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Disrupting Polyisoprenylated Protein Function for Pancreatic Cancer Therapy
Başlık:
Disrupting Polyisoprenylated Protein Function for Pancreatic Cancer Therapy
Yazar:
Nkembo, Augustine T., author.
ISBN:
9780438009127
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (152 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Nazarius S. Lamango Committee members: Edward Agyare; Selina Darling-Reed; Hernan Flores-Rozas; Bridg'ette Israel; Anthony M. Ndifor.
Özet:
Pancreatic cancer (PC) incidence and death rates are still on the rise and it remains the fourth leading cause of cancer-related deaths in the US with 5-year survival rate of less than 4%. The estimate for 2016 indicates that 53,070 people will be diagnosed with pancreatic cancer and 41,780 people will die of the disease. It is most prevalent in African Americans. Some risk factors for PC include genetic predisposition, tobacco use and exposure to carcinogens, diabetes and chronic pancreatitis. The threats from this disease are only increasing and current predictions are that it will be the second leading cause of cancer-related deaths in the US by 2030.
More than 80% of PC is diagnosed when it has metastasized due to lack of early detection biomarkers. The poor prognosis for PC has been linked to the presence of constitutively active K-Ras proteins found in over 90% cases. Constitutively active K-Ras activates downstream effectors that drive uncontrolled cell growth, differentiation and metastasis. Various approaches to mitigate the K-Ras activity and its signaling pathways for cancer therapy have been explored. Ras superfamily of proteins undergoes polyisoprenylation catalyzed by enzymes for proper membrane localization and signaling. The polyisoprenylated methylated protein methyl esterase (PMPMEase) plays an important role in the polyisoprenylated pathway that features a reversible step. PMPMEase catalyzes the demethylation of the C-terminal cysteinyl methylesters generated by isoprenylcysteine carboxyl methyltransferase (Icmt) enzyme thereby creating an equilibrium shift towards the demethylated forms of the proteins. This shift could cause significant changes in balance of biological activity due to disruption of membrane localization and protein-protein interactions, thereby impacting pathways that regulate cell proliferation, migration and angiogenesis.
The polyisoprenylated cysteinyl amide inhibitors (PCAIs) were recently developed as a novel class of potential therapies for cancers with K-Ras mutations. The purpose of this study was to determine the effects of PCAIs as a potential novel class of small molecules for PC therapy. The effects of the PCAIs on cell viability, proliferation, survival, apoptosis, migration, colony formation and cytoskeletal F-actin organization on four human PC cell lines expressing wild type or mutant K-Ras were examined. PCAIs induced apoptosis with EC 50 values ranging from 2.4 to 5.1, 2.0 to 7.3, 1.8 to 3.3 and 7.0 to 33 microM in MIAPaCa-2, BxPC-3, Panc10.05 and HPAF-II cells, respectively. Ethidium bromide/acridine orange analysis suggests an apoptotic cell death mechanism while annexin v/propidium iodide flow cytometry analysis also revealed apoptosis and cell arrest at the G0/G1 phase. Submicromolar concentrations of PCAIs significantly inhibited MIAPaCa-2 cell migration and invasion in the wound-healing and matrigel assays, respectively. Treatment with 0.2 microM PCAIs disrupted the F-actin structures causing the cells to shrink and become rounded upon.
The effects of PCAIs on angiogenesis, that is essential for all solid tumor growth, therapeutic resistance and metastasis, the latest accounting for 90% of cancer deaths, was also investigated. Antiangiogenic therapies have involved targeting pro-angiogenic growth factors and specific pathways such as VEGF pathway with monoclonal antibodies to ligand, receptor and tyrosine kinase inhibitors as well as targeting distinct features of the tumor vessels to disrupt vascular functions. We hypothesized that if the PCAIs disrupt the mutant monomeric G-protein that are downstream of the RTKs, then they will effectively block angiogenesis and potentially be more effective than the monoclonal antibody and kinase inhibitor drugs that target the RTKs. In the study we determined the effects of PCAIs on human umbilical vein endothelial cells (HUVEC) tube formation, cell viability, cell migration and invasion. The effects of the PCAIs were also tested on the chick chorioallantoic membrane (CAM) and zebrafish embryos models for their effect on angiogenesis. The PCAIs, NSL-BA-040 and NSL-BA-055 inhibited HUVEC tube formation in a concentration dependent manner, effectively blocking tube formation at the sub-cytotoxic concentration of 0.5 microM. Also at 0.5 microM, NSL-BA-040 75% of VEGF-stimulated HUVEC migration and invasion in scratched and matrigel assays. These concentrations were approximately 4- to 15-fold lower than the EC50 values against the viability of the PC cells with EC50 values ranging from 1.8 to 7.5 microM. Compared to the EC50 values of 8 to over 50 microM against the viability of human embryonic kidney cells (HEK-293), the concentrations that block angiogenesis were 16- to over 100-fold lower. In the CAM and zebrafish assays, we observed a proportional decrease in the number of vessels with increasing PCAIs concentrations. The PCAIs inhibited angiogenesis in zebrafish embryos at concentrations that are non-lethal to HEK cells. That the PCAIs can exert this effect at significantly sub-cytotoxic concentrations bodes well for their potential therapeutic safety. (Abstract shortened by ProQuest.).
Notlar:
School code: 0872
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(677874.1) | 677874-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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