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Designing and Testing of Novel Taxanes to Probe the Highly Complex Mechanisms by Which Taxanes Bind to Microtubules and Cause Cytotoxicity to Cancer Cells.

ABSTRACT: Our previous work identified an intermediate binding site for taxanes in the microtubule nanopore. The goal of this study was to test derivatives of paclitaxel designed to bind to this intermediate site differentially depending on the isotype of β-tubulin. Since β-tubulin isotypes have tissue-dependent expression--specifically, the βIII isotype is very abundant in aggressive tumors and much less common in normal tissues--this is expected to lead to tubulin targeted drugs that are more efficacious and have less side effects. Seven derivatives of paclitaxel were designed and four of these were amenable for synthesis in sufficient purity and yield for further testing in breast cancer model cell lines. None of the derivatives studied were superior to currently used taxanes, however computer simulations provided insights into the activity of the derivatives. Our results suggest that neither binding to the intermediate binding site nor the final binding site is sufficient to explain the activities of the derivative taxanes studied. These findings highlight the need to iteratively improve on the design of taxanes based on their activity in model systems. Knowledge gained on the ability of the engineered drugs to bind to targets and bring about activity in a predictable manner is a step towards personalizing therapies.

SUBMITTER: St George M

PROVIDER: S-EPMC4460180 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Designing and Testing of Novel Taxanes to Probe the Highly Complex Mechanisms by Which Taxanes Bind to Microtubules and Cause Cytotoxicity to Cancer Cells.

St George Marc M Ayoub Ahmed T AT Banerjee Asok A Churchill Cassandra D M CD Winter Philip P Klobukowski Mariusz M Cass Carol E CE Ludueña Richard F RF Tuszynski Jack A JA Damaraju Sambasivarao S

PloS one 20150608 6

Our previous work identified an intermediate binding site for taxanes in the microtubule nanopore. The goal of this study was to test derivatives of paclitaxel designed to bind to this intermediate site differentially depending on the isotype of β-tubulin. Since β-tubulin isotypes have tissue-dependent expression--specifically, the βIII isotype is very abundant in aggressive tumors and much less common in normal tissues--this is expected to lead to tubulin targeted drugs that are more efficaciou ...[more]

PMID: 26052950

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Project description:Diaphanous-related formin-3 (DIAPH3), a cytoskeletal regulator of the formin family, is lost at high frequency in metastatic breast and prostate cancers and has characteristics of a non-canonical metastasis suppressor. We previously demonstrated that DIAPH3 silencing evokes transition to an “amoeboid” phenotype, characterized by rapid motility, RhoA/ROCK and MEK/ERK pathway activation, dynamic membrane blebbing, and increased shedding of microvesicles. Here we report that low DIAPH3 mRNA expression correlates with reduced survival in multiple cancer patient cohorts. In line with induction of amoeboid behavior, traction force microscopy (TFM) revealed that polarized force generation, contractility, and response to substrate stiffness are reduced by DIAPH3 loss. Proteomic analyses revealed that DIAPH3 precipitates with tubulins, and reciprocal co-immunoprecipitation analyses revealed greater binding of DIAPH3 to MT polymers than soluble tubulin. DIAPH3 also bound to acetylated-tubulin (Ac-tubulin), suggesting association with a stable MT population. DIAPH3 silencing reduced Ac-tubulin and increased the cellular content of dynamic MT, as indicated by TFM and live cell imaging. DIAPH3 silencing also increased responsiveness to MT-disrupting agents. Treatment with the taxanes paclitaxel and docetaxel, and the non-taxane epothilone B, induced a greater change in Ac-tubulin when cells lacked DIAPH3. Intracellular accumulation of Oregon Green 488-paclitaxel was also increased by DIAPH3 loss, and accordingly, DIAPH3 silencing enhanced cytotoxicity by paclitaxel, docetaxel, or epothilone B. Gene expression profiles of breast cancer patients treated with chemotherapeutic regimens containing taxanes revealed an association of low DIAPH3 expression with improved relapse-free survival. Collectively, these results suggest that regulation of MT stability/dynamics by DIAPH3 enhances amoeboid tumor cell susceptibility to microtubule poisons. These findings have potential therapeutic implications.

Dataset Information

Designing and Testing of Novel Taxanes to Probe the Highly Complex Mechanisms by Which Taxanes Bind to Microtubules and Cause Cytotoxicity to Cancer Cells.

Publications

Designing and Testing of Novel Taxanes to Probe the Highly Complex Mechanisms by Which Taxanes Bind to Microtubules and Cause Cytotoxicity to Cancer Cells.

Similar Datasets

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