Enzyme Abnormality in Human Leukaemia

Abstract

CHANGES in the concentrations of several enzymes in leukaemic leucocytes have been reported, including increases in acid phosphatase¹, dihydrofolate reductase², and the first three enzymes in the pathway for the de novo biosynthesis of pyrimidine³. A reduction in the activity of some enzymes has also been reported, for example, alkaline phosphatase^4,5, lactic dehydrogenase⁶ and deoxythymidine phosphorylase⁷. In general, it is not clear whether these changes in concentrations are caused by abnormalities of the leukaemic process itself, or simply the consequence of a decrease in the percentage of mature cells in the peripheral blood. It is therefore important to show that the enzyme defect persists in the presence of a complete clinical and haematological remission. There have so far been few reports dealing with this question. This is partly because of the difficulty of procuring sufficient leucocytes for study because patients in remission have normal or low normal white blood cell counts. Thus most documented cases of enzyme abnormalities in leukaemia have been reported from studies with immature cells. Exceptions to this are the observations on the concentrations of leucocyte alkaline phosphatase (AP). This enzyme is low or absent in the leucocytes of patients with chronic myelogenous leukaemia (CML)^4,5, and remains low in some patients in remission even though the number of mature cells in the peripheral blood is normal^4,5,8,9.