High CD33 expression levels in acute myeloid leukemia cells carrying the nucleophosmin (NPM1) mutation.

The CD33 antigen is expressed on the blast cells of most cases of acute myeloid leukemia and represents a suitable tumor-associated target antigen for antibody-based therapies. The aim of this study was to investigate the relationship between the CD33 levels quantified by mean fluorescence intensity and antibody binding capacity, and the presence/absence of NPM1 and FLT3 gene mutations in 99 newly diagnosed acute myeloid leukemia cases. The CD33 intensity evaluated as mean fluorescence intensity and antibody binding capacity was significantly higher in the NPM1-mutated acute myeloid leukemia cases compared to the NPM1-unmutated cases (P=0.0001 and P=0.0088, respectively). On the contrary, FLT3 gene mutations did not influence the levels of CD33 expression on the leukemic cells. These results establish a rational basis for the therapeutic use of anti-CD33 antibodies in NPM1-mutated acute myeloid leukemia patients.