Temperature-induced lipocalin-mediated membrane integrity: Possible implications for vindoline accumulation in Catharanthus roseus leaves.

Plant lipocalins perform diverse functions. Recently, allene oxide cyclase, a lipocalin family member, has been shown to co-express with vindoline pathway genes in Catharanthus roseus under various biotic/abiotic stresses. This brought focus to another family member, a temperature-induced lipocalin (CrTIL), which was selected for full-length cloning, tissue-specific expression profiling, in silico characterization, and upstream genomic region analysis for cis-regulatory elements. Stress-mediated variations in CrTIL expression were reflected as disturbances in cell membrane integrity, assayed through measurement of electrolyte leakage and lipid peroxidation product, MDA, which implicated the role of CrTIL in maintaining cell membrane integrity. For ascertaining the function of CrTIL in maintaining membrane stability and elucidating the relationship between CrTIL expression and vindoline content, if any, a direct approach was adopted, whereby CrTIL was transiently silenced and overexpressed in C. roseus. CrTIL silencing and overexpression confirmed its role in the maintenance of membrane integrity and indicated an inverse relationship of its expression with vindoline content. GFP fusion-based subcellular localization indicated membrane localization of CrTIL, which was in agreement with its role in maintaining membrane integrity. Altogether, the role of CrTIL in maintaining membrane structure has possible implications for the intracellular sequestration, storage, and viability of vindoline.

Thermodynamic and structural profiles of multi-target binding of vinblastine in solution.

Structural information about drug-receptor interactions is paramount in drug discovery and subsequent optimization processes. Drugs can bind to multiple potential targets as they contain common chemical entities in their structures. Understanding the details of such interactions offer possibilities for repurposing and developing potent inhibitors of disease pathways. Vinblastine (VLB) is a potent anticancer molecule showing multiple receptor interactions with different affinities and degrees of structural perturbations. We have investigated the multi-target binding profile of VLB with DNA and human serum albumin (HSA) in a dynamic physiological environment using spectroscopic, molecular dynamics simulations, and quantum mechanical calculations to evaluate the structural features, mode, ligand and receptor flexibility, and energetics of complexation. These results confirm that VLB prefers to bind in the major groove of DNA with some inclination toward Thymidine residue and the TR-5 binding site in HSA with its catharanthine half making important contacts with both the receptors. Spectroscopic investigation at multiple temperatures has also proved that VLB binding is entropy driven indicating the major groove and TR-5 binding site of interaction. Finally, the overall binding is facilitated by van der Waals contacts and a few conventional H-bonds. VLB portrays reasonable conformational diversity on binding with multiple receptors.

A microbial supply chain for production of the anti-cancer drug vinblastine.

Monoterpene indole alkaloids (MIAs) are a diverse family of complex plant secondary metabolites with many medicinal properties, including the essential anti-cancer therapeutics vinblastine and vincristine1. As MIAs are difficult to chemically synthesize, the world's supply chain for vinblastine relies on low-yielding extraction and purification of the precursors vindoline and catharanthine from the plant Catharanthus roseus, which is then followed by simple in vitro chemical coupling and reduction to form vinblastine at an industrial scale2,3. Here, we demonstrate the de novo microbial biosynthesis of vindoline and catharanthine using a highly engineered yeast, and in vitro chemical coupling to vinblastine. The study showcases a very long biosynthetic pathway refactored into a microbial cell factory, including 30 enzymatic steps beyond the yeast native metabolites geranyl pyrophosphate and tryptophan to catharanthine and vindoline. In total, 56 genetic edits were performed, including expression of 34 heterologous genes from plants, as well as deletions, knock-downs and overexpression of ten yeast genes to improve precursor supplies towards de novo production of catharanthine and vindoline, from which semisynthesis to vinblastine occurs. As the vinblastine pathway is one of the longest MIA biosynthetic pathways, this study positions yeast as a scalable platform to produce more than 3,000 natural MIAs and a virtually infinite number of new-to-nature analogues.

A highly sensitive bioanalytical method for the quantification of vinblastine, vincristine, vinorelbine and 4-O-deacetylvinorelbine in human plasma using LC-MS/MS.

