Vα24-invariant NKT cells mediate antitumor activity via killing of tumor-associated macrophages
Liping Song, … , Robert C. Seeger, Leonid S. Metelitsa
Liping Song, … , Robert C. Seeger, Leonid S. Metelitsa
Published May 1, 2009
Citation Information: J Clin Invest. 2009;119(6):1524-1536. https://doi.org/10.1172/JCI37869.
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Research Article

Vα24-invariant NKT cells mediate antitumor activity via killing of tumor-associated macrophages

Abstract

Tumor infiltration with Vα24-invariant NKT cells (NKTs) associates with favorable outcome in neuroblastoma and other cancers. Although NKTs can be directly cytotoxic against CD1d+ cells, the majority of human tumors are CD1d–. Therefore, the role of NKTs in cancer remains largely unknown. Here, we demonstrate that CD68+ tumor-associated monocytes/macrophages (TAMs) represented the majority of CD1d-expressing cells in primary human neuroblastomas. TAMs stimulated neuroblastoma growth in human cell lines and their xenografts in NOD/SCID mice via IL-6 production. Indeed, TAMs produced IL-6 in primary tumors and in the BM of patients with metastatic neuroblastoma. Gene expression analysis using TaqMan low-density arrays of 129 primary human neuroblastomas without MYCN amplification revealed that high-level expression of TAM-specific genes (CD14, CD16, IL6, IL6R, and TGFB1) was associated with poor 5-year event-free survival. While NKTs were not cytotoxic against neuroblastoma cells, they effectively killed monocytes pulsed with tumor cell lysate. The killing of monocytes was CD1d restricted because it was inhibited by a CD1d-specific mAb. Cotransfer of human monocytes and NKTs to tumor-bearing NOD/SCID mice decreased monocyte number at the tumor site and suppressed tumor growth compared with mice transferred with monocytes alone. Thus, killing of TAMs reveals what we believe to be a novel mechanism of NKT antitumor activity that relates to the disease outcome.

Authors

Liping Song, Shahab Asgharzadeh, Jill Salo, Kelly Engell, Hong-wei Wu, Richard Sposto, Tasnim Ara, Ayaka M. Silverman, Yves A. DeClerck, Robert C. Seeger, Leonid S. Metelitsa

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Figure 5

Myelomonocytic cells are a major source of IL-6 in BM with neuroblastoma metastases.

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Myelomonocytic cells are a major source of IL-6 in BM with neuroblastoma...
(A) Freshly isolated BM mononuclear cells from stage 4 neuroblastoma patients were analyzed for the presence of neuroblastoma cells by GD2 and CD56 (NCAM) co-expression and are shown as NB– (left) or NB+ (right) examples. Without any in vitro stimulation, cells were cultured in the presence of brefeldin A for 4 hours, followed by staining for the indicated surface markers and intracellular IL-6. The frequencies of IL-6–producing cells among all live cells (top), of monocytic cells among IL-6–producing cells (middle), and of IL-6–producing cells among monocytic cells (bottom) are shown. Representative plots from 16 NB– and 5 NB+ BM mononuclear cells. (B) As in A, NB+ and NB– BM morphonuclear cells were cultured overnight. In addition, 7 of 16 NB– BM morphonuclear cells were cultured in the presence of a CHLA-255 neuroblastoma cell–conditioned medium. IL-6 concentration in the supernatants was determined by CBAPlex. Horizontal bars indicate the mean values. P < 0.001 compared with NB– mononuclear cells cultured in nonconditioned medium, by 1-way ANOVA.