Abstract 2198: Possible circadian modulation of dihydropyrimidine dehydrogenase by mir-27a and mir-27b.

Abstract

Abstract 5-fluorouracil (5-FU) is a commonly administered chemotherapy drug used for the treatment of various aggressive cancers. Dihydropyrimidine dehydrogenase (DPD, encoded by the DPYD gene) is the rate limiting enzyme of the 5-flourouracil (5-FU) catabolic pathway, and as such limits the amount of drug available for conversion into active metabolites. Reduced expression of DPD has been linked to severe adverse toxicity to 5-FU, including mucositis, diarrhea, hematological toxicities, and, in extreme cases, death. DPD has been previously shown to follow circadian patterns of expression in rodent models and in humans. Many microRNAs also exhibit circadian variations in expression and have been suggested to control oscillations in target protein expression. Using in silico prediction, we identified two putative binding domains for the microRNAs mir-27a and mir-27b within the DPYD gene. One of these sites is located in the 3’ untranslated region (UTR) and the other is located within the coding region just upstream from the stop codon. Using a reporter system, we show that mir-27a and mir-27b are able to bind to both predicted binding sites. Furthermore, over-expression of either microRNA reduced endogenous DPD protein levels in the HT-29 colon cancer cell line. To investigate mir-27a/b as a potential circadian regulator of DPD expression, expression was measured in livers collected at 4-hour intervals from chrono-synchronized mice. As expected, the circadian pattern of DPD enzyme activity closely matched that of DPD expression. The expression patterns for mir-27a and mir-27b were inverse of those for DPD expression and activity. These data suggest that mir-27a and mir-27b may direct circadian variations in DPD enzyme activity. Citation Format: Gabriel L. Butterfield, Steven M. Offer, Robert B. Diasio. Possible circadian modulation of dihydropyrimidine dehydrogenase by mir-27a and mir-27b. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2198. doi:10.1158/1538-7445.AM2013-2198