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Therapeutic effect against human xenograft tumors in nude mice by the third generation microtubule stabilizing epothilones.

ABSTRACT: The epothilones represent a promising class of natural product-based antitumor drug candidates. Although these compounds operate through a microtubule stabilization mechanism similar to that of taxol, the epothilones offer a major potential therapeutic advantage in that they retain their activity against multidrug-resistant cell lines. We have been systematically synthesizing and evaluating synthetic epothilone congeners that are not accessible through modification of the natural product itself. We report herein the results of biological investigations directed at two epothilone congeners: iso-fludelone and iso-dehydelone. Iso-fludelone, in particular, exhibits a number of properties that render it an excellent candidate for preclinical development, including biological stability, excellent solubility in water, and remarkable potency relative to other epothilones. In nude mouse xenograft settings, iso-fludelone was able to achieve therapeutic cures against a number of human cancer cell lines, including mammarian-MX-1, ovarian-SK-OV-3, and the fast-growing, refractory, subcutaneous neuroblastoma-SK-NAS. Strong therapeutic effect was observed against drug-resistant lung-A549/taxol and mammary-MCF-7/Adr xenografts. In addition, iso-fludelone was shown to exhibit a significant therapeutic effect against an intracranially implanted SK-NAS tumor.

SUBMITTER: Chou TC

PROVIDER: S-EPMC2529025 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature

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Therapeutic effect against human xenograft tumors in nude mice by the third generation microtubule stabilizing epothilones.

Chou Ting-Chao TC Zhang Xiuguo X Zhong Zi-Yang ZY Li Yong Y Feng Li L Eng Sara S Myles David R DR Johnson Robert R Wu Nian N Yin Ye Ingrid YI Wilson Rebecca M RM Danishefsky Samuel J SJ

Proceedings of the National Academy of Sciences of the United States of America 20080828 35

The epothilones represent a promising class of natural product-based antitumor drug candidates. Although these compounds operate through a microtubule stabilization mechanism similar to that of taxol, the epothilones offer a major potential therapeutic advantage in that they retain their activity against multidrug-resistant cell lines. We have been systematically synthesizing and evaluating synthetic epothilone congeners that are not accessible through modification of the natural product itself. ...[more]

PMID: 18755900

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Project description:BackgroundSurvivin is a dual function protein. It inhibits the apoptosis of cells by inhibiting caspases, and also promotes cell growth by stabilizing microtubules during mitosis. Over-expression of survivin has been demonstrated to induce drug-resistance to various chemo-therapeutic agents such as cisplatin (DNA damaging agent) and paclitaxel (microtubule stabilizer) in cancers. However, survivin-induced resistance to microtubule de-stabilizers such as Vinca alkaloids and Combretastatin A-4 (CA-4)-related compounds were seldom demonstrated in the past. Furthermore, the question remains as to whether survivin plays a dominant role in processing cytokinesis or inhibiting caspases activity in cells treated with anti-mitotic compounds. The purpose of this study is to evaluate the effect of survivin on the resistance and susceptibility of human cancer cells to microtubule de-stabilizer-induced cell death.ResultsBPR0L075 is a CA-4 analog that induces microtubule de-polymerization and subsequent caspase-dependent apoptosis. To study the relationship between the expression of survivin and the resistance to microtubule de-stabilizers, a KB-derived BPR0L075-resistant cancer cell line, KB-L30, was generated for this study. Here, we found that survivin was over-expressed in the KB-L30 cells. Down-regulation of survivin by siRNA induced hyper-sensitivity to BPR0L075 in KB cells and partially re-stored sensitivity to BPR0L075 in KB-L30 cells. Western blot analysis revealed that down-regulation of survivin induced microtubule de-stabilization in both KB and KB-L30 cells. However, the same treatment did not enhance the down-stream caspase-3/-7 activities in BPR0L075-treated KB cells. Translocation of a caspase-independent apoptosis-related molecule, apoptosis-inducing factor (AIF), from cytoplasm to the nucleus was observed in survivin-targeted KB cells under BPR0L075 treatment.ConclusionIn this study, survivin plays an important role in the stability of microtubules, but not with caspases inhibition. Over-expression of survivin counteracts the therapeutic effect of microtubule de-stabilizer BPR0L075 probably by stabilizing tubulin polymers, instead of the inhibition of caspase activity in cancer cells. Besides microtubule-related caspase-dependent cell death, caspase-independent mitotic cell death could be initiated in survivin/BPR0L075 combination treatments. We suggest that combining microtubule de-stabilizers with a survivin inhibitor may attribute to a better clinical outcome than the use of anti-mitotic monotherapy in clinical situations.

Project description:PurposeLarge-scale studies have revealed that appropriate antiangiogenic treatment enables the recovery of the normal structure and function of solid tumor vessels. Epigallocatechin-3-gallate (EGCG), a natural extract of green tea, has multiple effects on angiogenesis. However, normalization of blood vessels due to natural ingredients has not yet been reported. Therefore, we examined the microvasculature, microenvironment, and efficacy of EGCG combined with chemotherapy in a xenograft model.MethodsWe treated A549 cell (human lung adenocarcinoma cell line) xenograft-bearing nude mice with EGCG in vivo. CD31, αSMA, and collagen IV were labeled and detected using quantum-dot double-labeled immunofluorescence to measure microvessel density, microvessel pericyte-coverage index, and collagen IV expression. Vessel-perfusion function was determined by lectin injection, permeability by Evans blue extravasation, interstitial fluid pressure using the wick-in-needle technique, and hypoxia levels using a polarographic electrode and immunohistochemical pimonidazole labeling. Cisplatin concentration in tumor tissue was detected using graphite-furnace atomic absorption spectrophotometry. Xenograft mice were randomized into five groups: treated with saline, cisplatin, EGCG, EGCG + cisplatin on day 1, or EGCG + cisplatin during the vascular normalization window. Tumor-growth delay and tumor-suppression rate were measured to evaluate tumor growth.ResultsEGCG treatment in vivo caused temporary changes, including transient depression of microvessel density, microvessel pericyte-coverage index, and collagen IV expression, transient elevation of vessel perfusion and permeability, and decreased interstitial fluid pressure and hypoxia. During vascular normalization, pretreatment with EGCG increased cisplatin concentration in tumor tissue compared with treatment with cisplatin only. Tumor-growth delay after treatment in the five groups during the vascular normalization window was 6.3±1.51, 7.5±1.57, 8.3±1.79, 12.1±1.35, and 15.4±1.99 days, indicating synergistic EGCG-cisplatin effects, especially during the vascular normalization window (P<0.01).ConclusionEGCG-induced vascular normalization in human lung adenocarcinoma may be a novel modality for enhancing chemotherapy effects.

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Therapeutic effect against human xenograft tumors in nude mice by the third generation microtubule stabilizing epothilones.

Publications

Therapeutic effect against human xenograft tumors in nude mice by the third generation microtubule stabilizing epothilones.

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