Inherited and Acquired Determinants of Hepatic CYP3A Activity in Humans.

Human CYP3A enzymes (including CYP3A4 and CYP4A5) metabolize about 40% of all drugs and numerous other environmental and endogenous substances. CYP3A activity is highly variable within and between humans. As a consequence, therapy with standard doses often results in too low or too high blood and tissue concentrations resulting in therapeutic failure or dose-related adverse reactions. It is an unanswered question how much of the big interindividual variation in CYP3A activity is caused by genetic or by environmental factors. This question can be answered by the twin study approach. Using midazolam as CYP3A probe drug, we studied 43 monozygotic and 14 dizygotic twins and measured midazolam and its metabolite 1-OH-midazolam. In addition, endogenous biomarkers of CYP3A activity, 4ß-OH-cholesterol and 6ß-OH-cortisol, were analyzed. Additive genetic effects accounted for only 15% of the variation in midazolam AUC, whereas 48% was attributed to common environmental factors. In contrast, 73, 56, and 31% of 1-OH-midazolam, 4ß-OH-cholesterol and 6ß-OH-cortisol variation was due to genetic effects. There was a low phenotypic correlation between the four CYP3A biomarkers. Only between midazolam and its 1-OH-metabolite, and between midazolam and 6ß-OH-cortisol we found significant bivariate genetic correlations. Midazolam AUC differed depending on the CYP3A4∗22 variant (p = 0.001) whereas plasma 4ß-OH-cholesterol was significantly lower in homozygous carriers of CYP3A5∗3 (p = 0.02). Apparently, non-genomic factors played a dominant role in the inter-individual variation of the CYP3A probe drug midazolam. A small intra-individual pharmacokinetic variation after repeated administration of midazolam was rated earlier as indication of high heritability of CYP3A activity, but according to present data that could also largely be due to constant environmental factors and/or heritability of liver blood flow. The higher heritabilities of 4ß-OH-cholesterol and of 1-OH-midazolam may deserve further research on the underlying factors beyond CYP3A genes. Clinical Trial Registration: ClinicalTrials.gov: NCT01845194 and EUDRA-CT: 2008-006223-31.

The Circadian PER2 Enhancer Nobiletin Reverses the Deleterious Effects of Midazolam in Myocardial Ischemia and Reperfusion Injury.

BACKGROUND: Recently, we identified the circadian rhythm protein Period 2 (PER2) in robust cardioprotection from myocardial ischemia (MI). Based on findings that perioperative MI is the most common major cardiovascular complication and that anesthetics can alter the expression of PER2, we hypothesized that an anesthesia mediated downregulation of PER2 could be detrimental if myocardial ischemia and reperfusion (IR) would occur. METHODS AND RESULTS: We exposed mice to pentobarbital, fentanyl, ketamine, propofol, midazolam or isoflurane and determined cardiac Per2 mRNA levels. Unexpectedly, only midazolam treatment resulted in an immediate and significant downregulation of Per2 transcript levels. Subsequent studies in mice pretreated with midazolam using an in-situ mouse model for myocardial (IR)-injury revealed a significant and dramatic increase in infarct sizes or Troponin-I serum levels in the midazolam treated group when compared to controls. Using the recently identified flavonoid, nobiletin, as a PER2 enhancer completely abolished the deleterious effects of midazolam during myocardial IR-injury. Moreover, nobiletin treatment alone significantly reduced infarct sizes or Troponin I levels in wildtype but not in Per2-/- mice. Pharmacological studies on nobiletin like flavonoids revealed that only nobiletin and tangeritin, both found to enhance PER2, were cardioprotective in our murine model for myocardial IR-injury. CONCLUSION: We identified midazolam mediated downregulation of cardiac PER2 as an underlying mechanism for a deleterious effect of midazolam pretreatment in myocardial IR-injury. These findings highlight PER2 as a cardioprotective mechanism and suggest the PER2 enhancers nobiletin or tangeritin as a preventative therapy for myocardial IR-injury in the perioperative setting where midazolam pretreatment occurs frequently.

Low heritability in pharmacokinetics of talinolol: a pharmacogenetic twin study on the heritability of the pharmacokinetics of talinolol, a putative probe drug of MDR1 and other membrane transporters.

