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dc.contributor.authorBurkhart, Catherine Alyce
dc.date.accessioned2018-07-12T18:56:55Z
dc.date.available2018-07-12T18:56:55Z
dc.date.issued1998
dc.identifier.citationSource: Dissertation Abstracts International, Volume: 61-02, Section: B, page: 7980.;Advisors: Susan Band Horwitz.
dc.identifier.urihttps://yulib002.mc.yu.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:9961302
dc.identifier.urihttps://hdl.handle.net/20.500.12202/3834
dc.description.abstractTaxol is an antitumor agent that has been approved for the treatment of ovarian, breast and lung carcinomas. The major cellular target for Taxol is beta-tubulin. Taxol stabilizes microtubules leading to a mitotic block and apoptosis. Structure-activity studies have demonstrated that the cytotoxicity of this drug correlates with its ability to stabilize microtubules. Taxol can also induce tumor necrosis factor-alpha (TNF-alpha) gene expression in murine macrophages. Since TNF-alpha can be cytotoxic to tumor cells, the ability of Taxol to induce TNF-alpha may contribute to its overall efficacy. To address this question, a structure-activity study was performed using a series of Taxol analogs with varying degrees of cytotoxicity. RAW 264.7 murine macrophage cells were treated with Taxol and related taxanes, and then analyzed for TNF-alpha gene expression by northern blot analysis and a TNF bioassay. This study demonstrated that their was no correlation between the induction of TNF-alpha and cytotoxicity. Taxotere, a drug with a similar structure to Taxol, was unable to induce TNF-alpha gene expression even though it has demonstrated excellent activity against human tumors. These data suggest that TNF-alpha production does not contribute to the overall efficacy of Taxol. One obstacle to the successful use of Taxol is the development of drug resistance. In mammalian cells, there are 6--7 beta-tubulin isotypes. Our laboratory has demonstrated a dramatic increase in Mbeta2 (class II beta-tubulin) in a highly Taxol-resistant cell line, J7-T1, suggesting that increased Mbeta2 may contribute to Taxol resistance. To address this question, the E3-Mbeta2-42.3.5 cell line, which stably expresses Mbeta2 under the control of an ecdysone-inducible expression system, was developed. RT-PCR analysis demonstrated that E3-Mbeta2--42.3.5 had 3--5.5-fold more Mbeta2 than the control cell lines. An ∼2--3.5-fold increase in class II protein was apparent by western blot and FACS analysis. The effects of Taxol on D-Mbeta2--42.3.5, as determined by cytotoxicity assays, flow cytometry, and immunofluorescence, were similar to the control cell lines, suggesting that increased expression of Mbeta2 is not a significant mechanism of Taxol resistance. The two studies presented here contribute to a better understanding of the mechanisms of action and of resistance to Taxol.
dc.publisherProQuest Dissertations & Theses
dc.subjectPharmacology.
dc.titleTaxol: Mechanisms of action and resistance
dc.typeDissertation


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