Mab AU1 reacts specifically with uroplakin III present in the superficial cell layer of the urothelium. The binding region has been localized on the extracellular part of the antigen. Together with the uroplakins UP Ia, UP Ib and UP II, uroplakin III contributes in constituting the asymmetrical unit membrane of the plaques of urothelial superficial (umbrella) cells. Uroplakin is a membrane glycoprotein (47 kD) and has been shown to be a specific marker of terminal urothelial differentia-tion (Wu et al. 1993 & 1194).Antibody AU1 strongly stains the urothelial surface membrane in paraffin sections of human renal pelvis, ureter, bladder, and urethra. About 60% of human transitional cell carci-nomas (including metastases) maintain focal (sometimes very limited) expression of uroplakin III. Until now, no uroplakin staining was found in any non-urothelial carcinoma (Moll et al. 1995). Uroplakin III may thus serve as a specific urothelial differentiation marker in cases of metastatic carcinomas with unclear primary tumor.
Moll, R., Wu, X.-R., Lin, J.-H. & Sunt, T.-T. Uroplakins, Specific Membrane Proteins of Urothelial Umbrella Cells, as Histological Markers of Metastatic Transitional Cell Carcinomas. Am. J. Pathol. 147, 1383–1397 (1995).Wu, X.-R. et al. Mammalian Uroplakins: A group of highly conserved urothelial differentiation-related membrane proteins. J. Biol. Chem. 269, 13716–13724 (1994).Wu, X. R. & Sun, T. T. Molecular cloning of a 47 kDa tissue-specific and differentiation-dependent urothelial cell surface glycoprotein. J. Cell Sci. 106, 31–43 (1993).