ABSTRACT
Lack of sufficient cellular activity of asparagine synthetase (AS) in blast cells compared with normal tissue is thought to be the basis of the antileukaemic effect of L-asparaginase in acute lymphoblastic leukaemia (ALL). Although L-asparaginase is routinely used in ALL, its role and value in the treatment of acute myelogenous leukaemia (AML) is still being discussed. To evaluate the pharmacological basis for L-asparaginase treatment, we established pretreatment monitoring of the intracellular AS activity in blast cells of patients with AML and ALL. There was no general difference in AS activity between ALL and AML samples. Significantly lower AS activity, however, was found in the B-lineage ALL subgroups as well as AML-M5.
Subject(s)
Antineoplastic Agents/therapeutic use , Asparaginase/therapeutic use , Aspartate-Ammonia Ligase/metabolism , Leukemia, Myeloid, Acute/drug therapy , Leukemia, Myeloid, Acute/enzymology , Adolescent , Analysis of Variance , Child , Child, Preschool , Humans , Infant , Leukemia, B-Cell/enzymology , Precursor Cell Lymphoblastic Leukemia-Lymphoma/enzymologyABSTRACT
OBJECTIVE: To determine the association between catheter-related thromboses and hereditary causes of thrombophilia, including the factor V Leiden mutation, deficiencies of protein C or protein S, or increased lipoprotein (a). STUDY DESIGN: To evaluate the incidence of genetic risk factors for familial thrombophilia in catheter-related thrombosis, 163 consecutively admitted infants and children (cardiac disease and catheter placement [C] n = 140; Broviac catheter [B] n = 23) were prospectively investigated. In addition, an age-matched, healthy control group undergoing elective surgery (S: n = 155) was investigated. RESULTS: Heterozygous factor V Leiden mutation was diagnosed in 20 of the 318 study subjects (C: n = 5; B: n = 4; S: n = 11), homozygous factor V Leiden mutation was found in two subjects (C: n = 1; S: n = 1), protein C deficiency type I was diagnosed in nine subjects (C: n = 4; B: n = 1; S: n = 4), and five subjects showed increased lipoprotein (a) (C: n = 3; S: n = 2). The frequency of thrombosis (C: n = 13; B: n = 5) in patients with familial thrombophilia was significantly higher (p < 0.0001; chi square: 27.79) in the catheter groups (15 of 17 subjects) than in control subjects after minor elective surgery (none of 18). Fifteen of the 18 infants with thrombosis had congenital thrombophilia; two children with congenital thrombophilia did not have documented thrombosis, and three infants with vascular occlusion had no inherited predisposition to thrombophilia. CONCLUSIONS: Genetic risk factors for familial thrombophilia play an important role in the manifestation of catheter-related thromboembolism in children.
Subject(s)
Catheterization, Central Venous/adverse effects , Factor V/genetics , Lipoprotein(a)/genetics , Protein C Deficiency , Protein C/genetics , Thrombophilia/genetics , Thrombophlebitis/etiology , Adolescent , Child , Child, Preschool , Heterozygote , Humans , Infant , Infant, Newborn , Point Mutation , Prospective StudiesABSTRACT
To determine to what extent the Arg506 to Gln mutation in the factor V gene influences the fibrinolytic response after 20 min venous occlusion (VO) we investigated a population of APC resistant children (n = 60) and a group of age-matched healthy controls (n = 25). After 20 min VO, symptomatic (n = 30) carriers of the common factor V mutation showed significantly reduced t-PA activities compared with asymptomatic (n = 30) carriers (p <0.0001) and healthy controls (p <0.0001). In contrast, PAI 1 activity was significantly (p <0.0001) higher before and after VO in children with the factor V mutation compared with healthy children. No difference was found between symptomatic and asymptomatic probands. A significantly lower PAI 1 antigen decrease along with a lower t-PA antigen release was found in the APC resistant children compared with the controls. No significant difference was seen between individuals with and without previous vascular insults. As the lack of t-PA activity after VO in symptomatic carriers is the most conspicuous result, we suggest that the factor V gene mutation itself might induce the fibrinolytic impairment by increasing the thrombin levels and thus increasing the recently described thrombin-activable fibrinolysis inhibitor (TAFI).
Subject(s)
Factor V/genetics , Fibrinolysis , Point Mutation , Protein C/physiology , Thrombophlebitis/blood , Arginine/genetics , Child , Fibrinolysis/genetics , Glutamine/genetics , Humans , Plasminogen Activator Inhibitor 1/blood , Thrombophlebitis/genetics , Tissue Plasminogen Activator/metabolismABSTRACT
Dahlbäck et al. recently described in vitro resistance to the anticoagulant response of activated protein C (APC), in the majority of cases associated with the Arg506 to Gln point mutation in the factor V gene in thrombophilic patients. To determine to what extent this common gene mutation affects the risk of childhood stroke, its occurrence was prospectively investigated in a population of children with ischaemic stroke. Over a 2-year period the Arg506 to Gln mutation, factor V, protein C, protein S, antithrombin, antiphospholipid antibodies and lipoprotein (a) [Lp(a)] were measured in 14 infants and children with acute ischaemic stroke. Heterozygous factor V Leiden mutation (n = 4), homozygous factor V Leiden mutation (n = 1), protein C deficiency type I (n = 3) and increased Lp(a) (n = 2) were diagnosed in the children investigated. Seven of 14 patients showed an underlying disease and additionally risk factors were present in nine of 14 children. Data of this study indicate that deficiencies in the protein C anticoagulant pathway play an important role in the aetiology of childhood stroke. However, additional triggering factors may promote early manifestation of thromboembolism in children with inherited defects of clotting inhibitors.