A highly sensitive method was developed for the quantification of vinblastine, vincristine, vinorelbine, and its active metabolite 4-O-deacetylvinorelbine in human plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Deuterated isotopes were used as internal standard and liquid-liquid extraction with tert-butyl methyl ether (TBME) was used for sample pre-treatment. The final extract was injected on a C18 column (50 × 2.1 mm ID, 5 µm). Gradient elution was used in combination with Reversed Phase chromatography to elute the analytes and internal standards from the column in 5 min and the API4000 triple quadrupole MS detector was operating in the positive ion mode. The calibration model, accuracy and precision, selectivity and specificity, dilution integrity, carryover, matrix factor and recovery, and stability were evaluated over a concentration range from 0.025 to 10 ng/mL for vinblastine, vinorelbine, and 4-O-deacetylvinorelbine and from 0.1 to 40 ng/mL for vincristine. The intra- and inter-assay bias and precisions were within ± 12.4% and ≤ 10.6%, respectively. This method was successfully applied to study the pharmacokinetics of vincristine in paediatrics and vinorelbine and 4-O-deacetylvinorelbine using in vivo mouse models.

Engineering Catharanthus roseus monoterpenoid indole alkaloid pathway in yeast.

Catharanthus roseus (Madagascar periwinkle), a medicinal plant possessing high pharmacological attributes, is widely recognized for the biosynthesis of anticancer monoterpenoid indole alkaloids (MIAs) - vinblastine and vincristine. The plant is known to biosynthesize more than 130 different bioactive MIAs, highly acclaimed in traditional and modern medicinal therapies. The MIA biosynthesis is strictly regulated at developmental and spatial-temporal stages and requires a well-defined cellular and sub-cellular compartmentation for completion of the entire MIAs biosynthesis. However, due to their cytotoxic nature, the production of vinblastine and vincristine occurs in low concentrations in planta and the absence of chemical synthesis alternatives projects a huge gap in demand and supply, leading to high market price. With research investigations spanning more than four decades, plant tissue culture and metabolic engineering (ME)-based studies were attempted to explore, understand, explain, improve and enhance the MIA biosynthesis using homologous and heterologous systems. Presently, metabolic engineering and synthetic biology are the two powerful tools that are contributing majorly in elucidating MIA biosynthesis. This review concentrates mainly on the efforts made through metabolic engineering of MIAs in heterologous microbial factories. KEY POINTS: • Yeast engineering provides alternative production source of phytomolecules • Yeast engineering also helps to discover missing plant pathway enzymes and genes.

Synthesis of Novel Vindoline-Chrysin Hybrids.

Vinca alkaloids are well-known microtubule targeting agents, which are used against some types of cancer. Vindoline is one of the monomeric Vinca alkaloids which does not have anti-tumor effect, although its derivatives have serious impact on the field of these indole alkaloids. Chrysin is a secondary plant metabolite, which has broad-spectrum biological activity, among others anticancer activity. Chrysin had shown synergic effect with several antiproliferative compounds (e. g., doxorubicin, cisplatin and ciglitazone), therefore, we attempted the synthesis of a novel vindoline-chrysin hybrid molecule. However, in the first case a diphenylamine structure was isolated. The mechanism of the unexpected reaction was studied, and then the originally targeted hybrid was synthesized by a reverse route coupling. A further hybrid was produced using a different site of the molecule. The antitumor activities were determined against 60 human tumor cell lines (NCI60), where the aimed hybrid showed low micromolar GI50 values on most of the cell lines.

Addition of Vindoline to p-Benzoquinone: Regiochemistry, Stereochemistry and Symmetry Considerations.

