POLY(ALPHA-2,8-DEAMINONEURAMINIC ACID) IS EXPRESSED IN LUNG ON A SINGLE 150-KDA GLYCOPROTEIN AND IS AN ONCODEVELOPMENTAL ANTIGEN

Homopolymers of alpha 2,8-linked N-acetylneuraminic acid [poly(alpha 2 ,8-Neu5Ac)] of the neural cell adhesion molecule NCAM have been shown to be temporally expressed during lung development and represent a mar ker for small cell lung carcinoma, We report the presence of a further polysialic acid in lung that consists of oligo/polymers of alpha 2,8- linked deaminoneuraminic acid residues [poly(alpha 2,8-KDN)], as detec ted with a monoclonal antibody in conjunction with a specific sialidas e. Although the various cell types forming the bronchi, alveolar septs , and blood vessels were positive for poly(alpha 2,8-KDN) by immunohis tochemistry, this polysialic acid was found on a single 150-kDa glycop rotein by immunoblot analysis. The poly(alpha 2,8-KDN)-bearing glycopr otein was not related to an NCAM protein based on immunochemical crite ria. The expression of the poly(alpha 2,8-KDN) was developmentally reg ulated as evidenced by its gradual disappearance in the rat lung paren chyma commencing 1 week after birth, In adult lung the blood vessel en dothelia and the smooth muscle fibers of both blood vessels and bronch i were positive but not the bronchial and alveolar epithelium. The pol y(alpha 2,8-KDN)-bearing 150-kDa glycoprotein became reexpressed in va rious histological types of lung carcinomas and cell lines derived fro m them and represents a new oncodevelopmental antigen in lung.