title: microRNAs miR-27a and miR-27b directly regulate liver dihydropyrimidine dehydrogenase expression through two conserved binding sites.
abstract: Dihydropyrimidine dehydrogenase (DPD, encoded by DPYD) is the rate-limiting enzyme in the uracil catabolic pathway and has a pivotal role in the pharmacokinetics of the commonly prescribed anticancer drug 5-fluorouracil (5-FU). Deficiency of DPD, whether due to inadequate expression or deleterious variants in DPYD, has been linked to severe toxic responses to 5-FU. Little is known about the mechanisms governing DPD expression in the liver. In this report, we show increased accumulation of RNA-induced silencing complex (RISC) proteins on DPYD mRNA in cells overexpressing the highly homologous microRNAs (miRNA) miR-27a and miR-27b. These miRNAs were shown to repress DPD expression through two conserved recognition sites in DPYD. The IC50 of 5-FU for HCT116 cells overexpressing miR-27a or miR-27b was 4.4 μmol/L (both), significantly lower than that for cells expressing a nontargeting (scramble) control miRNA (14.3 μmol/L; P = 3.3 × 10(-5) and P = 1.5 × 10(-7), respectively). Mouse liver DPD enzyme activity was inversely correlated with expression levels of miR-27a (R(2) = 0.49; P = 0.0012) and miR-27b (R(2) = 0.29; P = 0.022). A common variant in the hairpin loop region of hsa-mir-27a (rs895819) was also shown to be associated with elevated expression of the miR-27a in a panel of cell lines (P = 0.029) and in a transgenic overexpression model (P = 0.0011). Furthermore, rs895819 was associated with reduced DPD enzyme activity (P = 0.028) in a cohort of 40 healthy volunteers. Taken together, these results suggest that miR-27a and miR-27b expression may be pharmacologically relevant modulators of DPD enzyme function in the liver. Furthermore, our data suggest that rs895819 may be a potential risk allele for 5-FU sensitivity.
authors.affiliation: Corresponding Author: Robert B. Diasio, Mayo Clinic Cancer Center, 200 1st Street Southwest, Rochester, MN 55905. diasio.robert@mayo.edu.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Offer
authors.forename: Gabriel L
authors.initials: GL
authors.lastname: Butterfield
authors.forename: Calvin R
authors.initials: CR
authors.lastname: Jerde
authors.forename: Croix C
authors.initials: CC
authors.lastname: Fossum
authors.forename: Natalie J
authors.initials: NJ
authors.lastname: Wegner
authors.forename: Robert B
authors.initials: RB
authors.lastname: Diasio
mesh_terms: D000818:Animals; D001665:Binding Sites; D054067:Dihydropyrimidine Dehydrogenase Deficiency / Q000235:genetics* / Q000378:metabolism; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000096:biosynthesis*; D005472:Fluorouracil / Q000008:administration & dosage / Q000009:adverse effects*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D008099:Liver / Q000201:enzymology; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D009369:Neoplasms / Q000150:complications / Q000188:drug therapy
chemical_list: C531388:MIRN27 microRNA, human; D035683:MicroRNAs; D042943:Dihydrouracil Dehydrogenase (NADP); D005472:Fluorouracil