Inhibition of Intestinal Pyrimidine Nucleoside Phosphorylases

The activity of 5-deoxy-5-fluorouridine (dFUR) depends on its activation to 5-fluorouracil (FU) by pyrimidine nucleoside phosphorylases. These enzymes are found in tumors and normal tissues, with the highest activity in the small intestines. The present study examined the inhibition of dFUR phosphorolysis in intestinal tissues. dFUR metabolism in intestinal homogenates was inhibited by uracil (U), uridine (UR), and thymidine (TdR), which are the normal substrates for the phosphorylases. Conversely dFUR reduced the metabolism of these inhibitors. A good agreement was found between the observed data and the computer-fitted data using the equations for competitive inhibition between dFUR and the inhibitors. In the absence of inhibitors, the V _max of dFUR phosphorolysis was 47.1 ± 4.9 µM/min and the apparent K _m was 910 ± 167 µM. The V _max was unaltered by the inhibitors, while the K _m was increased with increasing inhibitor concentrations. The maximal inhibition of dFUR metabolism by UR and TdR was about 80%. The K _i,'s were 372 µM for U, 87.2 µM for UR, and 112 µM for TdR and are orders of magnitude higher than their reported endogenous serum concentrations. The rate of dFUR phosphorolysis to FU in the intact intestinal epithelial crypt cells, indicated by the ratio of FU to dFUR in the intracellular fluid, was reduced by UR in a concentration-dependent fashion. These data indicate that the naturally occurring pyrimidines inhibit competitively the dFUR metabolism by the intestinal phosphorylases, that this inhibition occurs at concentrations much higher than the circulating endogenous levels, and that phosphorolysis is the major route of dFUR metabolism.     

补骨脂化学成分的研究

目的:对补骨脂的化学成分进行研究.方法:运用硅胶柱层析、Sephadex LH-20柱层析等手段进行分离,运用UV、IR、1HNMR、13CNMR、MS等波谱方法进行结构鉴定.结果:共分离鉴定了7个化合物,分别为异补骨脂素(isopsoralen,1),补骨脂素(psoralen,2),补骨脂定(psoralidin,3),补骨脂查耳酮(bavachalcone,4),补骨脂二氢黄酮(bavachin,5),大豆苷(daidzin,6)和尿嘧啶(uracil,7).结论:化合物6和7为首次从补骨脂属植物中分离得到.     

Multidisciplinary treatment strategy for locally advanced gastric cancer: A systematic review

BackgroundMultidisciplinary management of patients with locally advanced gastric cancer (LAGC) remains unstandardized worldwide. We performed a systemic review to summarize the advancements, regional differences, and current recommended multidisciplinary treatment strategies for LAGC.MethodsEligible studies were identified through a comprehensive search of PubMed, Web of Science, Cochrane Library databases and Embase. Phase 3 randomized controlled trials which investigated survival of patients with LAGC who underwent gastrectomy with pre-/perioperative, postoperative chemotherapy, or chemoradiotherapy were included.ResultsIn total, we identified 11 studies of pre-/perioperative chemotherapy, 38 of postoperative chemotherapy, and 14 of chemoradiotherapy. In Europe and the USA, the current standard of care is perioperative chemotherapy for patients with LAGC using the regimen of 5-FU, folinic acid, oxaliplatin and docetaxel (FLOT). In Eastern Asia, upfront gastrectomy and postoperative chemotherapy is commonly used. The S-1 monotherapy or a regimen of capecitabine and oxaliplatin (CapOx) are used for patients with stage II disease, and the CapOx regimen or the S-1 plus docetaxel regimen are recommended for those with stage III Gastric cancer (GC). The addition of postoperative radiotherapy to peri- or postoperative chemotherapy is currently not recommended. Additionally, clinical trials testing targeted therapy and immunotherapy are increasingly performed worldwide.ConclusionsRecent clinical trials showed a survival benefit of peri-over postoperative chemotherapy and chemoradiotherapy. As such, this strategy may have a potential as a global standard for patients with LAGC. Outcome of the ongoing clinical trials is expected to establish the global standard of multidisciplinary treatment strategy in patients with LAGC.     

