Activation of the cell membrane angiotensin AT2 receptors in human leiomyosarcoma cells induces differentiation and apoptosis by a PPARγ - dependent mechanism.

Angiotensin II (Ang II), the main effector peptide of the renin-angiotensin system (RAS), acting on AT1 and AT2 receptors participates in the regulation of proliferation, differentiation and apoptosis in tumour cells. The peroxisome-proliferator activated receptor γ (PPARγ) and its ligands exert anti-tumour effects in various human cancer cell lines. The present study investigates the effects initiated by AT1- and AT2 receptor stimulation in SK-UT-1 cells, a human leiomyosarcoma cell line, and clarifies the role of the PPARγ in the AT2 receptor-induced differentiation and apoptosis.Selective stimulation of AT1- and AT2 receptors was achieved by incubation of the cells with Ang II (10-6 M) in the presence of the selective AT2 receptor antagonist, PD 123177 (10-6 M) and the AT1 receptor antagonist, losartan (10-5 M), respectively, the selective PPARγ antagonist, GW 9662, was used at concentration 10-6 M. The expression of smooth muscle cell differentiation markers, SM22α and calponin, was analysed at RNA- and protein levels using RT PCR and Western blot, which was also used to quantify Bcl-2-, Bax- and cleaved caspase-3 proteins. The translocation of the AT2-receptor interacting protein 1 (ATIP1) to the nuclei was studied by Western blot and immunofluorescence staining. The mitochondrial status and the metabolic activity in response to AT1- and AT2 receptor activation were assessed by the quantification of 99mTc - sestamibi and 2´-deoxy-2´-[18F]fluoro-D-glucose uptake.AT1 receptor stimulation did not exert any profound effects in quiescent SK-UT-1 cells. The effects induced by Ang II acting on AT2 receptors were time-dependent. A short, 3 - 6 h lasting stimulation promotes differentiation, i.e increases in the mRNA- and protein levels of SM22α and calponin, whereas a sustained stimulation for 48 h activates the intrinsic apoptotic pathway, as evidenced by reduced cell numbers, down-regulation of the anti-apoptotic Bcl-2 protein and increased levels of the Bax protein and cleaved caspase-3. The effects were reversed by the PPARγ antagonist, GW 9662, clearly implying a PPARγ-dependent mechanism. Our results also demonstrate a co-localisation of the AT2-receptor interacting protein, ATIP1, and the PPARγ in nuclei of SK-UT-1 cells and an accumulation of ATIP1 in the nuclear fraction in response to AT2 receptor stimulation. The regulation of the differentiation and apoptosis via the AT2 receptor favours an important functional role of this receptor in quiescent, slow-cycling SK-UT-1 cells and provides the rationale for the use of AT1 receptor antagonists for the treatment of human leiomyosarcomas.

Epigenetics in Drug Response.

Hereditary genetic variation has been identified to contribute significantly to drug response. More recently, there is increasing evidence that individual phenotypic differences may also result from epigenetic alterations such as histone-acetylation or DNA-methylation. Moreover, interactions with noncoding RNAs contribute to protein expression and may modulate drug action. Currently, intriguing developments of novel therapeutic approaches through epigenetic drugs are emerging. The overall complexity of epigenetics in drug action, however, is so far only little understood.

Pharmacogenomic or -epigenomic biomarkers in drug treatment: Two sides of the same medal?

Interindividual differences in expression of ADME genes are controlled by both genetic and epigenetic factors. Much emphasis has been made to describe the genetic influence, whereas the epigenetic part is not fully understood. Currently, we utilize mainly genetic biomarkers for optimization of drug therapy, although many rare genetic variants are not taken into consideration. Now, also epigenomic biomarkers are at hand and together genetic and epigenetic biomarkers can indeed improve the predictability of drug treatment.

Pharmacological treatment of pain: future trends and novel insights.

The pharmacological treatment of chronic pain is generally hampered by a limited clinical outcome. Hence, there is a strong need for new therapeutic concepts considering the identification of novel targets and related drugs, but also optimization of established therapeutic regimes through individualization. In this issue, focused on "Pain," we discuss some of the recent new concepts in pain treatment, understanding of pain heterogeneity, and subsequent optimization of analgesic treatment, but also novel insights into interactions of nonopioids.

Effects of CYP2B6 genetic polymorphisms in patients receiving cyclophosphamide combination chemotherapy for breast cancer.

