去甲基化剂5-氮杂-2''''-脱氧胞苷对胃癌细胞生物学行为的影响

目的:探讨去甲基化剂5氮杂2’脱氧胞苷(5AzaCdR)对胃癌细胞生物学行为的影响。方法:使用浓度5×106mol/L和105mol/L的5AzaCdR处理胃癌细胞株AGS、SGC7901、MKN28及MKN45。通过MTT、平板克隆实验观察处理前、后细胞的生长活性,RTPCR检测处理前、后抑癌基因RASSF1AmRNA表达的改变,并应用流式细胞仪进行细胞周期和凋亡率的分析。结果:4株胃癌细胞经不同浓度之5AzaCdR处理后,与对照组相比,生长速度出现不同程度减慢;实验组AGS细胞较对照组细胞克隆形成率显著降低(32.4%、28.5%比57.0%,P<0.01);5AzaCdR处理后,3株无RASSF1AmRNA表达的细胞(AGS、MKN28和SGC7901)均检出基因重新表达;处理前后4株胃癌细胞无明显G1期、G2/M期改变,AGS细胞凋亡率由0.6%增至18.6%和20.2%,MKN28细胞亦出现凋亡率由1.85%增至3.85%和6.61%。结论:去甲基化剂5AzaCdR对胃癌细胞生长周期无显著影响,可能系通过诱导抑癌基因再表达或凋亡等途径,间接抑制胃癌细胞的生长。     

Microsomal mediated metabolism of dialkylaryltriazenes

Summary The oxidative N-demethylation was investigated for a series of 3,3-dimethyl-1-phenyl-triazenes. Triazenes, deactivated with halogene atoms in the phenylring, were expected to be better demethylated. The results do indicate a good trend that substitution of the ring with deactivating atoms and extent of demethylation compare well. The percentages of demethylation were: For 3,3-dimethyl-1-phenyltriazene, 45%; for 3,3-dimethyl-1 (4-chlorophenyl)-triazene, 92%; for 3,3-dimethyl-1(4-bromophenyl)triazene, 89%; for 3,3-dimethyl-1-(2,4,6-trichlorophenyl)triazene, 122%; and for 3,3-dimethyl-1-(2,4,6-tribromophenyl)triazene, 85%.     

Further studies on aberrant gene expression associated with arsenic-induced malignant transformation in rat liver TRL1215 cells

Chronic arsenic exposure of rat liver epithelial TRL1215 cells induced malignant transformation in a concentration-dependent manner. To further define the molecular events of these arsenic-transformed cells (termed CAsE cells), gene expressions associated with arsenic carcinogenesis or influenced by methylation were examined. Real-time RT-PCR showed that at carcinogenic concentrations (500 nM, and to a less extent 250 nM of arsenite), the expressions of alpha-fetoprotein (AFP), Wilm's tumor protein-1 (WT-1), c-jun, c-myc, H-ras, c-met and hepatocyte growth factor, heme oxygenase-1, superoxide dismutase-1, glutathione-S-transferase-pi and metallothionein-1 (MT) were increased between 3 to 12-fold, while expressions of insulin-like growth factor II (IGF-II) and fibroblast growth factor receptor (FGFR1) were essentially abolished. These changes were not significant at the non-carcinogenic concentration (125 nM), except for IGF-II. The positive cell-cycle regulators cyclin D1 and PCNA were overexpressed in CAsE cells, while the negative regulators p21 and p16 were suppressed. Western-blot confirmed increases in AFP, WT-1, cyclin D1 and decreases in p16 and p21 protein in CAsE cells. The CAsE cells over-expressed MT but the demethylating agent 5-aza-deoxycytidine (5-aza-dC, 2.5 microM, 72 h) stimulated further MT expression. 5-Aza-deoxycytidine restored the loss of expression of p21 in CAsE cells to control levels, but did not restore the expression of p16, IGF-II, or FGFR1, indicating the loss of expression of these genes is due to factors other than DNA methylation changes. Overall, an intricate variety of gene expression changes occur in arsenic-induced malignant transformation of liver cells including oncogene activation and alterations in expression of genes critical to growth regulation.     

Demethylation of l-3-methoxytyrosine in vivo

Summary After administration of purified l-¹⁴C-3-methoxytyrosine (l-¹⁴C-3-MTO) to rats, the fractions of labelled amino acids, catecholamines and phenolcarboxylic acids of urine and brain have been separated by column chromatography. Prior to performing the quantitative determinations, the individual metabolites of each urinary fraction and of the cerebral catecholamine fraction were isolated by paper chromatography using different systems. Susbtantial amounts of ¹⁴C-3,4-dihydroxyphenylacetic acid (¹⁴C-DOPAC) as well as some ¹⁴C-3,4-dihydroxyphenylalanine (¹⁴C-DOPA) and traces of dopamine (DA) appeared in the urine. Furthermore, small amounts of ¹⁴C-DA and ¹⁴C-norepinephrine were found in the brain with two different chromatographic systems. The urinary excretion of ¹⁴C-DOPAC and ¹⁴C-DA was increased by pretreatment with dopacetamide, an inhibitor of catechol-3-O-methyl-transferase. A possible contamination of the l-¹⁴C-3-MTO with traces of l-¹⁴C-DOPA as a major source of the dihydroxylated metabolites has been ruled out. It is concluded that part of l-3-MTO undergoes demethylation in vivo and that the finding of DA in brain and urine after administration of l-3-MTO is not an artifact.     

