Detailed Characterization of a High-molecular-weight Glycoprotein Secreted by Lung Cancer Cells |
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Authors: | Noritaka Nonaka Ken-ichi Manaka Kunihiko Kobayashi Hidematsu Hirai |
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Institution: | Tumour Laboratory, Higashitokura 1–15–3, Kokubunji, Tokyo 185;Department of Development, Shino-Test Corporation, Oonodai 2–29–14, Sagamihara, Kanagawa 229;Department of Pathology, Dokkyo University School of Medicine, Mibu, Tochigi 321–02;Department of Laboratory Medicine, School of Medicine, Hokkaido University, North 15 West 7, Kita-ku, Sapporo, Hokkaido 060 |
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Abstract: | A cancer-associated, high-molecular-weight glycoprotein antigen (6B3·Ag) recognized by monoclonal antibody 6B3 was purified from culture medium of human large cell lung carcinoma cell line (HLC-2) and characterized biochemically and immunochemically. The 6B3·Ag was purified more than 1,200-fold with a yield of 30% by salting out, precipitation by acidification at pH 4.5, and chromatographies on Sepharose 4B and concanavalin A-Sepharose. The molecular weight of 6B3·Ag is approximately 1,000,000 and the molecule is a homodecamer of 94,000 subnnits. The 6B3·Ag is a glycoprotein containing 22.9% sugars, consisting of both N - and O -glycoside chains. The N-terminal 19 amino acids were determined and only 4 out of 19 amino acid residues were different from those of an antigen, L3, secreted by lung carcinoma cell line Calu-1. The serum level of 6B3·Ag was determined in normal adults as well as patients with various diseases by enzyme-linked immunosorbent assay. The mean serum level of 6B3-Ag was 3.1 μg/ml, ranging from 1.6 to 6.2 μg/ml in 131 healthy adults. When the cut-off value was set at 6.2 μg/ml, the incidence of positive values in the sera was elevated not only in malignant diseases such as hepatoma (73%) and leukemia (62%), but also in benign diseases such as chronic hepatitis (42%) and liver cirrhosis (63%). While the incidence of positive values was elevated in advanced liver diseases, namely, chronic hepatitis, liver cirrhosis and hepatoma, the cancer specificity of 6B3·Ag did not appear to be high. |
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Keywords: | High-molecular-weight glycoprotein Chemical properties Serum level |
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