PURPOSE: The purpose of this study was to measure the frequency of three CYP2B6 [CYP2B6*4 (rs2279343), CYP2B6*5 (rs3211371) and CYP2B6*9 (rs3745274)] alleles in patients with breast cancer receiving cyclophosphamide (CP) therapy and test whether these variants are predictors of CP-associated toxicity and efficacy. METHODS: A total of 145 female breast cancer patients admitted to the American University of Beirut Medical Center for breast cancer-related therapy were included. Chart review was performed for collection of toxicity data. A time-to-event analysis was performed with a subset of 38 patients. RESULTS: The minor allele frequencies of CYP2B6*9, CYP2B6*4 and CYP2B6*5 were 0.27, 0.29 and 0.07, respectively. CYP2B6 *5/*6, *6/*9 or *6/*6 haplotypes were associated with a significantly shorter time to recurrence of the disease. There were no significant associations with myelo-toxicity. CONCLUSIONS: This is the first report on the pharmacogenetic profile of patients with breast cancer and the therapeutic and myelo-toxic behavior of CP in women from an Arab Middle Eastern country. Our results show that genotyping for these CYP2B6 alleles does not help in personalizing therapy from a toxicity perspective, and the association of shorter survival in these subjects with homozygous variants is interesting yet insufficient to justify routine genotyping prior to therapy, or to consider using a higher CP dose. Larger future studies or meta-analyses will be needed to further clarify the potential implication of these genetic polymorphisms.

Functional gene variants of CYP3A4.

Cytochrome P450 3A4 (CYP3A4) is involved in the metabolism of more drugs in clinical use than any other foreign compound-metabolizing enzyme in humans. Recently, increasing evidence has been found showing that variants in the CYP3A4 gene have functional significance and--in rare cases--lead to loss of activity, implying tremendous consequences for patients. This review article highlights the functional consequences of all CYP3A4 variants recognized by the Human Cytochrome P450 (CYP) Allele Nomenclature Database.

Progress in pharmacogenomics: bridging the gap from research to practice.

Genetic information is increasingly used to optimize clinical treatment of patients, but obstacles remain to practical implementation as well as challenges to our understanding of genetic variation in drug response. These areas that particularly require research attention include gene-environment interactions, the consequences of genetic variation, and the impact of epigenetics on gene expression and function. In this issue of Clinical Pharmacology & Therapeutics focused on pharmacogenetics, we discuss some of the recent advances in understanding from a variety of viewpoints.

Identification and characterization of a defective CYP3A4 genotype in a kidney transplant patient with severely diminished tacrolimus clearance.

Cytochrome P450 3A4 (CYP3A4) is a major drug-metabolizing enzyme that is widely investigated. So far, no homozygous inactive variant has been described. We report on a 19-year-old kidney transplant patient suffering from Alport syndrome, who experienced unexpected high tacrolimus plasma trough levels during immunosuppressant therapy. Because nonadherence, liver failure, or drug-drug interactions could be excluded, we hypothesized a diminished metabolism of the drug caused by mutations in the main detoxification enzyme, CYP3A4. Exome sequencing revealed a novel single-nucleotide polymorphism (c.802C>T) resulting in a premature stop codon in CYP3A4 exon 5. Accordingly, no CYP3A4 protein could be detected in kidney biopsy tissue, and there was lack of expression in HepG2 cells transiently transfected with the mutated CYP3A4. In addition, the patient harbored inactive CYP3A5*3, resulting in loss of function of the entire CYP3A locus, explaining the deteriorated tacrolimus clearance. This is, to our knowledge, the first case of a complete failure of CYP3A4 in humans.

A phase I pharmacokinetic study of matuzumab in combination with paclitaxel in patients with EGFR-expressing advanced non-small cell lung cancer.

