Clarifying the importance of CYP2C19 and PON1 in the mechanism of clopidogrel bioactivation and in vivo antiplatelet response

AimsIt is thought that clopidogrel bioactivation and antiplatelet response are related to cytochrome P450 2C19 (CYP2C19). However, a recent study challenged this notion by proposing CYP2C19 as wholly irrelevant, while identifying paraoxonase-1 (PON1) and its Q192R polymorphism as the major driver of clopidogrel bioactivation and efficacy. The aim of this study was to systematically elucidate the mechanism and relative contribution of PON1 in comparison to CYP2C19 to clopidogrel bioactivation and antiplatelet response.Methods and resultsFirst, the influence of CYP2C19 and PON1 polymorphisms and plasma paraoxonase activity on clopidogrel active metabolite (H4) levels and antiplatelet response was assessed in a cohort of healthy subjects (n = 21) after administration of a single 75 mg dose of clopidogrel. There was a remarkably good correlation between H4 AUC (0-8 h) and antiplatelet response (r2 = 0.78). Furthermore, CYP2C19 but not PON1 genotype was predictive of H4 levels and antiplatelet response. There was no correlation between plasma paraoxonase activity and H4 levels. Secondly, metabolic profiling of clopidogrel in vitro confirmed the role of CYP2C19 in bioactivating clopidogrel to H4. However, heterologous expression of PON1 in cell-based systems revealed that PON1 cannot generate H4, but mediates the formation of another thiol metabolite, termed Endo. Importantly, Endo plasma levels in humans are nearly 20-fold lower than H4 and was not associated with any antiplatelet response.ConclusionOur results demonstrate that PON1 does not mediate clopidogrel active metabolite formation or antiplatelet action, while CYP2C19 activity and genotype remains a predictor of clopidogrel pharmacokinetics and antiplatelet response. © 2012 The Author

Docetaxel plus cisplatin is effective for patients with metastatic breast cancer resistant to previous anthracycline treatment: a phase II clinical trial

BACKGROUND: Patients with metastatic breast cancer (MBC) are frequently exposed to high cumulative doses of anthracyclines and are at risk of resistance and cardiotoxicity. This phase II trial evaluated the efficacy and toxicity of docetaxel plus cisplatin, as salvage chemotherapy in patients with MBC resistant to prior anthracyclines. METHODS: Patients with MBC that had progressed after at least one prior chemotherapy regimen containing anthracyclines received docetaxel 75 mg/m(2 )followed by cisplatin 60 mg/m(2 )every 3 weeks for a maximum of 6 cycles or until disease progression. RESULTS: Between Jan 2000 and May 2002, 24 patients with tumors primary resistant and 15 with secondary resistant disease were accrued. All 39 patients were evaluable for safety and 36 for efficacy. The objective response rate was 31% (95% CI, 16–45%) with 3 complete responses. The median time to disease progression was 7 months, and the median overall survival was 23 months (median follow-up of 41 months). Neutropenia was the most frequently observed severe hematologic toxicity (39% of patients), whereas asthenia and nausea were the most common non-hematologic toxicities. No treatment-related death was observed. CONCLUSION: In conclusion, we found docetaxel plus cisplatin to be an active and safe chemotherapy regimen for patients with MBC resistant to anthracyclines

Is risk of central nervous system (CNS) relapse related to adjuvant taxane treatment in node-positive breast cancer? Results of the CNS substudy in the intergroup phase III BIG 02-98 trial

