A protein–sugar molecule, CD99, occurs more frequently than normal on stem cells responsible for blood cancers, including acute myeloid leukemia (AML) and the related myelodysplastic syndromes (MDS). This is the finding of a study led by researchers from NYU Langone Medical Center and Memorial Sloan Kettering Cancer Center, and published online January 25 in the journal Science Translational Medicine.

Building on this discovery, the study authors designed an antibody that recognizes and destroys CD99–covered leukemia cells while sparing normal blood stem cells, a finding confirmed by experiments in human cells and in mice with AML cells. Antibodies are immune system proteins that stick to a specific target, like a protein on the surface of invading bacterium. In recent years, researchers have become capable of engineering antibodies so that they target disease–related molecules.

“Our findings not only identify a new molecule expressed on stem cells that drive these human malignancies, but we show that antibodies against this target can directly kill human AML stem cells,” says corresponding study author Christopher Y. Park, MD, PhD, associate professor in the Department of Pathology at NYU Langone and its Perlmutter Cancer Center.

“While we still have important details to work out, CD99 is likely to be an exploitable therapeutic target for most AML and MDS patients, and we are working urgently to finalize a therapy for human testing,” says Park.