Elsevier

Neoplasia

Volume 6, Issue 1, January–February 2004, Pages 15-22
Neoplasia

Interleukin 13 Mutants of Enhanced Avidity Toward the Glioma-Associated Receptor, IL13Rα21

https://doi.org/10.1016/S1476-5586(04)80049-6Get rights and content
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open access

Abstract

Interleukin 13 (IL13) binds a receptor that is highly overexpressed in malignant gliomas, IL13Rα2. IL13 protein is composed of four helices: α-helix A, B, C, and D, and we found a new “hot spot” in α-helix D that is crucial for the binding of IL13 to IL13Rα2. Lys105 plus Lys-106 and Arg-109 represent this hot spot. In the current study, we have made substitutions at these three positions in IL13. We examined both neutralization of an IL13-based cytotoxin's glioma cell killing and direct receptor binding of the new IL13 mutants. We observed that Lys-105 and Arg-109 are critical for IL13 binding to IL13Rα2, indeed. However, new mutants of important properties were identified with regard to tumor targeting. IL13.K105R mutant, in which lysine was substituted by arginine, neutralized the killing of IL13Rα2-positive cells by IL13-based cytotoxin more efficiently than wild-type IL13. However, IL13.K105L or IL13X105A was deprived of any such activity. Furthermore, IL13.K105R and IL13.R109K competed 77-and 27-fold better, respectively, with the binding of [125]IL13 to the IL13Rα2 binding sites when compared with wild-type IL13. Thus, we have uncovered the first forms of IL13 of higher avidity toward IL13Rα2. These mutants should prove useful in the further design of anticancer diagnostics/therapeutics.

Keywords

Interleukin 13
IL13Rα2
mutants
brain tumors
tumor-specific

Abbreviations

CD
circular dichroism
FPLC
fast protein liquid chromatography
GBM
glioblastoma multiforme
h
human
HGA
high-grade astrocytoma
IL4
interleukin 4
IL13
interleukin 13
IPTG
isopropyl-lthio-β-D-galactopyranoside
m
murine
NITS
3-(4,5dimethylthiazol-2yl)-5-(3-carboxy-methoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt
PAGE
polyacrylamide gel electrophoresis
PE
Pseudomonas exotoxin
PMS
phenazine methosulfate
SDS
sodium dodecyl sulfate

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This work was supported by NIH/NCI grant 2R01 CA 74145.