Dissertation/Thesis Abstract

SCFA-hexosamines: Understanding anti-cancer mechanisms through chemical biology and molecular modeling
by Meledeo, Michael Adam, Ph.D., The Johns Hopkins University, 2009, 119; 3410194
Abstract (Summary)

This thesis concerns the use a special class of hybrid sugars, the short-chain fatty acid (SCFA) hexosamines, and their use in cancer treatment. This class of molecules pairs a core ManNAc sugar with lipophilic SCFA side chains (affixed at the free hydroxyl positions via ester linkage) which endow the sugar with a much greater degree of membrane permeability. The lead compound, Bu 4ManNAc, which initially demonstrated effects including inhibition of cell cycle progression and induction of apoptosis, is compared with two of its primary hydrolysis products (3,4,6-O-Bu3ManNAc and 1,3,4-O-Bu3ManNAc). Interestingly, these two compounds have very different activities; the 3,4,6-O-compound was even more toxic to cancer cells than Bu4ManNAc, while the 1,3,4- O-compound was significantly less toxic, while maintaining the expected increase in sialic acid pathway flux.

A variety of toxicity studies were pursued beginning with viability and cell cycle analysis of cells exposed to the 3,4,6-O-Bu 3ManNAc and Bu4ManNAc analogs (non-toxic 1,3,4-O -Bu3ManNAc was often compared as well), followed by an examination of specific apoptosis mechanisms, and concluded by data demonstrating the effects of analogs on a specific protein of interest, AKT1. Additionally, some preliminary studies with the next generation of analogs, Bu4ManNPr and 3,4,6-O-Bu3ManNPr were conducted.

Since these molecules rely on prominent ester bonds connecting the SCFA to the sugar, a set of experiments was conducted examining the interaction of the SCFA-ManNAc analogs with esterase. Three different avenues of exploration were pursued, beginning with chemical analysis of analogs intentionally exposed to esterase, followed by an examination of the biological effects on cells treated with these post-esterase exposure analogs. Finally, molecular modeling of esterase-analog interaction provided some insight into the differential effects between the 3,4,6-O- and 1,3,4-O-Bu 3ManNAc analogs.

Because the goal was to determine the chemotherapeutic properties of the toxic analogs, pilot studies featuring the use of the 3,4,6-O -Bu3ManNAc analog in mice were conducted. This set of studies first examined the effects of treatment in a healthy animal and was followed by use in a tumor mouse model. Finally, some brief attempts at improved drug delivery are discussed by employing a polymer microparticle encapsulation of the analog, again for use in cell culture.

Indexing (document details)
Advisor: Yarema, Kevin J.
School: The Johns Hopkins University
School Location: United States -- Maryland
Source: DAI-B 71/05, Dissertation Abstracts International
Subjects: Molecular biology, Cellular biology, Biomedical engineering
Keywords: Anticancer, Cancer treatment, Hexosamines, Short chain fatty acids
Publication Number: 3410194
ISBN: 978-1-124-00589-8
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