Microtubule assembly dynamics: an attractive target for anticancer drugs

Microtubules, composed of αβ tubulin dimers, are dynamic polymers of eukaryotic cells. They play important roles in various cellular functions including mitosis. Microtubules exhibit differential dynamic behaviors during different phases of the cell cycle. Inhibition of the microtubule assembly dynamics causes cell cycle arrest leading to apoptosis; thus, qualifying them as important drug targets for treating several diseases including cancer, neuronal, fungal, and parasitic diseases. Although several microtubule-targeted drugs are successfully being used in cancer chemotherapy, the development of resistance against these drugs and their inherent toxicities warrant the development of new agents with improved efficacy. Several antimicrotubule agents are currently being evaluated for their possible uses in cancer chemotherapy. Benomyl, griseofulvin, and sulfonamides have been used as antifungal and antibacterial drugs. Recent reports have shown that these drugs have potent antitumor potential. These agents are shown to inhibit proliferation of different types of tumor cells and induce apoptosis by targeting microtubule assembly dynamics. However, unlike vincas and taxanes, which inhibit cancer cell proliferation in nanomolar concentration range, these agents act in micromolar range and are considered to have limited toxicities. Here, we suggest that these drugs may have a significant use in cancer chemotherapy when used in combination with other anticancer drugs

Smart and secure medical device gateway for managing patient recovery

Patients recuperating from orthopedic surgery require frequent monitoring and hospital visits with a wealth of personal medical data generated both on and off-site, making it challenging to maintain records. This paper discusses a secure blockchain-based data management software to enable safe remote access without compromising patient information. The BlockTrack software developed at our group will be customized to interface with modules for orthopedic recuperation monitoring. Modules can consist of ultrasonic bone health monitoring sensors, connected to relay nodes that can transmit patient data to the BlockTrack mobile app, which then intercepts the information to be stored securely on a cloud-based Blockchain network. Each record will have a unique ID enabled by Blockchain, for secure access and review of patient information by other parties, including doctors and pharmacists. Key findings are discussed with a goal to further develop this solution

Dietary antioxidant curcumin inhibits microtubule assembly through tubulin binding

Curcumin, a component of turmeric, has potent antitumor activity against several tumor types. However, its molecular target and mechanism of antiproliferative activity are not clear. Here, we identified curcumin as a novel antimicrotubule agent. We have examined the effects of curcumin on cellular microtubules and on reconstituted microtubules in vitro. Curcumin inhibited HeLa and MCF-7 cell proliferation in a concentration-dependent manner with IC50 of 13.8±0.7μm and 12±0.6μm, respectively. At higher inhibitory concentrations (>10μm), curcumin induced significant depolymerization of interphase microtubules and mitotic spindle microtubules of HeLa and MCF-7 cells. However, at low inhibitory concentrations there were minimal effects on cellular microtubules. It disrupted microtubule assembly in vitro, reduced GTPase activity, and induced tubulin aggregation. Curcumin bound to tubulin at a single site with a dissociation constant of 2.4±0.4μm and the binding of curcumin to tubulin induced conformational changes in tubulin. Colchicine and podophyllotoxin partly inhibited the binding of curcumin to tubulin, while vinblastine had no effect on the curcumin-tubulin interactions. The data together suggested that curcumin may inhibit cancer cells proliferation by perturbing microtubule assembly dynamics and may be used to develop efficacious curcumin analogues for cancer chemotherapy

Griseofulvin stabilizes microtubule dynamics, activates p53 and inhibits the proliferation of MCF-7 cells synergistically with vinblastine

<p>Abstract</p> <p>Background</p> <p>Griseofulvin, an antifungal drug, has recently been shown to inhibit proliferation of various types of cancer cells and to inhibit tumor growth in athymic mice. Due to its low toxicity, griseofulvin has drawn considerable attention for its potential use in cancer chemotherapy. This work aims to understand how griseofulvin suppresses microtubule dynamics in living cells and sought to elucidate the antimitotic and antiproliferative action of the drug.</p> <p>Methods</p> <p>The effects of griseofulvin on the dynamics of individual microtubules in live MCF-7 cells were measured by confocal microscopy. Immunofluorescence microscopy, western blotting and flow cytometry were used to analyze the effects of griseofulvin on spindle microtubule organization, cell cycle progression and apoptosis. Further, interactions of purified tubulin with griseofulvin were studied <it>in vitro </it>by spectrophotometry and spectrofluorimetry. Docking analysis was performed using autodock4 and LigandFit module of Discovery Studio 2.1.</p> <p>Results</p> <p>Griseofulvin strongly suppressed the dynamic instability of individual microtubules in live MCF-7 cells by reducing the rate and extent of the growing and shortening phases. At or near half-maximal proliferation inhibitory concentration, griseofulvin dampened the dynamicity of microtubules in MCF-7 cells without significantly disrupting the microtubule network. Griseofulvin-induced mitotic arrest was associated with several mitotic abnormalities like misaligned chromosomes, multipolar spindles, misegregated chromosomes resulting in cells containing fragmented nuclei. These fragmented nuclei were found to contain increased concentration of p53. Using both computational and experimental approaches, we provided evidence suggesting that griseofulvin binds to tubulin in two different sites; one site overlaps with the paclitaxel binding site while the second site is located at the αβ intra-dimer interface. In combination studies, griseofulvin and vinblastine were found to exert synergistic effects against MCF-7 cell proliferation.</p> <p>Conclusions</p> <p>The study provided evidence suggesting that griseofulvin shares its binding site in tubulin with paclitaxel and kinetically suppresses microtubule dynamics in a similar manner. The results revealed the antimitotic mechanism of action of griseofulvin and provided evidence suggesting that griseofulvin alone and/or in combination with vinblastine may have promising role in breast cancer chemotherapy.</p

