MOLECULAR ANALYSIS OF A GENE, BB1, OVEREXPRESSED IN BLADDER AND BREAST-CARCINOMA

The AN43 antigen is a new bladder tumor marker which is present in bla dder cancer specimens as well as breast cancer specimens (1). Our obje ctive was to clone the AN43 gene and determine its possible role in bl adder and breast tumorigenesis. A bladder tumor cell cDNA expression l ibrary was made and screened with a murine monoclonal antibody to the AN43 antigen. A 1897 by cDNA clone was isolated following expression s creening with the AN43 antibody and named BB1. Following DNA sequencin g, the BB1 cDNA clone was determined to have no homology to any known gene when screened through GenBank. RNA analysis demonstrated increase d expression of BB1 mRNA in metastatic breast and bladder carcinomas r elative to normal breast epithelium and urothelium. Treatment with gam ma-interferon resulted in decreased mRNA expression. BB1 nRNA expressi on is increased in malignant cells relative to normal cells and is dow n-regulated following gamma-interferon treatment and therefore may hav e a role in tumor progression. Further characterization and functional analysis of this novel gene will be useful in understanding tumor dev elopment and metastatic potential.