Requirement of Arsenic Biomethylation for Oxidative DNA Damage
Requirement of Arsenic Biomethylation for Oxidative DNA Damage
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DOI：
10.1093/jnci/djp414
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发表时间：
2009-12-16
影响因子：
10.3
通讯作者：
Waalkes, Michael P.
中科院分区：
文献类型：
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作者：
Kojima, Chikara;Ramirez, Dario C.;Waalkes, Michael P.
无机砷是一种环境致癌物，可通过多种机制发挥作用，包括在体内形成甲基化衍生物。亚砷酸钠（高达5.0 μ M）使砷甲基化能力TRL 1215大鼠肝上皮细胞在暴露18周的裸鼠和砷甲基化缺陷RWPE-1人前列腺上皮细胞在暴露30周的致瘤性。本研究采用免疫自旋捕获法（immuno-spin trapping method）检测了亚砷酸钠对TRL 1215细胞和RWPE-1细胞，或对甲基化活性正常的UROtsa/F35细胞和甲基化缺陷的UROtsa人尿路上皮细胞的慢性作用后，砷生物甲基化在氧化性DNA损伤（ODD）中的作用。通过酶谱分析、transwell法测定细胞侵袭力和软琼脂法测定细胞集落形成，比较了在有和没有亚硒酸盐（一种砷生物甲基化抑制剂）的情况下，以评估ODD在向体外癌症表型转变中的作用。将TRL 1215细胞培养至1.0 μ M亚砷酸钠，5-18周时ODD显著增加（例如，1.0 μ M亚砷酸盐16周时，为对照组的1138%，95%置信区间[CI] = 797%至1481%），而甲基化缺陷的RWPE-1细胞暴露于高达5.0 μ M的亚砷酸盐中30周内并没有增加ODD。用亚硒酸钠抑制砷的生物甲基化作用，可消除TRL 1215细胞中砷诱导的ODD和侵袭力、集落形成以及MMP-2和MMP-9的高分泌。砷诱导UROtsa/F35甲基化细胞的ODD（例如，在16周时，1.0 μ M亚砷酸盐为对照的225%，95%CI = 188%至262%），但在砷甲基化缺陷的UROtsa细胞中没有，ODD水平对应于增加的侵袭力，集落形成，砷生物甲基化似乎是砷诱导的ODD所必需的，并且在某些细胞中似乎与加速转化为体外癌症表型有关。
Inorganic arsenic is an environmental carcinogen that may act through multiple mechanisms including formation of methylated derivatives in vivo. Sodium arsenite (up to 5.0 mu M) renders arsenic methylation-competent TRL1215 rat liver epithelial cells tumorigenic in nude mice at 18 weeks of exposure and arsenic methylation-deficient RWPE-1 human prostate epithelial cells tumorigenic at 30 weeks of exposure. We assessed the role of arsenic biomethylation in oxidative DNA damage (ODD) using a recently developed immuno-spin trapping method.Immuno-spin trapping was used to measure ODD after chronic exposure of cultured TRL1215 vs RWPE-1 cells, or of methylation-competent UROtsa/F35 vs methylation-deficient UROtsa human urothelial cells, to sodium arsenite. Secreted matrix metalloproteinase (MMP)-2 and -9 activity, as analyzed by zymography, cellular invasiveness by using a transwell assay, and colony formation by using soft agar assay were compared in cells exposed to arsenite with and without selenite, an arsenic biomethylation inhibitor, to assess the role of ODD in the transition to an in vitro cancer phenotype.Exposure of methylation-competent TRL1215 cells to up to 1.0 mu M sodium arsenite was followed by a substantial increase in ODD at 5-18 weeks (eg, at 16 weeks with 1.0 mu M arsenite, 1138% of control, 95% confidence interval [CI] = 797% to 1481%), whereas exposure of methylation-deficient RWPE-1 cells to up to 5.0 mu M arsenite did not increase ODD for a 30-week period. Inhibition of arsenic biomethylation with sodium selenite abolished arsenic-induced ODD and invasiveness, colony formation, and MMP-2 and -9 hypersecretion in TRL1215 cells. Arsenic induced ODD in methylation-competent UROtsa/F35 cells (eg, at 16 weeks, with 1.0 mu M arsenite 225% of control, 95% CI = 188% to 262%) but not in arsenic methylation-deficient UROtsa cells, and ODD levels corresponded to the levels of increased invasiveness, colony formation, and hypersecretion of active MMP-2 and -9 seen after transformation to an in vitro cancer phenotype.Arsenic biomethylation appears to be obligatory for arsenic-induced ODD and appears linked in some cells with the accelerated transition to an in vitro cancer phenotype.