A hybridoma cell line secreting an IgM monoclonal antibody (MAb) was produced after immunizing a mouse with RT4 cells and a crude suspension of human bladder carcinoma cells (WHO grades II and III TCC). This MAb reacted with RT4 target cells derived from a human transitional bladder cancer but failed to react with a majority of non-bladder cancer cell lines. Immunohistological studies indicate that this MAb reacts inconstantly with normal bladder: in positive cases only a few superficial cells (5% to 10% umbrella cells) are stained but not intermediate or basal cells of the urothelium. This MAb was evaluated on 118 tumors: it reacted with tumor tissue in a majority of grade I (79.5%) and grade II papillary TCC (77.3%), less with grade III papillary TCC (45%) and very rarely with invasive non-papillary TCC (14%). In cases of flat lesions a strong reactivity of superficial, intermediate and/or basal layer cells was observed in 50% of moderate and severe dysplasia and in all cell layers of carcinomas in situ (CIS)(9/9).

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The monoclonal antibody (MoAb) BL2-10D1 directed against a tumor-associated antigen of human bladder cancer was used to identify tumor cells obtained by bladder washing or voided urine. The reactivity of BL2-10D1 MoAb was detected by an immunoperoxidase method and evaluated in ten healthy donors and in a series of 65 patients. The 65 patients studied were divided into three groups: ten with nontumor bladder disease (group A); 36 with bladder carcinoma (group B); and 19 with a history of bladder neoplasia but no visible tumor at the time of cytologic sampling (group C). The results were compared with the standard cytologic diagnosis on Papanicolaou-stained preparations. Conventional cytologic study showed a high false-negative rate in low-grade tumors (transitional cell carcinomas [TCC] Grades 1 and 2, 1/4 and 4/17, respectively). All urine from patients with a histologically proved TCC Grade 1 were stained with BL2-10D1 MoAb. Cytologic findings from patients with TCC Grade 2 (17 cases) contained positive cells in 14 cases and failed to react in three cases. Furthermore, whereas urine from patients with TCC Grade 2 or 3 was not always stained with BL2-10D1 MoAb, all patients with dysplastic lesions (three cases) or carcinoma in situ (5 cases) showed a positive reactivity. Such results suggest that BL2-10D1 MoAb may be considered as a valuable adjunct to the classical methods of early detection and follow-up of bladder cancer. However, a larger scale study is needed for MoAb BL2-10D1 to be proposed as an aid to improve the diagnostic sensitivity of urine cytologic investigation in the follow-up of patients treated for recurring bladder cancer, and for the screening of workers exposed to potent bladder carcinogens.

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