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 bladder cancer specimens as well as breast cancer specimens (1). Our objective was to clone the AN43 gene and determine its possible role in bladder and breast tumorigenesis. A bladder tumor cell cDNA expression library was made and screened with a murine monoclonal antibody to the AN43 antigen. A 1897 bp cDNA clone was isolated following expression screening with the AN43 antibody and named BB1. Following DNA sequencing, the BB1 cDNA clone was determined to have no homology to any known gene when screened through GenBank. RNA analysis demonstrated increased expression of BB1 mRNA in metastatic breast and bladder carcinomas relative to normal breast epithelium and urothelium. Treatment with gamma-interferon resulted in decreased mRNA expression. BB1 mRNA expression is increased in malignant cells relative to normal cells and is down-regulated following gamma-interferon treatment and therefore may have a role in tumor progression. Further characterization and functional analysis of this novel gene will be useful in understanding tumor development and metastatic potential.