Abstract 18405: Warfarin Dose Requirements and Polymorphisms in MicroRNA and Nuclear Receptor Genes

Background and Aim: The marked inter-individual variability in warfarin dose requirement is mainly attributed to the variants of the main target genes across the warfarin pharmacological pathway, i.e. cytochrome P-450 (CYP) 2C9, CYP3A4, ABCB1, vitamin K epoxide reductase complex subunit 1 (VKORC1) and epoxide hydrolase 1 (EPHX1). The expression of these genes is primarily regulated by a complex network of nuclear receptors (NR) which are encoded, in turn, by polymorphic genes. Furthermore, microRNAs (miRNA) can reduce the expression of both warfarin target genes and the genes encoding NRs. We investigated whether the variants of genes encoding i) warfarin targets, ii) NRs involved in the regulation of the targets and iii) miRNA involved in the regulation of NRs and the targets, are associated with warfarin dose requirements. Methods and Results: The study was performed using the Quebec Warfarin Cohort consisting of 988 new warfarin users who were recruited over a period of 3 years and were followed-up for 12 months. The candidate genes were selected according to the literature and included 5 warfarin target genes, 9 NRs genes and 29 miRNA genes. SNPs with MAFu003e0.01 within these genes were selected for the present study from the NCBI database. Genotyping was previously performed using Omni 2.5 array (Illumina, CA) and iPLEX ADME CYP2C9/VKORC1 panel (Agena, CA) and missing SNPs were imputed. We tested the effect of SNPs on the log-transformed values of dose at 3-month post-initiation using multivariate linear regression analysis, and the adjusted significance threshold was set to 2.49 x 10-4. A total of 3970 SNPs, including 702 in target genes, 3162 in NRs and 106 in miRNA genes were studied. For the association with warfarin dose, 137 SNPs in CYP2C9 and VKORC1 were significant, as well as 3 SNPs in nuclear vitamin D receptor (VDR) gene: rs4760658, β = -0,0852, P = 7,32x10-5; rs11168293, β = -0,0809, P = 1,78x10-4; rs4760655, β = -0,0799, P = 2,15x10-4. None of the variants in miRNA genes showed a significant association with warfarin dose. Conclusions: Variants in the gene encoding VDR, a nuclear receptor which has been previously shown to be involved in the regulation of CYP2C9, CYP3A4 and ABCB1, may contribute to the variability in response to warfarin.