Skip to main content
. 2011 Feb 8;6(2):e16702. doi: 10.1371/journal.pone.0016702

Figure 4. Incomplete DNA methylation recovery after 5-Aza-dC treatment.

Figure 4

DLC1 CpG island methylation and mRNA expression in SMMC-7721 cells during the 5-Aza-dC treatment (Day 0 to Day 4) and recovery (Day 4 to Day 170) were determined. Approximately 10% of the overall DNA methylation on the DLC1 5′UTR (A) and 1st exon (B) was permanently lost after 5-Aza-dC treatment. Quantitatively analysis was done by pyrosequencing, and the average methylation of 10 and 8 CpG dinucleotides on 5′UTR and first exon, respectively, was obtained from three independent experiments and is presented as mean ± SEM. (C). Consistently, a low level of residual DLC1 gene expression in 5-Aza-dC-recovered cells could be detected in SMMC-7721 cells (up to 170 days). (D). Residual DLC1 gene expression was significantly higher (P = 0.0010, t-test) in the 5-Aza-dC-recovered cells that were re-administered with 5-Aza-dC (comparing day 16 and day 129, i.e. 12 days after 1st and 2nd 5-Aza-dC treatment), suggesting that multiple administrations may be required to ensure complete demethylation of tumor suppressor genes following treatment with 5-Aza-dC. Opened circles and rectangles indicate the start and the end of 5-Aza-dC treatment, respectively (Mean ± SEM, N = 4).