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 of gene expression (SAGE), we identified PSCA as one of the most abundant transcripts in a differentiated urothelial tumor, As assessed by Northern blotting, PSCA is highly expressed in normal urothelium and noninvasive urothelial tumors, In contrast to the previously reported overexpression of PSCA in progressive and invasive forms of prostate cancer, we found a markedly reduced expression in undifferentiated bladder carcinoma. In addition, several aberrant splicing products derived from the PSCA gene were found in urothelial tumors. Furthermore, PSCA mRNA was highly abundant in normal esophagus and stomach, but was undetectable in esophageal or gastric tumors. The PSCA expression appeared to depend on cell contact, since mRNA levels were increased when RT112 bladder carcinoma cells were grown to confluence. Our data suggest that PSCA could serve as a potential marker for the early carcinogenesis in urothelial and gastric tissues and that its expression is specific for epithelial cells, (C) 2000 Academic Press.