Sialylated Protein Protects Human Leukemia Cells From Destruction

Researchers have identified a previously unrecognized mechanism that human leukemia cells use to evade the immune system, involving a protein that creates a physical sugar-coated barrier. This discovery, published April 9, 2026, in the journal Science, suggests that a protein called CD43 acts as a shield, protecting cancer cells from being destroyed by the body’s immune defenses.

The study was conducted by scientists from the Broad Institute, Mass General Brigham, and the Dana-Farber Cancer Institute. The team found that the CD43 protein on the surface of leukemia cells is so heavily coated in sugar molecules—a process known as sialylation—that it forms a physical barrier. This barrier prevents macrophages, a type of immune cell responsible for engulfing and destroying pathogens and abnormal cells, from attacking the leukemia cells.

The Mechanism of the Sialic Shield

The research team uncovered this phenomenon by analyzing thousands of genes across the entire genome of leukemia cells. Their findings indicate that the sugar coating on CD43 does not merely send a chemical signal to the immune system but instead functions as a literal shield. This physical obstruction prevents the immune system’s macrophages from reaching and destroying the cancer cells.

This mechanism differs from other known ways that cancer cells avoid immune detection. The researchers noted a contrast between CD43 and CD47, which is widely recognized as a don’t-eat-me signal. While CD47 works by sending a signal to the immune system to prevent attack, the CD43 protein creates a tangible physical obstruction through its heavy sugar coating.

Potential for New Immunotherapies

The identification of the CD43 shield opens a new potential path for cancer treatment. Because this protein is central to the cancer’s ability to hide from the immune system, targeting and blocking CD43 could expose leukemia cells to immune attack, making them vulnerable to destruction by macrophages.

Discovering this phenomenon opens up a new avenue for cancer immunotherapy. We think that the concept of cancers hiding behind sugar-coated proteins is not only important for leukemia, but likely other cancers as well.

Todd Golub, Dana-Farber pediatric oncologist, director of the Broad Institute and co-senior author of the study

The researchers believe that this strategy of using sugar-coated proteins to shield against immune attacks may not be limited to leukemia. They suggest that other types of cancer might employ similar proteins to protect themselves from the immune system, which could expand the application of CD43-targeting therapies to a broader range of malignancies.

Context of Cancer Immune Evasion

Leukemia is known for its ability to dodge the immune system, a characteristic that often makes it resistant to many of the newest generations of cancer immunotherapies. By identifying the specific role of the sialylated CD43 protein, researchers have pinpointed a key part of the cancer’s disguise.

The discovery highlights the complexity of glycosylation—the process by which sugar molecules are attached to proteins—and its clinical implications in oncology. When proteins are heavily sialylated, as seen with CD43 in human acute myeloid leukemia (AML) cells, they can fundamentally alter how the immune system interacts with the cell surface.

The findings suggest that the physical properties of the cell surface, specifically the density and type of sugar coatings, are as critical to cancer survival as the chemical signaling molecules previously targeted by immunotherapies.

Future research will likely focus on developing agents that can specifically block or remove the sugar coating from CD43 to determine if this can effectively trigger an immune response against leukemia and other sugar-shielded cancers.