A NOVEL ANTIGEN DEFINED BY MONOCLONAL-ANTIBODY CR101 IS ASSOCIATED WITH SMALL-CELL LUNG-CARCINOMA

Small cell lung carcinoma (SCLC) represents about 25% of all lung canc ers. Human SCLC shows neuroendocrine features such as the production o f neural peptide hormones, marker enzymes and neurosecretory granules, and the expression of neural cell adhesion molecules (NCAMs). Althoug h SCLC is sensitive to both chemotherapy and radiation, prognosis rema ins poor due to the appearance of post-treatment chemo- and radioresis tant variants. Monoclonal antibodies (MAbs) have been developed that b ind to SCLC tumor antigens. We have used similar technology to define another SCLC marker designated gP94/115. The MAb CR101 binds to a high ly glycosylated, cell-surface antigen associated with SCLC. In vitro e xpression of the antigen appears to be restricted to cell lines of SCL C origin. Enzymatic removal of the sugars resolves the antigen into tw o proteins of 94 and 115 kD by sodium dodecyl sulfate-polyacrylamide g el electrophoresis (SDS-PAGE). Fluorescence-activated cell sorting (FA CS) analysis confirms the antibody's specificity. These results indica te that CR101 may recognize a novel protein expressed by SCLC.