Construction, affinity maturation, and biological characterization of an anti-tumor-associated glycoprotein-72 humanized antibody

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Title
Construction, affinity maturation, and biological characterization of an anti-tumor-associated glycoprotein-72 humanized antibody
Author(s)
S O Yoon; T S Lee; Sang Jick Kim; M H Jang; Y J Kang; J H Park; K S Kim; H S Lee; Chun Jeih Ryu; N R Gonzales; S V S Kashmiri; S M Lim; C W Choi; Hyo Jeong Hong
Bibliographic Citation
Journal of Biological Chemistry, vol. 281, no. 11, pp. 6985-6992
Publication Year
2006
Abstract
The tumor-associated glycoprotein (TAG)-72 is expressed in the majority of human adenocarcinomas but is rarely expressed in most normal tissues, which makes it a potential target for the diagnosis and therapy of a variety of human cancers. Here we describe the construction, affinity maturation, and biological characterization of an anti-TAG-72 humanized antibody with minimum potential immunogenicity. The humanized antibody was constructed by grafting only the specificity-determining residues (SDRs) within the complementarity-determining regions (CDRs) onto homologous human immunoglobulin germ line segments while retaining two mouse heavy chain framework residues that support the conformation of the CDRs. The resulting humanized antibody (AKA) showed only about 2-fold lower affinity compared with the original murine monoclonal antibody CC49 and 27-fold lower reactivity to patient serum compared with the humanized antibody HuCC49 that was constructed by CDR grafting. The affinity of AKA was improved by random mutagenesis of the heavy chain CDR3 (HCDR3). The highest affinity variant (3E8) showed 22-fold higher affinity compared with AKA and retained the original epitope specificity. Mutational analysis of the HCDR3 residues revealed that the replacement of Asn97 by isoleucine or valine was critical for the affinity maturation. The 3E8 labeled with 125I or 131I showed efficient tumor targeting or therapeutic effects, respectively, in athymic mice with human colon carcinoma xenografts, suggesting that 3E8 may be beneficial for the diagnosis and therapy of tumors expressing TAG-72.
ISSN
0021-9258
Publisher
Amer Soc Biochemistry Molecular Biology Inc
DOI
http://dx.doi.org/10.1074/jbc.M511165200
Type
Article
Appears in Collections:
Synthetic Biology and Bioengineering Research Institute > Synthetic Biology Research Center > 1. Journal Articles
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