Kinetic stabilization of microtubule dynamic instability by benomyl increases the nuclear transport of p53

Using time-lapse confocal microscopy and enhanced green fluorescent protein–tubulin transfected MCF-7 cells, we found that a tubulin-targeted antimitotic agent, benomyl at its half-maximal proliferation inhibitory concentration (5 μM) strongly suppressed the rate and extent of growing and shortening excursions of individual microtubules in MCF-7 cells without noticeably depolymerizing the microtubule network or decreasing the polymerized mass of tubulin. Further, benomyl treatment caused an increase in the acetylation level of microtubules suggesting that it stabilizes microtubules. Under the conditions that suppressed the dynamic instability, a sharp increase in the nuclear accumulation of p53 in MCF-7 cells was observed in the presence of benomyl. Up regulation of bax and the increased nuclear accumulation of p21 upon benomyl treatment confirmed the activation of p53. Cisplatin caused an increase in the translocation of p53 into the nucleus in the presence of lower effective concentrations of benomyl while a decrease in the nuclear accumulation of p53 was observed in the presence of high concentrations of benomyl suggesting that the stabilized microtubules assist in the nuclear transportation of p53. Furthermore, increased localization of the light chain of the minus end directed motor protein dynein was detected on the microtubules in the benomyl-treated cells indicating that the suppression of microtubule dynamics may influence the binding of dynein on the microtubules and dynein-mediated cargo transport. Together the data indicate that benomyl inhibits mitosis primarily by suppressing the dynamic instability of microtubules and support the hypothesis that the kinetic stabilization of microtubules enhances the microtubule-mediated transport of p53 into the nucleus.© Elsevie

Antibacterial and anticancer activity of the purified cashew nut shell liquid: implications in cancer chemotherapy and wound healing

<p>The cashew nut shell liquid (CNSL) from the cashew nut shell of <i>Anacardium occidentale</i> L. has been used to treat skin infections, cracks on soles of feet and cancerous ulcers. In this study, we have purified the technical CNSL, systematically evaluated its anticancer, antibacterial and wound healing activity. The LC-MS data revealed that the purified CNSL contains the compounds, cardanol, anacardic acid and methylcardol. It inhibited the proliferation of HeLa cells with an IC₅₀ of 0.004%(v/v) and caused moderate mitotic block with spindle abnormality. It induced apoptosis in HeLa cells and accelerated wound closure in L929 cells. It inhibited the growth of <i>Bacillus subtilis</i> with an IC₅₀ of 0.35%(v/v) and the treated cells exhibited elongated morphology indicating that suppression of cell division is one of the possible mechanisms of its action. The study suggests that the purified CNSL might have potential applications in anticancer and antibacterial drug development.</p

Benomyl and Colchicine Synergistically Inhibit Cell Proliferation and Mitosis: Evidence of Distinct Binding Sites for These Agents in Tubulin †

International audienceBenomyl, a tubulin-targeted antimitotic antifungal agent, belongs to the benzimidazole group of compounds, which are known to inhibit the binding of colchicine to tubulin. Therefore, benomyl was thought to bind at or near the colchicine-binding site on tubulin. However, recent mutational studies in yeast and fluorescence studies involving competitive binding of benomyl and colchicine on goat brain tubulin suggested that benomyl may bind to tubulin at a site distinct from the colchicine-binding site. We set out to examine whether colchicine and benomyl bind to tubulin at distinct sites using a human cervical cancer (HeLa) cell line with the thinking that these agents should exert either additive or synergistic activity on cell proliferation if their binding sites on tubulin are different. We found that benomyl and colchicine synergistically inhibited the proliferation of HeLa cells and blocked their cell cycle progression at mitosis. The synergistic activity of benomyl and colchicine was also apparent from their strong depolymerizing effects on both the spindle and interphase microtubules when used in combinations, providing further evidence that these agents bind to tubulin at different sites. Using NMR spectroscopy, we finally demonstrated that benomyl and colchicine bind to tubulin at different sites and that the binding of colchicine seems to positively influence the binding of benomyl to tubulin and vice versa. Further, an analysis of the saturation transfer difference NMR data yielded an interesting insight into the colchicine−tubulin interaction. The data presented in this study provided a mechanistic understanding of the synergistic effects of benomyl and colchicine on HeLa cell proliferation

Unravelling the spatial diversity of Indian precipitation teleconnections via a non-linear multi-scale approach

A better understanding of precipitation dynamics in the Indian subcontinent is required since India’s society depends heavily on reliable monsoon forecasts. We introduce a non-linear, multiscale approach, based on wavelets and event synchronization, for unravelling teleconnection influences on precipitation. We consider those climate patterns with the highest relevance for Indian precipitation. Our results suggest significant influences which are not well captured by only the wavelet coherence analysis, the state-of-the-art method in understanding linkages at multiple timescales.We find substantial variation across India and across timescales. In particular, El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) mainly influence precipitation in the south-east at interannual and decadal scales, respectively, whereas the North Atlantic Oscillation (NAO) has a strong connection to precipitation, particularly in the northern regions. The effect of the Pacific Decadal Oscillation (PDO) stretches across the whole country, whereas the Atlantic Multidecadal Oscillation (AMO) influences precipitation particularly in the central arid and semi-arid regions. The proposed method provides a powerful approach for capturing the dynamics of precipitation and, hence, helps improve precipitation forecasting