Vindoline and catharanthine are the major alkaloids of Catharanthus roseus and are extracted in large quantities to prepare the pharmaceutically important Vinca type alkaloids vincaleukoblastine, vincristine and navelbine. The higher yield of vindoline relative to catharanthine makes it an attractive substrate for developing new chemistry and adding value to the plant. In this context, we have reacted vindoline with a selection of electrophiles among which benzoquinone. Conditions were developed to optimize the synthesis of a mono-adduct, of five bis-adducts, and of tri-adducts and tetra-adducts, several of these adducts being mixtures of conformational isomers. Copper(II) was added to the reactions to promote reoxidation of the intermediate hydroquinones and simplify the reaction products. The structures were solved by spectroscopic means and by symmetry considerations. Among the bis-isomers, the 2,3-diadduct consists of three unseparable species, two major ones with an axis of symmetry, thus giving a single set of signals and existing as two different species with indistinguishable NMR spectra. The third and minor isomer has no symmetry and therefore exhibits nonequivalence in the signals of the two vindoline moieties. These isomers are designated as syn (minor) and anti (major) and there exists a high energy barrier between them making their interconversion difficult. DFT calculations on simplified model compounds demonstrate that the syn-anti interconversion is not possible at room temperature on the NMR chemical shift time scale. These molecules are not rigid and calculations showed a back-and-forth conrotatory motion of the two vindolines. This "windshield wiper" effect is responsible for the observation of exchange correlations in the NOESY spectra. The same phenomenon is observed with the higher molecular weight adducts, which are also mixtures of rotational isomers. The same lack of rotations between syn and anti isomers is responsible for the formation of four tri-adducts and of seven tetra-adducts. On a biological standpoint, the mono adduct displayed anti-inflammatory properties at the 5 µM level while the di-adducts and tri-adducts showed moderate cytotoxicity against Au565, and HeLa cancer cell lines.

Optimization of Tabersonine Methoxylation to Increase Vindoline Precursor Synthesis in Yeast Cell Factories.

Plant specialized metabolites are widely used in the pharmaceutical industry, including the monoterpene indole alkaloids (MIAs) vinblastine and vincristine, which both display anticancer activity. Both compounds can be obtained through the chemical condensation of their precursors vindoline and catharanthine extracted from leaves of the Madagascar periwinkle. However, the extensive use of these molecules in chemotherapy increases precursor demand and results in recurrent shortages, explaining why the development of alternative production approaches, such microbial cell factories, is mandatory. In this context, the precursor-directed biosynthesis of vindoline from tabersonine in yeast-expressing heterologous biosynthetic genes is of particular interest but has not reached high production scales to date. To circumvent production bottlenecks, the metabolic flux was channeled towards the MIA of interest by modulating the copy number of the first two genes of the vindoline biosynthetic pathway, namely tabersonine 16-hydroxylase and tabersonine-16-O-methyltransferase. Increasing gene copies resulted in an optimized methoxylation of tabersonine and overcame the competition for tabersonine access with the third enzyme of the pathway, tabersonine 3-oxygenase, which exhibits a high substrate promiscuity. Through this approach, we successfully created a yeast strain that produces the fourth biosynthetic intermediate of vindoline without accumulation of other intermediates or undesired side-products. This optimization will probably pave the way towards the future development of yeast cell factories to produce vindoline at an industrial scale.

Ultra-trace speciation analysis of Cr(III) and Cr(VI) in rice using species-specific isotope dilution and HPLC-ICP-MS.

The study aims to clarify the current controversy related to conflicting reports on whether presence of Cr(VI) in rice is possible or not. For this purpose, a method was employed for the single run speciation analysis of Cr(III) and Cr(VI) in rice samples using species-specific isotope dilution (SS-ID) and high performance liquid chromatography coupled to inductively coupled mass-spectrometry (HPLC-ICP-MS) and selective single run species complexation/derivatisation. The quantification limits (LOQs) were 0.014 µg kg-1 for Cr(III) and 0.047 µg kg-1 for Cr(VI), while the detection limits (LODs) were 0.004 and 0.014 µg kg-1 for Cr(III) and Cr(VI), respectively. A total of 10 rice samples of different origin and colour (depending on the type of industrial processing) were analysed in this study. The content of Cr(VI) was below the limit of quantification in all of the rice samples analysed, while the Cr(III) levels ranged between 0.59 (whole grain rice) up to 104 µg kg-1 (brown rice). All samples were also analysed for their total Cr (Crtotal) content by ICP-MS solely and the results were in all cases comparable with the Cr(III) levels determined in the same samples. To assess the stability of Cr(III) and Cr(VI) in rice, one sample was spiked with Cr(III) and Cr(VI) (individually) at different levels (5.0, 10, 15 and 20 µg kg-1), held for 2 h, and then analysed by SS-ID HPLC-ICP-MS. The results showed a complete reduction of Cr(VI) to Cr(III), while Cr(III) remained stable at all spiking levels. These findings support the general statement from the European Food Safety Authority related to the complete absence of Cr(VI) in foods and confirms that Cr in rice is found solely as Cr(III) species.

