NUDT15 is a key genetic factor for prediction of hematotoxicity in pediatric patients who received a standard low dosage regimen of 6-mercaptopurine

6-Mercaptopurine (6-MP) is commonly used for treatment of acute lymphoblastic leukemia (ALL). The incidence of hematotoxicity caused by this drug is quite high in Asians even using a standard low dosage regimen. The present study was aimed to elucidate the impact of thiopurine S-methyltransferase (TPMT), a nucleoside diphosphate-linked moiety X-type motif 15 (NUDT15), inosine triphosphatase (ITPA) and ATP Binding Cassette Subfamily C Member 4 (ABCC4) polymorphisms on hematotoxicity in pediatric patients who received a standard low starting dose of 6-MP. One hundred and sixty-nine pediatric patients were enrolled and their genotypes were determined. Patients who carried NUDT15¹3 and NUDT15¹2 genotypes were at a 10–15 fold higher risk of severe neutropenia than those of the wild-type during the early months of the maintenance phase. Risk of neutropenia was not significantly increased in patients with other NUDT15 variants as well as in patients with TPMT, ITPA or ABCC4 variants. These results suggest that NUDT15 polymorphisms particularly, NUDT15¹3 and NUDT15¹2, play major roles in 6-MP-induced severe hematotoxicity even when using a standard low dosage of 6-MP and genotyping of these variants is necessary in order to obtain precise tolerance doses and avoid severe hematotoxicity in pediatric patients.     

Lobucavir-induced proliferative changes in mice

Nucleoside analogues are used in the treatment of viral infections, including those caused by human immunodeficiency virus, cytomegalovirus, and herpes virus. These drugs are beneficial in the treatment of human disease, but are associated with toxicities that often limit their intended therapeutic use, including anemia, neutropenia, peripheral neuropathy, and myopathy. Some of these compounds have been reported to be carcinogenic in rodents. To investigate the carcinogenic potential of lobucavir, a nucleoside analogue, three groups of 60 male and female mice were orally administered lobucavir at daily doses of 10, 50, and 250 mg/kg (males) or 30, 150, and 750 mg/kg (females) over a period of 104 weeks. Two identical groups of 60 male and female mice each served as controls. The morphology and the incidence of neoplasms is described and compared with the tumor spectrum of other nucleoside analogues. Light microscopically, lobucavir-induced neoplastic lesions consisted of upper digestive tract squamous cell neoplasia in males and females; cervical, vaginal, and cutaneous squamous cell neoplasia in females; and Hardarian gland adenomas and adenocarcinomas in male mice. These results suggest that long-term administration of lobucavir causes neoplasia in mice, the spectrum of which resembles that observed after long-term administration of zidovudine or ganciclovir.     

慢性乙型病毒性肝炎治疗新方法

就当前慢性乙肝治疗的新方法、新进展作一综述。     

Histochemical characteristics of diphosphate nucleoside consumption in cat and rat nervous system.

Consumption of diphosphate nucleosides is investigated by histochemical methods in rat and cat nervous system. Results show NDP-ase is effectively in histological sections from animals previously perfused with glutaraldehyde or formaldehyde. Histochemical reaction is increased in presence of Ca++, Mg++, Mn++ or imidazole and inhibited by L-DOPA and Noradrenaline in incubation medium. A comparative study of TPP-ase and NDP-ase activities to dilucidate the identity of both enzymes is described.     

The concentrative nucleoside transporter family,SLC28

The SLC28 family consists of three subtypes of sodium-dependent, concentrative nucleoside transporters, CNT1, CNT2, and CNT3 (SLC28A1, SLC28A2, and SLC28A3, respectively), that transport both naturally occurring nucleosides and synthetic nucleoside analogs used in the treatment of various diseases. These subtypes differ in their substrate specificities: CNT1 is pyrimidine-nucleoside preferring, CNT2 is purine-nucleoside preferring, and CNT3 transports both pyrimidine and purine nucleosides. Recent studies have identified key amino acid residues that are determinants of pyrimidine and purine specificity of CNT1 and CNT2. The tissue distributions of the CNTs vary: CNT1 is localized primarily in epithelia, whereas CNT2 and CNT3 have more generalized distributions. Nucleoside transporters in the SLC28 and SLC29 families play critical roles in nucleoside salvage pathways where they mediate the first step of nucleotide biosynthesis. In addition, these transporters work in concert to terminate adenosine signaling. SLC28 family members are crucial determinants of response to a variety of anticancer and antiviral nucleoside analogs, as they modulate the entry of these analogs into target tissues. Further, this family is involved in the absorption and disposition of many nucleoside analogs. Several CNT single nucleoside polymorphisms (SNPs) have been identified, but have yet to be characterized.     

