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dc.contributor.advisor Pizzo, Salvatore V. en_US
dc.contributor.advisor Dewhirst, Mark W. en_US
dc.contributor.advisor Fields, Timothy A. en_US
dc.contributor.advisor Kontos, Christopher D. en_US
dc.contributor.advisor Staats, Herman F. en_US
dc.contributor.author Quinones, Quintin Jose en_US
dc.date.accessioned 2009-05-01T18:34:37Z
dc.date.available 2011-07-26T04:30:04Z
dc.date.issued 2009 en_US
dc.identifier.uri http://hdl.handle.net/10161/1172
dc.description Dissertation en_US
dc.description.abstract <p>Selective therapeutic targeting of tumors requires identification of differences between the homeostatic requirements of cancer and host cells. One such difference is the manner in which cancer cells acquire energy. Cancer cells often grow in an environment of local hypoxia; under these conditions tumor cells depend on glycolysis for energy, but are unable to perform oxidative phosphorylation. Many tumor cells, despite normoxic conditions, continue to perform glycolysis without oxidative phosphorylation. The net result of glycolysis without oxidative phosphorylation is twofold: the need to consume a greater amount of glucose than a non-cancerous host cell, and the burden of increased intracellular lactic acid. The proteins responsible for the transport of lactic acid in and out of cells are known as the monocarboxylate transporters (MCTs). Monocarboxylate Transporter 1 (MCT1) and Monocarboxylate Transporter 4 (MCT4) are the MCTs that play a major role in the transport of lactic acid. Tumor cells depend on MCT1 and MCT4 activity to excrete excess intracellular lactic acid to maintain neutral intracellular pH and homeostasis. Using human neuroblastoma and prostate cancer cell lines this work demonstrates that tumor cells can be selectively targeted tumor under conditions of hypoxia or acidosis in vitro with the drug lonidamine, with a small molecule inhibitor selective for MCT1, or with RNA interference of MCT1. Inhibition of MCT1 activity in neuroblastoma cells under acidic extracellular conditions results in intracellular acidification and cell death. MCT1 mRNA is expressed in human neuroblastoma and positively correlated with clinical risk profile. Inhibition of MCT1 activity in hypoxic prostate cancer cells results in a reduction of lactate excretion, decreased intracellular pH, inhibition of ATP production, and subsequent cell death. MCT1 expression in sections of human prostate tumors has been demonstrated to validate MCT1 as a target in prostate cancer.</p> <p>Through the Pasteur and Warburg effects, tumors have an increased demand for glucose. Some cancers store glycogen, but the reasons for this are largely unknown. It is hypothesized that tumor glycogen is used to promote tumor survival during transient hypoxia or low glucose, and that the mechanisms by which glycogen is stored is a potential therapeutic target in cancer. Tumors from human cell lines (WiDr, PC3, FaDu) have been grown in nude mice, sectioned and stained to measure glycogen storage. Using consecutive frozen sections, levels of hypoxia, glucose, lactate, ATP, and CD31, an endothelial cell marker, have been determined. These sections have been employed to elucidate the "architecture" of tumor metabolism in terms of vessel distance. Additionally, PAS-stained EF5 labeled human tumor samples were used to obtain calibrated hypoxia measurements to correlate with PAS. These studies demonstrate a correlation between hypoxia and the formation of glycogen deposits in human tumors and nude mouse xenografts. In cell culture, formation of glycogen deposits after exposure to hypoxia has been demonstrated, in addition to expression of glycogen synthase in human cancer cell lines.</p> <p>The development of novel selective cancer chemotherapeutics will require the identification of differences between cancerous cells and normal host cells to exploit as targets. Several differences in metabolism, including the need to excrete excess lactic acid and store glycogen under hypoxic conditions, are such targets. Novel therapeutics exploiting these targets should be effective against cancer cells and minimally toxic to host cells.</p> en_US
dc.format.extent 4114052 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Health Sciences, Oncology en_US
dc.subject monocarboxylate transporter en_US
dc.subject MCT en_US
dc.subject glycogen en_US
dc.subject cancer en_US
dc.subject metabolism en_US
dc.subject hypoxia en_US
dc.title Metabolic Targeting of Cancer Cells: Two Molecular Mechanisms Involving Glucose Metabolism en_US
dc.type Dissertation en_US
dc.department Pathology en_US
duke.embargo.months 24 en_US

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