Alpha‐actinin‐4 (ACTN4) gene amplification is a predictive biomarker for adjuvant chemotherapy with tegafur/uracil in stage I lung adenocarcinomas

Although adjuvant tegafur/uracil (UFT) is recommended for patients with completely resected stage I non‐small‐cell lung cancer (NSCLC) in Japan, only one‐third of cases has received adjuvant chemotherapy (ADJ) according to real‐world data. Therefore, robust predictive biomarkers for selecting ADJ or observation (OBS) without ADJ are needed. Patients who underwent complete resection of stage I lung adenocarcinoma with or without adjuvant UFT were enrolled. The status of ACTN4 gene amplification was analyzed by FISH. Statistical analyses to determine whether the status of ACTN4 gene amplification affected recurrence‐free survival (RFS) were carried out. Formalin‐fixed, paraffin‐embedded samples from 1136 lung adenocarcinomas were submitted for analysis of ACTN4 gene amplification. Ninety‐nine (8.9%) of 1114 cases were positive for ACTN4 gene amplification. In the subgroup analysis of patients aged 65 years or older, the ADJ group had better RFS than the OBS group in the ACTN4‐positive cohort (hazard ratio [HR], 0.084, 95% confidence interval [CI], 0.009‐0.806; P = .032). The difference in RFS between the ADJ group and the OBS group was not significant in ACTN4‐negative cases (all ages: HR, 1.214; 95% CI, 0.848‐1.738; P = .289). Analyses of ACTN4 gene amplification contributed to the decision regarding postoperative ADJ for stage I lung adenocarcinomas, preventing recurrence, improving the quality of medical care, preventing the unnecessary side‐effects of ADJ, and saving medical costs.     

Oral uracil‐tegafur plus leucovorin vs fluorouracil bolus plus leucovorin for advanced colorectal cancer: a meta‐analysis of five randomized controlled trials

Aim The aim of this study was to evaluate systematically the efficacy and safety of oral uracil‐tegafur (UFT) plus leucovorin (LV) compared with infusional fluorouracil (5‐FU) plus LV for advanced colorectal cancer. Method Eligible studies were identified from Medline, Embase and the Cochrane Library. The end‐points included overall survival and overall tumour response rate, and toxicity including leucopenia, febrile neutropenia, stomatitis/mucositis and diarrhoea. Results Five randomized controlled trials were identified. Pooled data demonstrated no difference in overall survival between the oral UFT plus LV regimen and the 5‐FU bolus plus LV regimen [hazard ratio 1.013; 95% confidence interval (CI) 0.911–1.127].The fixed‐effect pooled estimate for overall tumour response rate showed no significant difference between the two regimens (relative risk 0.893; 0.672–1.187). Grade 3–4 leucopenia [odds ratio (OR) 0.126; 955 CI 0.048–0.326], grade 1–4 leucopenia (OR 0.089; 95% CI 0.067–0.119) and grade1–4 febrile neutropenia (OR 0.020; 95% CI 0.004–0.102) were significantly less prominent in the oral UFT regimens. For nonhaematological toxicities, grade 3–4 stomatitis/mucositis (OR 0.075; 95% CI 0.039–0.146), grade 3–4 infection (OR 0.484; 95% CI 0.310–0.758), grade 1–4 infection (OR 0.672; 95% CI 0.547–0.826, P < 0.001), grade 1–4 diarrhoea (OR 0.743; 95% CI 0.626–0.881) were also less likely to happen in patients in the oral UFT plus LV regimen, while there was no significant difference between the two treatment regimens with respect to grade 1–4 stomatitis/mucositis (OR 0.278; 95% CI 0.053–1.456) and grade 3–4 (OR 1.174; 95% CI 0.983–1.403) diarrhoea. Conclusion Oral UFT or 5‐FU bolus combined with LV results in similar overall survival and tumour response rates for advanced colorectal cancer. The former treatment regimen is greatly superior in terms of toxicity, especially haematological toxicity.     