Matuzumab is a humanized IgG1 EGFR monoclonal antibody. This phase I study investigated the tolerability, safety and pharmacokinetics (PK) of matuzumab in combination with paclitaxel in patients with EGFR-expressing advanced non-small cell lung cancer (NSCLC). Six dose levels/schedules of matuzumab were explored in combination with paclitaxel. Dose was escalated from 100 mg to 1,600 mg on a modified Fibonacci scheme according to the incidence of dose-limiting toxicity (DLT) over the first two cycles. DLT was assessed in patients who completed the first two treatment cycles or who stopped treatment because of a DLT during those cycles. Patients with non-progressive disease could then continue to receive study treatment for up to 6 months. The safety population comprised 44 patients, with DLT evaluable in 33. The maximum tolerated dose was not reached, with only one DLT reported at the 1,600 mg 3-weekly dose level. The most frequent grade 3/4 adverse events across all cycles were dyspnea (23 %) and neutropenia (11 %). Matuzumab exhibited non-linear PK, with accumulation after escalation and repeated dosing. Tumor growth control was seen in 15/44 (34 %) patients, including 5/9 (56 %) at the 800 mg weekly dose level. Matuzumab combined with paclitaxel was generally well tolerated in patients with advanced NSCLC. There was some evidence of anticancer activity in relation to the matuzumab 800 mg weekly dose.

Elimination half-life of anti-Müllerian hormone.

CONTEXT: Anti-Müllerian hormone (AMH) is a glycoprotein that is secreted by the granulosa cells in the human ovary. In the postpubertal female, circulating AMH reflects the number of follicles within the ovary. It is mandatory to know the serum elimination half-life (t(1/2)) of AMH to study in vivo short-term changes of the hormone. OBJECTIVE: Our objective was to determine the kinetics of decay of AMH in the human female. PATIENTS, DESIGN, AND SETTING: Premenopausal women undergoing total abdominal hysterectomy plus bilateral salpingo-oophorectomy participated in this cohort study (n = 21) at an academic tertiary referral center. INTERVENTIONS: Serum samples were obtained immediately before surgery and in 12-h intervals thereafter for 8 d. MAIN OUTCOME MEASURE: AMH elimination was calculated, applying a one-compartment model with first-order kinetics. RESULTS: Mean preoperative AMH levels were 0.67 ng/ml (range, 0.1-1.78 ng/ml) and dropped to 0.08 ng/ml within 84 h after surgery. The AMH decay followed first-order kinetics. The mean terminal t(1/2) of AMH was calculated as 27.6 ± 0.8 h. CONCLUSION: AMH elimination reaches approximately 84% after 3 d, approximately 91% after 4 d, approximately 95% after 5 d, and can be considered complete after 8 d.

Impact of ABCC2 haplotypes on transcriptional and posttranscriptional gene regulation and function.

ABCC2 (MRP2) is an important export pump, expressed at tissue barriers. The genetic variants -24C>T, 1249G>A and 3972C>T are leading to inter-individual differences of bioavailability of various endogenous and exogenous compounds. Considering ABCC2 haplotypes, we investigated DNA-protein binding properties, mRNA secondary structure, mRNA stability, protein expression and transport activity in various cell lines and analyzed the bioavailability of talinolol in 24 healthy Caucasian volunteers; -24C>T had no clear influence on DNA-protein binding and the mRNA stability did not differ significantly. In transfected HEK293T/17 cells, haplotypes H9 (CGT), H10 (TGC) and H12 (TGT) had significantly lower protein expression, whereas H2 (CAC) exhibited significantly increased protein expression compared to the wild type (H1, CGC): 32.7 ± 8.8, 73.1 ± 6.3; 44.0 ± 15.5 and 115.2 ± 8.2%, respectively. This corresponded with efflux rates of the fluorescent dye glutathione-methylfluorescein in vitro and by trend with talinolol bioavailability in vivo. In conclusion our results show a haplotype-dependent influence on transport capacity of ABCC2, which seems to be mainly based on posttranscriptional modification of protein expression rather than transport rates.

Influence of CYP3A4, CYP3A5, and ABCB1 genotype and expression on budesonide pharmacokinetics: a possible role of intestinal CYP3A4 expression.

Budesonide treatment of chronic inflammatory bowel disease commonly leads to non-response or adverse reactions, possibly because of alterations in efflux transport mediated by the ABCB1 gene product P-glycoprotein or metabolism by CYP3A isoenzymes. Two groups, each consisting of nine healthy volunteers, one with the CYP3A5(*)1/(*)3 genotype (expressors) and the other with the CYP3A5(*)3/(*)3 genotype (non-expressors), were given a single oral dose of 9 mg budesonide. Plasma and urine concentrations of budesonide and its major metabolites were determined using liquid chromatography-tandem mass spectrometry. Subsequently, rectosigmoidal biopsies were taken for analysis of messenger RNA (mRNA) expression. Budesonide pharmacokinetics did not differ between genotype groups. However, intestinal CYP3A4 expression was shown to correlate directly with partial metabolic clearances of 16-hydroxy-prednisolone (r(2) = 0.30; P = 0.010) and 6-hydroxy-budesonide (r(2) = 0.25; P = 0.016), but inversely with budesonide AUC(0-24 h) (r(2) = 0.18; P = 0.040). Interestingly, a strong correlation was found between CYP3A5 and ABCB1 expression in CYP3A5 expressors (r(2) = 0.79; P = 0.001). This study suggests that intestinal CYP3A4 expression has an impact on budesonide pharmacokinetics. Moreover, CYP3A5 and ABCB1 expression appears to be coregulated.

