Paclitaxel, an antimitotic agent that promotes microtubule assembly, is one of the most potent anti-cancer drugs in clinical use. Its ability to cure disease, however, is limited by the problem of drug resistance;i.e., many patients who initially respond to paclitaxel suffer relapses and become refractory to further treatment. The goal of this project is characterization of the cellular mechanisms responsible for this phenomenon. Mammalian cell tubulin is encoded by a multigene family that produces distinct gene products, or isotypes. One prominent mechanism of resistance involves mutations in tubulin genes that alter microtubule assembly in a way that counteracts the action of the drug. It is not yet clear, however, which mutations and which tubulin genes are involved. To obtain this information, mammalian cell mutants will be selected for resistance to paclitaxel following transfection of site-directed or randomly mutagenized tubulin cDNAs. Transfected DMA from cells that survive in paclitaxel will be sequenced to identify tubulin mutations responsible for resistance, and changes in microtubule assembly in these cell lines will be examined to identify the mechanism responsible for resistance. Additonal studies will use overexpression or silencing of various tubulin genes to test the hypothesis that altered synthesis of specific tubulin isotypes may also contribute to the drug resistance phenotype. Finally, the microtubule interacting proteins stathmin and MCAK will be overexpressed, silenced, and mutagenized to determine whether changes in these microtubule regulators are capable of conferring resistance to antimitotic drugs. The activity of stathmin and MCAK in cells with varying tubulin composition and tubulin mutations will also be measured to explore the possibility that drug resistance may sometimes occur because of altered tubulin-stathmin or tubulin-MCAK interactions. The nformation obtained from the studies in this proposal will be important for characterizing the mechanism of action of antimitotic drugs, developing assays to detect drug resistant cells in human tumors, and formulating strategies to circumvent drug resistance when it occurs.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-ONC-Q (01))
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Fu, Yali
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University of Texas Health Science Center Houston
Schools of Medicine
United States
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Ganguly, Anutosh; Yang, Hailing; Zhang, Hong et al. (2013) Microtubule dynamics control tail retraction in migrating vascular endothelial cells. Mol Cancer Ther 12:2837-46
Yin, Shanghua; Zeng, Changqing; Hari, Malathi et al. (2013) Paclitaxel resistance by random mutagenesis of ?-tubulin. Cytoskeleton (Hoboken) 70:849-62
Ganguly, Anutosh; Yang, Hailing; Sharma, Ritu et al. (2012) The role of microtubules and their dynamics in cell migration. J Biol Chem 287:43359-69
Yin, Shanghua; Zeng, Changqing; Hari, Malathi et al. (2012) Random mutagenesis of ?-tubulin defines a set of dispersed mutations that confer paclitaxel resistance. Pharm Res 29:2994-3006
Ganguly, Anutosh; Bhattacharya, Rajat; Cabral, Fernando (2012) Control of MCAK degradation and removal from centromeres. Cytoskeleton (Hoboken) 69:303-11
Ganguly, Anutosh; Yang, Hailing; Cabral, Fernando (2011) Overexpression of mitotic centromere-associated Kinesin stimulates microtubule detachment and confers resistance to paclitaxel. Mol Cancer Ther 10:929-37
Ganguly, Anutosh; Yang, Hailing; Cabral, Fernando (2011) Class III ýý-tubulin counteracts the ability of paclitaxel to inhibit cell migration. Oncotarget 2:368-77
Yang, Hailing; Ganguly, Anutosh; Yin, Shanghua et al. (2011) Megakaryocyte lineage-specific class VI ýý-tubulin suppresses microtubule dynamics, fragments microtubules, and blocks cell division. Cytoskeleton (Hoboken) 68:175-87
Ganguly, Anutosh; Cabral, Fernando (2011) New insights into mechanisms of resistance to microtubule inhibitors. Biochim Biophys Acta 1816:164-71
Ganguly, Anutosh; Yang, Hailing; Pedroza, Mesias et al. (2011) Mitotic centromere-associated kinesin (MCAK) mediates paclitaxel resistance. J Biol Chem 286:36378-84

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