Reduced expression of PSCA, a member of the LY-6 family of cell surface antigens, in bladder, esophagus, and stomach tumors

Prostate stem cell antigen (PSCA) is a member of the LY-6 family of surface proteins that is overexpressed in prostate cancer, Using serial analysis o f gene expression (SAGE), we identified PSCA as one of the most abundant tr anscripts in a differentiated urothelial tumor, As assessed by Northern blo tting, PSCA is highly expressed in normal urothelium and noninvasive urothe lial tumors, In contrast to the previously reported overexpression of PSCA in progressive and invasive forms of prostate cancer, we found a markedly r educed expression in undifferentiated bladder carcinoma. In addition, sever al aberrant splicing products derived from the PSCA gene were found in urot helial tumors. Furthermore, PSCA mRNA was highly abundant in normal esophag us and stomach, but was undetectable in esophageal or gastric tumors. The P SCA expression appeared to depend on cell contact, since mRNA levels were i ncreased when RT112 bladder carcinoma cells were grown to confluence. Our d ata suggest that PSCA could serve as a potential marker for the early carci nogenesis in urothelial and gastric tissues and that its expression is spec ific for epithelial cells, (C) 2000 Academic Press.