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Immunotherapy strategies that harness the body’s innate immune system have long focused on a central concept: cancer cells evade destruction by displaying “don’t eat me” signals that inhibit macrophages. Blocking these signals, most notably CD47, has been a major therapeutic goal. Yet in acute myeloid leukemia (AML), clinical responses to CD47-targeting therapies have been inconsistent, raising questions about whether additional immune evasion mechanisms are at play.
A new study published in Science by researchers at Mass General Brigham, Dana-Farber Cancer Institute, and the Broad Institute suggests that the field may have been overlooking a more dominant signal. The team identifies CD43, a heavily glycosylated surface protein, as a key regulator of macrophage evasion in AML.
Revisiting macrophage immune evasion
Macrophages are critical components of the innate immune system, capable of recognizing and engulfing tumor cells through phagocytosis. This process is regulated by a balance between pro-phagocytic “eat me” signals and inhibitory “don’t eat me” signals expressed on the surface of cancer cells.
Therapeutic efforts have largely focused on CD47, a well-characterized inhibitory signal that binds to SIRPα on macrophages to suppress phagocytosis. However, the limited success of CD47 inhibitors in AML has suggested that this pathway may not fully account for immune evasion in these cancers.
To systematically explore alternative mechanisms, the researchers performed a genome-scale loss-of-function screen in AML cell lines, turning off genes one by one and assessing their impact on macrophage recognition.
CD43 emerges as a dominant signal
The results were unexpected. While CD47 had only a modest effect, CD43 stood out as a major determinant of whether leukemia cells were engulfed by macrophages.
The study reveals that CD43 functions not simply as a surface marker, but as part of a broader protective structure. Specifically, its sialylated form creates a dense, glycosylation-based barrier that interferes with immune recognition.
As described by the authors, “Sialylated CD43 forms a glyco-immune barrier that restrains anti-leukemic immunity.”
This finding introduces a new conceptual framework for immune evasion in AML—one that emphasizes the role of glycosylation and surface architecture, rather than individual receptor–ligand interactions alone.
Explaining limits of current therapies
The identification of CD43 helps clarify why targeting CD47 alone has not produced the expected therapeutic outcomes in AML. If CD43-mediated shielding plays a dominant role, then blocking CD47 may be insufficient to restore effective macrophage activity.
The study suggests that immune evasion in AML is more complex than previously appreciated, involving multiple overlapping mechanisms that together suppress phagocytosis.
By uncovering this additional layer, the work highlights the need for combination strategies or alternative targets in macrophage-based immunotherapy.
A new therapeutic opportunity
From a translational perspective, CD43 represents a promising new target. Interventions that disrupt its glycosylation or block its function could weaken the protective barrier surrounding leukemia cells, making them more susceptible to immune clearance.
Because CD43 operates through a distinct mechanism, targeting it could complement existing therapies rather than replace them. Combining CD43 inhibition with CD47 blockade or other immunotherapies may enhance overall efficacy.
The findings also point to the broader relevance of glyco-immune interactions in cancer. Similar glycosylation-dependent barriers may exist in other tumor types, suggesting that the implications of this work could extend beyond AML.
A shift toward glyco-immunology
The study reflects a growing recognition of the role of glycobiology in cancer and immunology. While protein-based signaling pathways have dominated the field, complex carbohydrate structures on the cell surface are increasingly understood to play critical roles in immune recognition.
By identifying CD43 as a key mediator of immune evasion, the research highlights how these glycosylated molecules can shape interactions between cancer cells and the immune system.
Looking ahead
Although the findings are based on preclinical models, the researchers believe that they provide a strong rationale for further investigation in patient samples and clinical settings. Future studies will be needed to determine how CD43 expression varies across AML subtypes and whether it correlates with treatment response.
If validated, targeting CD43 could represent a new direction for immunotherapy in AML—one that addresses a fundamental mechanism of immune escape.
More broadly, the work highlights the importance of revisiting established paradigms in cancer biology. By moving beyond well-studied targets like CD47 and systematically exploring the full landscape of immune interactions, researchers are uncovering new vulnerabilities that could be exploited therapeutically.
