To test the hypothesis that analyses of drug targets for polymorphism will help to establish gene-based information for the treatment of cancer patients, we investigated the functional single-nucleotide polymorphisms in the human cytidine deaminase (HDCA) gene. The cDNAs from 52 leukaemia/lymphoma samples and 169 control blood samples were direct-sequenced and analysed for the polymorphisms. Three different polymorphisms (A79C, G208A and T435C) were identified in the coding region of the HDCA gene and displayed allelic frequencies of 20.1%, 4.3% and 70.1%, respectively. No association with susceptibility to disease was observed. A novel polymorphism, G208A produced an alanine to threonine substitution (A70T) within the conserved catalytic domain. By introduction of the polymorphic HCDA genes into the yeast CDA-null mutants, the HCDA-70T showed 40% and 32% activity of prototype for cytidine and ara-C substrates, respectively (P < 0.01). The ara-C IC50 value of the yeast transformants carrying HCDA-70T was 757 +/- 33 micromol and was significantly lower (P < 0.01) than that of prototype (941 +/- 58 micromol). This study demonstrated a population characterized with 208A genotype for, which potentially leads one more sensitive to ara-C treatment than prototype. Accumulation of polymorphisms in the genes responsible for drug metabolism and determination of polymorphism-induced biological variations could provide the additional therapeutic strategies in risk-stratified protocols for the treatment of childhood malignancies.

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The exact mechanisms as to how platelets influence blood-borne metastasis remain poorly understood. Gangliosides, sialic acid-containing glycosphingolipids, are associated with tumor progression and metastasis in humans. Gangliosides isolated from tumor cells promote collagen-stimulated platelet aggregation and ATP secretion and enhance platelet adhesion to immobilized collagen. Gangliosides interact with a number of cell surface receptors including integrin receptors. In this study, we examined the effects of α2β1 integrin-mediated platelet adhesion to collagen and phosphotyrosine signaling of focal adhesion kinase, p125FAK (FAK). platelets pre-incubated with neuroblastoma tumor gangliosides (NBTGs) or their major component GD2 (disialoganglioside) were more adherent to immobilized collagen (OD570 0.43±0.12, 0.39±0.13) compared to platelets pre-incubated with MTB (0.14±0.06, p<0.001); the effect of NBTGs was blocked by F-17 anti-α2 antibody. Pre-incubation of platelets with NBTGs resulted in a marked increase in the phosphotyrosine content of p125FAK in the adherent platelets compared to the MTB-pre-incubated adherent platelets. F-17 anti-α2 antibody decreased protein tyrosine phosphorylation of NBTG-incubated platelets adherent to collagen. These results indicate that the tumor gangliosides enhance platelet adhesion to extracellular matrix collagen by upregulating integrin α2β1-mediated tyrosine phosphorylation of p125FAK, thereby providing insight into how this interaction may be involved in neuroblastoma metastasis.

γ-Glutamyl hydrolase (GGH) plays a central role in folate metabolism and antifolate action. Polymorphism in the human GGH gene (GGH) was associated with efficacy and side effects of methotrexate for treatment of acute lymphoblastic leukemia (ALL). This study aimed to identify polymorphisms of GGH in Chinese. Seventy-one children with ALL, 25 children with acute myeloid leukemia (AML), and 132 children with nonmalignancy as control were included. Human GGH cDNAs were prepared and analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR)-denaturing gradient gel electrophoresis. The detected variants were further confirmed by DNA sequencing. Novel variant GGH cDNA was cloned, expressed, and characterized. Allelic frequency of GGH 452C→T polymorphism was determined as 9.2% (CT, 11/71; TT, 1/71) in the ALL group, 8.0% (CT, 4/25; TT, 0/25) in the AML group, and 9.1% (TT, 4/132; T/C, 16/132) in the controls, respectively. The total allelic frequency in the Chinese population (9.0%) was higher than those reported in Japanese (5.6%) and African Americans (4.4%), and was similar to Caucasians (10.0%). Association of 452TT+TC with increased rate of hepatotoxicity and mucositis was observed in the ALL patients. Two novel mutations were determined in the coding region of GGH in 2 boys with ALL: one of the mutations was a double nonsynonymous heterozygote (841AG+845AG, K257E/N258S), the other was a nonsynonymous heterozygote (797AG, K242R). The corresponding double-mutant protein showed unchanged enzymatic activity by functional analysis. Allele frequency of GGH C452T polymorphism is determined for the first time among Chinese. A novel double nonsynonymous mutation of GGH was identified in a boy with ALL.