Soluble cell membrane antigens associated with bladder cancer

Summary Separated soluble membrane components present on bladder cancer cells were screened for their ability to produce cell-mediated immune responses, and those antigens that were tumor-associated (TAA) were purified and identified. A total of 812 tests of control and cancer antigens were performed in 110 patients. In a series of 384 skin tests performed in 28 patients with crude antigens separated by gel filtration and a series of 322 skin tests performed in 60 patients with semipurified antigens further separated by gradient polyacrylamide gel electrophoresis, the average 48-h induration response in those patients who reacted was not significantly different in relation to the stage of cancer. Preoperative patients responded to a tumor-associated antigen, and postoperative patients responded not only to the tumor-associated antigen, but also to a tissue-associated antigen, which may possibly contain tumor-related components. Of these bladder cancer patients, 78% had a positive delayed hypersensitivity reaction to skin tests with 30 g semipurified bladder cancer TAA, whereas only 53% had reactions to one or more of the recall antigens used, which included SKSD, candida, dermatophytin, PPD, and mumps. TAA was also isolated and identified on bladder cancer tissue culture line T-24. More highly purified bladder TAA was highly specific in controlled skin tests for delayed hypersensitivity reaction to 5 g per test in 20 patients. The amount of TAA present on primary bladder tumor cells is approximately 0.2 pg, and on T-24 cell it is approximately 0.04 pg; this is approximately 2% of the soluble protein on a primary bladder cancer cell and about 0.8% of the soluble protein on a T-24 cell. Reactions with TAA in leukocyte migration inhibition tests were partial; TAA is a very weak reactant in double diffusion tests; TAA shows promise in indirect immunofluorescent tests, in some complement fixation tests, and for use in enzyme-linked immunoadsorbent assays. Bladder cancer TAA is a simple polypeptide, fairly stable, with an estimated molecular size of approximately 40,000 daltons. The tissue-associated antigen reacts in double diffusion with sera from patients with benign and malignant bladder conditions, and is a polypeptide of approximately 80,000 daltons; whether this less specific antigen is a dimer containing the TAA component must still be determined.