Abstract
Tumor-associated macrophages (TAMs) have recently emerged as potentially crucial therapeutic targets for cancer. Thus, the development of macrophage-mediated phagocytosis assays is vital for preclinical drug screening of different tumor cells. This assay can be used to evaluate the effect of anti-cancer therapy, such as immunotherapy, radiotherapy, and chemotherapy, on different tumor cells. Here, we describe the in-vitro phagocytosis assay in detail. As an example of immunotherapy treatment, we used a monoclonal antibody to block an anti-phagocytic signal (CD47) to evaluate the assay using human brain tumor cells and monocyte-derived macrophages. We also demonstrated that this assay can be used to evaluate the effect of different irradiation doses on the phagocytosis of brain tumor cells. This functional assay is fast, accurate, and highly reproducible. Furthermore, the results successfully demonstrate that anti-CD47 antibodies and irradiation can enhance the macrophage-mediated phagocytosis of brain tumors.
Highlights
Macrophages are cells of the innate immune system present in almost all human tissues
The monocytes in the blood are recruited to the tumor microenvironment and differentiate into tumor-associated macrophages (TAMs) [3,4]
Differentiation of Monocytes to Macrophages Efficiency The differentiation efficiency of monocytes to macrophages was evaluated by flow cytometry using fluorescently labeled CD14 and CD11b antibodies
Summary
Macrophages are cells of the innate immune system present in almost all human tissues. Most macrophages are derived from monocytes in the peripheral blood circulation [1,2]. The monocytes in the blood are recruited to the tumor microenvironment and differentiate into tumor-associated macrophages (TAMs) [3,4]. TAMs contribute to tumor development and progression by secreting different inflammatory cytokines [5]. Tumor cells express specific surface proteins such as CD47, PD-L1, MHC-I, and CD24 that prevent macrophages from attacking them and may contribute to metastasis and tumor growth [6,7,8]. Review began 09/30/2020 Review ended 10/11/2020 Published 10/15/2020
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