BACKGROUND: Efflux transporters like MDR1 and MRP2 may modulate the pharmacokinetics of about 50 % of all drugs. It is currently unknown how much of the variation in the activities of important drug membrane transporters like MDR1 or MRP2 is determined by genetic or by environmental factors. In this study we assessed the heritability of the pharmacokinetics of talinolol as a putative probe drug for MDR1 and possibly other membrane transporters. METHODS: Talinolol pharmacokinetics were investigated in a repeated dose study in 42 monozygotic and 13 same-sex dizygotic twin pairs. The oral clearance of talinolol was predefined as the primary parameter. Heritability was analyzed by structural equation modeling and by within- and between-subject variance and talinolol clearance was correlated with polymorphisms in MDR1, MRP2, BCRP, MDR5, OATP1B1, and OCT1. RESULTS: Talinolol clearance varied approximately ninefold in the studied sample of healthy volunteers. The correlation of clearances between siblings was not significantly different for the monozygotic and dizygotic pairs. All data analyses consistently showed that variation of talinolol pharmacokinetics was mainly determined by environmental effects. Structural equation modeling attributed 53.5 % of the variation of oral clearance to common environmental effects influencing both siblings to the same extent and 46.5 % to unique environmental effects randomly affecting individual subjects. Talinolol pharmacokinetics were significantly dependent on sex, body mass index, total protein consumption, and vegetable consumption. CONCLUSIONS: The twin study revealed that environmental factors explained much more of the variation in pharmacokinetics of talinolol than genetic factors. TRIAL REGISTRATION: European clinical trials database number: EUDRA-CT 2008-006223-31. Registered 26 September 2008. ClinicalTrials.gov number: NCT01845194 .

The dual pathway inhibitor rigosertib is effective in direct patient tumor xenografts of head and neck squamous cell carcinomas.

The dual pathway inhibitor rigosertib inhibits phosphoinositide 3-kinase (PI3K) pathway activation as well as polo-like kinase 1 (PLK1) activity across a broad spectrum of cancer cell lines. The importance of PIK3CA alterations in squamous cell carcinoma of the head and neck (HNSCC) has raised interest in exploring agents targeting PI3K, the product of PIK3CA. The genetic and molecular basis of rigosertib treatment response was investigated in a panel of 16 HNSCC cell lines, and direct patient tumor xenografts from eight patients with HNSCC [four HPV-serotype16 (HPV16)-positive]. HNSCC cell lines and xenografts were characterized by pathway enrichment gene expression analysis, exon sequencing, gene copy number, Western blotting, and immunohistochemistry (IHC). Rigosertib had potent antiproliferative effects on 11 of 16 HPV(-) HNSCC cell lines. Treatment sensitivity was confirmed in two cell lines using an orthotopic in vivo xenograft model. Growth reduction after rigosertib treatment was observed in three of eight HNSCC direct patient tumor lines. The responsive tumor lines carried a combination of a PI3KCA-activating event (amplification or mutation) and a p53-inactivating event (either HPV16- or mutation-mediated TP53 inactivation). In this study, we evaluated the in vitro and in vivo efficacy of rigosertib in both HPV(+) and HPV(-) HNSCCs, focusing on inhibition of the PI3K pathway. Although consistent inhibition of the PI3K pathway was not evident in HNSCC, we identified a combination of PI3K/TP53 events necessary, but not sufficient, for rigosertib sensitivity.

A patient tumor transplant model of squamous cell cancer identifies PI3K inhibitors as candidate therapeutics in defined molecular bins.

