Ewing’s sarcoma (ES) is an aggressive and rare malignancy that primarily afflicts children and young adults. Patients with metastases have the worst prognosis. We have previously demonstrated that locally delivered mesenchymal stromal/stem cells (MSCs) can control ES growth releasing tumor necrosis factor-related apoptosis inducing ligand (TRAIL). However, considering the nature of the disease, new MSC strategies for metastatic ES are needed, accounting that ES can express high levels of the disialoganglioside GD2. To optimize the MSC affinity for tumors, we recently developed a bi-functional (BF) strategy where MSCs expressing TRAIL were further modified by a truncated anti-GD2 chimeric antigen receptor (GD2 tCAR). Here, anti-GD2 BF MSCs delivering a soluble variant of TRAIL (sTRAIL) were challenged in several in vitro and in vivo models, including a metastatic ES xenotransplant.
Co-expression in MSCs of GD2 tCAR together with sTRAIL was obtained by lentiviral vectors. The BF MSC binding to GD2-positive ES cells was verified in a cell-to-cell interaction assay. Cytotoxicity by BF MSCs was assessed by 2D and 3D cocultures. Tumor targeting and killing by BF MSCs was then investigated in a metastatic ES xenotransplant by in vivo imaging and ddPCR.
In vitro data demonstrated both tumor affinity and killing of BF MSCs. The in vivo model closely mimicking the disseminated ES, with lung and liver as the main metastatic sites, demonstrated that MSCs were able to counteract ES growth in the lung with a significant reduction in tumor signal. As for the liver, a slight though not significant antitumor effect was observed. Evidence on engraftment of BF MSCs into ES metastatic sites was also provided indicating that GD2 tCAR ameliorated the tumor targeting of BF MSCs.
Our work represents the first attempt to target metastatic ES by MSCs delivering an anticancer molecule. With the limitation of a monotherapy approach, BF MSCs promise to pave the way for an improved therapeutic delivery of TRAIL to treat metastatic ES and other deadly GD2-positive malignancies.
University of Modena and Reggio Emilia.
This work was supported in part by grants from the Association ASEOP and from MIUR “Dipartimenti Eccellenti” 2017.
G. Golinelli: supported by an AIRC fellowship for Italy Grant. G. Grisendi, C. Spano, G. Casari: Honoraria (self): Rigenerand Srl. M. Dominici: Honoraria (self), Advisory/Consultancy, Leadership role: Rigenerand Srl. All other authors have declared no conflicts of interest.