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A Preclinical Mouse Model of Osteosarcoma to Define the Extracellular Vesicle-mediated Communication Between Tumor and Mesenchymal Stem Cells
Published on: May 6, 2018
Tumor-derived G-CSF induces an immunosuppressive microenvironment in an osteosarcoma model, reducing response to
Michele Pezzella1, Concetta Quintarelli1,2, Maria C Quadraccia1,3
1Department of Onco-Haematology and Cell and Gene Therapy, Bambino Gesù Children's Hospital, IRCCS, San Paolo N°15 Street, 00146, Rome, Italy.
Abstract:
Sarcomas are rare, mesenchymal tumors, representing about 10-15% of all childhood cancers. GD2 is a suitable target for chimeric antigen receptor (CAR) T-cell therapy due to its overexpression in several solid tumors. In this preclinical study, we investigated the potential use of iCasp9.2A.GD2.CAR-CD28.4-1BBζ (CAR.GD2) T-cells as a treatment option for patients who have GD2-positive sarcomas and we sought to identify factors shaping hostile tumor microenvironment in this setting. GD2 expression was evaluated by flow-cytometry on primary tumor biopsies of pediatric sarcoma patients. GD2 expression in sarcoma cells was also evaluated in response to an enhancer of zeste homolog 2 (EZH2) inhibitor (Tazemetostat). The antitumor activity of CAR.GD2 T-cells was evaluated both in vitro and in vivo preclinical models of orthotopic and/or metastatic soft-tissue and bone sarcomas. GD2 expression was detected in 55% of the primary tumors. Notably, the Osteosarcoma and Alveolar Rhabdomyosarcomas subtypes exhibited the highest GD2 expression levels, while Ewing sarcoma showed the lowest. CAR.GD2 T-cells show a significant tumor control both in vitro and in vivo models of GD2-expressing tumors. Pretreatment with an EZH2 inhibitor (Tazemetostat) upregulating GD2 expression, sensitizes GD2dim sarcoma cells to CAR.GD2 T-cells cytotoxic activity. Moreover, in mouse models of disseminated Rhabdomyosarcomas and orthotopic Osteosarcoma, CAR.GD2 T-cells showed both a vigorous anti-tumor activity and long-term persistence as compared to un-transduced T-cells. The presence of immunosuppressive murine myeloid-derived suppressor (MDSC) cells significantly reduces long-term anti-tumour activity of infused CAR.GD2 T-cells. Tumor-derived G-CSF was found to be one of the key factors driving expansion of immunosuppressive murine and human MDSC, thus indirectly limiting the efficacy of CAR.GD2 T-cells. Our preclinical data strongly suggest that CAR.GD2 T-cells hold promise as a potential therapeutic option for the treatment of patients with GD2-positive sarcomas. Strategies to tackle hostile immunosuppressive MDSC are desirable to optimize CAR.GD2 T-cell activity.
Insights
Chimeric antigen receptor (CAR) T-cell therapy targeting GD2 shows promise for GD2-positive sarcomas. Enhancing GD2 expression and overcoming immunosuppressive cells are key to optimizing this CAR T-cell therapy.
Area of Science:
- Oncology
- Immunotherapy
- Pediatric Cancer Research
Background:
- Sarcomas are rare childhood cancers of mesenchymal origin.
- GD2 is a cell surface target overexpressed in several solid tumors, including some sarcomas.
- Chimeric antigen receptor (CAR) T-cell therapy offers a potential treatment avenue for GD2-positive malignancies.
Purpose of the Study:
- To investigate the therapeutic potential of GD2-specific CAR T-cells (CAR.GD2) for pediatric sarcomas.
- To evaluate GD2 expression levels in various sarcoma subtypes.
- To identify factors within the tumor microenvironment that may affect CAR T-cell efficacy.
Main Methods:
- Flow cytometry was used to assess GD2 expression on primary pediatric sarcoma biopsies.
- GD2 expression was evaluated following treatment with an enhancer of zeste homolog 2 (EZH2) inhibitor, Tazemetostat.
- In vitro and in vivo preclinical models of soft-tissue and bone sarcomas were utilized to assess CAR.GD2 T-cell antitumor activity.
- The impact of myeloid-derived suppressor cells (MDSCs) and tumor-derived G-CSF on CAR T-cell efficacy was investigated.
Main Results:
- GD2 expression was detected in 55% of primary sarcomas, with high levels in Osteosarcoma and Alveolar Rhabdomyosarcoma, and low levels in Ewing sarcoma.
- CAR.GD2 T-cells demonstrated significant in vitro and in vivo antitumor activity against GD2-expressing tumors.
- Tazemetostat pretreatment upregulated GD2 expression, sensitizing GD2-low sarcoma cells to CAR.GD2 T-cell-mediated killing.
- CAR.GD2 T-cells exhibited robust antitumor activity and long-term persistence in preclinical sarcoma models.
- Immunosuppressive MDSCs, driven by tumor-derived G-CSF, were found to limit the long-term efficacy of CAR.GD2 T-cells.
Conclusions:
- CAR.GD2 T-cells represent a promising therapeutic strategy for patients with GD2-positive sarcomas.
- Targeting GD2, potentially in combination with EZH2 inhibition, can enhance treatment efficacy.
- Strategies to mitigate the immunosuppressive tumor microenvironment, particularly targeting MDSCs, are crucial for optimizing CAR.GD2 T-cell therapy outcomes.
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