Toll-like receptor 3-mediated suppression of TRAMP prostate cancer shows the critical role of type I interferons in tumor immune surveillance.
Inflammation has increasingly been recognized as a critical component influencing tumor growth. Recent reports have revealed conflicting evidence for the role of Toll-like receptors (TLR) in modulating tumorigenesis. In our study, we implicate TLR3 in mediating immune surveillance with increased growth of implanted transgenic adenocarcinoma of the mouse prostate (TRAMP) tumors in TLR3(-/-) compared with TLR3(+/+) mice. Activation of TLR3 by polyinosinic-polycytidylic acid (polyI:C) leads to induction of multiple inflammatory pathways, including NF-kappaB, mitogen-activated protein kinases, and interferon (IFN) regulatory factors. We explored the potential of TLR3 stimulation in prostate cancer immunotherapy and showed that treatment with polyI:C can strongly suppress both s.c. implanted TRAMP tumors in syngenic mice as well as orthotopic prostate cancers in TRAMP C57Bl6 x FvB F1 Tg(+/-) transgenic mice. Treated tumors remained well differentiated to moderately differentiated with increased infiltration of T lymphocytes and natural killer (NK) cells compared with poorly differentiated adenocarcinoma observed in untreated tumors. Like TLR3(-/-) mice, IFN-alpha receptor 1 (IFNAR1)(-/-) mice exhibited reduced tumor surveillance and impaired tumor suppression following polyI:C treatment. We observed that type I IFN-dependent induction of cytokines was responsible for NK activation, with depletion of NK cells leading to increased tumor growth as well as expansion of CD4(+)CD25(+)Foxp3(+) T regulatory lymphocytes. Our study therefore delineates the importance of IFNAR-dependent functions in TLR3-mediated tumor suppression and supports the use of TLR3 agonists for prostate cancer immune-based therapies.
Department of Urology, University of California at Los Angeles, 10833 Le Conte Avenue, P.O. Box 951738, Los Angeles, CA 90095-1738, USA. aichin@ucla.edu
Arnold I
AI
Chin
Andrea K
AK
Miyahira
Anthony
A
Covarrubias
Juli
J
Teague
Beichu
B
Guo
Paul W
PW
Dempsey
Genhong
G
Cheng
D000818:Animals; D048708:Cell Growth Processes / Q000187:drug effects / Q000276:immunology; D045744:Cell Line, Tumor; D007108:Immune Tolerance; D007369:Interferon Inducers / Q000494:pharmacology; D007370:Interferon Type I / Q000276:immunology*; D053645:Interleukin-2 Receptor alpha Subunit / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011070:Poly I-C / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology; D053633:Receptor, Interferon alpha-beta / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D051196:Toll-Like Receptor 3 / Q000276:immunology*
C508032:Ifnar1 protein, mouse; C508018:Il2ra protein, mouse; D007369:Interferon Inducers; D007370:Interferon Type I; D053645:Interleukin-2 Receptor alpha Subunit; C519703:TLR3 protein, mouse; D051196:Toll-Like Receptor 3; D053633:Receptor, Interferon alpha-beta; D011070:Poly I-C