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- Title
- POLYAMINE TRANSPORT INHIBITOR EFFECTS ON PANCREATIC CANCER PROLIFERATION CELLS IN VIVO.
- Creator
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Hogan, Frederick, Altomare, Deborah, University of Central Florida
- Abstract / Description
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Pancreatic cancer is a serious disease, one in which the survival rate over five years is less than 6%. (1) Often, malignant tumors will exhibit uncontrolled proliferation and it is postulated that they have high metabolic needs. One of the areas of interest in cancer metabolism is the unique need for large amounts of polyamines in order to sustain this uncontrolled proliferation. Polyamines are organic compounds that all cells need for proliferation and differentiation. (2) Cells obtain...
Show morePancreatic cancer is a serious disease, one in which the survival rate over five years is less than 6%. (1) Often, malignant tumors will exhibit uncontrolled proliferation and it is postulated that they have high metabolic needs. One of the areas of interest in cancer metabolism is the unique need for large amounts of polyamines in order to sustain this uncontrolled proliferation. Polyamines are organic compounds that all cells need for proliferation and differentiation. (2) Cells obtain polyamines by manufacture of them directly or obtain them from the environment through their transport across the cell membrane. When cancer cells have limited access to polyamines they enter apoptosis, or controlled cell death. In animal models of cancer, cellular apoptosis can be tracked by measuring tumor weights as well as histological methods. It is known that difluromethylornithine (DFMO), a polyamine synthesis inhibitor, has shown some success in reducing tumor weights. (3) Cells deprived of the ability to manufacture polyamines will resort to transporting existing polyamines from the environment for their use. (3) It is believed that a polyamine transport inhibitor (PTI) can be designed and used in conjunction with DFMO to completely deprive cancer cells of polyamines and increase rates of apoptosis in tumor cells. Through this study the interaction of DFMO with newly identified PTI will be analyzed. A mouse model with tumor cells in the pancreas will give a picture of how cancer cells react to DFMO / PTI in vivo. The findings allow us to postulate how targeted compounds interact with protein signaling pathways that may be important for regulating response to inhibitors of polyamine synthesis and/or transport.
Show less - Date Issued
- 2015
- Identifier
- CFH0004749, ucf:45395
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004749
- Title
- A chemical and genetic approach to study the polyamine transport system in Drosophila.
- Creator
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Wang, Minpei, Vonkalm, Laurence, Phanstiel, Otto, Teter, Kenneth, Ballantyne, John, University of Central Florida
- Abstract / Description
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Polyamines are small cationic molecules that play important roles in most vital cellular processes including cell growth and proliferation, regulation of chromatin structure, translation and programmed cell death. Cellular polyamine pools are maintained by a balance between biosynthesis and transport (export and import). Increased polyamine biosynthesis activity and an active transport system are characteristics of many cancer cell lines, and polyamine depletion has been shown to be a viable...
Show morePolyamines are small cationic molecules that play important roles in most vital cellular processes including cell growth and proliferation, regulation of chromatin structure, translation and programmed cell death. Cellular polyamine pools are maintained by a balance between biosynthesis and transport (export and import). Increased polyamine biosynthesis activity and an active transport system are characteristics of many cancer cell lines, and polyamine depletion has been shown to be a viable anticancer strategy. Polyamine levels can be depleted by ?-difluoromethylornithine (DFMO), an inhibitor of the key polyamine biosynthesis enzyme ornithine decarboxylase. However, malignant cells often circumvent DFMO therapy by up-regulating polyamine import; therefore, there is a need to develop compounds that inhibit polyamine transport. Collectively, DFMO and polyamine transport inhibitors provide the basis for a combination therapy leading to effective intracellular polyamine depletion. Using a Drosophila leg imaginal disc model for polyamine transport, I studied three candidate transport inhibitors (Ant444, Trimer44 and Triamide44) for their ability to inhibit transport in the Drosophila model. Ant444 and Trimer44 effectively inhibited the uptake of the toxic polyamine analog Ant44 that gains entry to cells via the polyamine transport system. Ant444 and Trimer44 were also able to inhibit the import of exogenous polyamines into DFMO-treated imaginal discs. Triamide44 was an ineffective inhibitor, however a structurally redesigned compound, Triamide444, showed a 50-fold increase in transport inhibition and was comparable to Ant444 and Trimer44. Ant444 and Trimer44 showed differences in their relative abilities to block import of specific polyamines, and I therefore asked if a cocktail of these inhibitors would be more effective than either alone. My data show that a cocktail of polyamine transport inhibitors is more effective than single inhibitors when used in combination with DFMO, and suggests the existence of multiple polyamine transport systems. To further the development of effective transport inhibitors it is important to identify components of the transport system. The mechanism of polyamine transport in multicellular organisms including mammals is still unknown. Our laboratory has developed a simple assay to detect components of the transport system using RNAi knockdown and over-expression of candidate genes. However, the assay requires that animals live until the pupal stage of development. Pleiotropic effects of individual gene products following over-expression or knockdown may result in early developmental lethality for reasons unrelated to polyamine transport. Our assay is based on the GAL4/UAS system and involves the use of enhancers driving GAL4 expression (GAL4 driver). GAL4 in turn determines the expression level of UAS-candidate gene constructs (UAS responder). I reasoned that in some cases it might be possible to bypass early lethality by judicious choice of drivers that reduce responder expression, thus permitting survival to the pupal phase. To this end, I used five imaginal disc drivers (30A, 71B, 32B, 69B, and T80) as well as a ubiquitously expressed control driver to over-express and knockdown EGFR and components of the Rho signaling pathway. The relative strength of each driver was ranked, and I was able to demonstrate in principle that animals could survive to later stages of development in a manner that correlated with the relative strength of the driver. The approach I developed is broadly applicable to other studies of Drosophila development.To identify new components of the polyamine transport system I studied the role of proteoglycans in this process. The proteoglycan glypican-1 has been previously implicated in mammalian polyamine transport. In particular, the heparin sulfate side chains of glypican-1 appear to play an important role. In order to extend our knowledge of the role of proteoglycans in polyamine transport, I examined the role of the core proteoglycans perlecan and syndecan as well as genes encoding enzymes in the heparin sulfate and chondroitin sulfate biosynthetic pathways. I was able to confirm a role for glypican-1 in polyamine transport in imaginal discs but not in whole animals. This may indicate that glypican-1 is not required for polyamine uptake through the gut. Studies of genes encoding perlecan, syndecan and enzymes in the heparin sulfate and chondroitin sulfate biosynthetic pathways did not reveal a role for these genes in polyamine transport. These studies were conducted in whole animals and my data may reflect tissue-specific differences between the imaginal disc and gut transport systems where transport in imaginal discs is proteoglycan dependent and transport in the gut is not.
Show less - Date Issued
- 2017
- Identifier
- CFE0007297, ucf:52162
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007297