Targeted therapy development in head and neck squamous cell carcinoma (HNSCC) is challenging given the rarity of activating mutations. Additionally, HNSCC incidence is increasing related to human papillomavirus (HPV). We sought to develop an in vivo model derived from patients reflecting the evolving HNSCC epidemiologic landscape, and use it to identify new therapies. Primary and relapsed tumors from HNSCC patients, both HPV+ and HPV-, were implanted on mice, giving rise to 25 strains. Resulting xenografts were characterized by detecting key mutations, measuring protein expression by IHC and gene expression/pathway analysis by mRNA-sequencing. Drug efficacy studies were run with representative xenografts using the approved drug cetuximab as well as the new PI3K inhibitor PX-866. Tumors maintained their original morphology, genetic profiles and drug susceptibilities through serial passaging. The genetic makeup of these tumors was consistent with known frequencies of TP53, PI3KCA, NOTCH1 and NOTCH2 mutations. Because the EGFR inhibitor cetuximab is a standard HNSCC therapy, we tested its efficacy and observed a wide spectrum of efficacy. Cetuximab-resistant strains had higher PI3K/Akt pathway gene expression and protein activation than cetuximab-sensitive strains. The PI3K inhibitor PX-866 had anti-tumor efficacy in HNSCC models with PIK3CA alterations. Finally, PI3K inhibition was effective in two cases with NOTCH1 inactivating mutations. In summary, we have developed an HNSCC model covering its clinical spectrum whose major genetic alterations and susceptibility to anticancer agents represent contemporary HNSCC. This model enables to prospectively test therapeutic-oriented hypotheses leading to personalized medicine.

Hedgehog signaling alters reliance on EGF receptor signaling and mediates anti-EGFR therapeutic resistance in head and neck cancer.

The EGF receptor (EGFR)-directed monoclonal antibody cetuximab is the only targeted therapy approved for the treatment of squamous cell carcinoma of the head and neck (HNSCC) but is only effective in a minority of patients. Epithelial-to-mesenchymal transition (EMT) has been implicated as a drug resistance mechanism in multiple cancers, and the EGFR and Hedgehog pathways (HhP) are relevant to this process, but the interplay between the two pathways has not been defined in HNSCC. Here, we show that HNSCC cells that were naturally sensitive to EGFR inhibition over time developed increased expression of the HhP transcription factor GLI1 as they became resistant after long-term EGFR inhibitor exposure. This robustly correlated with an increase in vimentin expression. Conversely, the HhP negatively regulated an EGFR-dependent, EMT-like state in HNSCC cells, and pharmacologic or genetic inhibition of HhP signaling pushed cells further into an EGFR-dependent phenotype, increasing expression of ZEB1 and VIM. In vivo treatment with cetuximab resulted in tumor shrinkage in four of six HNSCC patient-derived xenografts; however, they eventually regrew. Cetuximab in combination with the HhP inhibitor IPI-926 eliminated tumors in two cases and significantly delayed regrowth in the other two cases. Expression of EMT genes TWIST and ZEB2 was increased in sensitive xenografts, suggesting a possible resistant mesenchymal population. In summary, we report that EGFR-dependent HNSCC cells can undergo both EGFR-dependent and -independent EMT and HhP signaling is a regulator in both processes. Cetuximab plus IPI-926 forces tumor cells into an EGFR-dependent state, delaying or completely blocking tumor recurrence.

C2 domain-containing phosphoprotein CDP138 regulates GLUT4 insertion into the plasma membrane.

The protein kinase B(ß) (Akt2) pathway is known to mediate insulin-stimulated glucose transport through increasing glucose transporter GLUT4 translocation from intracellular stores to the plasma membrane (PM). Combining quantitative phosphoproteomics with RNAi-based functional analyses, we show that a previously uncharacterized 138 kDa C2 domain-containing phosphoprotein (CDP138) is a substrate for Akt2, and is required for optimal insulin-stimulated glucose transport, GLUT4 translocation, and fusion of GLUT4 vesicles with the PM in live adipocytes. The purified C2 domain is capable of binding Ca(2+) and lipid membranes. CDP138 mutants lacking the Ca(2+)-binding sites in the C2 domain or Akt2 phosphorylation site S197 inhibit insulin-stimulated GLUT4 insertion into the PM, a rate-limiting step of GLUT4 translocation. Interestingly, CDP138 is dynamically associated with the PM and GLUT4-containing vesicles in response to insulin stimulation. Together, these results suggest that CDP138 is a key molecule linking the Akt2 pathway to the regulation of GLUT4 vesicle-PM fusion.

Carvedilol pharmacokinetics and pharmacodynamics in relation to CYP2D6 and ADRB pharmacogenetics.

