We propose to investigate and determine the effect of a novel microRNA (miRNA)-mediated pathway in drug disposition and drug resistance. Elevated expression of drug transporters such as ABCB1 (MDR1) contributes to drug resistance mediated by active drug export. Expression of these transporters is transcriptionally controlled by two major xenobiotic receptors, constitutive androstane receptor (CAR) and pregnane X receptor (PXR), both of which function as heterodimers with retinoid X receptor (RXR). Whereas PXR is ligand- activated, CAR is constitutively active in the absence of ligand, and its expression leads to that of its transcriptional targets. Recent studies have provided evidence of miRNA-mediated drug resistance. Our preliminary studies found that miR-137 is down-regulated in doxorubicin-resistant cells, while CAR and MDR1 are up-regulated. We found that miR-137 and CAR form an unusual negative feedback loop wherein miR-137 directly reduces CAR levels, and CAR negatively regulates miR-137 expression. We also found that CAR inverse agonists reduce MDR1 and increase miR-137 levels, and have developed a novel CAR inverse agonist (LTC27) that is potent and selective for CAR. Importantly, ectopically expressed miR-137 reduces CAR and MDR1, and re-sensitizes doxorubicin-resistant cells to doxorubicin both in vitro and in vivo;suggesting that drug resistance can be reversed. However synthetic miRNAs have limited bioavailability because of their low stability and cellular uptake. By screening, we identified vorinostat (or SAHA) that induces miR-137 expression and reduce MDR1 level. SAHA, a drug approved by FDA, is an inhibitor of histone deacetylases (HDACs);HDAC inhibition can disrupt the transcriptionally repressive CAR-HDAC1 complex. Our preliminary data lead us to hypothesize that increasing miR-137 levels or inhibiting CAR will reduce MDR1 in drug-resistant cells, thereby increasing intracellular drug accumulation and re-sensitizing the cells;that HDAC inhibitors induce miR-137 expression, at least partly by relieving the repressive effect of CAR, and can reverse drug resistance. To test these hypotheses, we will determine (1) the extent to which doxorubicin resistance is reversed by ectopic expression of miR-137;(2) the extent to which doxorubicin resistance is reversed by CAR inverse agonists;and (3) the mechanism by which miR-137 expression is induced, and the extent to which drug resistance is reversed by HDAC inhibitors, in our unique doxorubicin- resistant models. We will also examine the HDAC1-CAR-miR-137 promoter complex and determine the extent to which the complex is disrupted by HDAC inhibitors. These studies will illustrate how drug resistance is acquired and identify potential treatments to reverse resistance.

Public Health Relevance

We propose to investigate the role of a novel microRNA-mediated pathway in the development of drug resistance, a leading cause of treatment failure. We will determine the mechanism and effects of a novel compound, and an FDA-approved drug on inducing the expression of this microRNA to increase intracellular drug accumulation and re-sensitize drug-resistant cells to chemotherapeutic agents. The results of our proposed studies will illustrate how drug resistance is acquired and identify potential therapeutic approach to reverse drug resistance and improve treatment efficacy.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM110034-01
Application #
8670437
Study Section
Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
Program Officer
Okita, Richard T
Project Start
2014-05-01
Project End
2018-02-28
Budget Start
2014-05-01
Budget End
2015-02-28
Support Year
1
Fiscal Year
2014
Total Cost
$332,500
Indirect Cost
$142,500
Name
St. Jude Children's Research Hospital
Department
Type
DUNS #
067717892
City
Memphis
State
TN
Country
United States
Zip Code
38105
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Lin, Wenwei; Goktug, Asli N; Wu, Jing et al. (2017) High-Throughput Screening Identifies 1,4,5-Substituted 1,2,3-Triazole Analogs as Potent and Specific Antagonists of Pregnane X Receptor. Assay Drug Dev Technol 15:383-394
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Beard, Jordan A; Tenga, Alexa; Hills, Justin et al. (2016) The orphan nuclear receptor NR4A2 is part of a p53-microRNA-34 network. Sci Rep 6:25108
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Oladimeji, Peter; Cui, Hongmei; Zhang, Chen et al. (2016) Regulation of PXR and CAR by protein-protein interaction and signaling crosstalk. Expert Opin Drug Metab Toxicol 12:997-1010

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