Primary tumor cells express CD32. A, Expression levels of FCGR2A across TCGA tumors were assessed by GEPIA. TCGA study abbreviations: LAML, acute myeloid leukemia; BLCA, bladder urothelial carcinoma; BRCA, breast invasive carcinoma; CESC, cervical squamous cell carcinoma and endocervical adenocarcinoma; COAD, colon adenocarcinoma; KIRP, kidney renal papillary carcinoma; LIHC, liver hepatocellular carcinoma; LUAD, lung adenocarcinoma; LUSC, lung squamous cell carcinoma; PRAD, prostate adenocarcinoma; STAD, stomach adenocarcinoma; UCS, uterine carcinosarcoma. B, Lung tumor tissue arrays were subjected to IHC to detect CD32 expression in LUAD and LUSC (×400). C, LAML cells were stained with anti-CD32 or isotype control Abs and analyzed by flow cytometry. D, iNKT cells sorted using Vα24-FITC Ab/FITC MicroBeads were maintained in the presence of IL2 overnight, washed twice, and then cultured in fresh medium with IL2 for 4 or 5 days. iNKT cells treated with the 6B11 mAb (50 ng/mL) overnight were washed and cocultured with LAML or K562 cells (control) at an E/T ratio of 2:1. A CD107a assay was then performed. PT, patient.
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.
