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Characterization of an Epithelial and a Tumor-associated Human Small Cell Lung Carcinoma Glycoprotein Antigen¹

Division of Oncology, Department of Medicine, University Hospital of Zürich, Switzerland [R. W., R. A. S.], and Department of Pathology, New England Deaconess Hospital, Boston, Massachusetts [C. J. O.]

The small cell carcinoma (SCC) antigens recognized by LAM2 and LAM8 antibody were characterized by comparison of their tissue expression and analysis of their biochemical composition. LAM2, but not LAM8 antigen could be demonstrated in lipid extracts of SCC cells. By immunohistochemical staining the SCC antigen LAM2 was shown to be an epithelial type membrane antigen. Immunoblotting experiments and competition solid phase radioimmunoassays showed LAM2 antigen to be a native conformation of a glycoprotein with major bands at M_r 100,000–120,000 and a minor band at M_r 210,000. L-Fucose was a dominant part of the epitope which appeared to be closely related to be carbohydrate epitope of the blood group antigen H(O). The tumor-associated membrane antigen LAM8 was shown to be a glycoprotein with major bands at M_r 90,000–135,000 and a minor band at M_r 200,000. Neuraminic acid was the predominant part of the carbohydrate epitope. LAM8 antibody recognized a structure in the saliva of Le^a positive probands, but untreated and neuraminidase-treated SCC extracts were unreactive with anti-Le^a antibody. Anti CA 19-9 (sialo-Le^a antigen) and LAM2 antibodies did not compete for LAM8 binding in direct radioimmunoassays. The sialo-GP_90–135 antigen recognized by LAM8 antibody therefore is likely to represent a novel tumor antigen.

¹ Supported by the Swiss Cancer League (FOR.302.85).

² To whom requests for reprints should be addressed, at Division of Oncology, University Hospital, CH-8091 Zürich, Switzerland.

Received 10/24/86. Revised 3/16/87. Accepted 4/15/87.