Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.767219
Title: Expression of sigma receptors in human cancer cell lines and effects of novel sigma-2 ligands on their proliferation
Author: Abbas, Haider
ISNI:       0000 0004 7658 3759
Awarding Body: University of Wolverhampton
Current Institution: University of Wolverhampton
Date of Award: 2018
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Abstract:
Sigma receptors originally thought to be an opioid receptor is now categorized as a distinct class of receptor. There are two main subtypes, the sigma-1 receptor and an uncharacterised binding site, named the sigma-2 binding site. The presence of the sigma-2 binding site shows high correlation with proliferation of cells and is associated with cancer. I have categorized sigma-1 and sigma-2 binding sites in 11 human tumour cell lines. I have demonstrated that tumour cell lines from a range of tissues express both sigma-1 and sigma-2 binding sites. One exception is the MCF7 breast cancer cell line, which lacks sigma-1 receptors. I show that the quantitation of sigma-2 binding sites using the "masking" protocols are flawed, significantly overestimating levels of sigma-2 binding sites. I propose novel protocols to determine levels of sigma-1 receptors and sigma-2 binding sites in cell lines and tissue. Using radioligand binding assays in MCF7 cells, I have characterised novel sigma-2 ligands. These ligands are simple ammonium salts containing a single nitrogen atom. They are simpler than the previously recognised pharmacophore for the sigma-2 site. I have shown that these simple ammonium salts show graded affinity for the sigma-2 binding site. The highest affinity ligands were dihexylammonium (pKi 7.58) and dioctylammonium (pKi 7.9). I have used these ammonium salts and previously characterised ligands to determine sigma-2 binding site biology. I have shown that the biological activity of these drugs is related neither to their hydrophobicity nor their ability to effect calcium signalling in cells. I propose that the Hill slope of binding is inversely related to the efficacy of a ligand to inhibit metabolic activity of cancer cells. Furthermore, I offer an explanation as to why concentrations of sigma-2 ligands far higher than their determined binding affinities are required to inhibit metabolic activity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.767219  DOI: Not available
Keywords: Sigma-1 ; sigma-2 ; receptor ; cancer ; ammonium salts ; proliferation ; MCF7 cells ; radioligand binding ; structure-activity relationship
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