Fig. 1

Transcriptional silencing of NSUN7 by promoter CpG island hypermethylation in cancer cell lines. (A) Percentage of human cancer cell lines from the Sanger panel, classified by primary tumor site, with a hypermethylated NSUN7 promoter. Total number of cell lines is shown on top of each bar. (B) Correlation analysis between NSUN7 promoter methylation (mean β-value) and NSUN7 transcript expression (Z-score) in cancer cell lines. Spearman’s rank correlation test with its p-value and the associated rho coefficient are shown. (C) Bisulfite genomic sequencing of NSUN7-promoter CpG Island in HCC cell lines, plus a normal liver sample. CpG dinucleotides are represented as short vertical lines, NSUN7 TSS is indicated by a black arrow, and unmethylated or methylated cytosines are represented as white or black squares, respectively. Single clones are shown for each sample (n > 10). (D) Absolute methylation β-values of NSUN7 promoter-associated CpGs analyzed by the 450 K DNA methylation microarray. Green, unmethylated; red, methylated. Data from the studied HCC cell lines, and six normal liver samples are shown. (E) NSUN7 expression in the HCC cells and two normal livers at the RNA level, analyzed by real-time PCR. (F) NSUN7 transcript expression is restored in the three NSUN7 hypermethylated cell lines (SNU-423, SNU-398 and HUH-7) by treatment with the demethylating agent 5-aza-2′-deoxycytidine (5-Aza-dC). RNA expression data shown represent the mean ± S.D. of biological triplicates, and p-values were calculated by a Student’s T test. ***p-value < 0.001, ****p-value < 0.0001