Clinical importance of Thymidine kinase-1 in children with acute lymphoblastic leukemia as a prognostic tumor marker

Abstract

Background: Acute lymphoblastic leukemia (ALL) is a complex heterogeneous disorder characterized by the proliferation of immature lymphoid cells in the bone marrow, peripheral blood, and other organs. It is the most common form ofcancer and predominant subtype of leukemia in children.Thymidine kinase-1 (TK-1) is a key enzyme in DNA precursor synthesis.Presence of this marker in the cell is an indicator of activecell proliferation, so elevated TK-1 indicates active tumor growth.Aims of study 1- To evaluate the level of Tk_1 in newly diagnosed pediatric ALL.2-To correlate the level of TK_1 marker with hematological and clinical parameters.3-To evaluate the patient’s level of TK-1 in serum after induction of chemotherapy.Patients and methods: This prospective cross sectional study was conducted on 35 pediatric patients with newly diagnosed untreated ALL and 20 non leukemic individuals as a control. Diagnosis was based on morphology ,cytochemistry of the peripheralblood and/or bone marrow aspirate smears by expert hematologist with flow cytometric immunophenotyping test.The patient’s peripheral blood and bone marrow samples were re-evaluated morphologically at day 28 from the start of chemotherapy for assessment of complete remission (CR) achievement and for measuring serum Thymidine kinase-1 by ELISAResults: In this study,the mean TK-1 level was significantly higher in patients at diagnosis than controls.The mean TK-1 level was significantly higher in patients in failure to induction than patients in remission and controls.No significant differences in mean TK-1 level between patients in remission and controls.TK-1 showed a significant positive correlation with total WBC andblast counts and the only significant association was that patients with LAP had significantly higher TK-1 level than those without LAP.Conclusion:1-TK-1levels seem to be a very good parameter during follow up, because of:acceptable sensitivity, low cost and elimination the need of requirements forscreening B.M samples.2-TK-1levels were positively correlated with WBC count and blast%.