＜正＞ Background Aberrant DNA methylation plays a key role in human carcinogenesis.5-aza-2’-deoxycytidine inhibitsDNA methylation and induces the expression of genes putatively silenced by promoter methylation in vitro.There are fewstudies of the biological and clinical significance of 5-aza-2’-deoxycytidine in human hepatocellular carcinoma.This studyexplored the mechanism of 5-aza-2’-deoxycytidine targeting transcriptional repressor complexes affecting global geneexpression in hepatocellular carcinoma cell line.Methods High density oligonucleotide gene expression microarrays were used to examine the effects of5-aza-2’-deoxycytidine treatments on human hepatocellular carcinoma cell line SMMC-7721.The 5’ ends of the genesupregulated or downregulated in this manner were compared with BLAST database to determine whether they mighthave promoter CpG islands.Flow cytometry was used to detect stages of the cell cycle and apoptosis of SMMC-7721after being treated with 5-aza-2’-deoxycytidine.Results Data obtained 3 days after 4 days of treatment with 5-aza-2’-deoxycytidine showed that more genes wereinduced in tumorigenic cells including genes that function in cell proliferation,differentiation,regulation of transcription,and cytokine signalling.Approximately 30% of induced genes did not have CpG islands within their 5’ regions,suggestingthat some genes activated by 5-aza-2’-deoxycytidine may not result from the direct inhibition of promoter methylation.This phenomenon may contribute to a number of upregulated genes involving regulation of transcription in the treatedcell.Results showed that 100 μmol/L 5-aza-2’-deoxycytidine blocked cell cycle at S/G2-M phase increasing rate ofapoptosis.Notably,we found differential expression of molecular action in the methylation although DNAmethyltransferases did not show significant difference in the treated cell line.Conclusion 5-aza-2’-deoxycytidine could restore some silenced genes expression independently of DNA methylationinhibition and expression of DNA methyltransferases.
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