Partially circumventing peripheral tolerance for oncogene-specific prostate cancer immunotherapy.

Autor: Neeley YC; Department of Urology, Surgery, and Pathology, University of Michigan. Ann Arbor, Michigan, USA., Arredouani MS, Hollenbeck B, Eng MH, Rubin MA, Sanda MG
Jazyk: angličtina
Zdroj: The Prostate [Prostate] 2008 May 15; Vol. 68 (7), pp. 715-27.
DOI: 10.1002/pros.20689
Abstrakt: Background: Failure of cancer immunotherapy is essentially due to immunological tolerance to tumor-associated antigens (TAAs), as these antigens are also expressed in healthy tissues.
Methods: Here, we used transgenic adenocarcinoma of mouse prostate (TRAMP) mice, which develop lethal prostate cancer due to prostate-specific expression of SV40 T antigen (Tag), to evaluate effects of prostatic transformation on oncogene TAA-specific tolerance and to test the possibility of breaking such tolerance using a modified recombinant vaccinia virus.
Results: We showed that Tag expression in TRAMP mice is uniquely extra-thymic, and levels of prostatic Tag expression positively correlate with malignant transformation of the prostate. Yet, young tumor-free TRAMP mice were tolerant to Tag antigen. We therefore attempted overcoming such peripheral oncogene-specific T cell tolerance through immunization with a vaccinia construct encoding Tag immunogenic epitopes. This vaccination modality showed that oncogene-specific tolerance was successfully overcome by effective in vivo priming of Tag-specific cytotoxic T cells (CTLs). However, this was restricted to young TRAMP mice. Tag-specific CTL from "tumor naïve" young TRAMP mice showed significant anti-tumor efficacy in vivo by eliminating established heterotopic prostate tumors and prolonging survival in SCID mice harboring Tag-expressing tumors. In contrast, older TRAMP mice with established prostate tumors exhibited oncogene-specific tolerance as evidenced by failure to generate Tag-specific CTL following Tag-specific immunization.
Conclusions: Peripheral tolerance can be overcome for effective anti-tumor therapy following oncogene-specific immunization. However, this ability to elicit oncogene-specific CTL is impeded in the tumor-bearing host, in the context of increased oncogene expression associated with tumor progression.
((c) 2008 Wiley-Liss, Inc.)
Databáze: MEDLINE
Externí odkaz: