Tissue riboflavin levels and C20orf54 protein expression are regulated by C20orf54 hypermethylation in Kazak's esophageal cancer

C20orf54 is a riboflavin transporter gene that involved in the intestinal absorption of riboflavin, which is required for normal cellular functions in all aerobic forms of life. The posttranscriptional regulation of C20orf54 expression and its association with epigenetic modifications in cancer development remain unclear. We aimed to study C20orf54 hypermethylation and its regulation on C20orf54 protein expression in Kazak's esophageal squamous cell carcinoma (ESCC) patients. The methylation sequences of C20orf54 promoter regions were mapped in the esophageal cancer cell line, ECa109. MassARRAY analysis was used to quantitatively detect methylated DNA from Kazak's ESCC and normal adjacent tissues (NAT). C20orf54 protein expression and tissue riboflavin levels were assessed via immunohistochemistry and enzyme-linked immunosorbent assay, respectively. We identified 7 CpG sites that were methylated from 12 CpG sites of C20orf54 in ECa109 cells. The quantitative analysis of single CpG site methylation showed 5 CpG sites significant differences in methylation levels between ESCC and NAT. C20orf54 methylation was significantly higher in ESCC tissues (0.4758 +/- 0.0199) than in NAT (0.3574 +/- 0.0183). Riboflavin was also significantly decreased in ESCC tissues (17.32 +/- 3.54 mu g/L) than in normal esophageal epithelia (22.12 +/- 4.01 mu g/L). Increasing the methylation levels of C20orf54 promoter regions tended to decrease C20orf54 protein expression. An inverse association between tissue riboflavin levels and the methylation level of C20orf54 in ESCC tissues was also found. This suggests that C20orf54 may play a protective role in Kazak's ESCC by modulating riboflavin absorption.