Abstract 3974: Insulin-like growth factor-1 receptor (IGF-1R) inhibition promotes expansion of human NK cells with potent antitumor activity against Ewing sarcoma cells

Despite optimization of modern treatment strategies, patients with primary metastatic Ewing sarcomas or with relapsed disease have a poor prognosis. The insulin-like growth factor 1 receptor (IGF-1R) pathway is a target of the disease-defining translocations and important for the biology of Ewing sarcomas. IGF-1R antagonists have shown activity in some patients with refractory disease. More effective therapeutic IGF-1R targeting will rely on optimal combinations of IGF-1R mAbs with conventional or innovative therapies. Specifically, adoptive transfer of activated NK cells may have therapeutic benefit in Ewing sarcoma without adding toxicity. Modulatory or synergistic interactions between novel drugs and cellular therapies as a basis for potent combinations have only started to be explored. Here, we investigated the effects of IGF-1R-specific mAbs on the in vitro activation and expansion of human NK cells and their cytolytic activity against Ewing sarcoma cells. Freshly isolated PBMCs from 6 healthy donors were stimulated with irradiated K-562 in the presence or absence of two different inhibitory IGF-1R mAbs and expanded for up to 23 days. 7 of 8 NK cell cultures expanded in vitro at superior rates (3.3+/-1.2 fold) when IGF-1R mAbs were present in the cultures. These findings were reproduced in a stimulator cell free system based on magnetic cell sorting and subsequent stimulation of NK cells. Thus, IGF-1R-induced increases of NK cell expansion do not rely on interactions with bystander cells. Non-specific Fc-mediated NK cell stimulation was excluded by experiments using whole IgG as control. NK cells were found to surface-express IGF-1R and respond to coincubation with IGF-1R mAb with receptor downregulation (n=3). We conclude that direct effects of IGF-1R mAbs on the IGF-1R pathway in NK cells are likely to induce their activation and expansion. The expression of differentiation markers and activating receptors by in vitro activated and expanded NK cells was unaffected by IGF-1R antagonists. Upon coincubation with the Ewing sarcoma cell lines TC-71, TC-32 and VH-64 and with the newly established, low-passage cell culture DC-ES-6, NK cells that were activated and expanded in the presence and absence of IGF-1R antibody showed comparable, potent and reproducible degranulation responses by CD107a upregulation. Twenty-four hour preincubation of the Ewing sarcoma cell lines with IGF-1R mAb or presence of the mAbs during coculture also did not affect Ewing-sarcoma induced NK cell degranulation responses. We conclude that human NK cells respond to IGF-1R mAb inhibition with superior expansion kinetics while maintaining potent antitumor responses against Ewing sarcoma. Combining adoptive NK cell transfer with IGF-1R targeting may be an efficient means to eliminate minimal residual disease after conventional therapy and thereby rescue patients at highest risk of relapse. Citation Format: Silke Landmeier, Andrea-Caroline Krueger, Stephanie Piepke, Saskia Janneschuetz, Bianca Altvater, Sareetha Kailayangiri, Christian Spurny, Heribert Juergens, Claudia Rossig. Insulin-like growth factor-1 receptor (IGF-1R) inhibition promotes expansion of human NK cells with potent antitumor activity against Ewing sarcoma cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3974. doi:10.1158/1538-7445.AM2014-3974