Uroplakin expression in the urothelial tumors of cows

Expression of uroplakins (UPs) was investigated in 20 bladder tumors from c ows that had been suffering from chronic enzootic hematuria for several yea rs. In dysplastic urothelium and papillomatous proliferations, UP expressio n was evident both as luminal and intercellular staining. UPs appeared to c learly define the plasma membrane of luminal cells and the borders of cells placed in deeper layers, whether or not these intermediate cells were adja cent to superficial ones. Occasionally, some intermediate cells showed a re markable cytoplasmic immunoreactivity. The pattern of UPs in grade I tumors was characterized by an evident discontinuity of luminal staining and by t he presence of numerous intermediate cells showing a diffuse intracytoplasm ic positivity for UPs. In grade H tumors, there was a decrease of luminal a nd intermediate cells showing UP expression and an apparent increase of clu sters of intermediate cells with intracytoplasmic reactivity for UPs. In gr ade III tumors, immunoreactivity was heterogeneously distributed and a seve re loss of UP-positive luminal and intermediate cells could be seen. Focall y, superficial and deeper cells showed strong membraneous immunoreactivity that marked and delimited single cells, with complete circumferential perip heral staining clearly evident. UP expression in bladder tumors of cows rep orted in this study is similar to the UP pattern of some urothelial tumors in humans. Although UP expression is remarkably changed in bladder carcinog enesis of cattle, the UP gene(s) remains expressed during cell transformati on and tumor progression.