Expression of 5′-nucleotidase (CD73) related to other differentiation antigens in leukemias of B-cell lineage

Ecto-5′ nucleotidase (5′NT; CD73) expression was studied with a monoclonal antibody (7G2) and a radiochemical assay and compared with the expression of other antigens in B-cell-lineage leukemias on cells from 100 leukemic patients and two cell lines. A B-cell origin was confirmed by the expression of CD19 and HLA-DR. Four stages of B-cell leukemias were defined: stage I (pro-B) as CD10^-, cytoplasmic μ (cμ^-), surface lg (slg^-); stage II (cALL) as CD10⁺/cμu^-/ slg^-; stage III (pre-B) as CD10^+or-/cμ⁺/slg^-; and stage IV (B) as CD10^-/cμ^-/slg⁺. A linear correlation was found between immunohistochemical and radiochemical determination of 5′ NT (r = .86). 5′NT expression was low in T-cell leukemias and stage I, high in stages II and III, and low again in stage IV of B-cell leukemias. 5′NT expression was not related to cμ, CD20, CD21, CD22, CD34, and terminal deoxynucleotidyl transferase (TdT) expression, but was significantly related to CD10 and inversely related to κ/λ expression. However, the 5′NT activity in CD10⁺ leukemias (stages II and III) shows a very wide range. Within the group of CD10⁺ leukemias no differences were detected between 5′NT⁺ and 5′NT^- cells in their expression of other B-cell antigens. We conclude that the place of 5′NT in leukemias corresponding to early stages of B-cell development has been characterized. 5′NT is expressed in CD10⁺ stages and decreases before the expression of slgs. Future studies should make clear whether a high expression of this enzyme in CD10⁺ stages is a normal maturation phenomenon or a malignant phenomenon.