Bladder carcinomas and normal urothelium universally express gp200-MR6, a molecule functionally associated with the interleukin 4 receptor (CD 124).

Monoclonal antibody MR6 detects gp200-MR6, a molecule functionally associated with the interleukin 4 (IL- 4) receptor. Positive immunolabeling with MAb MR6 was obtained in 28/28 transitional cell carcinomas of the bladder, representing a range of different grades and stages of disease, as well as in all control non-neoplastic urothelia. The expression of mutant p53 protein and epidermal growth factor receptor was detected in 14/28 and 20/28 cases respectively. Proliferation indices, determined by Ki67 labeling, ranged from 5% to 95% among these tumours. The universal expression of gp200-MR6 in neoplastic and non-neoplastic urothelium has important implications for the possible use of IL-4 in tumour therapy and suggests that IL- 4 may play a role in differentiation and homeostasis of urothelium and other mucosal epithelia.