CD47 Gene Editing    

CD47 is a 47 kDa protein that appears at a position of 70 kDa upon SDS-PAGE due to its hyperglycosylated structure. It has five transmembrane helices, a N-terminal extracellular IgV domain, and a C-terminal cytoplasmic short variable spliced tail. CD47, also known as integrin-associated protein (IAP), is a widely expressed trans-membrane glycoprotein. It offers a "do not eat" signal through binding to the N-terminus of signal regulatory protein alpha (SIRPα) on immune cells and inhibits phagocytosis. The interaction between SIRP-α and CD47 determines the function between cells and cells, which may affect tumor cell proliferation, migration, invasion and immune cell activation and apoptosis in the blood microenvironment and various immune environment. The pathological role of CD47 is often the reason why malignant cancer cells escape immune-surveillance. CD47 overexpression is found to be associated with poor prognosis in leukemia, bladder cancer, non-Hodgkin's lymphoma, breast cancer, and other cancers. In particular, cancer stem cells are able to resist phagocytosis by overexpressing CD47. These findings broaden the pharmaceutical interest in using CD47 as a potential therapeutic target to eliminate cancer cells.

Mechanism of CD47-targeted Control of Cancer Cells

Recently, accumulating data indicate that the CD47-SIRPα axis is a key immune checkpoint in various cancers including hematological malignancies, similar to that of the PD-1/PD-L1 checkpoint for solid tumors. CD47-SIRPα blockade has become a next-generation immune checkpoint disruption strategy in various malignancies after PD-1/PD-L1. By inhibiting the 4N1K peptides, anti-SIRPα antibodies, anti-CD47 antibodies, and CD47-SIRPα axis prevent the “do not eat me” signaling in macrophages, thus increasing the phagocytosis of tumor cells by these macrophages. It was also found that anti-CD47 antibodies can promote antibody-dependent cellular phagocytosis (ADCP) by modulating cancer cells. In addition, anti-CD47 antibodies can activate antibody-dependent cellular cytotoxicity (ADCC) by opsonizing and eliminating cancer cells by neutrophils. In the latter case, the anti-tumor effects associated with inhibition of the CD47-SIRPα axis act through the innate immune system. However, there is evidence that some anti-tumor effects associated with inhibition of CD47 may also be due to activation of the acquired immune system. In fact, it has been found that CD47-SIRPα axis inhibitors can promote macrophage-mediated phagocytosis of cancer cells. Subsequently, macrophages may, as APCs, present cancer cell antigens to T cells through MHC class II. After activation of CD8+ T cells, cancer cells can also be targeted by CD8+ T cells and then destroyed. Therefore, inhibition of the CD47-SIRPα axis can enhance cancer cell phagocytosis by dendritic cells, migration of dendritic cells to T cell zones in secondary lymph nodes, present cancer cell antigens to T cells, and activate CD8+ T cells.

Figure 1. Antibodies targeting the CD47–SIRPα axis to treat cancer. (Hayat S M G, et al., 2020)

Therapeutic Targeting of CD47

CD47 signaling resulting from increased expression of TSP1 may play a central role in the pathophysiology of several major diseases of aging. Therefore, CD47 could be an effective therapeutic target in cardiovascular disease to increase blood flow to ischemic tissues. Animal studies further showed that targeting CD47 could improve healing in diet-induced vasculopathy and ameliorate the effects of cardiac hypertrophy. The protective activities of antibodies targeting CD47 in liver and kidney ischemia-reperfusion injury models suggest applications in organ transplantation. Antibodies targeting CD47 to block SIRPa signaling are entering clinical testing to enhance macrophage-mediated clearance of cancers, but the same humanized antibody may also block TSP1-induced signaling through CD47. In cancer, such antibodies could also enhance cytotoxic CD8 T cell antitumor responses when combined with radiotherapy.

Strategies targeting the CD47-SIRPα axis, such as antibodies, miRNAs, and inhibitory peptides, also demonstrated promising results for the treatment of hematological neoplasms. Combinations of CD47 inhibitory strategies and other anti-cancer therapies such as anti-CD19, anti-CD20, and others showed promising results suggesting a synergistic therapeutic effect. Early clinical phase 1/2 studies have shown encouraging therapeutic effects with tolerable AEs. Various strategies, such as priming with small doses to eliminate aging RBC, as well as many newly developed BsAbs, are being investigated in trying to circumvent the hemolytic anemia and thrombocytopenia that can occur due to the expression of CD47 on red blood cells and platelets. Additional clinical trials are needed to determine the clinical efficacy of these strategies.

CD47 Gene Editing Services

CRISPR/Cas9 Platform^CB, one of the leading biotechnological companies specializing in gene editing, is dedicated to offering comprehensive CRISPR/Cas9 gene-editing services to a wide range of genomics researchers. Based on our platform, we can help you effectively CD47 gene deleted, inserted or point mutated in cells or animals by CRISPR/Cas9 technology.

• CD47 Gene Knockout: We offer CD47 gene knockout cell line and knockout animal model generation service with high quality. Typically, we develop CRISPR-mediated gene editing cell lines including HEK239T, Hela, HepG2, U87, but we can use other cell lines according to your requirements. Our one-stop KO animal model generation service covers from sgRNA design and construction, pronuclear microinjection to Founders genotyping and breeding.
• CD47 Gene Knockin: CRISPR/Cas9 Platform^CB provides the one-stop CD47 knock-in cell line and knockout animal model generation services, including point mutation and gene insertion. Our expert staff has succeeded in dozens of CD47 knock-in cell line generation projects, including stem cells, tumor cells and even difficult-to-handle cells. We also have extensive experience in incorporating CRISPR/Cas9 technology into animal models, which have been fully recognized by our clients.

If you have any questions, please feel free to contact us.

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