In silico identification of microRNAs predicted to regulate the drug metabolizing cytochrome P450 genes

OBJECTIVE: Cytochrome P450 (CYP) enzymes exhibit high interindividual variability that is not completely explained by known environmental and genetic factors. To further understand this variability, we hypothesized that microRNAs (miRNAs) may regulate CYP expression. METHODS: MiRNA identification algorithms were used to identify the miRNAs that are predicted to regulate twelve major drug metabolizing CYPs and to identify polymorphisms in CYP mRNA 3'-UTRs that are predicted to interfere with normal mRNA-miRNA interactions. RESULTS: All twelve CYPs were predicted to be targets of miRNAs. Additionally, 38 SNPs in CYP mRNA 3'-UTRs were predicted to interfere with miRNA targeting of mRNAs. These predicted miRNAs and SNPs are candidates for future in vitro studies focused on understanding the molecular regulation of these CYP genes. CONCLUSION: These in silico results provide strong support for a role of miRNA in the regulation and variability of CYP expression

MECHANISMS OF VARIABILITY IN CYP2D6 METABOLISM: THE CONTRIBUTIONS OF POLYMORPHISMS, COPY NUMBER VARIATIONS AND microRNA

Indiana University-Purdue University Indianapolis (IUPUI)Cytochrome P450 2D6 (CYP2D6) is an important drug metabolizing enzyme that is involved in the metabolism of 20-25% of commonly prescribed drugs. There is interindividual variability in CYP2D6 enzyme activity and this leads to compromised metabolism of many drugs. Genetic and environmental factors explain only a part of the interindividual variability; the other factors that contribute to this variability are largely unknown. Hence, it becomes important to study CYP2D6 to understand the endogenous and exogenous factors that control its activity. The specific objective of this research was to determine the contribution of genetic and epigenetic factors in the regulation of CYP2D6 expression and activity. The specific aims were: (1) to identify the common CYP2D6 polymorphisms in Vietnamese and Filipino women with breast cancer and evaluate its association with plasma concentrations of endoxifen (an active metabolite of the breast cancer therapeutic drug, tamoxifen); (2) to identify the CYP2D6 copy number variations (CNVs) in these women and evaluate their association with endoxifen concentration; and (3) to identify microRNAs (miRNAs) that regulate the expression of CYP2D6 directly or indirectly. The results of this study indicated that: (1) in Vietnamese and Filipino women, the reduced function allele CYP2D6*10 was frequent (~55%) and it was significantly associated with reduced endoxifen concentration; (2) in these women, only 39% carried two copies of the CYP2D6 gene, the rest had a genomic imbalance for CYP2D6, primarily involving the CYP2D6(*36)n-*10 allele. However, carrying multiple copies of CYP2D6*36 allele did not significantly affect CYP2D6 activity, suggesting that multiple copies of a gene does not always translate to additive effects; and (3) microRNAs were identified to target HNF4A, a transcriptional factor that regulates CYP2D6 expression. These miRNAs are likely to play an important role in the indirect regulation of CYP2D6. Taken together, these results emphasize on the role of polymorphisms, CNVs and possibly miRNAs in the regulation of CYP2D6. These clinically important biomarkers will help to improve the efficacy and reduce the side effects of many CYP2D6 substrate drugs and thus contribute to personalization of drug therapy

Evaluation and use of a serological assay for the detection of antibodies to Lawsonia intracellularis in swine

