Ras Oncogene-Mediated Progressive Silencing of Extracellular Superoxide Dismutase in Tumorigenesis

Figure 3

Effect of the demethylation reagent 5-azacytidine on SOD3 mRNA expression. (a–c) Nthy cells modeling normal human thyroid cells showed similar SOD3 mRNA expression in nontreated and treated control cells, whereas the mRNA production was significantly increased in 5-azacytidine-treated papillary TPC1 and anaplastic 8505c thyroid cancer cells. (d–f) Similar to the human cells, no alteration in sod3 mRNA was observed in rat PC Cl3 cells modeling normal rat thyroid cells after hypomethylation treatment, whereas the treatment induced increased mRNA synthesis in PTC1 and E1A oncogene-transfected cells. (g–j) The hypomethylation treatment did not affect normal rat thyroid FRLT5 cells or FRLT5 clone V13 cells harboring low 1.4-fold RAS activity, whereas a significant increase in the sod3 mRNA production was observed in clones V21 and V39 harboring 10-fold and 35-fold RAS activity, respectively. The data are expressed as the mean ± SD. The values are represented (, , and ).

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