Journal
JOURNAL OF IMMUNOLOGY
Volume 188, Issue 12, Pages 6156-6164Publisher
AMER ASSOC IMMUNOLOGISTS
DOI: 10.4049/jimmunol.1102604
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Funding
- Center for Cancer Research, National Cancer Institute, National Institutes of Health
- National Cancer Institute, National Institutes of Health [N01-CO-12400]
- Howard Hughes Medical Institute, Ludwig Center for Cancer Immunotherapy
- Prostate Cancer Foundation
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IL-15 has potential as an immunotherapeutic agent for cancer treatment because it is a critical factor for the proliferation and activation of NK and CD8(+) T cells. However, monotherapy of patients with malignancy with IL-15 that has been initiated may not be optimal, because of the limited expression of the private receptor, IL-15R alpha. We demonstrated greater CD8 T cell-mediated therapeutic efficacy using a combination regimen of murine IL-15 administered with an agonistic anti-CD40 Ab (FGK4.5) that led to increased IL-15R alpha expression on dendritic cells (DCs), as well as other cell types, in a syngeneic established TRAMP-C2 tumor model. Seventy to one hundred percent of TRAMP-C2 tumor-bearing wild-type C57BL/6 mice in the combination group manifested sustained remissions, whereas only 0-30% in the anti-CD40-alone group and none in the murine IL-15-alone group became tumor free (p < 0.001). However, the combination regimen showed less efficacy in TRAMP-C2 tumor-bearing IL-15R alpha(-/-) mice than in wild-type mice. The combination regimen significantly increased the numbers of TRAMP-C2 tumor-specific SPAS-1/SNC9-H-8 tetramer(+)CD8(+) T cells, which were associated with the protection from tumor development on rechallenge with TRAMP-C2 tumor cells. Using an in vitro cytolytic assay that involved NK cells primed by wild-type or IL-15R alpha(-/-) bone marrow-derived DCs, we demonstrated that the expression of IL-15R alpha by DCs appeared to be required for optimal IL-15-induced NK priming and killing. These findings support the view that anti-CD40-mediated augmented IL-15R alpha expression was critical in IL-15-associated sustained remissions observed in TRAMP-C2 tumor-bearing mice receiving combination therapy. The Journal of Immunology, 2012, 188: 6156-6164.
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