The essential role of interferon-gamma during interleukin-12 therapy for murine transitional cell carcinoma of the bladder.
OBJECTIVE
Recombinant interleukin (IL)-12 and adenoviral IL-12 gene therapy have been shown to be potent therapeutic interventions for murine transitional cell carcinoma (TCC) of the bladder in vivo. We investigated the mechanisms through which IL-12 induces antibladder cancer immunity.


METHODS
The ability of IL-12 to enhance interferon-gamma (IFN-gamma) expression, a major T-helper type 1 cytokine, was analyzed in murine serum, urine and splenocyte cultures. MB49, a murine TCC line, was treated with IFN-gamma and evaluated for its proliferation, surface molecule expression and sensitivity to splenocyte mediated cytotoxicity. Neutralizing antiIFN-gamma antibody was applied to test the role of IFN-gamma in the IL-12 therapy of MB49 tumor.


RESULTS
IL-12 was observed to significantly increase IFN-gamma concentrations in serum and urine as well as in splenocyte cultures. While IL-12 had no direct activity against TCC in vitro, IFN-gamma showed potent dose dependent antiproliferative and pro-apoptotic activity, which was further enhanced by supplementation of tumor necrosis factor-alpha. In addition, IFN-gamma substantially up-regulated the expression of surface immune molecules on TCC cells, including MHC-I, MHC-II, ICAM-I, B7.1, B7.2 and Fas. Maximum splenocyte mediated cytotoxicity against TCC was enhanced by pretreatment of target bladder cancer cells with IFN-gamma plus tumor necrosis factor-alpha. Furthermore, IL-2 in combination with IL-12 further enhanced splenocyte mediated cytotoxicity. The in vivo antibladder cancer activity of IL-12 was abolished by concurrent treatment with antibodies to IFN-gamma.


CONCLUSIONS
This study strongly suggests that IFN-gamma has an essential role in IL-12 induced antibladder tumor immunity. Activation of host effector immune cells by IL-12 is also required for induction of optimal tumor destruction in IL-12 therapy.
O'Donnell
Michael A
MA
Department of Urology, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242, USA. odonnell@uiowa.edu
Luo
Yi
Y
Hunter
Sharon E
SE
Chen
Xiaohong
X
Hayes
Lori L
LL
Clinton
Steven K
SK
D000818:Animals; D002295:Carcinoma, Transitional Cell / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D002455:Cell Division; D045744:Cell Line, Tumor; D007371:Interferon-gamma / Q000627:therapeutic use*; D018664:Interleukin-12 / Q000627:therapeutic use*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D013154:Spleen / Q000166:cytology / Q000276:immunology; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D019014:fas Receptor / Q000276:immunology
D019014:fas Receptor; D018664:Interleukin-12; D007371:Interferon-gamma