Abstract
BackgroundIn pediatric sarcomas, outcomes of established therapies still remain poor, especially due to high-grade resistances to chemotherapeutic compounds. Taking novel biological approaches into account, virotherapy was found to be efficient in many pediatric sarcoma types. Also NK cell therapy was denoted to represent a promising upcoming strategy for pediatric sarcoma patients. We here investigated a combinatorial approach employing oncolytic measles vaccine virotherapeutics (MeV) together with activated human NK cells (or PBMCs).MethodsThe human sarcoma cell lines A673 and HT1080 were used to evaluate the efficacy of this combinatorial treatment modality. Oncolysis was determined by measuring real-time cell proliferation using the xCELLigence RTCA SP system. Furthermore, expression of receptors on NK cells and the respective ligands on A673 cells was analyzed by flow cytometry. To measure the protein release of activated NK cells a LEGENDplex™ assay was performed.ResultsMonotherapy with MeV led to a time- and dose-dependent oncolytic reduction of A673 and HT1080 sarcoma tumor cell masses. Concurrently, such MeV infections did not change the expression of NK cell ligands MICA/B, ULBP1, 2, and 3, CD112, and CD155. As shown by real-time proliferation assays, infections of A673 and HT1080 sarcoma cells with MeV followed by co-culture with activated NK cells or PBMCs led to enhanced sarcoma cell destruction when compared to the respective monotherapies. In parallel, this dual therapy resulted in an increased release of granzymes, perforin, and granulysin from NK cells. In contrast, expression of activation and ontogenesis receptors on NK cells was not found to be altered after co-culture with MeV-infected A673 sarcoma cells.ConclusionsTaken together, the combined treatment strategy comprising oncolytic MeV and activated NK cells resulted in enhanced oncolysis of A673 and HT1080 cells when compared to the respective monotherapies. In parallel, we observed an increased release of NK cell activation markers upon co-culture with MeV-infected A673 human sarcoma cells. These results support the onset of clinical trials combining oncolytic virotherapy with NK cell based immunotherapies.
Highlights
In pediatric sarcomas, outcomes of established therapies still remain poor, especially due to highgrade resistances to chemotherapeutic compounds
Oncolytic activity of measles vaccine virus on sarcoma cells To investigate a combinatorial approach employing oncolytic measles vaccine virus together with activated Natural killer (NK) cells or peripheral whole blood mononuclear cells (PBMCs) we used the human extraosseous Ewing sarcoma cell line A673 and the human fibrosarcoma cell line HT1080, which previously had been shown to be susceptible to measles vaccine virotherapeutics (MeV)-mediated oncolysis when using our suicide gene-armed MeV (MeV-SCD) oncolytic virus
There are many clinical trials investigating the immunotherapeutic effect of NK cell restoration for the treatment of cancer; there are two ongoing clinical trials utilizing NK cells (NCT01807468, NCT02100891) including pediatric solid tumors such as pediatric sarcomas. We examined both strategies in cell culture to restore the potent tumoricidal functionalities of NK cells in the pediatric extraosseous Ewing sarcoma model A673 and in the human fibrosarcoma cell line HT1080 by oncolytic virotherapy with a novel measles vaccine virus expressing the GFP marker protein (MeVGFP) [43] as monotherapy as well as in a combinatorial treatment modality of MeV-based virotherapy together with NK cell-based therapy
Summary
Outcomes of established therapies still remain poor, especially due to highgrade resistances to chemotherapeutic compounds. Taking novel biological approaches into account, virotherapy was found to be efficient in many pediatric sarcoma types. NK cell therapy was denoted to represent a promising upcoming strategy for pediatric sarcoma patients. We here investigated a combinatorial approach employing oncolytic measles vaccine virotherapeutics (MeV) together with activated human NK cells (or PBMCs). The herpes simplex virus (HSV)-based virotherapeutic compound ImlygicTM already has been approved for patients suffering from advanced stage melanoma [7]. A single shot highdose application of a measles vaccine virus (MeV) encoding a marker protein (MeV-NIS) resulted in a long-term tumor remission for more than five years in a patient suffering from advanced stage multiple myeloma [8]
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