5-Aza-2-deoxycytidine Enhances the Sensitivity of 5-Fluorouracil by Demethylation of the Thymidine Phosphorylase Promoter.

BACKGROUND/AIM: 5-Aza-2-deoxycytidine (5-Aza-CdR) enhances the sensitivity to 5-fluorouracil (5-FU), but the molecular mechanism is not fully understood. The aim of this study was to investigate the molecular mechanism that enhances the sensitivity to 5-FU treated with 5-Aza-CdR via thymidine phosphorylase (TP).

MATERIALS AND

METHODS

The sensitivity to drugs was determined on several cancer cell lines by the MTT assay. Protein and mRNA levels were examined by immunoblot and RT-PCR, respectively. Gene silencing, binding of Sp1 to DNA and methylation of DNA was performed by siRNA, ChIP assay and sodium bisulfate genomic sequencing, respectively.

RESULTS

Sp1-binding sites in the TP promoter were methylated in epidermoid carcinoma. 5-Aza-CdR demethylated Sp1-binding sites and enhanced sensitivity to 5-FU.

CONCLUSION

Demethylation of Sp1-binding sites by 5-Aza-CdR was a key factor enhancing 5-FU sensitivity, which may enable more effective treatments for cancer patients with the combination of 5-Aza-CdR and 5-FU.