A bypass mechanism of abiraterone-resistant prostate cancer: Accumulating CYP17A1 substrates activate androgen receptor signaling

Background: Intratumoral steroidogenesis and its potential relevance in castration‐ resistant prostate cancer (CRPC) and in cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17A1)‐inhibitor treated hormone‐naïve and patients with CRPC are not well established. In this study, we tested if substrates for de novo steroidogenesis accumulating during CYP17A1 inhibition may drive cell growth in relevant preclinical models. Methods: PCa cell lines and their respective CRPC sublines were used to model CRPC in vitro. Precursor steroids pregnenolone (Preg) and progesterone (Prog) served as substrate for de novo steroid synthesis. TAK700 (orteronel), abiraterone, and small interfering RNA (siRNA) against CYP17A1 were used to block CYP17A1 enzyme activity. The antiandrogen RD162 was used to assess androgen receptor (AR) involvement. Cell growth was measured by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. AR‐ target gene expression was quantified by reverse transcription polymerase chain reaction (RT‐PCR). Nuclear import studies using cells with green fluorescent protein (GFP)‐tagged AR were performed to assess the potential of precursor steroids to directly activate AR. Results: Preg and Prog stimulated cell proliferation and AR target gene expression in VCaP, DuCaP, LNCaP, and their respective CRPC sublines. The antiandrogen RD162, but not CYP17A1 inhibition with TAK700, abiraterone or siRNA, was able to block Preg‐ and Prog‐induced proliferation. In contrast to TAK700, abiraterone also affected dihydrotestosterone‐induced cell growth, indicating direct AR binding. Furthermore, Prog‐induced AR translocation was not affected by treatment with TAK700 or abiraterone, while it was effectively blocked by the AR antagonist enzalutamide, further demonstrating the direct AR activation by Prog. Conclusion: Activation of the AR by clinically relevant levels of Preg and Prog accumulating in abiraterone‐treated patients may act as a driver for CRPC. These data provide a scientific rationale for combining CYP17A1 inhibitors with antiandrogens, particularly in patients with overexpressed or mutated‐AR

Efficacy, safety and tolerability of 3 day azithromycin versus 10 day co-amoxiclav in the treatment of children with acute lower respiratory tract infections

To compare the efficacy, safety and tolerability of a 3 day course of azithromycin with a 10 day course of co-amoxiclav in the treatment of children with acute lower respiratory tract infection (LRTI), 118 patients with community-acquired LRTI were included in a multicentre randomized double-blind, double-dummy study. The diagnosis of LRTI was based on the presence of respiratory signs and symptoms in combination with consolidation on a chest radiograph or clinical evidence of LRTI. Patients received oral azithromycin suspension (10 mg/kg/24 h) or placebo in one dose for 3 days and co-amoxiclav (45/11.25 mg/kg/24 h) or placebo in three doses for 10 days. Of 110 eligible patients, 56 and 54 patients, respectively, were treated with azithromycin or co-amoxiclav. The percentage of patients cured or clinically improved at days 10-13 (primary endpoint) was 91% for azithromycin and 87% for co-amoxiclav. This difference of 4% (90% confidence interval: -6%, +14%) was not statistically significant (P= 0.55). Significantly (P = 0.01) more related adverse events were found in the co-amoxiclav group. This was largely due to a higher percentage (43% versus 19%) of gastrointestinal complaints. A 3 day course of azithromycin (three doses) is as effective in the treatment of LRTI in children as a 10 day course of co-amoxiclav (30 doses). The azithromycin group had fewer adverse events. We conclude that azithromycin is an effective, safe and well-tolerated drug in the treatment of children with LRTI. An additional advantage is the easy administration and short duration of therapy

Heparin immobilization reduces thrombogenicity of small-caliber expanded polytetrafluoroethylene grafts