Pathways Related to the Anti-Cancer Effects of Metabolites Derived from Cerrado Biome Native Plants: An Update and Bioinformatics Analysis on Oral Squamous Cell Carcinoma.

BACKGROUND: Oral cancer is a significant health problem worldwide. Oral squamous cell carcinoma (OSCC) is a malignant neoplasm of epithelial cells that mostly affects different anatomical sites in the head and neck and derives from the squamous epithelium or displays similar morphological characteristics. Generally, OSCC is often the end stage of several changes in the stratified squamous epithelium, which begin as epithelial dysplasia and progress by breaking the basement membrane and invading adjacent tissues. Several plant-based drugs with potent anti-cancer effects are considered inexpensive treatments with limited side effects for cancer and other diseases. OBJECTIVE: The aim of this review is to explore whether some Brazilian plant extracts or constituents exhibit anti-tumorigenic activity or have a cytotoxic effect on human oral carcinoma cells. METHODS: Briefly, OSCC and several metabolites derived from Brazilian plants (i.e., flavonoids, vinblastine, irinotecan, etoposide and paclitaxel) were used as keywords to search the literature on PubMed, GenBank and GeneCards. RESULTS: The results showed that these five chemical compounds found in Cerrado Biome plants exhibit anti-neoplastic effects. Evaluating the compounds revealed that they play a main role in the regulation of cell proliferation. CONCLUSION: Preserving and utilising the biodiversity of our planet, especially in unique ecosystems, such as the Cerrado Biome, may prove essential to preserving and promoting human health in modern contexts.

In Vitro Antidiabetic and Antioxidant Effects of Different Extracts of Catharanthus roseus and Its Indole Alkaloid, Vindoline.

The Catharanthus roseus plant has been used traditionally to treat diabetes mellitus. Scientific evidence supporting the antidiabetic effects of this plant's active ingredient-vindoline has not been fully evaluated. In this study, extracts of C. roseus and vindoline were tested for antioxidant activities, alpha amylase and alpha glucosidase inhibitory activities and insulin secretory effects in pancreatic RIN-5F cell line cultured in the absence of glucose, at low and high glucose concentrations. The methanolic extract of the plant showed the highest antioxidant activities in addition to the high total polyphenolic content (p < 0.05). The HPLC results exhibited increased concentration of vindoline in the dichloromethane and the ethylacetate extracts. Vindoline showed noticeable antioxidant activity when compared to ascorbic acid at p < 0.05 and significantly improved the in vitro insulin secretion. The intracellular reactive oxygen species formation in glucotoxicity-induced cells was significantly reduced following treatment with vindoline, methanolic and the dichloromethane extracts when compared to the high glucose untreated control (p < 0.05). Plant extracts and vindoline showed weaker inhibitory effects on the activities of carbohydrate metabolizing enzymes when compared to acarbose, which inhibited the activities of the enzymes by 80%. The plant extracts also exhibited weak alpha amylase and alpha glucosidase inhibitory effects.

Investigation of Dextran-Coated Superparamagnetic Nanoparticles for Targeted Vinblastine Controlled Release, Delivery, Apoptosis Induction, and Gene Expression in Pancreatic Cancer Cells.

