Two monoclonal antibodies against small-cell lung cancer show existence of synergism in binding.
Murine IgG1 monoclonal antibodies (mAbs), ITK-2 and ITK-3, were generated against a small-cell lung cancer (SCLC) cell line. Enzyme-linked immunosorbent assay using a variety of established cell lines as substrates, immunoperoxidase staining of freshly frozen tissue sections, and fluorescence-activated cell sorter analysis of peripheral blood leukocytes showed that these mAbs recognize a part of the SCLC-associated cluster 1 antigen. In immunoprecipitation studies, both ITK-2 and ITK-3 bound to a 145-kDa glycoprotein of SCLC cell membrane extracts, as did MOC-1 and NKH-1, which both recognize the cluster 1 antigen. However, because the binding of 125I-labeled ITK-2 to SCLC cells was not inhibited by MOC-1 or NKH-1, the binding site of ITK-2 on SCLC cells appeared to be different from that of either MOC-1 or NKH-1. Unexpectedly, binding of 125I-labeled ITK-2 to SCLC cells increased in the presence of ITK-3. This ITK-3-induced increase in ITK-2 binding was due partly to an increase in the number of binding sites for ITK-2 on SCLC cells. Addition of ITK-3 may, therefore, improve the effectiveness of ITK-2-based tumor detection or therapy.
Saito
S
S
Third Department of Internal Medicine, Osaka University School of Medicine, Japan.
Inoue
T
T
Kawase
I
I
Hara
H
H
Tanio
Y
Y
Tachibana
I
I
Hayashi
S
S
Watanabe
M
M
Matsunashi
M
M
Osaki
T
T
D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D000951:Antigens, Neoplasm / Q000032:analysis / Q000276:immunology; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive / Q000187:drug effects; D018288:Carcinoma, Small Cell / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007074:Immunoglobulin G; D008175:Lung Neoplasms / Q000276:immunology*; D011863:Radioimmunoassay; D014407:Tumor Cells, Cultured; D014415:Tunicamycin / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D007074:Immunoglobulin G; D014415:Tunicamycin