AIMS: Carvedilol is an effective treatment in hypertension and chronic heart failure. The medical impact of polymorphisms in CYP2D6 and in the ß-adrenergic receptors ADRB1 and ADRB2 on the pharmacokinetics and pharmacodynamics of carvedilol is controversial. METHODS: After carvedilol 25 mg was administered to 110 volunteers, concentrations were enantioselectively quantified and effects on resting and exercise-induced heart rate and blood pressure were analyzed using population pharmacokinetic, pharmacodynamic and pharmacogenetic modeling. RESULTS: There were significant CYP2D6 allele-specific differences in carvedilol pharmacokinetics, but the CYP2D6 genotype had no effect on heart rate, blood pressure or adverse effects. ADRB1 Gly49 was associated with higher baseline heart rates and with greater carvedilol effects on exercise heart rates. Carriers of ADRB2 Gln27 had greater reduction in resting blood pressure by carvedilol compared with Glu27. CONCLUSION: Carvedilol is a drug where CYP2D6-related pharmacokinetic variation is apparently not carried forward into pharmacodynamic variation. Although current knowledge does not allow utilizing ADRB1 and ADRB2 genotypes for clinical treatment decisions, our data should stimulate further research on the impact of these genotypes in health and disease.

Amelogenin-based sex identification as a strategy to control the identity of DNA samples in genetic association studies.

Misassignment between DNA samples and clinical or epidemiological data may compromise the results of genetic association studies. Genotyping in replicates or controlling for Hardy-Weinberg equilibrium cannot identify misassignments caused by sample mix-ups. DNA-based sex identification (sex typing) is currently the best strategy to identify mix-ups. Here we review the available methods and present validated protocols for sex typing. The protocols are based on single-nucleotide differences between the human amelogenin genes, AMELX and AMELY, and are optimized for real-time PCR (TaqMan), primer-extension (SNaPshot) and PCR-RFLP genotyping platforms. In addition, we review the limitations of the sex-typing strategy, including a limited ability to identify single sample mix-ups, the dependence of the power of this approach on the sex distribution in the study population, and rare genetic conditions. Alternative strategies for mix-up identification and possible consequences of mix-up identification are also discussed.

Recent in vitro findings of negative inotropy of pantoprazole did not translate into clinically relevant effects on left ventricular function in healthy volunteers.

PURPOSE: Reports on cardiac problems with oral proton pump inhibitors have caused extensive safety reviews by the US Food and Drug Administration. We provide additional data on acute cardiac effects of an intravenous application. METHODS: Echocardiography was performed in 18 healthy volunteers after administration of a common high-dose regimen of pantoprazole (80 mg i.v. bolus followed by 8 mg/h for 1 h) or placebo. DESIGN: The design included a randomized, double-blind, placebo-controlled cross-over trial. RESULTS: Ejection fraction (%, mean +/- SE) in the treatment group (placebo group) was 60.7 +/- 1.1 (61.2 +/- 1.7) at baseline, and 62.6 +/- 1.1 (62.1 +/- 1.9), 64.7 +/- 1.6 (63.5 +/- 1.3), 62.6 +/- 1.6 (61.0 +/- 1.6) and 63.0 +/- 1.4 (61.8 +/- 1.5) at 7.5, 15, 30 and 60 min after bolus application, respectively (p = n.s.). Similarly, no significant changes were found for cardiac output, cardiac index, blood pressure and heart rate. In contrast, gastric pH that was used as a treatment control was significantly increased 60 min after the application of pantoprazole as compared to baseline and to placebo. CONCLUSIONS: Pantoprazole as injection is safe in healthy subjects with respect to cardiac contractile function. However, in view of recent reports of negative inotropy of the drug, further studies in heart failure patients are required.

Bioinformatic and functional analysis of TGFBR1 polymorphisms.