恩再适注射液中咪唑丙烯酸、尿嘧啶、次黄嘌呤及黄嘌呤的含量测定

目的:建立同时测定恩再适注射液中4个主要成分咪唑丙烯酸、尿嘧啶、次黄嘌呤及黄嘌呤的高效液相色谱方法。方法:色谱柱为 Inertsil ODS 3柱(250 mm×4.6 mm,5 μm),流动相为甲醇-0.3%醋酸水溶液(1:99),流速:0.8 mL·min~(-1),柱温:25℃,检测波长:254 nm。结果:咪唑丙烯酸的线性范围为1.00～25.00μg·mL~(-1),平均回收率为101.5%;尿嘧啶的线性范围为0.995～19.50μg·mL~(-1),平均回收率为93.1%;次黄嘌呤的线性范围为0.20～5.00μg·mL~(-1),平均回收率为92.2%;黄嘌呤的线性范围为2.03～48.72μg·mL~(-1),平均回收率为97.0%。结论:本方法简便,准确,实现了多组分的快速同时测定,为制定恩再适注射液的质量标准提供了参考依据。     

人参四逆汤活性成分的分离和鉴定

目的 研究人参四逆汤的活性成分。方法 利用硅胶色谱柱分离技术，通过理化方法及光谱分析鉴定其化学结构。结果 从人参四逆汤水溶液中，分得7个化合物，分别鉴定为人参皂苷-Rb1、-Rb21、-Rc、-Rd、-Re、-Rg1和尿嘧啶。结论 首次从人参四逆汤水溶液中分得这些化合物。     

Increased uracil misincorporation in lymphocytes from folate-deficient rats

The development of certain human cancers has been linked with inadequate intake of folates. The effects of folate deficiency in vivo on DNA stability (strand breakage, misincorporated uracil and oxidative base damage) in lymphocytes isolated from rats fed a diet deficient in folic acid was determined. Because the metabolic pathways of folate and other methyl donors are closely coupled, the effects of methionine and choline deficiency alone or in combination with folate deficiency were determined. Feeding male Hooded Lister rats a folate-free diet for 10 weeks created a moderate folate deficiency (25-50% (approx.) decrease in plasma, red blood cell and hepatic folate concentrations (P < 0.05) and a 20% rise in plasma homocysteine (P < 0.05)). Lymphocyte DNA strand breakage was increased successively in all groups after 4 weeks and 8 weeks on the diet (50-100% (approx.) after 8 weeks). Only low folate specifically and progressively induced uracil misincorporation throughout the study (100% (approx.) after 8 weeks). Neither folate deficiency nor choline/methionine deficiency altered oxidative DNA base damage. In summary, moderate folate deficiency in vivo is associated with a decrease in DNA stability, measured as increased DNA strand breakage and misincorporated uracil.     

Cytosolic and mitochondrial deoxyribonucleotidases: activity with substrate analogs,inhibitors and implications for therapy

Nucleoside analogs act as prodrugs that must be converted to 5'-phosphates by intracellular kinases to become active in the treatment of viral and oncological diseases. Activation may be reversed by dephosphorylation if the 5'-phosphates are substrates for 5'-nucleotidases. Dephosphorylation by cytosolic enzymes decreases the efficacy of the analogs, whereas dephosphorylation by mitochondrial enzymes may decrease mitochondrial toxicity. Both effects may influence the outcome of therapy. We investigated the dephosphorylation of the 5'-phosphates of commonly used nucleoside analogs by two cytosolic (cN-II and dNT-1) and one mitochondrial (dNT-2) nucleotidase. Most uracil/thymine nucleotide analogs were dephosphorylated by all three human enzymes but cytosine-containing nucleotide analogs were inactive. Only cN-II showed some activity with the monophosphates of the two purine analogs 2-chloro-2'-deoxyadenosine and 9-beta-D-arabinosylguanine. We conclude that overproduction of any of the three 5'-nucleotidases cannot explain development of resistance against cytosine analogs but that overproduction of cN-II could lead to resistance against purine analogs. Of the tested analogs, only (E)-5-(2-bromovinyl)-2'-deoxyuridine was preferentially dephosphorylated by mitochondrial dNT-2. We propose that in future developments of analogs this aspect be considered in order to reduce mitochondrial toxicity. We tested inhibition of dNT-1 and dNT-2 by a large variety of synthetic metabolically stable nucleoside phosphonate analogs and found one (PMcP-U) that inhibited dNT-1 and dNT-2 competitively and a second (DPB-T) that inhibited dNT-2 by mixed inhibition. Both inhibitors are useful for specific 5'-nucleotidase assays and structural studies and may open up possibilities for therapy.