A clinical trial on absorption and N-acetylation of oral and rectal mesalazine.

BACKGROUND: Mesalazine (5-ASA) is a standard treatment for ulcerative colitis. Extent of absorption and N-acetylation determine systemic exposure to 5-ASA, and are thereby relevant for the safety of the treatment. The aim of the study was to compare absorption and N-acetylation of 5-ASA following rectal or oral drug administration. Healthy subjects were compared to patients with ulcerative colitis to evaluate the impact of chronic inflammation of colorectal mucosa on disposition of 5-ASA. MATERIALS AND METHODS: First, 12 healthy adults were randomized to receive 2 g of 5-ASA by each of four different formulations: oral delayed release granules, 30 mL enema, 60 mL rectal foam, and 120 mL rectal foam. Second, 12 patients with active ulcerative colitis received 60 mL rectal foam. Pharmacokinetic analysis was performed by determination of 5-ASA and its acetylated, pharmacologically inactive metabolite (Ac-5-ASA) in plasma and urine. RESULTS: First, systemic exposure to 5-ASA was markedly lower after rectal drug administration as compared to oral dosing (P < 0.001; e.g. median relative bioavailability of 60 mL rectal foam: 36%). Second, N-acetylation of rectal 5-ASA was lower in patients than in healthy subjects [area under the curve (AUC) ratio Ac-5-ASA/5-ASA: 1.6 +/- 0.5 vs. 2.3 +/- 0.4, mean +/- SD, P < 0.01]. High peak plasma concentrations of 5-ASA were correlated with high microscopic disease activity (r = 0.67, P < 0.05). CONCLUSIONS: Rectal delivery of 5-ASA results in low systemic drug exposure with potentially reduced toxicity in comparison with oral drug administration. Chronic inflammation of colorectal mucosa might be a relevant source of variability in pharmacokinetics of 5-ASA.

Influence of polymorphisms of ABCB1 and ABCC2 on mRNA and protein expression in normal and cancerous kidney cortex.

There is increasing evidence that polymorphisms of the adenosine 5' triphosphate membrane transporters ABCB1 (P-glycoprotein, MDR1) may affect expression and function, whereas less information is available about the impact of ABCC2 (multidrug resistance-associated protein (MRP2)) single-nucleotide polymorphisms . Particularly, their role in human kidney for drug elimination and in the etiology of renal cell carcinoma is poorly understood. ABCB1 and ABCC2 mRNA and protein expression levels were determined by real-time polymerase chain reaction or immunohistochemistry in kidney cancer and adjacent unaffected cortex tissue of 82 nephrectomized renal cell cancer (RCC) patients (63 clear-cell RCC (CCRCC), 19 non-CCRCC). The DNA of all patients was genotyped for ABCB1 -2352G>A, -692T>C, 2677G>T/A (Ala893Ser/Thr), and 3435C>T, and ABCC2 -24C>T, 1249G>A (Val417Ile) and 3972C>T. ABCB1 and ABCC2 were less expressed in CCRCC than in normal cortex on mRNA as well as on protein level. Although the overall genotype frequency distribution did not differ between the patients and a matched control group, ABCB1 2677T/A and 3435T genotypes were associated with higher (P=0.02 and P=0.04) and ABCC2 -24 T with lower mRNA levels in normal tissues (0.03). The expression of ABCB1 and ABCC2 was not related to genetic variants in RCC tissue. In a reporter gene assay in HepG2 cells, the ABCC2 -24T construct showed an 18.7% reduced activity (P=0.003). In conclusion, ABCB1 and ABCC2 genotypes modulate the expression in the unaffected renal cortex of RCC patients, possibly contributing to inter-individual differences in drug and xenobiotics elimination. Their role in RCC cancer susceptibility or chemotherapy resistance needs further elucidation.