Porcine proliferative enteropathy (PPE) is a common and economically important gastro-intestinal disease of swine caused by the intracellular bacterium, Lawsonia intracellularis. Conventional tests to detect antibody responses to L. intracellularisinclude the immuno-peroxidase monolayer assay (IPMA), immuno-fluorescent antibody test (IFAT) and a lipopolysaccharide ELISA (LPS-ELISA). These tests are not commercially available. Therefore, objective of this study is to evaluate the performance of a commercial L. intracellularis blocking ELISA. Performance of the commercial ELISA was compared to the IPMA and LPS-ELISA using serum from experimentally infected animals (N = 40). The prevalence of L. intracellularis sero-positive animals was assessed by comparing suspect and randomly selected sera (N = 394). The commercial ELISA, IPMA and a non-commercial lipopolysaccharide (LPS) LPS-ELISA showed a 95% correlation when tested using experimentally derived known status samples. When compared to the IPMA the sensitivity of the commercial ELISA was 91% while the specificity was 100%. Therefore, the diagnostic sensitivity and specificity of the commercial L. intracellularis ELISA was comparable to the LPS-ELISA and IPMA. A comparison of suspect and randomly selected field samples with the commercial ELISA indicated that L. intracellularis sero-positivity is widespread and does not correlate with possible disease status

Differential quantification of CYP2D6 gene copy number by four different quantitative real-time PCR assays

Copy number variations (CNVs) in the CYP2D6 gene contribute to interindividual variation in drug metabolism. As the most common duplicated allele in Asian populations is the nonfunctional CYP2D6*36 allele, the goal of this study was to identify CNV assays that can differentiate between multiple copies of the CYP2D6*36 allele and multiple copies of other CYP2D6 alleles. We determined CYP2D6 gene copy numbers in 32 individuals with known CYP2D6 CNVs from the Coriell Japanese-Chinese panel using four quantitative real-time PCR assays. These assays target different regions of the CYP2D6 gene: 5'-flanking region, intron 2, intron 6, and exon 9 (Ex9). The specific target site of the Ex9 assay was verified by sequencing the PCR amplicon. Three of the CYP2D6 CNV assays (5'-flanking region, intron 2, and intron 6) estimated CYP2D6 copy numbers that were concordant for all 32 individuals. However, the Ex9 assay was concordant in only 10 of 32 samples. The 10 concordant samples did not contain any CYP2D6*36 alleles and the 22 discordant samples contained at least one CYP2D6*36 allele. In addition, the Ex9 assay accurately quantified all of the non-CYP2D6*36 alleles in all samples. Ex9 amplicon sequencing indicated that it targets a region of CYP2D6 exon 9 that undergoes partial gene-conversion in the CYP2D6*36 allele. In conclusion, CYP2D6 Ex9 CNV assay can be used to determine the copy number of non-CYP2D6*36 alleles. Selective amplification of non-CYP2D6*36 sequence by the Ex9 assay should be useful in determining the number of functional copies of CYP2D6 in Asian populations

Genome-Wide Discovery of Drug-Dependent Human Liver Regulatory Elements

Inter-individual variation in gene regulatory elements is hypothesized to play a causative role in adverse drug reactions and reduced drug activity. However, relatively little is known about the location and function of drug-dependent elements. To uncover drug-associated elements in a genome-wide manner, we performed RNA-seq and ChIP-seq using antibodies against the pregnane X receptor (PXR) and three active regulatory marks (p300, H3K4me1, H3K27ac) on primary human hepatocytes treated with rifampin or vehicle control. Rifampin and PXR were chosen since they are part of the CYP3A4 pathway, which is known to account for the metabolism of more than 50% of all prescribed drugs. We selected 227 proximal promoters for genes with rifampin-dependent expression or nearby PXR/p300 occupancy sites and assayed their ability to induce luciferase in rifampin-treated HepG2 cells, finding only 10 (4.4%) that exhibited drug-dependent activity. As this result suggested a role for distal enhancer modules, we searched more broadly to identify 1,297 genomic regions bearing a conditional PXR occupancy as well as all three active regulatory marks. These regions are enriched near genes that function in the metabolism of xenobiotics, specifically members of the cytochrome P450 family. We performed enhancer assays in rifampin-treated HepG2 cells for 42 of these sequences as well as 7 sequences that overlap linkage-disequilibrium blocks defined by lead SNPs from pharmacogenomic GWAS studies, revealing 15/42 and 4/7 to be functional enhancers, respectively. A common African haplotype in one of these enhancers in the GSTA locus was found to exhibit potential rifampin hypersensitivity. Combined, our results further suggest that enhancers are the predominant targets of rifampin-induced PXR activation, provide a genome-wide catalog of PXR targets and serve as a model for the identification of drug-responsive regulatory elements

