Date of Award

Summer 1997

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program/Concentration

Biomedical Sciences

Committee Director

Roy L. Wiliams

Committee Director

Mark S. Elliot

Committee Member

Patricia A. Pleban

Committee Member

Paul Ratz

Abstract

The function of the type II estrogen binding site (EBS) has yet to be determined. However, a high affinity ligand for the binding site has been identified through HPLC and GC-MS. This ligand, MeHPLA, bears a structural relationship to a group of compounds called "phytoestrogens" which, along with MeHPLA, have been observed to suppress the cellular proliferation of estrogen sensitive MCF-7 breast cancer cells in vitro. Additionally, MeHPLA has been observed to suppress the growth of rat uteri in vivo. The high affinity of MeHPLA for the type II EBS suggests that this interaction is responsible for the observed suppression of cell growth. If this interaction is the mode of cell growth suppression, then the chiral center of MeHPLA might be expected to change the binding affinity of the ligand and the associated cellular activity. In this study, the enantiomers of MeHPLA were synthesized and separated by three methods. The methods included the use of the enantioselective catalyst, oxazoborolidine, the enzyme, lactate dehydrogenase, and the diastereomeric separation using a chiral amine. When the methods were compared, it was found that the method using the diastereomeric separation gave the superior yield for the two enantiomers. Binding studies for the enantiomers to the type II EBS showed that the L-MeHPLA isomer has a higher affinity for the binding site. However, binding affinity did not translate into cell growth suppression. Both enantiomers had the equivalent ability to suppress cellular growth. The conclusion is that the interaction of MeHPLA with the type II binding site may not be the mode by which cell growth suppression is achieved. This was supported by the evaluation of MeHPLA against LnCap prostate cancer cells and HxGC3 colon cancer cells in culture. Type II binding sites have been observed in prostate and colon cancer cell lines. However, their existence in these particular cell lines have not been confirmed. Some cellular growth suppression was observed in these cell lines upon treatment with MeHPLA. The possible function of MeHPLA was also compared to other phytoestrogens that appear to act independently of the type II EBS. Their activity was compared to a group of compounds known as xenoestrogens. MeHPLA, phytoestrogens, and xenoestrogens have the ability to stimulate, inhibit, or compromise normal or malignant cells with in the reproductive tract.

Comments

Dissertation submitted to the Faculty of Eastern Virginia Medical School and Old Dominion University in Partial Fulfillment of the Requirement for the Degree of Doctor of Philosophy in Biomedical Sciences.

DOI

10.25777/xh05-5d92

ISBN

9780591603934

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