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 anti-cancer 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 miR-27a and miR-27b. These microRNAs were shown to repress DPD expression through two conserved recognition sites in DPYD. The IC50 of 5-FU for HCT116 cells over-expressing miR-27a or miR-27b was 4.4 μM (both), significantly lower than that for cells expressing a non-targeting (scramble) control microRNA (14.3 μM; 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 (R2=0.49, P=0.0012) and miR-27b (R2=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.

miR-27b synergizes with anticancer drugs via p53 activation and CYP1B1 suppression

“…Interestingly, although CYP1B1 is barely detected in non-cancerous tissues, the protein levels of CYP1B1 are elevated in various types of malignant cancers including liver cancers and kidney cancers [58], which suggest that CYP1B1 may represent a tumor-specific target. Intriguingly, a recent study showed miR-27b-dependent regulation of dihydropyrimidine dehydrogenase, a rate-limiting enzyme in metabolism of 5-fluorouracil, further suggesting a key role of miR-27b in the detoxification of anticancer drugs [59]. Taken together, the combinational therapy of miR-27b and anticancer drugs greatly cuts off the "escape route" for cancer cells by both increasing p53-mediated cell death and suppressing CYP1B1-mediated drug detoxification ( Figure 6J).…”

Rs895819 in MIR27A improves the predictive value of DPYD variants to identify patients at risk of severe fluoropyrimidine‐associated toxicity

“…Expression of miR27a in murine liver was found to negatively correlate with DPYD mRNA level (R 2 5 0.45, p 5 0.0023) and DPD activity (R 2 5 0.49, p 5 0.0012). 19 Polymorphisms in MIR27A, the gene encoding miR-27a, have been shown to influence miR-27a expression. 19,20 A common A>G polymorphism in MIR27A, rs895819, was found to increase miR-27a expression in lymphoblastoid cell lines, and was associated with reduced DPD activity in peripheral blood mononuclear cells (PBMCs) of human volunteers.…”

“…19 Polymorphisms in MIR27A, the gene encoding miR-27a, have been shown to influence miR-27a expression. 19,20 A common A>G polymorphism in MIR27A, rs895819, was found to increase miR-27a expression in lymphoblastoid cell lines, and was associated with reduced DPD activity in peripheral blood mononuclear cells (PBMCs) of human volunteers. 19 The latter suggests that rs895819 may have a relevant effect on 5-FU metabolism.…”

“…19,20 A common A>G polymorphism in MIR27A, rs895819, was found to increase miR-27a expression in lymphoblastoid cell lines, and was associated with reduced DPD activity in peripheral blood mononuclear cells (PBMCs) of human volunteers. 19 The latter suggests that rs895819 may have a relevant effect on 5-FU metabolism. 19 We previously showed that among patients with DPYD risk-associated variants DPYD*2A, c.2846A>T, c.1679T>G or c.1129-5923C>G, patients who also had the rs895819 variant (G) allele were at strongly increased risk of fluoropyrimidine-associated toxicity compared with patients without the rs895819 variant allele (OR 7.4 for each additional rs895819 variant allele present in combination with a DPYD variant, 95% CI: 1.7-31.9, p 5 0.0073).…”

“…19 The latter suggests that rs895819 may have a relevant effect on 5-FU metabolism. 19 We previously showed that among patients with DPYD risk-associated variants DPYD*2A, c.2846A>T, c.1679T>G or c.1129-5923C>G, patients who also had the rs895819 variant (G) allele were at strongly increased risk of fluoropyrimidine-associated toxicity compared with patients without the rs895819 variant allele (OR 7.4 for each additional rs895819 variant allele present in combination with a DPYD variant, 95% CI: 1.7-31.9, p 5 0.0073). 21 Importantly, there was a large difference in PPV for severe toxicity between patients with and without rs895819.…”