Background: Breast cancer central nervous system (CNS) metastases are an increasingly important problem because of high CNS relapse rates in patients treated with trastuzumab and/or taxanes. Patients and methods: We evaluated data from 2887 node-positive breast cancer patients randomised in the BIG 02-98 trial comparing anthracycline-based adjuvant chemotherapy (control arms) to anthracycline-docetaxel-based sequential or concurrent chemotherapy (experimental arms). After a median follow-up of 5 years, 403 patients had died and detailed information on CNS relapse was collected for these patients. Results: CNS relapse occurred in 4.0% of control patients and 3.7% of docetaxel-treated patients. CNS relapse occurred in 27% of deceased patients in both treatment groups. CNS relapse was usually accompanied by neurologic symptoms (90%), and 25% of patients with CNS relapse died without evidence of extra-CNS relapse. Only 20% of patients survived 1 year from the diagnosis of CNS relapse. Prognosis of CNS relapse was worse for patients with meningeal carcinomatosis when compared with brain metastases. Unexpected findings included a higher rate of positive cerebrospinal fluid cytology (8% versus 3%) and more frequent use of magnetic resonance imaging for diagnosis (47% versus 30%) in the docetaxel-treated patients. Conclusion: There is no evidence that adjuvant docetaxel treatment is associated with an increased frequency of CNS relaps

Clinical and genetic determinants of warfarin pharmacokinetics and pharmacodynamics during treatment initiation

Variable warfarin response during treatment initiation poses a significant challenge to providing optimal anticoagulation therapy. We investigated the determinants of initial warfarin response in a cohort of 167 patients. During the first nine days of treatment with pharmacogenetics-guided dosing, S-warfarin plasma levels and international normalized ratio were obtained to serve as inputs to a pharmacokinetic-pharmacodynamic (PK-PD) model. Individual PK (S-warfarin clearance) and PD (I max) parameter values were estimated. Regression analysis demonstrated that CYP2C9 genotype, kidney function, and gender were independent determinants of S-warfarin clearance. The values for I max were dependent on VKORC1 and CYP4F2 genotypes, vitamin K status (as measured by plasma concentrations of proteins induced by vitamin K absence, PIVKA-II) and weight. Importantly, indication for warfarin was a major independent determinant of I max during initiation, where PD sensitivity was greater in atrial fibrillation than venous thromboembolism. To demonstrate the utility of the global PK-PD model, we compared the predicted initial anticoagulation responses with previously established warfarin dosing algorithms. These insights and modeling approaches have application to personalized warfarin therapy. © 2011 Gong et al

The Role of TLR4 in the Paclitaxel Effects on Neuronal Growth In Vitro

Paclitaxel (Pac) is an antitumor agent that is widely used for treatment of solid cancers. While being effective as a chemotherapeutic agent, Pac in high doses is neurotoxic, specifically targeting sensory innervations. In view of these toxic effects associated with conventional chemotherapy, decreasing the dose of Pac has been recently suggested as an alternative approach, which might limit neurotoxicity and immunosuppression. However, it remains unclear if low doses of Pac retain its neurotoxic properties or might exhibit unusual effects on neuronal cells. The goal of this study was to analyze the concentration-dependent effect of Pac on isolated and cultured DRG neuronal cells from wild-type and TLR4 knockout mice. Three different morphological parameters were analyzed: the number of neurons which developed neurites, the number of neurites per cell and the total length of neurites per cell. Our data demonstrate that low concentrations of Pac (0.1 nM and 0.5 nM) do not influence the neuronal growth in cultures in both wild type and TLR4 knockout mice. Higher concentrations of Pac (1-100 nM) had a significant effect on DRG neurons from wild type mice, affecting the number of neurons which developed neurites, number of neurites per cell, and the length of neurites. In DRG from TLR4 knockout mice high concentrations of Pac showed a similar effect on the number of neurons which developed neurites and the length of neurites. At the same time, the number of neurites per cell, indicating the process of growth cone initiation, was not affected by high concentrations of Pac. Thus, our data showed that Pac in high concentrations has a significant damaging effect on axonal growth and that this effect is partially mediated through TLR4 pathways. Low doses of Pac are devoid of neuronal toxicity and thus can be safely used in a chemomodulation mode. © 2013 Ustinova et al

What lies beneath: exploring links between asylum policy and hate crime in the UK

