EXPRESSION OF CD44V2 IN TRANSITIONAL-CELL CARCINOMA OF THE URINARY-BLADDER AND IN URINE

CD44 is the principal cell surface receptor for hyaluronate. Variant f orms of the receptor, produced by alternative splicing, have been foun d to be associated with tumor progression in a variety of cancers. Bas ed on investigations at the RNA level, it has recently been proposed t hat expression of CD44 variant V2 was present in urothelial cancer but not in normal urothelium. Since a distinctive marker for urothelial c ancer would be extremely useful, frozen sections of normal urothelium and urothelial cancer were examined for expression of standard CD44 an d CD44V2. Frozen sections of specimens of 35 patients with transitiona l cell carcinoma of the bladder, 16 specimens of normal bladder and 5 ureters were examined. Immunohistochemical staining was performed usin g a polyclonal antibody to CD44V2 (PAB CD44V2), a monoclonal antibody to CD44V2 (MAB CD44V2) and a monoclonal antibody to CD44S (MAB CD44S). CD44V2 and CD44S were also measured in lysates of urine sediments fro m 21 patients by enzyme-linked immunoabsorbent assay (ELISA). All inve stigated transitional cell carcinomas expressed CD44V2. There was no d ifferentiation between invasive and noninvasive carcinoma. CD44V2 was also expressed in normal urothelium. Standard CD44 was expressed by th e transitional cell carcinoma, normal urothelium, musculature and inte rstitial tissue. The amount of CD44V2 and CD44S in lysates of urine se diments is not correlated to diagnosis. In contrast to investigations at the RNA level, CD44V2 on the protein level seems not to be a distin ctive marker for urothelial cancer. Therefore, CD44V2 will not be a us eful diagnostic marker for detection of transitional cell carcinoma.