In the current study, the surface of superparamagnetic iron oxide (SPION) was coated with dextran (DEX), and conjugated with folic acid (FA), to enhance the targeted delivery and uptake of vinblastine (VBL) in PANC-1 pancreatic cancer cells. Numerous analyses were performed to validate the prepared FA-DEX-VBL-SPION, such as field emission scanning transmission electron microscopy, high-resolution transmission electron microscopy, dynamic light scattering (DLS), Zeta Potential, Fourier transform infrared spectroscopy, and vibrating sample magnetometry (VSM). The delivery system capacity was evaluated by loading and release experiments. Moreover, in vitro biological studies, including a cytotoxicity study, cellular uptake assessment, apoptosis analysis, and real-time PCR, were carried out. The results revealed that the obtained nanocarrier was spherical with a suitable dispersion and without visible aggregation. Its average size, polydispersity, and zeta were 74 ± 13 nm, 0.080, and -45 mV, respectively. This dual functional nanocarrier also exhibited low cytotoxicity and a high apoptosis induction potential for successful VBL co-delivery. Real-time quantitative PCR analysis demonstrated the activation of caspase-3, NF-1, PDL-1, and H-ras inhibition, in PANC-1 cells treated with the FA-VBL-DEX-SPION nanostructure. Close inspection of the obtained data proved that the FA-VBL-DEX-SPION nanostructure possesses a noteworthy chemo-preventive effect on pancreatic cancer cells through the inhibition of cell proliferation and induction of apoptosis.

Transport Oligonucleotides-A Novel System for Intracellular Delivery of Antisense Therapeutics.

Biological activity of antisense oligonucleotides (asON), especially those with a neutral backbone, is often attenuated by poor cellular accumulation. In the present proof-of-concept study, we propose a novel delivery system for asONs which implies the delivery of modified antisense oligonucleotides by so-called transport oligonucleotides (tON), which are oligodeoxyribonucleotides complementary to asON conjugated with hydrophobic dodecyl moieties. Two types of tONs, bearing at the 5'-end up to three dodecyl residues attached through non-nucleotide inserts (TD series) or anchored directly to internucleotidic phosphate (TP series), were synthesized. tONs with three dodecyl residues efficiently delivered asON to cells without any signs of cytotoxicity and provided a transfection efficacy comparable to that achieved using Lipofectamine 2000. We found that, in the case of tON with three dodecyl residues, some tON/asON duplexes were excreted from the cells within extracellular vesicles at late stages of transfection. We confirmed the high efficacy of the novel and demonstrated that MDR1 mRNA targeted asON delivered by tON with three dodecyl residues significantly reduced the level of P-glycoprotein and increased the sensitivity of KB-8-5 human carcinoma cells to vinblastine. The obtained results demonstrate the efficacy of lipophilic oligonucleotide carriers and shows they are potentially capable of intracellular delivery of any kind of antisense oligonucleotides.

Biotechnological advancements in Catharanthus roseus (L.) G. Don.

Catharanthus roseus (L.) G. Don, also known as Madagascar periwinkle or Sadabahar, is a herbaceous plant belonging to the family Apocynaceae. Being a reservoir for more than 200 alkaloids, it reserves a place for itself in the list of important medicinal plants. Secondary metabolites are present in its leaves (e.g., vindoline, vinblastine, catharanthine, and vincristine) as well as basal stem and roots (e.g., ajmalicine, reserpine, serpentine, horhammericine, tabersonine, leurosine, catharanthine, lochnerine, and vindoline). Two of its alkaloids, vincristine and vinblastine (possessing anticancerous properties), are being used copiously in pharmaceutical industries. Till date, arrays of reports are available on in vitro biotechnological improvements of C. roseus. The present review article concentrates chiefly on various biotechnological advancements based on plant tissue culture techniques of the last three decades, for instance, regeneration via direct and indirect organogenesis, somatic embryogenesis, secondary metabolite production, synthetic seed production, clonal fidelity assessment, polyploidization, genetic transformation, and nanotechnology. It also portrays the importance of various factors influencing the success of in vitro biotechnological interventions in Catharanthus and further addresses several shortcomings that can be further explored to create a platform for upcoming innovative approaches. KEY POINTS: • C. roseus yields anticancerous vincristine and vinblastine used in pharma industry. •In vitro biotechnological interventions prompted major genetic advancements. • This review provides an insight on in vitro-based research achievements till date. • Key bottlenecks and prospective research methodologies have been identified herein.

Synthesis and Cytotoxic Activity of New Vindoline Derivatives Coupled to Natural and Synthetic Pharmacophores.

