Microsomal prostaglandin E synthase-1 (mPGES-1) is the terminal enzyme following cyclooxygenase-2 (COX-2) for the production of prostaglandin E₂(PGE₂), and has been identified as a novel therapeutic target for cancers. From an in silico screen aimed at developing novel small molecule inhibitors of mPGES-1, a 2-aminothiazole compound PGE0001 was identified from 13 putative hits based on its ability to reduce cellular PGE₂ and minimal COX-2 inhibition in vitro. Utilizing drug design strategies based on a 4-point pharmacophore model, we also discovered a new series of compounds exhibiting superior potency without inhibiting COX-2, as exemplified by compound PGE0056. In multiple cancer cell lines, both PGE0001 and PGE0056 reduced cytokine-stimulated PGE₂ release with submicromolar EC₅₀ values, although the two compounds exhibited differential kinetics. Importantly, these compounds showed promising anti-tumor effects in xenograft mouse models. Mice injected with the compounds also had reduced PGE₂ in serum. Surprisingly, none of the compounds inhibited mPGES-1 in cell-free assays, except for MK-886, a reported mPGES-1 inhibitor. In order to determine the mechanisms of action of PGE0001 and PGE0056, the PGE₂ synthesis cascade was extensively examined. Immunoblotting analysis suggested that the PGE₂ reduction in a short time frame was not due to alteration of the protein level of enzymes involved in PGE₂ synthesis/metabolism. So far, we have excluded upstream COX-1/2, phospholipase A₂, and other PGE synthases (mPGES-2 & cytosolic PGES) as major targets for PGE0001 or PGE0056. Interestingly, these compounds were found to inhibit a number of kinases implicated in cancer, presumably due to their structural feature. Although these alternative kinase targets may not sufficiently explain the mechanisms responsible for PGE₂ reduction, inhibition of them may strengthen the therapeutic potential of our compounds. We also implemented a target pull-down approach using biotinylated derivatives of these compounds, followed by proteomic analysis to isolate targets to which these compounds bind. As a result, we identified a couple of other enzymes involved in the arachidonic acid metabolic pathway, which need to be further validated. In summary, we identified novel classes of anti-inflammatory compounds with anti-tumor activity, although the mechanisms of action remain to be clarified.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/268614 |
| Date | January 2013 |
| Creators | Chang, Hui-Hua |
| Contributors | Meuillet, Emmanuelle J., Bowden, George T., Hartshorne, David J., Stratton, Steven P., Winzerling, Joy J. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | text, Electronic Dissertation |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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