CD43: A New Critical Immune Checkpoint in AML Beyond CD47

Researchers have identified O-glycosylated CD43 as a novel don’t eat me immune checkpoint in acute myeloid leukemia (AML), providing a potential new therapeutic target to improve the clearance of cancer cells by macrophages.

This finding addresses a critical gap in current AML treatments. While macrophages are known to be capable of mediating tumor control in AML and other diseases, existing therapeutic agents designed to enhance macrophage phagocytosis have not yet led to improved clinical outcomes.

Among these existing efforts are anti-CD47 neutralizing antibodies, which target the well-known CD47 immune checkpoint. However, the discovery of the role of CD43 suggests that leukemia cells utilize additional mechanisms to evade the immune system.

The Role of CD43 in Immune Evasion

CD43, specifically in its sialylated and O-glycosylated forms, functions as a glyco-immune barrier. This barrier effectively restrains the ability of macrophages to identify and engulf leukemia cells.

According to research published in Science, sialylated CD43 blocks immune clearance independently of the CD47 pathway. This means that even if the CD47 signal is neutralized, CD43 can still act as a shield, preventing macrophages from performing phagocytosis.

By operating independently of CD47, O-glycosylated CD43 serves as a distinct checkpoint that allows hematologic malignancies to persist by avoiding detection and destruction by the body’s own immune cells.

Implications for AML Therapy

The identification of CD43 as a critical checkpoint opens new avenues for treating acute myeloid leukemia. Because it operates separately from CD47, targeting CD43 may provide a way to boost macrophage phagocytosis where previous CD47-focused therapies failed.

The research suggests that targeting this specific O-glycosylated form of CD43 could enhance the clearance of tumor cells in hematologic malignancies.

This development is particularly significant given the difficulty of achieving positive clinical outcomes with current macrophage-enhancing agents in AML patients.

Scientific Context and Mechanism

The mechanism involves the creation of a physical and chemical barrier on the surface of the leukemia cell. Sialylation—the attachment of sialic acid sugars to the CD43 protein—contributes to the formation of this barrier.

When macrophages encounter these sialylated CD43 proteins, the don’t eat me signal is triggered, instructing the immune cell to leave the cancer cell alone rather than consuming it.

By disrupting this specific glycosylation or blocking the CD43 protein, scientists believe they can strip away this protection, making the AML cells vulnerable to macrophage-mediated destruction.