Fig. 2.

Analysis of the methylation status of the CYB5R2 promoter region in NPC cell lines, NPC primary tumors and NNE samples. a MSP analysis in NPC cell lines and NNEs. M methylated alleles, U unmethylated alleles. In vitro methylated DNA was used as a methylation-positive control and DNA from normal lymphocytes was the positive control for unmethylated alleles. The blank control was water. b MSP analysis in NPC biopsies and NNE, representative data is shown. c Methylation status of the 39 CpG sites of the CYB5R2 promoter in two NPC cell lines (TW03 and CNE2), two NPC biopsies (NPC15 and 27) and one NNE biopsy (NNE7). Five clones were randomly selected and sequenced for each sample. Different size filled sectors of the circles represent the fraction of methylated CpG. MSP primer locations are indicated by frames. d Restoration of CYB5R2 expression by treatment with 5-aza-dC in NPC cell lines. One NNE sample and CYB5R2 expression plasmid DNA were used as positive controls