as evidenced by a colorimetric caspase-3 assay and fluorescent double staining. It also elicited antimigratory and anti-invasive effects in a concentration-dependent manner, as evidenced by wound healing and Boyden chamber assays, respectively. Regarding their mechanism of action, 13AES derivatives were shown to inhibit tubulin polymerization, and computer simulations provided a possible explanation for the importance of the presence of the chlorophenyl ring on the estrane skeleton. 13AES3 is considered to be the first 13α-estrone derivative with a significant antineoplastic potency against SiHa cancer cells. Therefore, it might serve as a valuable lead molecule for the design of anticancer agents targeting cervical carcinomas.

New Combretastatin Analogs as Anticancer Agents: Design, Synthesis, Microtubules Polymerization Inhibition, and Molecular Docking Studies

A new series of 4-(4-methoxyphenyl)-5-(3,4,5-trimethoxyphenyl)-4H-1,2,4-triazole-3-thiol derivatives were synthesized as analogs for the anticancer drug combretastatin A-4 (CA-4) and characterized using FT-IR, 1 H-NMR, 13 CNMR, and HR-MS techniques. The new CA-4 analogs were designed to meet the structural requirements of the highest expected anticancer activity of CA-4 analogs by maintaining ring A 3,4,5-trimethoxyphenyl moiety, and at the same time varying the substituents effect of the triazole moiety (ring B). In silico analysis indicated that compound 3 has higher total energy and dipole moment than colchicine and the other analogs, and it has excellent distribution of electron density and is more stable, resulting in an increased binding affinity during tubulin inhibition. Additionally, compound 3 was found to interact with three apoptotic markers, namely p53, Bcl-2, and caspase 3. Compound 3 showed strong similarity to colchicine, and it has excellent pharmacokinetics properties and a good dynamic profile. The in vitro anti-proliferation studies showed that compound 3 is the most cytotoxic CA-4 analog against cancer cells (IC50 of 6.35 μM against Hep G2 hepatocarcinoma cells), and based on its selectivity index (4.7), compound 3 is a cancer cytotoxic-selective agent. As expected and similar to colchicine, compound 3-treated Hep G2 hepatocarcinoma cells were arrested at the G2/M phase resulting in induction of apoptosis. Compound 3 tubulin polymerization IC50 (9.50 μM) and effect on Vmax of tubulin polymerization was comparable to that of colchicine (5.49 μM). Taken together, the findings of the current study suggest that compound 3, through its binding to the colchicine-binding site at β-tubulin, is a promising microtubule-disrupting agent with excellent potential to be used as cancer therapeutic agent.

Discovery of novel N-benzylarylamide-dithiocarbamate based derivatives as dual inhibitors of tubulin polymerization and LSD1 that inhibit gastric cancers

In this work, N-benzylarylamide-dithiocarbamate based derivatives were designed, synthesized, and their biological activities as anticancer agents were explored. Some of the 33 target compounds displayed significant antiproliferative activities with IC₅₀ values at the double-digit nanomolar level. The representative compound I-25 (also named MY-943) not only showed the most effective inhibitory effects on three selected cancer cells MGC-803 (IC₅₀ = 0.017 μM), HCT-116 (IC₅₀ = 0.044 μM) and KYSE450 (IC₅₀ = 0.030 μM), but also exhibited low nanomolar IC₅₀ values from 0.019 to 0.253 μM against the other 11 cancer cells. Compound I-25 (MY-943) effectively inhibited tubulin polymerization and suppressed LSD1 at the enzymatic levels. Compound I-25 (MY-943) could act on the colchicine binding site of β-tubulin, thus disrupting the construction of cell microtubule network and affecting the mitosis. In addition, compound I-25 (MY-943) could dose-dependently induce the accumulation of H3K4me1/2 (MGC-803 and SGC-7091 cells) and H3K9me2 (SGC-7091 cells). Compound I-25 (MY-943) could induce G2/M phase arrest and cell apoptosis, and suppress migration in MGC-803 and SGC-7901 cells. In addition, compound I-25 (MY-943) significantly modulated the expression of apoptosis- and cycle-related proteins. Furthermore, the binding modes of compound I-25 (MY-943) with tubulin and LSD1 were explored by molecular docking. The results of in vivo anti-gastric cancer assays using in situ tumor models showed that compound I-25 (MY-943) effectively reduced the weight and volume of gastric cancer in vivo without obvious toxicity. All these findings suggested that the N-benzylarylamide-dithiocarbamate based derivative I-25 (MY-943) was an effective dual inhibitor of tubulin polymerization and LSD1 that inhibited gastric cancers.

Simple monocyclic pyrimidine analogs as microtubule targeting agents binding to the colchicine site

Complex natural products that bind to tubulin/microtubules come under the broad category of microtubule binding agents. The design of simplified analogs of previously reported bicyclic, microtubule depolymerizer, pyrrolo[2,3-d]pyrimidine, provided valuable structure-activity relationship data and led to the identification of novel monocyclic pyrimidine analogs of which 12 was 47-fold more potent (EC50 123 nM) for cellular microtubule depolymerization activity and 7.5-fold more potent (IC50 24.4 nM) at inhibiting the growth of MDA-MB-435 cancer cells, suggesting significantly better binding of the target within the colchicine site of tubulin compared to lead compound 1. This compound and others of this series of monocyclic pyrimidine analogs were able to overcome multidrug resistance due to the expression of the βIII-isotype of tubulin and P-glycoprotein. In vivo evaluation of the most potent analog 12 in an MDA-MB-435 xenograft mouse model indicated, along with paclitaxel, that both compounds showed a trend towards lower tumor volume however neither compound showed significant antitumor activity in the trial. To our knowledge these are the first examples of simple substituted monocyclic pyrimidines as colchicine site binding antitubulin compounds with potent antitumor activity.