Anti-CD47 Treatment Stimulates Phagocytosis of Glioblastoma by M1 and M2 Polarized Macrophages and Promotes M1 Polarized Macrophages In Vivo

Abstract

Tumor-associated macrophages (TAMs) represent an important cellular subset within the glioblastoma (WHO grade IV) microenvironment and are a potential therapeutic target. TAMs display a continuum of different polarization states between antitumorigenic M1 and protumorigenic M2 phenotypes, with a lower M1/M2 ratio correlating with worse prognosis. Here, we investigated the effect of macrophage polarization on anti-CD47 antibody-mediated phagocytosis of human glioblastoma cells in vitro, as well as the effect of anti-CD47 on the distribution of M1 versus M2 macrophages within human glioblastoma cells grown in mouse xenografts. Bone marrow-derived mouse macrophages and peripheral blood-derived human macrophages were polarized in vitro toward M1 or M2 phenotypes and verified by flow cytometry. Primary human glioblastoma cell lines were offered as targets to mouse and human M1 or M2 polarized macrophages in vitro. The addition of an anti-CD47 monoclonal antibody led to enhanced tumor-cell phagocytosis by mouse and human M1 and M2 macrophages. In both cases, the anti-CD47-induced phagocytosis by M1 was more prominent than that for M2. Dissected tumors from human glioblastoma xenografted within NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice and treated with anti-CD47 showed a significant increase of M1 macrophages within the tumor. These data show that anti-CD47 treatment leads to enhanced tumor cell phagocytosis by both M1 and M2 macrophage subtypes with a higher phagocytosis rate by M1 macrophages. Furthermore, these data demonstrate that anti-CD47 treatment alone can shift the phenotype of macrophages toward the M1 subtype in vivo.

CD47-blocking immunotherapies stimulate macrophage-mediated destruction of small-cell lung cancer

“…However, M2 macrophages may exhibit a greater capacity for phagocytosis in response to therapeutic antibody relative to proinflammatory M1 macrophages (41). A recent report has also demonstrated that both M1 and M2 macrophages perform phagocytosis in response to anti-CD47 treatment (42). Furthermore, treatment with anti-CD47 antibodies converted tumor-associated macrophages to an M1-like state in vivo (42).…”

“…A recent report has also demonstrated that both M1 and M2 macrophages perform phagocytosis in response to anti-CD47 treatment (42). Furthermore, treatment with anti-CD47 antibodies converted tumor-associated macrophages to an M1-like state in vivo (42). The dichotomy of M1 versus M2 polarization underrepresents the complexity of macrophage activation, which is dynamic and fluid with a plethora of potential activation states (30,43).…”

Characterization of cluster of differentiation�47 expression and its potential as a therapeutic target in esophageal squamous cell cancer

“…M1 macrophages exhibit anti-tumor activity and M2 macrophages exhibit pro-tumor activity (36). It has been demonstrated that blocking CD47-SIRPα signaling with anti-CD47 antibodies enhances phagocytic activity from M1 and M2 macrophages and promotes tumor regression (37). Furthermore, blocking CD47-SIRPα signaling enhances the macrophage phagocytosis of various tumor cells in vitro (18,22,38).…”

Chlorogenic acid inhibits glioblastoma growth through repolarizating macrophage from M2 to M1 phenotype

“…Thus, several research groups focused on M2-like TAMs as a potential targets for anticancer therapies and have gained encouraging results. In addition, skewing TAM differentiation away from the M2 to M1 phenotype promoted antitumor immune responses and reduced tumor growth and metastasis in hepatocellular carcinoma (HCC), prostate cancer, breast cancer and glioblastoma13141516. Furthermore, M1-type macrophages have been reported to be associated with prolonged survival time in patients with non small-cell lung cancer (NSCLC)1718.…”

“…These compounds include the natural products zoledronic acid19 and emodin20, therapeutic monoclonal antibodies including anti-CD471321 and the phosphatidylserine-targeting antibody 2aG414, and chemotherapy agents, doxycycline and metformin2223. Chlorogenic acid (5-caffeoylquinic acid, CHA), the ester formed between caffeic acid and quinic acid24, is a phenolic compound found in the human diet, in coffee, apples, pears and in green tea.…”