Clozapine-induced agranulocytosis in schizophrenic Caucasians: confirming clues for associations with human leukocyte class I and II antigens.

Clozapine-induced agranulocytosis (CA) is still among the least understood adverse drug reactions in psychopharmacology. In particular, its genetic background is far from being clarified. Within the framework of a case-control study, we performed human leukocyte antigen (HLA) genotyping and haplotype analyses in 42 non-Jewish Caucasian schizophrenic patients (N=42) suffering from CA and 75 non-Jewish Caucasian schizophrenic patients treated with clozapine without developing CA. While controlling for age (P<0.0001) and sex (P=0.835), testing of the alleles from both HLA-loci resulted in borderline results for Cw2 (P=0.085, odds ratio (OR)=0.36, 95% confidence interval (CI): 0.08-1.23), Cw7 (P=0.058, OR=2.0, 95% CI: 0.87-4.63) and DRB5*0201 (P=0.005, adjusted OR=22.15). For haplotype analysis, we obtained significant association results with CA for the two-locus haplotypes HLA-Cw-B (P=0.022) and HLA-DRB5-DRB4 (P=0.050), and for the three-locus haplotype HLA-Cw-B-DRB5 (P=0.030). The complex nature of CA implies that many genes might play a role, but currently, only HLA associations with CA are identified as clinically relevant.

CYP3A5 genotype markedly influences the pharmacokinetics of tacrolimus and sirolimus in kidney transplant recipients.

It is currently not clear whether the concentration-time curves of the immunosuppressants differ with respect to the CYP3A5, MDR1, or MRP2 genotype in dose-adapted stable kidney transplant patients. Dose/trough concentration ratios were obtained in 134 tacrolimus and 20 sirolimus-treated patients, and plasma concentration-time profiles were obtained from 16 (tacrolimus) and 10 (sirolimus) patients. Genotyping was carried out for CYP3A5 6986A>G; ABCB1 2677G>T/A, 3435C>T and ABCC2 -24C>T; 1249G>A; 3972C>T. Dose/trough concentration ratios were 0.67+/-0.3 and 1.36+/-0.73 x 10(3) l (P<0.00001) for tacrolimus and 0.42+/-0.17 and 0.84+/-0.46 x 10(3) l (P=0.18) for sirolimus in CYP3A5 non-expressors and expressors. The unadjusted tacrolimus area under curve (AUC)(0-12) was 106.8+/-17.5 ng/ml x h compared with 133.3+/-42.2 ng/ml x h (P=0.37) without affecting serum creatinine. Mean unadjusted AUC(0-24) of sirolimus did not differ significantly either. Therefore, CYP3A5 expressor status and not transporter variants is a main determinant of oral clearance, particularly for tacrolimus. Dose adaptation according to trough levels, however, appears to be sufficient to maintain similar concentration-time profiles.

Genotype and phenotype relationship in drug metabolism.

Pharmacogenetics, one of the fields of clinical pharmacology, studies how genetic factors influence drug response. If hereditary traits are taken into account appropriately before starting drug treatment, the type of drug and its dosage can be tailored to the individual patient's needs. Today, the relationships between dosage requirements and genetic variations in drug-metabolizing enzymes such as cytochrome P450 (CYP) 2D6, CYP2C9, and CYP2C19 or in drug transporters such as p-glycoprotein (ABCB1) and OATP-C (SLC21A6) are substantiated best. A standard dose will bring about more adverse effects than usual if enzymatic activity is lacking or feeble. Sometimes, however, therapeutic response might be better because of higher concentrations: proton pump inhibitors for eradication of Helicobacter pylori are more efficacious in carriers of a deficient CYP2C19 variant. In some cases, genetic tests can help distinguish between responders and nonresponders of a specific drug treatment, and genotype-based dosage is possible.

No benefit of 3,4-diaminopyridine in essential tremor: a placebo-controlled crossover study.

3,4-Diaminopyridine (3,4-DAP) is a potassium channel blocker that has recently demonstrated an antioscillatory effect in humans by significantly reducing downbeat nystagmus. Based on the presumed role of intrinsic oscillations in the pathophysiology of essential tremor (ET), the authors conducted a double-blind, placebo-controlled crossover study assessing the antitremor effect of a single dose of 3,4-DAP in 19 patients with ET. They did not find any significant change in tremor severity as measured by clinical ratings or accelerometry.