Soluble extracellular domains of human SIRPα and CD47 expressed in Escherichia coli enhances the phagocytosis of leukemia cells by macrophages in vitro

• Published in: Protein expression and purification 2012-09, Vol.85 (1), p.109-116
• Main Authors: Lin, Yan, Yan, Xue-Qian, Yang, Fang, Yang, Xin-Wei, Jiang, Xun, Zhao, Xing-Cheng, Zhu, Bing-Ke, Liu, Li, Qin, Hong-Yan, Liang, Ying-Min, Han, Hua
• Format: Article
• Language: English
• Subjects: Antigens, Differentiation - chemistry; Antigens, Differentiation - genetics; Antigens, Differentiation - immunology; Antigens, Differentiation - pharmacology; CD47; CD47 Antigen - chemistry; CD47 Antigen - genetics; CD47 Antigen - immunology; CD47 Antigen - pharmacology; Escherichia coli - genetics; Humans; Jurkat Cells; Leukemia; Leukemia, T-Cell - drug therapy; Leukemia, T-Cell - immunology; Macrophages; Macrophages - drug effects; Macrophages - immunology; Phagocytosis; Phagocytosis - drug effects; Prokaryoro expression; Protein Refolding; Protein Structure, Tertiary; Receptors, Immunologic - chemistry; Receptors, Immunologic - genetics; Receptors, Immunologic - immunology; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - immunology; Recombinant Fusion Proteins - pharmacology; Signal regulatory protein α
• ISSN: 1046-5928; 1096-0279
• DOI: 10.1016/j.pep.2012.07.002

► We characterized the soluble extracellular domains of human SIRPα and CD47. ► These fusion proteins could promote phagocytosis of tumor cells by macrophages. ► The hSIRPext binds to tumor cells via the specific interaction with CD47. Signal regulatory protein (SIRP) α, a transmembrane protein belonging to the immunoglobulin superfamily, is a receptor for CD47. The interaction between SIRPα and CD47 plays an important role in regulating the phagocytosis of leukemia cells and leukemia stem cells (LSCs) by macrophages. Blocking antibodies against CD47 have been shown to promote phagocytosis of LSCs by macrophages. Here, we consider an alternative way to interrupt the interaction between CD47 and SIRPα. We expressed the extracellular domains of the human SIRPα (hSIRPext) and the human CD47 (hCD47ext) in Escherichia coli as Trx fusion proteins, and purified them by using affinity chromatography. We show that the purified fusion protein Trx–SIRPext could interact in vitro with Trx–hCD47ext. Moreover, Trx–SIRPext could effectively bind to Jurkat T-ALL cells, which expressed CD47 at a high level. CD47ext, on the other hand, bound to human macrophages. In vitro phagocytosis assay showed that these fusion proteins could enhance the phagocytosis of Jurkat cells by macrophage, with Trx–hSIRPext showed a higher efficiency than Trx–CD47ext. These results indicated that the soluble Trx–hSIRPext and Trx–CD47ext polypeptides could be alternative molecules to interrupt CD47–SIRPα interaction between leukemia cells and macrophages, and might be potentially useful for the targeted therapy of leukemia.