ObjectiveThe patency of small-diameter expanded polytetrafluoroethylene (ePTFE) grafts for vascular reconstruction is impaired by acute thrombotic occlusion. Prosthetic materials are thrombogenic and cause platelet adhesion and activation of the coagulation cascade. Heparin is a potent anticoagulant drug widely used to prevent and treat thrombosis. A new ePTFE graft with long-term bonding of heparin is now commercially available in several European countries, but a basic analysis of its mechanism of action in humans has never been performed. This study was performed to evaluate the thrombogenicity of heparin-bonded ePTFE grafts compared with standard ePTFE in a newly developed human ex vivo model.MethodsNonanticoagulated blood was drawn from antecubital veins of 10 healthy donors with a 19-gauge needle. The proximal end of a 60-cm ePTFE vascular graft with a diameter of 3 mm was connected to the needle while the distal end was connected to a syringe, which was placed in a syringe pump. Every volunteer served as his or her own control by using a heparin-bonded ePTFE graft on one arm and a standard ePTFE graft on the other arm. The perfusions were performed over 6 minutes with a flow rate of 20 mL/min, corresponding to a shear rate of 74/s. Serial samples were taken at the distal end of the graft for determination of prothrombin fragment 1 + 2, fibrinopeptide A, and P-selectin expression on perfused platelets. Fibrin deposition and platelet deposition were studied by using scanning electronic microscopy.ResultsFibrinopeptide A production over time was significantly reduced on the heparin-bonded ePTFE grafts compared with standard ePTFE grafts (P < .05). There was no increase in the production of prothrombin fragment 1 + 2 or P selectin over time on either type of graft. Scanning electronic microscopy scanning showed platelet deposition and fibrin formation on standard ePTFE grafts, whereas no platelets or fibrin were observed on heparin-bonded ePTFE grafts.ConclusionsHeparin immobilization substantially reduces the thrombogenicity of small-diameter ePTFE in a newly developed human ex vivo model. In this study, we provide evidence that the mechanism of action of the heparin bonding is due not only to anticoagulant but also to antiplatelet effects. Heparin bonding may be an important improvement of ePTFE, resulting in better patency rates for vascular reconstructions.Clinical RelevanceHeparin immobilization reduces the thrombogenicity of small-caliber expanded polytetrafluoroethylene (ePTFE) grafts. The patency of small-diameter ePTFE grafts for vascular reconstruction is impaired by acute thrombotic occlusion. Prosthetic materials are thrombogenic and cause platelet adhesion and activation of the coagulation cascade. Heparin is a potent anticoagulant drug widely used to prevent and treat thrombosis. A new ePTFE graft with long-term bonding of heparin is now commercially available, but a basic analysis of its mechanism of action in humans has never been performed. This study was performed to evaluate the thrombogenicity of heparin-bonded ePTFE grafts compared with standard ePTFE in a newly developed human ex vivo model. We demonstrated that heparin immobilization reduces thrombogenicity on small-caliber ePTFE grafts. Heparin-bonded ePTFE grafts might therefore result in better patency rates for vascular reconstructions with vascular grafts

Vorapaxar in the secondary prevention of atherothrombotic events

Item does not contain fulltextBACKGROUND: Thrombin potently activates platelets through the protease-activated receptor PAR-1. Vorapaxar is a novel antiplatelet agent that selectively inhibits the cellular actions of thrombin through antagonism of PAR-1. METHODS: We randomly assigned 26,449 patients who had a history of myocardial infarction, ischemic stroke, or peripheral arterial disease to receive vorapaxar (2.5 mg daily) or matching placebo and followed them for a median of 30 months. The primary efficacy end point was the composite of death from cardiovascular causes, myocardial infarction, or stroke. After 2 years, the data and safety monitoring board recommended discontinuation of the study treatment in patients with a history of stroke owing to the risk of intracranial hemorrhage. RESULTS: At 3 years, the primary end point had occurred in 1028 patients (9.3%) in the vorapaxar group and in 1176 patients (10.5%) in the placebo group (hazard ratio for the vorapaxar group, 0.87; 95% confidence interval [CI], 0.80 to 0.94; P<0.001). Cardiovascular death, myocardial infarction, stroke, or recurrent ischemia leading to revascularization occurred in 1259 patients (11.2%) in the vorapaxar group and 1417 patients (12.4%) in the placebo group (hazard ratio, 0.88; 95% CI, 0.82 to 0.95; P=0.001). Moderate or severe bleeding occurred in 4.2% of patients who received vorapaxar and 2.5% of those who received placebo (hazard ratio, 1.66; 95% CI, 1.43 to 1.93; P<0.001). There was an increase in the rate of intracranial hemorrhage in the vorapaxar group (1.0%, vs. 0.5% in the placebo group; P<0.001). CONCLUSIONS: Inhibition of PAR-1 with vorapaxar reduced the risk of cardiovascular death or ischemic events in patients with stable atherosclerosis who were receiving standard therapy. However, it increased the risk of moderate or severe bleeding, including intracranial hemorrhage. (Funded by Merck; TRA 2P-TIMI 50 ClinicalTrials.gov number, NCT00526474.)

Genetic studies of body mass index yield new insights for obesity biology

Note: A full list of authors and affiliations appears at the end of the article. Obesity is heritable and predisposes to many diseases. To understand the genetic basis of obesity better, here we conduct a genome-wide association study and Metabochip meta-analysis of body mass index (BMI), a measure commonly used to define obesity and assess adiposity, in up to 339,224 individuals. This analysis identifies 97 BMI-associated loci (P 20% of BMI variation. Pathway analyses provide strong support for a role of the central nervous system in obesity susceptibility and implicate new genes and pathways, including those related to synaptic function, glutamate signalling, insulin secretion/action, energy metabolism, lipid biology and adipogenesis.</p