Evaluation of small molecule inhibitors of Pin1 for their effects on tissue factor within tumour cells

Adeniran, Oluremi Isola

Chemistry
December 2019

Thesis or dissertation


Rights
© 2019 Oluremi Isola Adeniran. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.
Abstract

Most standard anticancer drugs are non-selective in their cytotoxicity towards cancerous versus normal cells. Therefore, there is a need for the development of selective and targeted anticancer agents. Previous studies have reported upregulation of tissue factor (TF) as a regularly observed phenomenon in cancer cells. Others have also identified the cis-trans isomerization of pSer- Pro dipeptides by Pin1, controlled by the proline-directed phosphorylation motif, as an essential mechanism in tumor growth and metastasis. The inhibition of the activity of prolyl-protein cis-trans isomerase 1 (Pin1) has been reported to preclude TF release. This prevention therefore results in TF accumulation within the cancer cell. The intracellular TF accumulation consequently results in localisation of p53 within the nucleus of the cell, Bax protein overexpression and apoptotic cell death. The aim of this study is to explore the ability of synthetic pSer-Pro motif organic compounds to inhibit Pin1 and to prepare and test some new derivatives of a known small molecule Pin1 inhibitor, with a view to investigating their interference with the proliferative mechanisms specific to cancer cells and the outcome on TF activity and cellular apoptosis. The subsequent self-poisoning of the tumor cells, through the apoptotic mechanism would discriminate between normal and cancerous cells. The synthesis of the target proline-based dipeptide involved a one-pot in situ activation and coupling using a carbodiimide while preparation of its N-analogue involved a Hofmann-type oxidative decarboxylation of asparagine. An exploration of alternative, non-peptidic molecules for inhibition of Pin1 resulted in design of a class of structure-guided molecules derived from 5-(p-methoxyphenyl)-2-methylfuran-3-carbonyl amide. The derivatives were synthesised with modification to the original structure possibly to improve the efficiency. The derivativatization resulted in compounds differing in the amino acid moiety whereby the 3-(2-naphthyl)-D- alanine moiety in (30), was replaced with D-phenylalanine in (31), D-tyrosine in (32) and D-tryptophan in (33). Using a chromogenic TUNEL assay, cellular apoptosis was analysed 18 h post-treatment of MDA-MB-231 cells with vehicle control or each of the compunds (100 μM). Furthermore, localisation of p53 protein to the nucleus was analysed with a fluorescence microscope while Bax protein and bax mRNA expressions were measured by western blot analysis and RT-PCR respectively. Compared to the control sample, compound 32 demonstrated a reduction in number of cells and activity of TF while it demonstrated an increase in both p53 localisation within the nucleus and expression of Bax protein. Additionally, both 30 and 33 exhibited reduced activity towards the analysed parameters in the cells, whereas 31 was substantially inactive. The observed trend can be explained by the degree of ligand potency (efficiency) of the molecules in the active site of Pin1. Compound 32 is highly potent; compounds 30 and 33 are moderately potent whereas compound 31 is less potent. The result of this study suggests that these molecules may function possibly as potential small molecule Pin1 inhibitors and moderators of procoagulant activity of TF hence preventing the consequent growth of tumor cells.

Publisher
Department of Chemistry, The University of Hull
Supervisor
Boa, Andrew; Ettelaie, Camille
Sponsor (Organisation)
University of Abuja; Tertiary Education Trust Fund (Nigeria)
Qualification level
Doctoral
Qualification name
PhD
Language
English
Extent
3 MB
Identifier
hull:17800
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