Proteomic analysis of liver cancer cells treated with 5‐Aza‐2′‐deoxycytidine (AZA)

Abstract

Abstract5‐Aza‐2′‐deoxycytidine (AZA) is a potent inhibitor of DNA methylation that exhibits anti‐tumor activity in a variety of tumor cells via reactivation of tumor suppressor genes. However, few studies have been done on the biological and clinical significance of AZA in human hepatocellular carcinoma. To identify potential genes that may be aberrantly methylated and confer growth advantage to neoplastic cells and to better understand the molecular mechanism(s) underlying AZA anti‐tumor activity, a proteomics approach was used to annotate global gene expression changes of HepG2 cell line pre‐ and post‐treatment with AZA. A total of 56 differentially expressed proteins were identified by 2D gel analysis, 48 of which were up‐regulated while the remaining 8 were down regulated. Among the identified proteins, eight of these showed marked changed proteins, including seven up‐regulated proteins: glutathione S‐transferase P, protein DJ‐1, peroxiredoxin‐2, UMP‐CMP kinase, cytochrome c‐type heme lyase, enhancer of rudimentary homolog, profilin‐1, and one down‐regulated protein, heat‐shock protein β−1. The possible implication of these proteins in hepatocarcinogenesis is discussed. We tested two up‐regulated proteins, glutathione S‐transferase P and peroxiredoxin‐2, using RT‐PCR and their expression was consistent with the results obtained in the protein level. Both of these genes were methylated when methylation‐specific PCR was used against their promoter regions. Following treatment with AZA, the gene promoter regions were found to be unmethylated, concomitant with overexpression of the proteins compared to HepG2 cells without treatment. These data provide useful information in evaluating the therapeutic potential of AZA for the treatment of HCC. Drug Dev Res 69, 2009. © 2009 Wiley‐Liss, Inc.