BILIARY GLYCOPROTEIN MESSENGER-RNA EXPRESSION IS INCREASED IN PRIMARYLUNG-CANCER, ESPECIALLY IN SQUAMOUS-CELL CARCINOMA

Biliary glycoprotein (BGP), a member of the carcinoembryonic antigen g ene family, is a cell surface glycoprotein that has both a transmembra ne domain and a cytoplasmic domain. BGPs consist of at least four isof orms (BGPa, b, c, and d) and function in vitro as Ca2+-dependent homot ypic intercellular adhesion molecules. The mRNA expression of BGP gene was investigated in specimens of primary and metastatic cancer tissue s from 15 patients with primary lung cancer (six squamous cell carcino mas, five adenocarcinomas, and four small cell carcinomas). The specim ens were also compared with normal adjacent tissues of the same indivi duals with squamous cell carcinoma. BGP mRNA expression was increased in carcinomatous tissues of the primary site, especially in squamous c ell carcinoma, but was not detected in adjacent normal tissues by Nort hern blot analysis or in situ hybridization. Interestingly, BGP mRNA e xpression was apparently decreased in metastatic lesions compared with the primary site in the six individuals with squamous cell carcinoma. Furthermore, a loss of BGPa isoform was observed by reverse transcrip tase-polymerase chain reaction in four of six patients with squamous c ell carcinoma. These results suggest that the reduction of BGP express ion may play an important role in the process of metastasis through de creasing adhesive interactions with surrounding cells, especially in s quamous cell carcinoma.