Interleukin-6 production by bladder tumors is upregulated by BCG immunotherapy

To determine whether BCG therapy could upregulate interleukin-6 (IL-6) production in human transitional cell carcinomas (TCC).

Immunohistochemistry of tumor biopsies and urinary cytospins and ELISA studies of urine from bladder cancer patients and TCC cell-line supernatants, before and after exposure to BCG, were performed.

Constitutive staining for IL-6 was found in the majority of bladder tumors. Interleukin-6 was detected in the urine of all 13 patients with carcinoma in situ and increased 5-fold during BCG therapy. Levels were variable but were greater in nonresponders (p < 0.01). During therapy both detached bladder urothelial cells and polymorphonuclear leukocytes stained for IL-6. Production of IL-6 increased in only 3 cell lines after exposure to BCG, but all 7 cell lines showed increases after exposure to interferon-gamma (p = 0.015). Grade 3 cell lines showed much greater upregulation than grade 1 and 2 cell lines.

The increase in IL-6 during BCG therapy may be caused by urothelial cells as well as leukocytes. The higher levels seen in nonresponders may be due to either higher grade or persisting tumor.