Reactivity of Interleukin 13.E13C Mutant toward Interleukin 13 ReceptorsShana Kondor and Dr. Jeffrey Thompson, Biology Department, York College of PA

TF-1 Cell Proliferation

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Cytotoxicity Blocking Assaywith hIL13-CTX

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Competition Assay withhIL13.E13C-CTX

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PROJECT SUMMARY

Interleukin 13 (IL-13) is a pleiotropic cytokine comprised of four -helical regions (A-D) expressed in Th1 and Th2 lymphocytes, stimulated keratinocytes, activated mast cells, and transformed B lymphocytes (Kuznetsov and Puri 1999). Helices A and C bind to the shared receptor, while B and D bind to IL13 exclusive sites on cancer cells. Previous studies have shown success in decreasing normal cell affinity while maintaining cancer cell affinity (Thompson and Debinski 1999). The objectives are to create an IL13.E13C mutant, express the protein in Escherichia coli and human monocytes, and assess binding affinity and cytotoxicity through TF-1 proliferation and a cytotoxicity blocking assay with Glioblastoma cells. By mutating at position 13 on -helix A, affinity for normal cells should decrease while maintaining affinity for cancer cells. Replacing glutamic acid with cysteine creates a free sulfhydryl group for use as a cytotoxin attachment point. This mutated form of IL13 could be used as a chemotherapy aid that will allow it to target only cancer cells, leaving normal cells unharmed.

Although fairly extensive and ongoing research is being conducted regarding human Interleukin-13 (hIL-13) and its various mutants, the region of uncharted territory is vast. Understanding completely how hIL-13 interacts with its receptors on both normal and malignant cells could be a key component to developing a cancer-targeting drug. Only by continuing in the efforts of understanding the functionality of the protein can any knowledge be gained towards the subject. The proposed research involves a mutant of hIL-13 not yet studied, that being hIL13.E13C. This mutation resides on a protein domain that is involved with normal cell binding but not cancer cell binding. With this in mind, mutating at this position will hopefully eliminate binding affinity towards the normal cells while retaining its ability to bind with cancer cells, therefore making it able to target cancer cells only.

RESEARCH OBJECTIVES

1) Determine ability of IL13.E13C to target cancer cells2) Determine effectiveness of IL13.E13C as cytotoxin delivery complex3) Determine the difference, if any, between eukaryotic and prokaryotic protein expression4) Gain insight into IL13 structure and function to be related to other applications of IL13

INTRODUCTION

LITERATURE REVIEWThompson and Debinski, 1997• -helix A mutants both caused and failed to cause TF-1 cell

proliferation• All position 13 mutants except E13R and E13D failed to cause TF-1

proliferation• Position 13 mutants that failed to cause TF-1 proliferation were most

effective at blocking hIL13-CTX action on U-251 MG and SNB-19• Interaction with the hIL13 shared receptor depends on multiple factors

including amino acid size, electrostatics, and polarity

Mintz et al., 2002• High-grade astrocytomas bind IL13 and are sensitive to IL13

cytotoxins• IL13.E13K binds to HGA IL13 site 50X better than wild type IL13• Identified transcript for hIL13R 2 in HGA’s• HGA’s bind IL13 but not IL4• IL13.E13K completely blocked killing of HGA’s by cytotoxin

Kruse et al., 2002• IL4 and IL13 have individual signaling processes• Substrate binding and signaling strength vary depending on the

variant of IL4R protein• IL13 acts independently of IL4 in inducing pathophysiological features

of asthma

Wäldele et al., 2004• IL13 stimulates human T-cell leukemia virus type 1 (HTLV-1) through

up-regulation of IL13 by Tax, a viral transactivator• IL13 inhibits apoptosis and stimulates the cell cycle• Various cytokines that induce cell death are inhibited by IL13• IL13 linked to leukemogenesis as found through Hodgkin lymphoma

cell stimulation

Kuznetsov and Puri, 1999• IL13 inhibits B cell proliferation• Kinetic studies show heterogeneity in IL13 binding, possibly

explaining cytotoxicity of IL13 toxin in renal cell carcinomas

Aversa et al., 1993• IL13 and IL4 work independently to induce IgG4 and IgE synthesis• IL4 receptor complex and IL13 receptor complex are distinct receptors

that may have common components• B cell proliferation studies suggest that IL4 and IL13 bind the same

