title: Suppression of DPYD expression in RKO cells via DNA methylation in the regulatory region of the DPYD promoter: a potentially important epigenetic mechanism regulating DPYD expression.
abstract: Dihydropyrimidine dehydrogenase (DPD) is one of the factors that determine the efficacy and toxicity of 5-fluorouracil. Variations in DPD activity may result from alterations at the transcriptional level of the DPYD gene. Heterogeneity in DPYD expression has been reported, but the molecular mechanisms responsible for this remain unclear. We investigated methylation of the DPYD promoter as a mechanism for transcriptional regulation of DPYD in the RKO colorectal cancer cell line. We demonstrate that the active transcription machinery for DPYD is present in RKO cells, but promoter binding of Sp1, a transactivator of DPYD, was inhibited, which on subsequent examination was shown to be associated with dense promoter methylation. Treatment with 5-aza-2'-deoxycytidine alone or the combination of 5-aza-2'-deoxycytidine and trichostatin A induced demethylation of the promoter and markedly increased the DPYD mRNA level in RKO cells but not in unmethylated WiDr cells. Furthermore, in vitro methylation of the DPYD promoter decreased promoter activity. These data suggest an important role for methylation in DPYD suppression. The transcriptional suppression of DPYD by methylation may be responsible for the increased 5-fluorouracil sensitivity observed in some patients. This may also provide insight into the mechanism underlying the downregulation of DPYD in some colorectal cancers.
authors.affiliation: Mayo Clinic Cancer Center, Mayo Clinic, 200 First Street, SW, Rochester, MN 55905, USA.
authors.forename: Xue
authors.initials: X
authors.lastname: Zhang
authors.forename: Richie
authors.initials: R
authors.lastname: Soong
authors.forename: Kangsheng
authors.initials: K
authors.lastname: Wang
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: James R
authors.initials: JR
authors.lastname: Davie
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Guarcello
authors.forename: Robert B
authors.initials: RB
authors.lastname: Diasio
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D017931:DNA Primers / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D000077209:Decitabine; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000235:genetics*; D044127:Epigenesis, Genetic; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013489:Suppression, Genetic
chemical_list: D017931:DNA Primers; D004273:DNA, Neoplasm; D006877:Hydroxamic Acids; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D016329:Sp1 Transcription Factor; C012589:trichostatin A; D000077209:Decitabine; D042943:Dihydrouracil Dehydrogenase (NADP); D001374:Azacitidine