Genome-wide demethylation during neural differentiation of P19 embryonal carcinoma cells

Epigenetic regulation including DNA methylation plays an important role in several differentiation processes. We profiled global DNA methylation in the neural differentiation of P19 embryonic carcinoma cells using a microarray-based method called MIAMI. We found a genome-wide demethylation of genes. This suggests demethylation rather than methylation is important in neural differentiation. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

骨髓增生异常综合征患者移植前不同方案治疗对移植后结局影响的Meta分析

目的:系统性评价骨髓增生异常综合征（MDS）患者在异基因造血干细胞移植（allo-HSCT）前接受不同治疗方案对移植后长期复发及生存的影响。方法:检索Ovid、Cochrane Library、PubMed、Embase、中国期刊全文数据库、中文科技期刊数据库、万方数据库和中国生物医学文献数据库中从建库至2019年12月MDS患者行allo-HSCT前接受不同方案治疗的文献。对符合纳入标准的文献，由2名研究者按Cochrane系统评价方法，独立进行资料提取、质量评价并交叉核对。按治疗方法，将纳入文献中的病例分为去甲基化药物（地西他滨或阿扎胞苷）治疗组（去甲基化治疗组）和传统方案治疗组（包括化疗和支持治疗）（传统治疗组）。采用RevMan 5.3软件对各组总生存（OS）、复发、无复发死亡率（NRM）、无复发生存（RFS）进行分析。结果:共纳入10篇文献。Meta分析结果显示，传统治疗组中，化疗组与支持治疗组间3年OS率[44.6%（146/327）比35.5%（138/389）； OR=0.93，95% CI 0.38~2.27， P=0.87]、复发率[32.4%（106/327）比37.3%（145/389）； OR=1.00，95% CI 0.49~2.05， P=0.99]、NRM[26.3%（86/327）比27.0%（105/389）； OR=1.05，95% CI 0.75~1.49， P=0.77]、RFS率[9.2%（30/327）比12.6%（49/389）； OR=0.74，95% CI 0.26~2.10， P=0.57]差异均无统计学意义。去甲基化治疗组与传统治疗组间3年OS率[40.7%（165/405）比45.9%（290/632）； OR=0.98，95% CI 0.71~1.36， P=0.28]、复发率[32.6%（132/405）比38.3%（242/632）； OR=1.05，95% CI 0.79~2.05， P=0.25]、NRM[27.2%（110/405）比24.8%（157/632）； OR=0.81，95% CI 0.59~1.11， P=0.68]、RFS率[46.7%（189/405）比42.2%（267/632）； OR=0.84，95% CI 0.63~1.12， P=0.85]差异均无统计学意义。无论去甲基化治疗组与化疗组间、还是去甲基化治疗组与支持治疗组间，3年OS率、复发率、NRM、RFS率差异均无统计学意义（均 P>0.05）。 结论:MDS患者allo-HSCT前接受不同方案治疗对于移植后生存和复发均无明显影响。     

Practical demethylation of aryl methyl ethers using an odorless thiol reagent

A highly practical method for demethylation of aryl methyl ethers employing a long-chain thiol has been developed. Under the conditions described herein, clean and fast conversions to the desired phenolic compounds have been achieved with a broad range of substrates. Unlike other thiolate-mediated methods, this newly developed protocol features in-situ generation of sodium alkylthiolate using NaOH, and is almost free from foul smells and potentially harmful gases. It therefore provides an attractive option for the demethylation of aryl methyl ethers.     

Methylation and demethylation of intermediates selenide and methylselenol in the metabolism of selenium

All nutritional selenium sources are transformed into the assumed common intermediate selenide for the syntheses of selenoproteins for utilization and/or of selenosugar for excretion. Methylselenol [monomethylselenide, MMSe] is the assumed intermediate leading to other methylated metabolites, dimethylselenide (DMSe) and trimethylselenonium (TMSe) for excretion, and also to the intermediate selenide from methylselenocysteine and methylseleninic acid (MSA). Here, related methylation and demethylation reactions were studied in vitro by providing chemically reactive starting substrates (76Se-selenide, 77Se-MMSe and 82Se-DMSe) which were prepared in situ by the reduction of the corresponding labeled proximate precursors (76Se-selenite, 77Se-MSA and 82Se-dimethylselenoxide (DMSeO), respectively) with glutathione, the three substrates being incubated simultaneously in rat organ supernatants and homogenates. The resulting chemically labile reaction products were detected simultaneously by speciation analysis with HPLC-ICP-MS after converting the products and un-reacted substrates to the corresponding oxidized derivatives (selenite, MSA and DMSeO). The time-related changes in selenium isotope profiles showed that demethylation of MMSe to selenide was efficient but that of DMSe to MMSe was negligible, whereas methylation of selenide to MMSe, and MMSe to DMSe were efficient, and that of DMSe to TMSe occurred less efficiently. The present methylation and demethylation reactions on equilibrium between selenide, MMSe and DMSe without producing selenosugar and selenoproteins indicated that DMSe rather than TMSe is produced as the end product, suggesting that DMSe is to be excreted more abundantly than TMSe. Organ-dependent differences in the methylation and demethylation reactions were characterized for the liver, kidney and lung.