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dc.contributor.advisor Counter, Christopher M en_US
dc.contributor.author Lampson, Benjamin Logan en_US
dc.date.accessioned 2012-05-25T20:05:11Z
dc.date.available 2014-05-15T04:30:04Z
dc.date.issued 2012 en_US
dc.identifier.uri http://hdl.handle.net/10161/5394
dc.description Dissertation en_US
dc.description.abstract <p>RAS is a small GTPase that helps to convert extracellular cues into intracellular actions. It is the most commonly mutated oncogene and is found in an active mutant form in 90% of pancreatic cancers. Therefore, study of how this protein is made and then how this protein signals in the cell could provide the foundation for novel approaches to treat RAS-driven malignancies.</p><p>First I demonstrate that the level of protein expressed from the gene KRAS, but not the highly homologous gene HRAS, is limited in mammalian cells by an abundance of underrepresented (rare) codons in the encoding mRNA. KRAS mRNA from both ectopic plasmids as well as from the endogenous cellular gene is subject to slowed translation due to these rare codons within its coding sequence. This has consequences for tumorigenesis, as replacement of the rare codons with commonly used codons accelerates RAS driven tumor growth. This may extend beyond HRAS and KRAS, as many other homologous gene pairs show a high divergence in codon usage and protein expression, suggesting that this could be a wider phenomenon used by mammalian cells to regulate protein levels.</p><p>Second, I demonstrate that RAS driven tumors partially depend on eNOS for growth. Using genetically engineered mouse models that recapitulate the spontaneous development of pancreatic cancer, I demonstrate that the protein eNOS is progressively upregulated as tumors develop. I then demonstrate that genetic ablation of eNOS partially blocks the development of preinvasive pancreatic lesions in these mice, and trends toward increasing survival in mice that develop lethal pancreatic adenocarcinoma. Furthermore, I then show that inhibition of eNOS using the clinically tested small molecule L-NAME can also slow the development of preinvasive neoplasia and nonsignificantly increase survival, although not to the level of eNOS genetic ablation. These findings are applicable to a clinical setting, as in conjunction with others I show that L-NAME treatment of human pancreatic cancer xenografts halves their growth, even when the main side effect of L-NAME, hypertension, is treated.</p><p>Together, these studies provide a better understanding of how RAS functions within the cell, and thus, ultimately, how RAS driven cancers may be treated.</p> en_US
dc.subject Molecular biology en_US
dc.subject Cellular biology en_US
dc.subject Medicine en_US
dc.subject cancer en_US
dc.subject codon en_US
dc.subject eNOS en_US
dc.subject KRAS en_US
dc.subject pancreatic en_US
dc.subject translation en_US
dc.title Oncogenic KRAS Expression and Signaling en_US
dc.type Dissertation en_US
dc.department Pharmacology en_US
duke.embargo.months 24 en_US

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