6B11 mAb-treated iNKT cells suppress tumor growth in vivo. A,E,G, Schematic of iNKT cell therapy in vivo. B–D, Human IL7/IL15 knockin NSG mice were subcutaneously injected with K562 cells on day 0. iNKT cells treated with the 6B11 mAb (50 ng/mL) or mIgG1(50 ng/mL) overnight were washed and resuspended in PBS. B, iNKT cells were intratumorally injected on days 3, 5, 7, and 9 (n = 6 or 7 mice/group). B and C, Tumor size was measured every 2 days. D, Tumors were excised at day 13 and their weight was measured. F, Human IL7/IL15 knock-in NSG mice were subcutaneously injected with K562 cells on day 0. iNKT cells treated with the 6B11 mAb as described in B were intratumorally or intravenously injected on days 3, 5, 7, and 9 (n = 5 or 6 mice/group). H, Human IL7/IL15 knock-in NSG mice were subcutaneously injected with K562 cells on day 0. iNKT cells treated with the 6B11 mAb as described in B or untreated iNKT cells were intratumorally injected on days 3, 5, 7, and 9 (n = 5 or 6 mice/group). The 6B11 mAb was further intraperitoneally administrated to mice injected with untreated NKT cells. Data are representative of two independent experiments. Data represent the mean ± SEM. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.
Funding
MEXT | Japan Society for the Promotion of Science (JSPS)
Takeda Science Foundation (TSF)
Chiba University Futuristic Medical Fund
ARTICLE ABSTRACT
Invariant natural killer T (iNKT) cells play an essential role in antitumor immunity by exerting cytotoxicity and producing massive amounts of cytokines. iNKT cells express invariant T-cell receptors (TCR) to recognize their cognate glycolipid antigens such as α-galactosylceramide (α-GalCer) presented on CD1d. We recently reported that iNKT cells recognize CD1d-negative leukemia cell line K562 in a TCR-dependent manner. However, it remains controversial how iNKT cells use TCRs to recognize and exhibit cytotoxic activity toward CD1d-negative tumors cells without CD1d restriction. Here, we report that iNKT cells exerted cytotoxicity toward K562 cells via a carried over anti-Vα24 TCR mAb from positive selection by magnetic bead sorting. We found that addition of the anti-Vα24Jα18 TCR mAb (6B11 mAb) rendered iNKT cells cytotoxic to K562 cells in an FcγRII (CD32)-dependent manner. Moreover, iNKT cells treated with 6B11 mAb became cytotoxic to other CD32+ cell lines (U937 and Daudi). In addition, iNKT cells treated with 6B11 mAb suppressed K562 cell growth in a murine xenograft model in vivo. These data suggest that anti-iNKT TCR mAb treatment of iNKT cells can be applied as a therapeutic strategy to treat CD32+ cancers such as leukemia, lymphoma, and lung cancer.
Our findings unveiled that iNKT cells recognize and kill CD1d-negative target tumors via the anti-iNKT TCR mAb bound to CD32 at the tumor site, thereby bridging iNKT cells and CD1d-negative tumors. These findings shed light on the therapeutic potential of anti-iNKT TCR mAbs in NKT cell–based immunotherapy to treat CD1d-negative CD32+ cancers.