New Vinca alkaloid derivatives were synthesized to improve the biological activity of the natural alkaloid vindoline. To this end, experiments were performed to link vindoline with various structural units, such as amino acids, a 1,2,3-triazole derivative, morpholine, piperazine and N-methylpiperazine. The structure of the new compounds was characterized by NMR spectroscopy and mass spectrometry (MS). Several compounds exhibited in vitro antiproliferative activity against human gynecological cancer cell lines with IC50 values in the low micromolar concentration range.

Triarylaminium Radical Cation Promoted Coupling of Catharanthine with Vindoline: Diastereospecific Synthesis of Anhydrovinblastine and Reaction Scope.

A new triarylaminium radical cation promoted coupling of catharanthine with vindoline is disclosed, enlisting tris(4-bromophenyl)aminium hexachlororantimonate (BAHA, 1.1 equiv) in aqueous 0.05 N HCl/trifluoroethanol (1-10:1) at room temperature (25 °C), that provides anhydrovinblastine in superb yield (85%) with complete control of the newly formed quaternary C16' stereochemistry. A definition of the scope of aromatic substrates that participate with catharanthine in the BAHA-mediated diastereoselective coupling reaction and simplified indole substrates other than catharanthine that participate in the reaction are disclosed that identify the key structural features required for participation in the reaction, providing a generalized indole functionalization reaction that bears little structural relationship to catharanthine or vindoline.

Gene Expression Data Based Deep Learning Model for Accurate Prediction of Drug-Induced Liver Injury in Advance.

Drug-induced liver injury (DILI), one of the most common adverse effects, leads to drug development failure or withdrawal from the market in most cases, showing an emerging challenge that is to accurately predict DILI in the early stage. Recently, the vast amount of gene expression data provides us valuable information for distinguishing DILI on a genomic scale. Moreover, the deep learning algorithm is a powerful strategy to automatically learn important features from raw and noisy data and shows great success in the field of medical diagnosis. In this study, a gene expression data based deep learning model was developed to predict DILI in advance by using gene expression data associated with DILI collected from ArrayExpress and then optimized by feature gene selection and parameters optimization. In addition, the previous machine learning algorithm support vector machine (SVM) was also used to construct another prediction model based on the same data sets, comparing the model performance with the optimal DL model. Finally, the evaluation test using 198 randomly selected samples showed that the optimal DL model achieved 97.1% accuracy, 97.4% sensitivity, 96.8% specificity, 0.942 matthews correlation coefficient, and 0.989 area under the ROC curve, while the performance of SVM model only reached 88.9% accuracy, 78.8% sensitivity, 99.0% specificity, 0.794 matthews correlation coefficient, and 0.901 area under the ROC curve. Furthermore, external data sets verification and animal experiments were conducted to assess the optimal DL model performance. Finally, the predicted results of the optimal DL model were almost consistent with experiment results. These results indicated that our gene expression data based deep learning model could systematically and accurately predict DILI in advance. It could be a useful tool to provide safety information for drug discovery and clinical rational drug use in early stage and become an important part of drug safety assessment.

Vinblastine-Loaded Nanoparticles with Enhanced Tumor-Targeting Efficiency and Decreasing Toxicity: Developed by One-Step Molecular Imprinting Process.

Molecularly imprinted polymers have exhibited good performance as carriers on drug loading and sustained release. In this paper, vinblastine (VBL)-loaded polymeric nanoparticles (VBL-NPs) were prepared by a one-step molecular imprinting process, avoiding the waste and incomplete removal of the template, and evaluated as targeting carriers for VBL delivery after modification. Using acryloyl amino acid comonomers and disulfide cross-linkers, VBL-NPs were synthesized and then conjugated with poly(ethylene glycol)-folate. The dynamic size of the obtained VBL-NPs-PEG-FA was 258.3 nm (PDI = 0.250), and the encapsulation efficiency was 45.82 ± 1.45%. The nanoparticles of VBL-NPs-PEG-FA were able to completely release VBL during 48 h under a mimic tumor intracellular condition (pH 4.5, 10 mM glutathione (GSH)), displaying significant redox responsiveness, whereas the release rates were much slower in the mimic body liquid (pH 7.4, 2 µM GSH) and tumor extracellular environment (pH 6.5, 2 µM GSH). Furthermore, the carriers NPs-PEG-FA, prepared without VBL, showed satisfactory intrinsic hemocompatibility, cellular compatibility, and tumor-targeting properties: they could rapidly and efficiently accumulate to folate receptor positive Hela cells and then internalized via receptor-mediated endocytosis, and the retention in tumor tissues could last for over 48 h. Interestingly, VBL-NPs-PEG-FA could evidently increase the accumulation of VBL in tumor tissues while decreasing the distribution of VBL in organs, exert similar anticancer efficacy against Hela tumors in the xenograft model of nude mice to VBL injection, and significantly improve the abnormality of liver and spleen observed in VBL injection. VBL-NPs-PEG-FA has the potential to be the delivery carrier for VBL by enhancing the tumor-targeting efficacy of VBL and decreasing toxicity to normal tissues.