receptor• IL13 failed to bind the IL4 receptor on mouse BaF3 cells or monkey

COS-7 cells, but blocked IL4 binding on TF-1 cells

Vladich et al., 2005• Demonstrated that eukaryotic IL13 was much more active than

prokaryotic IL13 • Used COS-7 cell lines as eukaryotic model to compare with E. coli

prokaryotic model• COS-7 cells were transfected and assessed for IL13 concentrations

by ELISA, with correction factors to detect WT versus mutant

LITERATURE CITEDAversa, G., Punnonen, J., Cocks, B., de Waal Malefyt, R., Vega, F., Zurawski, S., Zurawski,

G. and deVries, J. 1993. An Interleukin 4 (IL-4) Mutant Protein Inhibits both IL-4 and IL-13-induced Human Immunoglobulin G4 (IgG4) and IgE Synthesis and B Cell Proliferation: Support for a Common Component Shared by IL-4 and IL-13 Receptors. Journal of Experimental Medicine 178:2213-2218.

Kruse, S., Braun, S. and Deichmann, K. 2002. Distinct signal transduction processes by IL-4 and IL-13 and influences from the Q551R variant of the human IL-4 receptor alpha chain. Respiratory Research 3:24.

Kuznetsov, V. and Puri, R. 1999. Kinetic Analysis of High Affinity Forms of Interleukin (IL)-13 Receptors: Suppression of IL-13 Binding by IL-2 Receptor Chain. Biophysical Journal 77: 154-172.

Mintz, A., Gibo, D., Slagel-Webb, B., Christensen, N. and Debinski, W. 2002. IL-13R2 is a Glioma-Restricted Receptor for Interleukin-13. Neoplasia 4:388-399.

Thompson, J. and Debinski, W. 1999. Mutants of Interleukin 13 with Altered Reactivity toward Interleukin 13 Receptors. Journal of Biological Chemistry 247:29944-29950.

Vladich, F., Brazille, S., Stern, D., Peck, M., Ghittoni, R. and Vercelli, D. 2005. IL-13 R130Q, a common variant associated with allergy and asthma, enhances effector mechanisms essential for human allergic inflammation. Journal of Clinical Investigation 115:747-754.

Wäldele, K., Schneider, G., Ruckes, T. and Grassmann, R. 2004. Interleukin-13 Overexpression by Tax Transactivation: a Potential Autocrine Stimulus in Human T-Cell Leukemia Virus-Infected Lymphocytes. Journal of Virology 78:6081-6090.

Create IL13.E13C mutant through point mutation of WT IL13

Transform E. coli with WT (Sample 1) and mutant (Sample 2) by transforming E. coli with respective samples + AmpR

Express Samples 1 and 2 by plating transformed E. coli on Ampicillin agar plates

Express WT (Sample 3) and mutant (Sample 4) with COS7 cell cultures for eukaryotic assay

Purify all samples

Test TF-1 Cytotoxicity Competition proliferation assay assay

(all samples) (all samples) (samples 2 + 4)

RESEARCH DESIGN

Solution Structure of Human IL13www.cytok.com/structure.php?start=80

EXPECTED RESULTSFigure 1 Figure 2

Figure 3

• Figure 1 shows hypothetical TF-1 cell proliferation of hIL13 (WT), IL13.E13C (prokaryotic expression) and IL13.E13C (eukaryotic expression). It is suspected that both mutants of IL13 will have decreased TF-1 cell proliferation due to lack of binding on the shared IL13/4 receptor. With large enough concentrations, however, cell proliferation will occur.• Figure 2 shows a hypothetical cytotoxicity blocking assay using hIL13-CTX. When competing with WT hIL13, blocking will occur approximately 50% because the cytotoxin bound hIL13 and the WT hIL13 should have similar binding affinities. When in competition with the mutants, however, blocking should occur, because the mutants are hoped to have better binding affinity for the IL13 specific receptor. It is hypothesized that the eukaryote expressed mutant will block slightly better because it has been found that eukaryote expressed IL13 is more active than the prokaryote expression.• Figure 3 shows a cytotoxicity blocking assay using IL13.E13C-CTX. It is suspected that the eukaryote expressed protein will effectively block the prokaryote expressed protein linked with the cytotoxin, because of findings that eukaryote expression is more effective.