5′-Nucleotidase Activity in Lymphocytes From Patients Affected by B-Cell Chronic Lymphocytic Leukemia

Objectives: The activity of membrane-bound ecto-5′-nucleotidase and soluble e-Ns and c-N-II 5′-nucleotidases was evaluated on lymphocytes from patients affected by B-cell chronic lymphocytic leukemia (B-CLL). A statistically significative decrease in ecto-5′-nucleotidase, e-Ns, and c-N-II activities was observed in peripheral blood lymphocytes and in B and T populations from affected individuals. Design and Methods: For the assay of ecto-5′-nucleotidase, e-Ns, and c-N-II activity we used a radioactive procedure coupled to HPLC. Since the ecto-5′-nucleotidase is identified as CD73 antigen, we performed immunofluorescence analysis using a specific monoclonal antibody. We analyzed ecto-5′-nucleotidase mRNA by RT-PCR to ascertain the possibility of an alteration in the transcription of its gene. Results: A decrease in ecto-5′-nucleotidase activity was correlated to reduction in ecto-5′-nucleotidase positive cells (CD73+) in leukemia patients. RT-PCR produced a fragment of the expected size and the specific mRNA was found expressed in both healthy subjects and leukemia patients. Conclusions: The decrease in ecto-5′-nucleotidase activity in patients with B-CLL is not due to loss of transcription of the specific mRNA. The presence of point mutations, splicing alteration, or posttranslational modifications must be investigated. If a defect at DNA or RNA level will be detected, the molecular analysis will be considered for diagnosis of B-cell chronic lymphocytic leukemia.