Circumventing resistance within the Ewing sarcoma microenvironment by combinatorial innate immunotherapy

Area of Science:

• Immunology
• Oncology
• Cell Biology

Background:

• Pediatric recurrent/metastatic Ewing sarcoma (ES) has poor survival rates, necessitating novel therapies.
• Natural killer (NK) cell function is impaired in the ES tumor microenvironment (TME) due to immunosuppression.
• Melanoma cell adhesion molecule (MCAM) is highly expressed on ES and linked to metastasis.

Purpose of the Study:

• To investigate novel immunotherapeutic strategies for Ewing sarcoma.
• To engineer chimeric antigen receptor (CAR) NK cells targeting MCAM for enhanced anti-tumor activity.
• To evaluate the combination of CAR-NK cells with IL-15 agonist (NKTR-255) and CD47 blockade (Magrolimab) for synergistic effects.

Main Methods:

• Transcriptome profiling and CIBERSORT analysis to understand NK cell resistance in ES TME.
• Engineering of anti-MCAM CAR-NK cells via mRNA electroporation.
• In vitro cytotoxicity assays and in vivo xenograft models (cell-based and patient-derived) to assess therapeutic efficacy.
• Measurement of interferon-γ, perforin, and macrophage phagocytosis.

Main Results:

• Anti-MCAM CAR-NK cells demonstrated specific cytotoxicity against MCAM-high ES cells, reducing lung metastasis and extending survival in vivo.
• NKTR-255 enhanced CAR-NK cell activity, while Magrolimab boosted macrophage phagocytosis of ES cells.
• Combination therapy significantly reduced primary tumor growth and prolonged survival in both cell- and PDX-based ES models.

Conclusions:

• Preclinical data support a novel immunotherapy approach for metastatic Ewing sarcoma.
• Combining tumor-targeting CAR-NK cells with IL-15 agonist and CD47 blockade shows significant anti-tumor efficacy.
• This innate immune-based strategy holds promise for treating MCAM-high malignant metastatic ES.