title: Development of tumor targeting anti-MUC-1 multimer: effects of di-scFv unpaired cysteine location on PEGylation and tumor binding.
abstract: MUC1 mucin expressed in epithelial cancer, such as prostate and breast, is aberrantly glycosylated providing unique targets for imaging and therapy. In order to create a broadly applicable construct to target these unique epitopes on metastatic cancer, we selected an antibody fragment (scFv) that binds both synthetic MUC1 core peptide and epithelial cancer cell-expressed MUC1, and developed a recombinant bivalent molecule (di-scFv). Genetically engineered modifications of the di-scFv were constructed to create five molecular versions, each having a free cysteine (di-scFv-c) at different locations for site-specific conjugation. The effects of the engineered cysteine in the varied sites were studied relative to tumor binding and polyethylene glycol-maleimide (PEG-Mal) conjugation (PEGylation). Escherichia coli production as well as binding to MUC1 core peptide, human tumor cell lines and human tumor biopsies, were comparable. However, the location of the engineered cysteine in these di-scFv-c did influence PEGylation efficiency of this free thiol; higher PEGylation efficiency occurred with this cysteine in the inter-scFv linkage. Di-scFv-c PEG, with the cysteine engineered after the fifth amino acid in the linker, was used as an example to demonstrate comparable antigen-binding to non-PEGylated di-scFv-c. In summary, novel anti-MUC1 di-scFv-c molecules can be efficiently produced, purified and conjugated by site-specific PEGylation without loss of immunoreactivity, thus providing flexible multidentate constructs for cancer-targeted imaging and therapy.
authors.affiliation: Department of Internal Medicine, Division of Hematology/Oncology, Section of Radiodiagnosis and Therapy, University of California Davis Cancer Center 1508 Alhambra Boulevard, Sacramento, CA 95816, USA.
authors.forename: Cheng-Yi
authors.initials: CY
authors.lastname: Xiong
authors.forename: Arutselvan
authors.initials: A
authors.lastname: Natarajan
authors.forename: Xu-Bao
authors.initials: XB
authors.lastname: Shi
authors.forename: Gerald L
authors.initials: GL
authors.lastname: Denardo
authors.forename: Sally J
authors.initials: SJ
authors.lastname: Denardo
mesh_terms: D045744:Cell Line, Tumor; D002846:Chromatography, Affinity; D003545:Cysteine / Q000378:metabolism*; D004847:Epithelial Cells / Q000276:immunology; D006031:Glycosylation; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000737:chemistry* / Q000276:immunology* / Q000302:isolation & purification / Q000378:metabolism; D008301:Maleimides / Q000378:metabolism; D018396:Mucin-1 / Q000276:immunology* / Q000378:metabolism; D011092:Polyethylene Glycols / Q000378:metabolism; D015202:Protein Engineering; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection
chemical_list: D007135:Immunoglobulin Variable Region; D008301:Maleimides; D018396:Mucin-1; D011994:Recombinant Proteins; C043592:maleimide; D011092:Polyethylene Glycols; D003545:Cysteine