Combinatorial macrophage induced innate immunotherapy against Ewing sarcoma: Turning "Two Keys" simultaneously.

Area of Science:

• Immunology
• Oncology
• Pharmacology

Background:

• Tumors, including Ewing sarcoma (ES), evade macrophage phagocytosis by upregulating CD47 and downregulating cell surface calreticulin (csCRT).
• Macrophages are crucial for clearing tumor cells, but their function is inhibited by anti-phagocytic signals like CD47.

Purpose of the Study:

• To investigate the combination of CD47 blockade (magrolimab, MAG) and doxorubicin (DOX) chemotherapy to enhance macrophage phagocytosis of ES cells.
• To evaluate the efficacy of this combined therapy in inhibiting ES tumor growth and metastasis in vitro and in vivo.

Main Methods:

• Macrophages were differentiated from human monocytes.
• In vitro phagocytosis assays, Annexin-V assay, and CRISPR/Cas9 for CD47 knockout were employed.
• Mouse models (ES cell-based and PDX) were used to assess tumor development, survival, and immune cell profiling via RNA-Seq and CIBERSORTx.

Main Results:

• Magrolimab (MAG) significantly increased ES cell phagocytosis and reduced tumor burden and mortality in mice.
• Doxorubicin (DOX) enhanced csCRT expression on ES cells in a dose- and time-dependent manner.
• The combination of DOX and MAG synergistically enhanced phagocytosis, decreased tumor burden and lung metastasis, and prolonged survival in vivo. CD38, CD209, CD163, and CD206 were identified as potential markers for phagocytic macrophages. Increased M2 macrophage infiltration and decreased Cd209 expression were observed in the tumor microenvironment.

Conclusions:

• Simultaneously targeting CD47 and enhancing csCRT expression reactivates macrophage phagocytic activity against ES.
• This dual-targeting strategy represents a promising, translatable therapeutic approach utilizing innate immunotherapy against high-risk metastatic ES.