Identification of Small Molecule Inhibitors of I-κB Kinase Pubblico

Yang, Xuesong (2010)

Permanent URL: https://etd.library.emory.edu/concern/etds/ng451h78w?locale=it
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Abstract

Abstract
Identification of Small Molecule Inhibitors of I-κB Kinase
By Xuesong Yang
Nuclear factor κB (NF-κB) transcription factor and its pivotal role in many physiological and pathological processes have been intensely studied for decades. Aberrant regulation of NF-κB and its controlling signaling pathway can result in many autoimmune diseases as well as cancer, making it a desirable therapeutic target for drug development. Many natural products such as curcumin have demonstrated their inhibition to NF-κB signaling pathway, which contributes to their anticancer therapeutic potential. To circumvent the problems of poor bioavailability and low potency with curcumin, while retaining its safety profile, many synthetic analogs derived from curcumin have been developed. EF24, a monoketone analog of curcumin, has been reported to have ten-fold better bioactivity than curcumin. In this study, a novel class of compounds derived from curcumin was tested for their anticancer activity. One compound, 3, 5-bis [(6-chloropyridin-2-yl) methylidene]-1-methyl-4-piperidone, named AM5, showed greater cytotoxic effect than EF24. Furthermore, AM5 was indicated to directly target NF-κB signaling pathway, by effectively blocking the nuclear translocation of NF-κB, impairing tumor necrosis factor (TNF)-α-induced I-κB phosphorylation and degradation, and directly inhibiting the catalytic activity of I-κB kinase. AM5 represents a new structure of curcumin analogs that targets NF-κB signaling more effectively, and the activities of compounds from the same class have shed lights on further optimization and modification of AM5 to improve its bioactivity for therapeutic application.

Identification of Small Molecule Inhibitors of I-κB Kinase
By
Xuesong Yang
B.S., Wuhan University, 2008
Advisor: Dennis C. Liotta, Ph.D
Advisor: Haian Fu, Ph.D
A Thesis submitted to the Faculty of the
James T. Laney School of Graduate Studies of Emory University
in partial fulfillment of the requirements for the degree of
Master of Science
in Chemistry
2010

Table of Contents

Table of Contents


Chapter 1: Introduction...1

1.1 NF-κB...2

1.1.1 Introduction of NF-κB...2
1.1.2 The role of NF-κB in immune response...3
1.1.3 The role of NF-κB in tumorigenesis...4
1.1.4 NF-κB signaling pathway...5

1.1.4.1 Classical NF-κB signaling pathway...5
1.1.4.2 Alternative NF-κB signaling pathway...6

1.1.5 Development of IKK inhibitors for therapeutic application...10

1.2 Curcumin...11

1.2.1 Introduction of curcumin...11
1.2.2 Therapeutic potential of curcumin...11
1.2.3 Therapeutic limitations of curcumin...12
1.2.4 Improving the pharmacological properties of curcumin...13

Chapter 2: Identification of a novel unsaturated monoketone analog of curcumin as a direct inhibitor of IKK-NF-κB signaling pathway...18

2.1 Introduction...19
2.2 Materials and Methods...19
2.3 Results...24

2.3.1 AM5 represents a favorable structure with improved cytotoxicity over EF24...24
2.3.2 AM5 effectively impairs the nuclear translocation of NF-κB...24
2.3.3 AM5 inhibits I-κB phosphorylation and degradation induced by TNF-α...25
2.3.4 AM5 directly inhibits the catalytic activity of IKKβ...26

2.4 Figure legends...28

Chapter 3: Discussion...41


List of Figures
Chapter 1

Figure 1.1 Members of NF-κB family...7
Figure 1.2 Main members of I-κB family...8
Figure 1.3 Two classes of NF-κB signaling pathway...9
Figure 1.4 Structures of curcumin and EF24...15

Chapter 2

Figure 2.1 The core structure of compounds with most improved cytotoxicity...31
Figure 2.2 AM5 exhibits better potency of cytotoxic effect than EF24 in cancer cells...32
Figure 2.3 AM5 inhibits NF-κB nuclear translocation induced by TNF-α...33
Figure 2.4 AM5 impairs TNF-α induced I-κB phosphorylation...34
Figure 2.5 AM5 inhibits TNF-α induced I-κB phosphorylation with a better potency than AM16...35
Figure 2.6 AM5 impairs TNF-α induced I-κB degradation...36
Figure 2.7 AM5 directly inhibits the catalytic activity of IKKβ...37

Chapter 3

Figure 3.1 Molecular mechanism for the action of AM5...45


List of Tables
Chapter 1

Table 1.1 Structures of AM compounds...16

Chapter 2

Table 2.1 IC50 (μM) values of cell toxicity for all 17 AM compounds and EF24...38
Table 2.2 Ranking of IC50 values of cell toxicity for all 17 AM compounds and EF24 39
Table 2.3 Ranking of IC50 values from NF-κB nuclear translocation assay for all 17 AM compounds and EF24 40

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