OBJECTIVES: The transforming growth factor-beta (TGFB) pathway has substantial impact on cellular functions, cell proliferation, and apoptosis. We used bioinformatics, gene expression, and cell biological assays to evaluate the functionality of frequent inherited germline polymorphisms in the TGFB receptor 1 (TGFBR1). METHODS: In an exploratory (n=55) and confirmatory (n=106) study, we analyzed the TGFB1 pathway after incubation with TGFbeta1 ligand and after exposure to X-rays in peripheral blood human mononuclear cells. Expression of TGFB pathway genes was assessed by real-time PCR, and cellular viability was analyzed by flow cytometry. A total of six polymorphisms including the deletion variant (*6A) were identified to tag currently known common genetic variations in TGFBR1 and were analyzed in relation to the phenotypes. RESULTS: In accordance with a negative feedback mechanism, incubations with the ligand TGFbeta1 was followed by up-regulation of the intracellular SMAD7 and down-regulation of the SMAD3 mRNA molecules. The TGFBR1*6A deletion variant attenuated the suppression of SMAD3 in response to TGFbeta1 (P=0.02, in both studies). Moreover, cells harboring *6A were more sensitive toward cytotoxic effects of irradiation (P=0.001 after adjustment for age and sex). Cells were particularly prone toward radiation toxicity when carrying, in addition to *6A, the variant allele of rs11568785, which exhibits a strong genetic selection signature. CONCLUSION: The *6A deletion and the linked rs11568785 polymorphisms seem to attenuate TGFB signaling. This should be considered not only for clinical-epidemiological studies on cancer susceptibility but may also be relevant for side effects from drugs or radiotherapy.

Hydrochlorothiazide efficacy and polymorphisms in ACE, ADD1 and GNB3 in healthy, male volunteers.

OBJECTIVE: The antihypertensive effect of thiazide diuretics has recently been associated with genetic variation in the angiotensin I-converting enzyme (ACE), alpha-adducin (ADD1) and the G protein subunit beta3 (GNB3). Analysis of short-term diuretic effects may provide insight into the mechanisms behind these findings. METHODS: A total of 103 male volunteers took 25 and 100 mg hydrochlorothiazide (HCT) after a placebo day, each. We measured volume, sodium, chloride, potassium, calcium excretion, blood pressure and heart rate. RESULTS: Excretion and cardiovascular parameters were highly constant between the 2 placebo days. The resting heart rate was 2-3 beats/minute (bpm) higher per ACE insertion allele on all 4 study days. The HCT-induced excretion of sodium, chloride and volume was independent of the genotypes. The additional potassium excretion induced by 100 mg HCT was 44+/-21, 33+/-27 and 16+/-26 mmol (mean+/-SD, p<0.001) in ACE II, ID and DD carriers and the same trend was observed after 25 mg HCT. As a second finding, the 100 mg HCT-induced calcium retention was 0.2+/-1.2, 0.7+/-0.8 and 1.7+/-2.1 mmol in ADD1 Gly/Gly, Gly/Trp and Trp/Trp carriers (p=0.002) and the same trend existed after 25 mg HCT. CONCLUSION: The effects of genetic polymorphisms were stronger with the higher diuretic dose. ACE insertion allele carriers appeared to be more prone to hypokalaemia than deletion allele carriers. ADD1 Trp460 carriers may especially benefit from the calcium-sparing effect of thiazides. Both associations should be further studied in long-term treatment with thiazide diuretics.

Anxiety- and novelty seeking-related personality traits and serotonin transporter gene polymorphisms.

The affection of human personality by the promoter and the intron 2 polymorphism in the serotonin transporter gene (SERT) is inconsistently reported. We aimed to clarify this situation by gender-specific haplotype-phenotype association. 98 women and 97 men completed the personality inventories NEO-PI-R and TPQ. The subjects were genotyped for the two SERT polymorphisms and the haplotypes were calculated. The short (S) and long (L) promoter alleles and the 12 and 10 repeat intron 2 alleles formed the haplotypes S 12, S 10, L 12 and L 10. In men, scores in the anxiety-related dimensions were higher in S 12 than in L 12 carriers. Opposite in direction, scores tended to be lower in S 10 than in L 10 carriers. In the novelty seeking-related dimensions, scores were higher in S 10 than in S 12 carriers. No association was observed in women. In conclusion, anxiety- and novelty seeking-related personality dimensions are differentially associated with different SERT haplotypes; the consistent restriction to men suggests common androgen regulation. Opposite trends with haplotypes including the same promoter alleles suggest contribution of group stratification to earlier inconsistent findings and call to further differentiate the molecular function and clinical implications of the SERT promoter polymorphism.