Ab-IL2 fusion proteins mediate NK cell immune synapse formation by polarizing CD25 to the target cell-effector cell interface

Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI 53711, USA.
Cancer Immunology and Immunotherapy (Impact Factor: 3.94). 07/2011; 60(12):1789-800. DOI: 10.1007/s00262-011-1072-9
Source: PubMed


The huKS-IL2 immunocytokine (IC) consists of IL2 fused to a mAb against EpCAM, while the hu14.18-IL2 IC recognizes the GD2 disialoganglioside. They are under evaluation for treatment of EpCAM(+) (ovarian) and GD2(+) (neuroblastoma and melanoma) malignancies because of their proven ability to enhance tumor cell killing by antibody-dependent cell-mediated cytotoxicity (ADCC) and by antitumor cytotoxic T cells. Here, we demonstrate that huKS-IL2 and hu14.18-IL2 bind to tumor cells via their antibody components and increase adhesion and activating immune synapse (AIS) formation with NK cells by engaging the immune cells' IL-2 receptors (IL2R). The NK leukemia cell line, NKL (which expresses high affinity IL2Rs), shows fivefold increase in binding to tumor targets when treated with IC compared to matching controls. This increase in binding is effectively inhibited by blocking antibodies against CD25, the α-chain of the IL2R. NK cells isolated from the peritoneal environment of ovarian cancer patients, known to be impaired in mediating ADCC, bind to huKS-IL2 via CD25. The increased binding between tumor and effector cells via ICs is due to the formation of AIS that are characterized by the simultaneous polarization of LFA-1, CD2 and F-actin at the cellular interface. AIS formation of peritoneal NK and NKL cells is inhibited by anti-CD25 blocking antibody and is 50-200% higher with IC versus the parent antibody. These findings demonstrate that the IL-2 component of the IC allows IL2Rs to function not only as receptors for this cytokine but also as facilitators of peritoneal NK cell binding to IC-coated tumor cells.

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    • "Alternative approaches for IL-2 based immunotherapy e.g. toxin conjugates, antibodies, fusion proteins, gene therapy are therefore currently being explored in various cancers (Eigentler et al., 2011; Telang et al., 2011; Gubbels et al., 2011). However, since IL-2 is essential for the development, survival and function of regulatory T (Treg) cells, which function to inhibit immune responses and prevent autoimmune disease, IL-2 may have a role in promoting T cell tolerance (an important consideration is the dose of IL-2 used as a low dose appears to favour tolerance over autoimmunity). "
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    Journal of immunological methods 11/2013; 397(s 1–2):1–7. DOI:10.1016/j.jim.2013.07.012 · 1.82 Impact Factor
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    • "Some IL-2 centered strategies have already been approved by the FDA for the treatment of metastatic melanoma [16] and renal cell carcinoma [17]. Intense research (basic, translational, and clinical) is also underway on the use of IL-2 and IL-2-antibody conjugates (immunocytokines) to boost the anti-cancer activities of NK [18] [19] [20] [21]. Our initial studies on the characterization of the global proteome of naïve and IL-2-stimulated human NK cells reveal a large number of proteins exhibiting changes in expression levels upon IL-2 stimulation. "
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    • "This bridging results in the formation of an AIS defined by the polarization of effector molecules including adhesion molecules and IL2Rs on the NKL cells to the immune synapse and the subsequent hu14.18-IL2 IC-facilitated NK cell-mediated tumor cell killing (Gubbels et al., 2011). It is possible that the beneficial effect of high affinity CD16 alleles may be less important with IC than with a conventional mAb. "
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