Evaluation and use of a serological assay for the detection of antibodies to Lawsonia intracellularis in swine

Porcine proliferative enteropathy (PPE) is a common and economically important gastro-intestinal disease of swine caused by the intracellular bacterium, Lawsonia intracellularis. Conventional tests to detect antibody responses to L. intracellularisinclude the immuno-peroxidase monolayer assay (IPMA), immuno-fluorescent antibody test (IFAT) and a lipopolysaccharide ELISA (LPS-ELISA). These tests are not commercially available. Therefore, objective of this study is to evaluate the performance of a commercial L. intracellularis blocking ELISA. Performance of the commercial ELISA was compared to the IPMA and LPS-ELISA using serum from experimentally infected animals (N = 40). The prevalence of L. intracellularis sero-positive animals was assessed by comparing suspect and randomly selected sera (N = 394). The commercial ELISA, IPMA and a non-commercial lipopolysaccharide (LPS) LPS-ELISA showed a 95% correlation when tested using experimentally derived known status samples. When compared to the IPMA the sensitivity of the commercial ELISA was 91% while the specificity was 100%. Therefore, the diagnostic sensitivity and specificity of the commercial L. intracellularis ELISA was comparable to the LPS-ELISA and IPMA. A comparison of suspect and randomly selected field samples with the commercial ELISA indicated that L. intracellularis sero-positivity is widespread and does not correlate with possible disease status.This article is from International Journal of Veterinary Science and Medicine 2 (2014); 109, doi: 10.1016/j.ijvsm.2014.08.001. Posted with permission.</p

An Overview of Genomic Biomarker Use in Cardiovascular Disease Clinical Trials.

Clinical trial designs targeting patient subgroups with certain genetic characteristics may enhance the efficiency of developing drugs for cardiovascular disease (CVD). To evaluate the extent to which genetic knowledge translates to the CVD pipeline, we analyzed how genomic biomarkers are utilized in trials. Phase II and III trial protocols for investigational new drugs for CVD and risk factors were evaluated for prospective and exploratory genomic biomarker use; drug targets were evaluated for the presence of evidence that genetic variations can impact CVD risk or drug response. We identified 134 programs (73 unique drug targets) and 147 clinical trials. Less than 1% (n&nbsp;=&nbsp;1/147) trials used a genomic biomarker prospectively for in-trial enrichment despite 32% (n&nbsp;=&nbsp;23/73) of the drug targets having evidence of genetic variations. Additionally, 46% (n&nbsp;=&nbsp;68/147) of the trials specified exploratory biomarker use. The results highlight an opportunity for more targeted CVD drug development by leveraging genomic biomarker knowledge

An Overview of Genomic Biomarker Use in Cardiovascular Disease Clinical Trials

Clinical trial designs targeting patient subgroups with certain genetic characteristics may enhance the efficiency of developing drugs for cardiovascular disease (CVD). To evaluate the extent to which genetic knowledge translates to the CVD pipeline, we analyzed how genomic biomarkers are utilized in trials. Phase II and III trial protocols for investigational new drugs for CVD and risk factors were evaluated for prospective and exploratory genomic biomarker use; drug targets were evaluated for the presence of evidence that genetic variations can impact CVD risk or drug response. We identified 134 programs (73 unique drug targets) and 147 clinical trials. Less than 1% (n&nbsp;=&nbsp;1/147) trials used a genomic biomarker prospectively for in-trial enrichment despite 32% (n&nbsp;=&nbsp;23/73) of the drug targets having evidence of genetic variations. Additionally, 46% (n&nbsp;=&nbsp;68/147) of the trials specified exploratory biomarker use. The results highlight an opportunity for more targeted CVD drug development by leveraging genomic biomarker knowledge