Functional expression of the renal organic cation transporter and P-glycoprotein inXenopus laevis oocytes

The hypothesis that P-glycoprotein (P-gp) mediates the renal secretion of organic cations was tested by functional expression of mRNAs in theXenopus laevis oocyte system. Efflux of 2-deoxytubercidin (dTub), a substrate for the renal organic cation transporter (OCT) but not for P-gp, was enhanced by injection of renal mRNA but not by injection of mRNA from P-gp-overexpressing cells (MDCK cells transduced with the cDNA for humanMDR1). The functional capacity of the MDCK-MDR mRNA was established by its ability to reduce, the steady-state uptake of a classical P-gp substrate, vinblastine. Thus, these data indicate OCT and P-gp to be distinct entities. TheXenopus oocyte system provides a functional approach to further characterize the OCT.Work supported by NIH Grant RO1DK41606 from the Institute for Digestive Diseases and Kidney, and NIH Cancer Center Core Grant, CA 16672 from the National Cancer Institute     

Antibiotic C3368-A,a fungus-derived nucleoside transport inhibitor,potentiates the activity of antitumor drugs

Antibiotic C3368-A (CA) is produced by a fungus strain from a soil sample collected in Antarctica. CA markedly inhibited radiolabeled thymidine and uridine transport in mouse Ehrlich carcinoma cells, its 50% inhibitory concentration (IC₅₀) being 4.6 and 7.7 M, respectively. In clonogenic assay, CA displayed a synergistic effect with methotrexate (MTX), mitomycin C (MMC), 5-fluorouracil (5FU), and Adriamycin (ADR) against human oral epidermoid carcinoma KB cells. CA also markedly enhanced the inhibitory effect of 5FU and ADR on the proliferation of human hepatoma BEL-7402 cells as determined by thep-nitrophenyl-N-acetyl--d-glucosaminide (NAG) enzyme-reaction assay. 5FU or ADR cytotoxicity was not augmented by CA in human fetal lung 2BS cells. In vivo, CA significantly potentiated the inhibitory effect of MMC against colon carcinoma 26 in mice. No significant augmentation of toxicity by the combination was found in treated mice. The results suggest that CA, the newly found nucleoside-tranport inhibitor, may be useful in potentiation of the effect of antitumor drugs.     

白花蛇舌草核苷体外抗肿瘤作用实验研究

目的 探讨白花蛇舌草中核苷的体外抗肿瘤作用.方法 采用24孔板培养法和MTT法观察白花蛇舌草核苷对人红白血病细胞株K562、人非小细胞肺癌细胞株A549的抑制作用.结果 显微镜下观察24孔板,白花蛇舌草核苷呈现明显的抗肿瘤作用.体外抑瘤实验表明,白花蛇舌草核苷对两种细胞株起效的最低药物浓度分别为100 μg/ml和50μg/ml,半数致死量IC50分别是248.1 μg/ml和147.7 μg/ml.结论 白花蛇舌草核苷具有抗肿瘤活性.     

肾脏中转运体对核苷类抗病毒药物的转运作用

药物转运体在药物的药动学和药效学过程中发挥重要作用,而核苷类抗病毒药物与其他药物的相互作用主要基于肾小管膜上表达的转运体。本论文分别对肾脏中参与核苷类抗病毒药物转运的转运体,几种主要核苷类抗病毒药物以及它们之间相互作用的研究现状进行了综述。     

Pharmacokinetics of 4′-cyano-2′-deoxyguanosine,a novel nucleoside analog inhibitor of the resistant hepatitis B virus,in a rat model of chronic kidney disease

IntroductionThe novel nucleoside analog, 4′-cyano-2′-deoxyguanosine (CdG), possesses inhibitory activity against both the wild-type and resistant hepatitis B virus. Since the dosage of the currently available nucleoside analog preparations needs to be adjusted, depending on renal function, we investigated the effect of renal dysfunction on the pharmacokinetics of CdG in a rat model of chronic kidney disease (CKD).MethodsCKD model rats were either intravenously or orally administered CdG at a dose of 1 mg/kg. The concentration of CdG in plasma, organs (liver and kidney) and urine samples were determined by means of a UPLC system interfaced with a TOF-MS system.ResultsFollowing intravenous administration, the plasma retention of CdG was prolonged in CKD model rats compared to healthy rats. In addition, the clearance of CdG was well correlated with plasma creatinine levels in CKD model rats. Similar to the results for intravenous administration, the plasma concentration profiles of CdG after oral administration were also found to be much higher in CKD model rats than in healthy rats. However, the results for the organ distribution and urinary excretion of CdG, the profiles of which were similar to that of healthy rats, indicated that CdG did not accumulate to a significant extent in the body.ConclusionThe extent of renal dysfunction has a direct influence on the pharmacokinetics (plasma retention) of CdG without a significant accumulation, indicating that the dosage of CdG will be dependent on the extent of renal function. .