This paper explores the link between increasing incidents of hate crime and the asylum policy of successive British governments with its central emphasis on deterrence. The constant problematisation of asylum seekers in the media and political discourse ensures that 'anti-immigrant' prejudice becomes mainstr earned as a common-sense response. The victims are not only the asylum seekers hoping for a better life but democratic society itself with its inherent values of pluralism and tolerance debased and destabilised

Quality of life and sexual function after high-dose or conventional chemotherapy for high-risk breast cancer

Three hundred and ninety women participated in the quality of life (QL) study of ACCOG1, a high-dose vs conventional adjuvant chemotherapy breast cancer trial, for patients with a high risk of relapse. Patients completed the European Organisation for Research and Treatment of Cancer QLQ-C30, questions on menopausal symptoms and the Sexual Activity Questionnaire. Pretreatment, 6,12, 24, 36, 48 and 60-month assessments were conducted. For the high dose group the median decrease in global QL at 6 months was significantly greater than in the conventional group. At 12 months, however, the median change had returned to 0 for both groups. Social functioning was also significantly lower in the high-dose group at 6 months, again returning to prebaseline levels for both groups after 12 months. The most persistent changes appear to be in the effect of treatment in both arms on sexual outcomes, reflected in problems with discomfort and pleasure. Both high-dose and conventional chemotherapy showed persisting negative effects on sexual health. This has not been previously reported as a long-term complication of high-dose chemotherapy. However, it did not have long-term affects on sexual habit, which appeared to return to pretreatment frequency and similar to that of conventional chemotherapy by about 12 months from treatment

Block sequential adriamycin CMF – optimal non-myeloablative chemotherapy for high risk adjuvant breast cancer?

After the publication of the 10-year survival data from Milan on the adjuvant use of the block sequential regimen consisting of four cycles of adriamycin followed by eight cycles of intravenous CMF, many centres adopted this as standard of care for high risk, multiple node-positive breast cancer. For this reason it was identified as the standard arm for the Anglo-Celtic adjuvant high-dose chemotherapy trial. This study reports on the experience of this regimen in 329 women with early breast cancer involving at least four axillary nodes, who were treated outside any adjuvant chemotherapy trial. At a median follow-up of 3 years, the overall 5-year disease-free survival is 61%, and the overall survival is 70%. These data confirm the efficacy of this regimen in non-trial patients, and, for the same high risk subgroup, indicate that this approach offers an outcome at least as good as that seen in the CALGB 9344 AC-Taxol arm, and the NCIC days 1 and 8 CEF

Protein kinase Cδ expression in breast cancer as measured by real-time PCR, western blotting and ELISA

The protein kinase C (PKC) family of genes encode serine/threonine kinases that regulate proliferation, apoptosis, cell survival and migration. Multiple isoforms of PKC have been described, one of which is PKCδ. Currently, it is unclear whether PKCδ is involved in promoting or inhibiting cancer formation/progression. The aim of this study was therefore to investigate the expression of PKCδ in human breast cancer and relate its levels to multiple parameters of tumour progression. Protein kinase Cδ expression at the mRNA level was measured using real-time PCR (n=208) and at protein level by both immunoblotting (n=94) and ELISA (n=98). Following immunoblotting, two proteins were identified, migrating with molecular masses of 78 and 160 kDa. The 78 kDa protein is likely to be the mature form of PKCδ but the identity of the 160 kDa form is unknown. Levels of both these proteins correlated weakly but significantly with PKCδ concentrations determined by ELISA (for the 78 kDa form, r=0.444, P<0.005, n=91 and for the 160 kDa form, r=0.237, P=0.023, n=91) and with PKCδ mRNA levels (for the 78 kDa form, r=0.351, P=0.001, n=94 and for the 160 kDa form, r=0.216, P=0.037, n=94). Protein kinase Cδ mRNA expression was significantly higher in oestrogen receptor (ER)-positive compared with ER-negative tumours (P=0.007, Mann–Whitney U-test). Increasing concentrations of PKCδ mRNA were associated with reduced overall patient survival (P=0.004). Our results are consistent with a role for PKCδ in breast cancer progression