Ultra-potent vinblastine analogues improve on-target activity of the parent microtubulin-targeting compound.

In recent efforts, several C20' urea vinblastine analogues were discovered that displayed remarkable potency against vinblastine-sensitive tumor cell lines (IC50 50-75 pM), being roughly 100-fold more potent than vinblastine, and that exhibited decreased susceptibility to Pgp efflux-derived resistance in a vinblastine-resistant cell line. Their extraordinary activity indicate that it is not likely or even possible that their cellular functional activity is derived from stoichiometric occupancy of the intracellular tubulin binding sites. Rather, their potency indicates sub-stoichiometric or even catalytic occupancy of candidate binding sites may be sufficient to disrupt tubulin dynamics or microtubule assembly during mitosis. We detail efforts to delineate the underlying behavior responsible for the increased potency and show that the ultra-potent extended C20' ureas retain the mechanistic behavior of vinblastine, display enhanced affinity for tubulin and on-target activity approximately 100-fold both in vitro and in HeLa cells, but do not show evidence of catalytic disassembly of microtubulin. We also use the analogues to show that, in live interphase cells, the effects of the vinblastine class of drugs do not display a catastrophic effect on the microtubule skeleton, but rather a subtler insult to its dynamicity, acting as sub-stoichiometric drugs that inhibit normal microtubulin maturation and dynamics.

Double-sides sticking mechanism of vinblastine interacting with α,ß-tubulin to get activity against cancer cells.

Vinblastine (VLB) and its derivatives have been used for clinical first-line drugs to treat various cancers. Due to the resistance and serious side effects from using VLB and its derivatives, there is a need to discover and develop novel VLB derivatives with high activity against cancer cells. In order to better discover and develop new VLB derivatives, we need to study the structural basis of VLB's anti-cancer cytotoxicity and the mechanism of its interaction with α,ß-tubulins. Based on the crystal structure of α,ß-microtubule complex protein, the molecular dynamics method including the sampling PMF method was used to study the variation of dissociation free energy (ΔG) of α,ß-tubulins under different system conditions, and then from which to study the mechanism of the interaction between VLB and α,ß-tubulins. The obtained results show that the dissociation of pure α,ß-tubulins requires 197.8 kJ·mol-1 for ΔG. When the VLB molecule exists between the interface of α,ß-tubulins, the dissociation ΔG of α,ß-tubulins reaches 220.5 kJ·mol-1, which is greater than that of pure α,ß-tubulin. The VLB molecule is formed by connecting a vindoline moiety (VM) molecule with a catharanthine moiety (CM) molecule through a carbon-carbon bond, which is a larger molecule. When the CM molecule exists in the middle of α,ß-tubulin interface, the dissociation ΔG of α,ß-tubulins is 46.2 kJ·mol-1, during which the CM moves with ß-tubulin. When the VM molecule exists between the middle of α,ß-tubulin interface, the dissociation ΔG of α,ß-tubulins is 86.7 kJ·mol-1, during which it moves with α-tubulin. Therefore, the VLB molecule is like a double-sides tape to stick α-tubulin and ß-tubulin together. The VLB molecule intervenes the dynamic equilibrium between dissociation and aggregation of α-tubulin and ß-tubulin by a double-sides sticking mechanism to exert high activity with toxicity against cancer cell. Besides, our results demonstrate that VLB has its structural basis for anticancer cytotoxicity due to its two compositions composed of a CM molecule and a VM molecule although they have little toxicity against cancer cell alone.