Correlation between methylation profile of promoter cpg islands of seven metastasis-associated genes and their expression states in six cell lines of liver origin.

Background & Objective: DNA methylation has been regarded as an important epigenetic signature reflecting the transcription state of DNA in cells. This study was to assess the correlation between methylation state of promoter CpG islands of metastasis-associated genes and their expression in 6 liver cell lines, including 5 cancerous.
Methods: Methylation specific polymerase chain reaction method (MSP) and DNA sequencing verification were used to analyze the methylation state of promoter CpG islands of 7 genes (ASPH, ENO3, ITGA9, LRP6, MTHFD2, OXCT, and SRP72) in 5 liver cancer cell lines (BEL-7402, SMMC-7721, Hep3B, HepG2, and HCCLM3), and 1 immortalized liver cell line (L-02). Expression of 6 genes in this list was assessed by the semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method.
Results: The methylation state of genes was either unmethylated or heterozygously methylated in these 7 liver cell lines. Except for no expression of OXCT gene was detected by RT-PCR in both HepG2 and HCCLM3 cells where it was heterozygously methylated, there was expression of genes in all the remaining cases.
Conclusion: Although expression state of genes in this study supported the general notion that hypermethylation state of promoter CpG islands of genes represents the silenced state of gene transcription, there were exceptions. Therefore, other mechanisms are likely to contribute to the observed expression state of these 7 genes in this study.