Background: Calcineurin is involved in T-lymphocyte activation as well as in the maturation of hematopoietic cells. Identification of this predominantly intracellular phosphatase and of calmodulin (CaM) in human sera warranted their assessment in different types of acute leukemias.
Methods: Phosphatase activity of calcineurin (CaN) was assayed, involving the measurement of trifluoperazine-sensitive neutral phosphatase, in sera of leukemic patients before and after treatment. Calcineurin and calmodulin contents were also determined by ELISA employing monoclonal antibodies specific to the proteins.
Results: The activity of calcineurin was decreased by 75% and 85% in sera of patients diagnosed either for acute lymphoid leukemia and acute myeloid leukemia, respectively, without apparent changes in calmodulin or calcineurin contents under both these conditions. In addition, the decreased calcineurin activity in acute myeloid leukemia was restored to levels comparable to non-leukemic individuals upon treatment. This was not observed in cases of acute lymphoid leukemia.
Conclusions: These results suggest diagnostic utility in the measurement of serum calcineurin activity in acute leukemia. Restoration of normal calcineurin activity in patients undergoing treatment for acute myeloid leukemia may provide a means to monitor patient response to the prescribed therapeutic regimen.