Sun Y, Colburn N H, Oberley L W
Cell Biology Section, National Cancer Institute, Frederick Cancer Research and Development Center, MD.
Oncol Res. 1993;5(3):127-32.
Altered levels of superoxide dismutase (SOD), the enzyme that scavenges toxic superoxide anion produced during normal metabolism or after oxidative insult, have been implicated in multistage carcinogenesis of both rodents and humans. Using a mouse liver cell model, we report here that after cellular immortalization, both copper- and zinc-containing superoxide dismutase (Cu,ZnSOD) and manganese superoxide dismutase (MnSOD) activities decreased dramatically and that cellular transformation further decreased MnSOD but not Cu,ZnSOD activity. Decreased enzyme activities seen in transformed cells (Tx) were due to decreased amounts of immunoreactive enzyme protein that results from decreased superoxide dismutase mRNA expression. This downregulation of gene expression may occur at the transcriptional level, as suggested by results with cycloheximide (Chx) and actinomycin D (AcD) treatments.
超氧化物歧化酶（SOD）是一种清除正常代谢过程中或氧化损伤后产生的有毒超氧阴离子的酶，其水平改变与啮齿动物和人类的多阶段致癌作用有关。利用小鼠肝细胞模型，我们在此报告，细胞永生化后，含铜和锌的超氧化物歧化酶（Cu,ZnSOD）和锰超氧化物歧化酶（MnSOD）的活性均显著降低，而细胞转化进一步降低了MnSOD的活性，但未降低Cu,ZnSOD的活性。转化细胞（Tx）中酶活性的降低是由于超氧化物歧化酶mRNA表达降低导致免疫反应性酶蛋白量减少所致。如用环己酰亚胺（Chx）和放线菌素D（AcD）处理的结果所示，基因表达的这种下调可能发生在转录水平。
